,transcriber's ,notes ,obvious typographical errors have been silently corrected4 ,variations in hyphenation have been standardised but all other spelling and punctuation remains unchanged4 ,footnotes are placed at the end of chapter4 ,italics are represented thus italic1 and superscripts thus 4 ,the periods of the satellites of ,uranus have been added to the table as specified in a subsequent note4 ,the layout of several tables has been modified to maintain clarity within wdth restrictions4 ,illustration3 ,,london ,,stereoscopic ,,co4 ,,photomezzotype4 ,,stanmore ,,observatory4 ,,inside ,,view4 ,,telescopic ,,work ,,for ,,starlight ,,evenings4 ,,by ,,william ,f4 ,,denning1 ,f4,r4,a4,s4 7,,formerly ,,president ,,of ,,the ,,liverpool ,,astronomical ,,society74 8,to ask or search ,i blame thee not1 for heaven ,is as the book of ,god before thee set1 ,wherein to read his wondrous works40 ,,milton4 ,,london3 ,,taylor ,,and ,,francis1 ,,red ,,lion ,,court1 ,,fleet ,,street4 #ahia4 ,all rights reserved4 ,illustration3 ,,alere ,,flammam4 ,,printed ,,by ,,taylor ,,and ,,francis1 ,,red ,,lion ,,court1 ,,fleet ,,street4 ,,preface4 ,it having been suggested by some kind friends that a series of articles on 8,telescopes and ,telescopic ,work10 which ,i wrote for the #8,journal of the ,liverpool ,astronomical ,society' in #ahhg-h1 should be reprinted1 ,i have undertaken the revision and rearrangement of the papers alluded to4 ,certain other contributions on 8,large and ,small ,telescopes10 8,planetary ,observations10 and kindred subjects1 which ,i furnished to #8,the ,observatory' and other scientific serials from time to time1 have also been included1 and the material so much altered and extended that it may be regarded as virtually new matter4 ,the work has outgrown my original intention1 but it proved so engrossing that it was found difficult to ensure greater brevity4 ,the combination of different papers has possibly had the effect of rendering the book more popular in some parts than in others4 ,this is not altogether unintentional1 for the aim has been to make the work intelligible to general readers1 while also containing facts and figures useful to amateur astronomers4 ,it is merely intended as a contribution to popular astronomy1 and asserts no rivalry with existing works1 many of which are essentially different in plan4 ,if any excuse were1 however1 needed for the issue of this volume it might be found in the rapid progress of astronomy1 which requires that new or revised works should be published at short intervals in order to represent existing knowledge4 ,the methods explained are approximate1 and technical points have been avoided with the view to engage the interest of beginners who may find it the stepping-stone to more advanced works and to more precise methods4 ,the object will be realized if observers derive any encouragement from its descriptions or value from its references1 and the author sincerely hopes that not a few of his readers will experience the same degree of pleasure in observation as he has done during many years4 ,no matter how humble the observer1 or how paltry the telescope1 astronomy is capable of furnishing an endless store of delight to its adherents4 ,its influences are elevating1 and many of its features possess the charms of novelty as well as mystery4 ,whoever contemplates the heavens with the right spirit reaps both pleasure and profit1 and many amateurs find a welcome relaxation to the cares of business in the companionship of their telescopes on 8starlight evenings40 ,the title chosen is not1 perhaps1 a comprehensive one1 but it covers most of the ground1 and no apology need be offered for dealing with one or two important objects not strictly within its scope4 ,for many of the illustrations ,i must express my indebtedness to the ,editors of the #8,observatory' to the ,council of the ,r4,a4,s41 to the proprietors of #8,nature1' to ,messrs4 ,browning1 ,calver1 ,cooke ,sons1 ,elger1 ,gore1 ,horne ,thornthwaite and ,wood1 ,klein1 and other friends4 ,the markings on ,venus and ,jupiter as represented on pages #aej and #ahj have come out much darker than was intended1 but these illustrations may have some value as showing the position and form of the features delineated4 ,it is difficult to reproduce delicate planetary markings in precisely the same characters as they are displayed in a good telescope4 ,the apparent orbits of the satellites of the planets1 delineated in figs4 #da1 #dd1 c41 are liable to changes depending on their variable position relatively to the ,earth1 and the diagrams are merely intended to give a good idea of these satellite systems4 ,w4 ,f4 ,d4 ,bishopston1 ,bristol1 #ahia4 ,plates ,i4 and ,,ii4 are views of the ,observatory and ,instruments recently erected by ,mr4 ,klein at ,stanmore1 ,middlesex1 lat4 #ea #cf #eg ,n41 long4 #j #ah #bb ,w4 ,the height above sea-level is #bfb feet4 ,the telescope is a #bj-;inch reflector by ,calver1 of #ib inches focus2 the tube is1 however1 #aeb inches long so as to cut off all extraneous rays4 ,it is mounted equatoreally1 and is provided with a finder of #f inches aperture--one of ,tulley's famous instruments a century ago4 ,the large telescope is fixed on a pillar of masonry #cg feet high1 and weighing #aae tons4 ,mr4 ,klein proposes to devote the resources of his establishment to astronomical photography1 and it has been provided with all the best appliances for this purpose4 ,the observatory is connected by telephone with ,mr4 ,klein's private residence1 and the timepieces and recording instruments are all electrically connected with a centre of observation in his study4 ,,contents4 ,,chapter ,i4 ,page ,,the ,,telescope1 ,,its ,,intention ,,and ,,the ,,development ,,of ,,its ,,powers #a ,,chapter ,,ii4 ,,relative ,,merits ,,of ,,large ,,and ,,small ,,telescopes #bj ,,chapter ,,iii4 ,,notes ,,on ,,telescopes ,,and ,,their ,,accessories #ch ,,chapter ,,iv4 ,,notes ,,on ,,telescopic ,,work #ff ,,chapter ,v4 ,,the ,,sun #hg ,,chapter ,,vi4 ,,the ,,moon #aac ,,chapter ,,vii4 ,,mercury #acg ,,chapter ,,viii4 ,,venus #ade ,,chapter ,,ix4 ,,mars #aee ,,chapter ,x4 ,,the ,,planetoids #afg ,,chapter ,,xi4 ,,jupiter #agj ,,chapter ,,xii4 ,,saturn #aie ,,chapter ,,xiii4 ,,uranus ,,and ,,neptune #bae ,,chapter ,,xiv4 ,,comets ,,and ,,comet-,,seeking #bbg ,,chapter ,,xv4 ,,meteors ,,and ,,meteoric ,,observations #bfj ,,chapter ,,xvi4 ,,the ,,stars #bhf ,,chapter ,,xvii4 ,,nebul ,,and ,,clusters ,,of ,,stars #cbd ,,notes ,,and ,,additions #cdg ,,index #cec ,,illustrations4 ,,plate ,i4 ,interior of ,mr4 ,klein's ,observatory ,frontispiece ,,ii4 ,view of ,mr4 ,klein's ,grounds and ,observatory ,to face p4 #hb ,,fig4 ,,page #a4 ,the ,galilean ,telescope #g #b4 ,royal ,observatory1 ,greenwich1 in ,flamsteed's time #h #c4 ,sir ,isaac ,newton #aj #d4 ,gregorian ,telescope #aj #e4 ,cassegrainian ,telescope #aa #f4 ,newtonian ,telescope #aa #g4 ,common ,refracting-,telescope #ab #h4 ,le ,mairean or ,herschelian ,telescope #ac #i4 #aj-;inch ,reflecting-,telescope on a ,german ,equatoreal1 by ,calver #ag #aj4 ,lord ,rosse's #f-;foot ,reflecting-,telescope #bb #aa4 ,refracting-,telescope1 by ,browning #cb #ab4 8,the ,popular ,reflector10 by ,calver #dj #ac4 #c-;inch ,refracting-,telescope1 by ,newton ,co4 #da #ad4 ,huygens's ,negative ,eyepiece #df #ae4 ,ramsden's ,positive ,eyepiece #dg #af4 ,berthon's ,dynamometer #ej #ag4 ,cooke and ,sons' ,educational ,telescope #eb #ah4 ,refracting-,telescope on a ,german ,equatoreal #fg #ai4 ,the ,author's ,telescope3 a #aj-;inch ,with-,browning ,reflector #gg #bj4 ,sun-spot of ,june #ai1 #ahhi #ie #ba4 ,solar ,eclipses visible in ,england1 #ahia to #aibb #ih #bb4 ,total ,solar ,eclipse of ,august #ai1 #ahhg #ih #bc4 ,belts of ,sun-spots1 visible ,oct4 #bi1 #ahfh #ajd #bd4 ,shadows cast by ,facul #aji #be4 ,light-spots and streaks on ,plato1 #ahgi-hb4 7,a4 ,stanley ,williams47 #abf #bf4 ,petavius and ,wrottesley at ,sunset4 7,t4 ,gwyn ,elger47 #abi #bg4 ,birt1 ,birt ,a1 and the ,straight ,wall4 7,t4 ,gwyn ,elger47 #acj #bh4 ,aristarchus and ,herodotus at ,sunrise4 7,t4 ,gwyn ,elger47 #acb #bi4 ,mercury as a ,morning ,star #adc #cj4 ,venus as an ,evening ,star #aej #ca4 ,mars1 #ahhf1 ,april #ac1 #i;h #ejm #aeg #cb4 ,orbits of the ,satellites of ,mars #aei #cc4 ,jupiter1 as drawn by ,dawes and others #agh #cd4 ,jupiter1 #ahhf1 ,april #i1 #aj;h #abm #ahj #ce4 ,occultation of ,jupiter1 ,aug4 #g1 #ahhi #ahf #cf4 ,jupiter and ,satellites seen in a small glass #ahg #cg4 ,shadows of ,jupiter's ,satellites ,,ii4 and ,,iii4 #aib #ch4 ,saturn as observed by ,cassini in ,august #afgf #aih #ci4 ,saturn1 #ahhe1 ,dec4 #bc1 #g;h #edm #bja #dj4 ,saturn as observed by ,f4 ,terby1 ,february #ahhg #bjc #da4 ,apparent orbits of the ,five ,inner ,satellites of ,saturn #bab #db4 ,transit of the ,shadow of ,titan #bac #dc4 ,uranus and his belts #bah #dd4 ,apparent orbits of the ,satellites of ,uranus #bba #de4 ,apparent orbit of the ,satellite of ,neptune #bbd #df4 ,mars1 ,saturn1 and ,regulus in same field1 ,sept4 #bj1 #ahhi #bbf #dg4 ,comet #ahfb ,,iii4 7,aug4 #ai1 #ahfb7 #bcg #dh4 ,sawerthal's ,comet1 #ahhh ,i4 7,march #be1 ,brooks7 #bcg #di4 ,brooks's ,double ,comet1 ,sept4 #ag1 #ahhi #bci #ej4 ,pons's ,comet 7#ahab74 ,telescopic view1 #ahhd1 ,jan4 #f #bdb #ea4 ,ditto4 ,ditto1 #ahhd1 ,jan4 #ba #bdb #eb4 ,radiation of ,meteors4 7,shower of early ,perseids1 #ahgh7 #bfc #ec4 ,double ,meteor4 ,curved ,meteor4 ,fireball #bfe #ed4 ,meteorite found in ,chili in #ahff #bfe #ee4 ,meteorite which fell at ,orgueil in #ahfd #bfe #ef4 ,fireball of ,nov4 #bc1 #ahgg1 #h;h #bdm 7,j4 ,plant47 #bfi #eg4 ,flight of ,telescopic ,meteors seen by ,w4 ,r4 ,brooks #bgb #eh4 ,meteor of ,dec4 #bh1 #ahhh1 #f;h #agm #bgg #ei4 ,large ,meteor and streak seen at ,jask #bgh #fj4 ,the ,constellation ,orion #bhi #fa4 ,diagram illustrating the ,measurement of ,angles of ,position #bia #fb4 ,double ,stars #cja #fc4 ,trapezium in ,orion as seen with the #cf-;inch refractor #cai #fd4 ,nebul and a ,star-cluster #ccf #fe4 ,nebula within a semicircle of stars #cdb ,,telescopic ,,work ,,for ,,starlight ,,evenings4 ,,chapter ,i4 ,,the ,,telescope1 ,,its ,,invention ,,and ,,the ,,development ,,of ,,its ,,powers4 ,the instrument which has so vastly extended our knowledge of the ,universe1 which has enabled us to acquire observations of remarkable precision1 and supplied the materials for many sublime speculations in ,astronomy1 was invented early in the seventeenth century4 ,apart from its special application as a means of exploring the heavens with a capacity that is truly marvellous1 it is a construction which has also been utilized in certain other departments with signal success4 ,it provided mankind with a medium through which to penetrate far beyond the reach of natural vision1 and to grasp objects and phenomena which had either eluded detection altogether or had only been seen in dim and uncertain characters4 ,it has also proved a very efficient instrument for various minor purposes of instruction and recreation4 ,the invention of the telescope formed a new era in astronomy2 and though1 with a few exceptions1 men were slow at first in availing themselves of its far-seeing resources1 scepticism was soon swept aside and its value became widely acknowledged4 ,but though the telescope was destined to effect work of the utmost import1 and to reach a very high degree of excellence in after times1 the result was achieved gradually4 ,step by step its powers were enlarged and its qualities perfected1 and thus the stream of astronomical discovery has been enabled to flow on1 stimulated by every increase in its capacity4 ,there is some question as to whom may be justly credited with the discovery of its principles of construction4 ,huygens1 in his #8,dioptrics1' remarks3--8,i should have no hesitation in placing above all the rest of mankind the individual who1 solely by his own reflections1 without the aid of any fortuitous circumstances1 should have achieved the invention of the telescope40 ,there is reason to conclude1 however1 that its discovery resulted from accident rather than from theory4 ,it is commonly supposed that ,galileo ,galilei is entitled to precedence2 but there is strong evidence to show that he had been anticipated4 ,in any case it must be admitted that ,galilei#a had priority in successfully utilizing its resources as a means of observational discovery2 for he it was who1 first of all men1 saw ,jupiter's satellites1 the crescent form of ,venus1 the mountains and craters on the ,moon1 and announced them to an incredible world4 ,it has been supposed1 and not without some basis of probability1 that a similar instrument to the telescope had been employed by the ancients2 for certain statements contained in old historical records would suggest that the ,greek philosophers had some means of extending their knowledge further than that permitted by the naked eye4 ,democritus remarked that the ,galaxy or 8,milky ,way0 was nothing but an assemblage of minute stars2 and it has been asked1 ,how could he have derived this information but by instrumental aid8 ,it is very probable he gained the knowledge by inferences having their source in close observation2 for anyone who attentively studies the face of the sky must be naturally led to conclude that the appearance of the 8,milky ,way0 is induced by immense and irregular clusterings of small stars4 ,in certain regions of the heavens there are clear indications of this3 the eye is enabled to glimpse some of the individual star-points1 and to observe how they blend and associate with the denser aggregations which give rise to the milky whiteness of the ,galaxy4 ,refracting lenses1 or 8burning-glasses10 were known at a very early period4 ,a lens1 roughly figured into a convex shape and obviously intended for magnifying objects1 has been recovered from the ruins of ,herculaneum1 buried in the ejections from ,vesuvius in the year #gi ,a4,d4 ,pliny and others refer to lenses that burnt by refraction1 and describe globules of glass or crystal which1 when exposed in the sun1 transmit sufficient heat to ignite combustible material4 ,the ancients undoubtedly used tubes in the conduct of their observations1 but no lenses seem to have been employed with them1 and their only utility consisted in the fact of their shutting out the extraneous rays of light4 ,but spectacles were certainly known at an early period4 ,concave emeralds are said to have been employed by ,nero in witnessing the combats of the gladiators1 and they appear to have been the same in effect as the spectacles worn by short-sighted people in our own times4 ,but the ancients supposed that the emerald possessed inherent qualities specially helpful to vision1 rather than that its utility resulted simply from its concavity of figure4 ,in the #acth century spectacles were more generally worn1 and the theory of their construction understood4 ,it is remarkable that the telescope did not come into use until so long afterwards4 ,vague references were made to such an instrument1 or rather suggestions as to the possibilities of its construction1 which show that1 although the principle had perhaps been conceived1 the idea was not successfully put into practice4 ,roger ,bacon1 who flourished in the #acth century1 wrote in his #8,opus ,majus'3--8,greater things may be performed by refracted light1 for1 from the foregoing principles1 follows easily that the greatest objects may be seen very small1 the remote very near1 and vice vers4 ,for we can give transparent bodies such form and position with respect to the eye and the object that the rays are refracted and bent to where we like1 so that we1 under any angle1 see the objects near or far1 and in that manner we can1 at a great distance1 read the smallest letters1 and we can count atoms and sand-grains1 on account of the greatness of the angle under which they are seen40 ,fracastor1 in a work published at ,venice in #aech1 states3--8,if we look through two eye-lenses1 placed the one upon the other1 everything will appear larger and nearer40 ,he also says3--8,there are made certain eye-lenses of such a thickness that if the moon or any other celestial body is viewed through them they appear to be so near that their distance does not exceed that of the steeples of public buildings40 ,in other writings will also be found intimations as to the important action of lenses2 and it is hardly accountable that a matter so valuable in its bearings was allowed to remain without practical issues4 ,the progressive tendency and the faculty of invention must indeed have been in an incipient stage1 and contrasts strongly with the singular avidity with which ideas are seized upon and realized in our own day4 ,many important discoveries have resulted from pure accident2 and it has been stated that the first bon fide telescope had its origin in the following incident3--,the children of a spectacle-maker1 ,zachariah ,jansen1 of ,middleberg1 in ,zealand1 were playing with some lenses1 and it chanced that they arranged two of them in such manner that1 to their astonishment1 the weathercock of an adjoining church appeared much enlarged and more distinct4 ,having mentioned the curious fact to their father1 he immediately turned it to account1 and1 by fixing two lenses on a board1 produced the first telescope6 ,this view of the case is1 however1 a very doubtful one1 and the invention may with far greater probability be attributed to ,hans ,lippersheim in #afjh4 ,galilei has little claim to be considered in this relation2 for he admitted that in #afji the news reached him that a ,dutchman had devised an appliance capable of showing distant objects with remarkable clearness4 ,he thereupon set to work and experimented with so much aptitude on the principles involved that he very soon produced a telescope for himself4 ,with this instrument he detected the four satellites of ,jupiter in #afaj1 and other successes shortly followed4 ,being naturally gratified with the improvements he had effected in its construction1 and with the wonderful discoveries he had made by its use1 we can almost excuse the enthusiasm which prompted him to attribute the invention to his own ingenuity4 ,but while according him the honour due to his sagacity in devoting this instrument to such excellent work1 we must not overlook the fact that his claim to priority cannot be justified4 ,indeed1 that ,galilei had usurped the title of inventor is mentioned in letters which passed between the scientific men of that time4 ,fuccari1 writing to ,kepler1 says3--8,galileo wants to be considered the inventor of the telescope1 though he1 as well as ,i and others1 first saw the telescope which a certain ,dutchman first brought with him to ,venice1 and although he has only improved it very little40 ,in a critical article by ,dr4 ,doberck#b1 in which this letter is quoted and the whole question reviewed with considerable care1 it is stated that ,hans ,lippersheim 7also known as ,jan ,lapprey71 who was born in ,wesel1 but afterwards settled at ,middleberg1 in the ,netherlands1 as a spectacle-maker1 was really the first to make a telescope1 and the following facts are quoted in confirmation3--8,he solicited the ,states1 as early as the #bnd ,october1 #afjh1 for a patent for thirty years1 or an annual pension for life1 for the instrument he had invented1 promising then only to construct such instruments for the ,government4 ,after inviting the inventor to improve the instrument and alter it so that they could look through it with both eyes at the same time1 the ,states determined1 on the #dth ,october1 that from every province one deputy should be elected to try the apparatus and make terms with him concerning the price4 ,this committee declared on the #fth ,october that it found the invention useful for the country1 and had offered the inventor #ijj florins for the instrument4 ,he had at first asked #cjjj florins for three instruments of rock-crystal4 ,he was then ordered to deliver the instrument within a certain time1 and the patent was promised him on condition that he kept the invention secret4 ,lapprey delivered the instrument in due time4 ,he had arranged it for both eyes1 and it was found satisfactory2 but they forced him1 against the agreement1 to deliver two other telescopes for the same money1 and refused the patent because it was evident that already several others had learned about the invention40 ,the material from which the glasses were figured appears to have been quartz2 and efforts were made to keep the invention a profound secret1 as it was thought it would prove valuable for 8strategetical purposes40 ,the cost of these primitive binoculars was about #ge each4 ,it is singular that1 after being allowed to rest so long1 the idea of telescopic construction should have been carried into effect by several persons almost simultaneously1 and that doubts and disputes arose as to precedence4 ,the probable explanation is that to one individual only priority was really due1 but that1 owing to the delays1 the secret could not be altogether concealed from two or three others who recognized the importance of the discovery and at once entered into competition with the original inventor4 ,each of these fashioned his instrument in a slightly different manner1 though the principle was similar in all2 and having in a great measure to rely upon his individual faculties in completing the task1 he considered himself in the light of an inventor and put forth claims accordingly4 ,not only were attempts made to assume the position of inventor1 but there arose fraudulent claimants to some of the discoveries which the instrument effected in the hands of ,galilei4 ,simon ,marius1 himself one of the very first to construct a telescope and apply it to the examination of the heavenly bodies1 asserted that he had seen the satellites of ,jupiter on ,december #bi1 #afji1 a few days before ,galilei1 who first glimpsed them on ,january #g1 #afaj4 ,humboldt1 in his #8,physical ,description of the ,heavens1' definitely ascribes the discovery of these moons to ,marius2 but other authorities uniformly reject the statement1 and accord to ,galilei the full credit4 ,it is stated that ,galilei's first instrument magnified only three times1 but he so far managed to amplify its resources that he was ultimately enabled to apply a power of #cj4 ,the lenses consisted of a double-convex object-glass1 and a small double-concave eye-glass placed in front of the focal image formed by the object-glass4 ,the ordinary opera-glass is constructed on a similar principle4 ,illustration3 ,fig4 #a4 ,the ,galilean ,telescope4 ,the discoveries which ,galilei effected with this crude and defective instrument caused a great sensation at the time4 ,he made them known through the medium of a publication which he issued under the title of #8,nuncius ,siderus1' or #8,the ,messenger of the ,stars4' ,in that superstitious age great ignorance prevailed1 bigotry was dominant1 and erroneous views of the solar system were upheld and taught by authority4 ,we can therefore readily conceive that ,galilei's discoveries1 and the direct inferences he put upon them1 being held antagonistic to the ruling doctrines1 would be received with incredulity and opposition4 ,his views were regarded as heretical4 ,in consequence of upholding the ,copernican system he suffered persecution1 and had to resort to artifice in the publication of his works4 ,but the marvels revealed by his telescope1 though discredited at first1 could not fail to meet with final acceptance1 for undeniable testimony to their reality was soon forthcoming4 ,they were not1 however1 regarded until long afterwards as affirming the views enunciated by their clever author4 ,ultimately the new astronomy1 based on the irrepressible evidence of the telescope1 and clad in all the habiliments of truth1 took the place of the old fallacious beliefs1 to form an enduring monument to ,copernicus and ,galilei1 who spent their lives in advancing its cause4 ,no special developments in the construction of the telescope appear to have taken place until nearly half a century subsequent to its invention4 ,kepler suggested an instrument formed of two convex lenses1 and ,scheiner and ,huygens made telescopes on this principle in the middle of the #agth century4 ,huygens found great advantage in the employment of a compound eyepiece consisting of two convex lenses1 which corrected the spherical aberration1 and1 besides being achromatic1 gave a much larger field than the single lens4 ,this eyepiece1 known as the 8,huygenian10 still finds favour with the makers of telescopes4 ,illustration3 ,fig4 #b4 ,royal ,observatory1 ,greenwich1 in ,flamsteed's time#c4 ,huygens may be said to have inaugurated the era of long telescopes4 ,he erected instruments of #ab and #bc feet1 having an aperture of #b-a_/c inches and powers of #dh1 #ej1 and #ib4 ,he afterwards produced one #abc feet in focal length and #f inches in aperture4 ,chief among his discoveries were the largest satellite of ,saturn 7,titan7 and the true form of ,saturn's ring4 ,hevelius of ,dantzic built an instrument #aej feet long1 which he fixed to a mast #ij feet in height1 and regulated by ropes and pulleys4 ,cassini1 at the ,observatory at ,paris1 had telescopes by ,campani of #hf1 #ajj1 and #acf ,french feet in length2 but the highest powers he used on these instruments do not appear to have exceeded #aej times4 ,he made such good use of them as to discover three of the satellites of ,saturn and the black division in the ring of that planet4 ,the largest object-glasses employed by ,hevelius and ,cassini were of #f1 #g1 and #h inches diameter4 ,this was during the latter half of the #agth century4 ,in #agab ,bradley made observations of ,venus1 and obtained measures of the planet's diameter1 with a telescope no less than #bab feet in focal length4 ,the instruments alluded to were manipulated with extreme difficulty1 and observations had to be conducted in a manner very trying to the observer4 ,tubes were sometimes dispensed with1 the object-glass being fixed to a pole and its position controlled by various contrivances--the observer being so far off1 however1 that he required the services of a good lantern in order to distinguish it6 ,the immoderate lengths of refracting-telescopes were necessary1 as partially avoiding the effects of chromatic aberration occasioned by the different refrangibility of the seven coloured rays which collectively make white light4 ,in other words1 the coloured rays having various indices of refraction cannot be brought to a coincident focus by transmission through a single lens4 ,thus the red rays have a longer focus than the violet rays1 and the immediate effect of the different refractions becomes apparent in the telescopic images1 which are fringed with colour and not sharply defined4 ,high magnifying powers serve to intensify the obstacle alluded to1 and thus the old observers found it imperative to employ eye-glasses not beyond a certain degree of convexity4 ,the great focal lengths of their object-lenses enabled moderate power to be obtained1 though the eye-glass itself had a focus of several inches and magnified very little4 ,sir ,isaac ,newton made many experiments upon colours1 and endeavoured to obviate the difficulties of chromatic aberration1 but erroneously concluded that it was not feasible4 ,he could devise no means to correct that dispersion of colour which1 in the telescopes of his day1 so greatly detracted from their effectiveness4 ,his failure seems to have had a prejudicial effect in delaying the solution of the difficulty1 which was not accomplished until many years afterwards4 ,illustration3 ,fig4 #c4 ,sir ,isaac ,newton#d4 ,illustration3 ,fig4 #d4 ,gregorian ,telescope4 ,the idea of reflecting-telescopes received mention as early as #afci2 but it was not until #affc that ,gregory described the instrument1 formed of concave mirrors1 which still bears his name4 ,he was not1 however1 proficient in mechanics1 and after some futile attempts to carry his theory into effect the exertion was relinquished4 ,in #afgc ,cassegrain revived the subject1 and proposed a modification of the form previously indicated by ,gregory4 ,instead of the small concave mirror1 he substituted a convex mirror placed nearer the speculum2 and this arrangement1 though it made the telescope shorter1 had the disadvantage of displaying objects in an inverted position4 ,but the utility of these instruments was not demonstrated in a practical form until #afgd1 when ,hooke1 the clever mechanician1 gave his attention to the subject and constructed the first one that was made of the kind4 ,illustration3 ,fig4 #e4 ,cassegrainian ,telescope4 ,in the meantime 7#afgb7 ,sir ,isaac ,newton had completed with his own hands a reflecting-telescope of another pattern4 ,in this the rays from the large concave speculum were received by a small plane mirror fixed centrally at the other end of the tube1 and inclined at an angle of #de2 so that the image was directed at right angles through an opening in the side1 and there magnified by the eye-lens4 ,but for a long period little progress was effected in regard to reflecting-telescopes1 owing to the difficulty of procuring metal well adapted for the making of specula4 ,illustration3 ,fig4 #f4 ,newtonian ,telescope4 ,in #agbi ,mr4 ,chester ,moor ,hall applied himself to the study of refracting-telescopes and discovered that1 by a combination of different glasses1 the colouring of the images might be eliminated4 ,it is stated that ,mr4 ,hall made several achromatic glasses in #agcc4 ,a quarter of a century after this ,john ,dollond independently arrived at the same result1 and took out a patent for achromatic telescopes4 ,he found1 by experiments with prisms1 that crown and flint glass operated unequally in regard to the divergency of colours induced by refraction2 and1 applying the principle further1 he obtained a virtually colourless telescope by assorting a convex crown lens with a concave flint lens as the object-glass4 ,dollond also made many instruments having triple object-lenses1 and in these it was supposed that previous defects were altogether obliterated4 ,two convex lenses of crown glass were combined with a concave lens of flint glass placed between them4 ,whether we regard ,hall or ,dollond as entitled to the most praise in connection with this important advance1 it is certain that it was one the value of which could hardly be overestimated4 ,it may be said to have formed a new era in practical astronomy4 ,instruments only #d or #e feet long could now be made equally if not more effective than those of #abc and #aej feet previously used by ,huygens and ,hevelius4 ,all the troubles incidental to these long unmanageable machines now disappeared1 and astronomers were at once provided with a handy little telescope capable of the finest performances4 ,illustration3 ,fig4 #g4 ,common ,refracting-,telescope4 ,reflecting-telescopes also underwent marked improvements in the eighteenth century4 ,short1 the optician1 who died in #agfh1 was deservedly celebrated for the excellent instruments he made of the ,gregorian form4 ,towards the latter part of the century ,william ,herschel1 by indomitable perseverance1 figured a considerable number of specula4 ,some of these were mounted as ,newtonians2 others were employed in the form known as the 8,front view10 in which a second mirror is dispensed with altogether1 and the rays from the large concave speculum are thrown to the side of the tube and direct to the eyepiece4 ,this construction is often mentioned as the 8,herschelian10 but the idea had long before been detailed by ,le ,maire4 ,in #agbh he presented a paper to the ,acadmie des ,sciences1 giving his plans for a new reflecting-telescope4 ,he proposed to suppress the small flat speculum in ,newtonians1 and 8by giving the large concave speculum a little inclination1 he threw the image1 formed in its focus1 to one side of the tube1 where1 an eye-glass magnifying it1 the observer viewed it1 his back at the time being turned towards the object in the heavens2 thus the light lost in the ,newtonian telescope by the second reflexion was saved40 ,illustration3 ,fig4 #h4 ,the ,le ,mairean or ,herschelian ,telescope4 ,after making several instruments of from #ah to #bd inches aperture1 ,herschel began one of larger calibre1 and it was finished on ,august #bh1 #aghi4 ,the occasion was rendered historical by the discovery of one of the faintest interior satellites of ,saturn1 ,enceladus4 ,the large telescope had a speculum #dh inches in diameter2 the tube was made of rolled or sheet iron1 and it was #ci ft4 #d in4 long and #d ft4 #aj in4 in diameter4 ,it was by far the largest instrument the world had seen up to that time2 but it cannot be said to have realized the expectations formed of its powers1 for its defining properties were evidently not on a par with its space-penetrating power4 ,many of ,herschel's best observations were made with much smaller instruments4 ,the large telescope1 which was mounted in ,herschel's garden at ,slough1 soon fell into comparative disuse1 and1 regarding it as incapable of further usefulness1 ,sir ,john ,herschel sealed it up on ,january #a1 #ahdj4 ,during the next half-century we hear of no attempts being made to surpass the large instrument which formed one of the working-tools of ,herschel4 ,then1 however1 ,lord ,rosse entered the field1 and in the #8,philosophical ,transactions' for #ahdj described a reflector of #c-;feet diameter which he had set up at his residence at ,parsonstown1 ,ireland4 ,in #ahde the same nobleman1 distinguished alike for his scientific attainments as for his generosity and urbanity of disposition1 erected another telescope1 the large speculum of which was #f feet in diameter1 #e inches in thickness1 and its weight #c tons4 ,lord ,rosse subsequently cast a duplicate speculum of #f feet and weighing #d tons4 ,in point of dimensions this instrument far exceeded that of ,herschel1 and it is still in use1 retaining its character as the largest1 though certainly not the best1 telescope in existence4 ,its tube is made of #a-;inch deal1 well bound together with iron hoops2 it is #ef feet long and #g feet in diameter4 ,mr4 ,lassell soon afterwards made large specula4 ,he erected one of #b-;feet aperture and #bj-;feet focus at his residence at ,starfield1 near ,liverpool1 and in #ahfa mounted one of #d-;feet diameter and #cg-;feet focus4 ,this instrument was for some time usefully employed by him at ,malta4 ,after ,mr4 ,lassell's return to ,england his great telescope remained in a dismantled state for several years1 and ultimately the speculum was broken up and 8consigned to the crucible of the bell-founder40 ,it is not a little remarkable that ,herschel1 ,rosse1 and ,lassell personally superintended and assisted in the construction of the monster instruments with which their names are so honourably associated4 ,in or about the year #ahfg a telescope of the ,cassegrainian form1 and having a metallic speculum #d feet in diameter and #bh-;feet focus1 was completed by ,grubb of ,dublin for the observatory at ,melbourne4 ,this instrument1 which cost something like #ad1jjj1 was found defective at first1 though the fault does not appear to have rested with the optician4 ,up to this period specula were formed of a metal in which copper and tin were largely represented4 ,but the days of metal specula were numbered4 ,leon ,foucault1 in the year #ahei1 published a valuable memoir in which he described the various ingenious methods he employed in figuring surfaces of glass to the required curve4 ,he furnished data for determining accuracy of figure4 ,formerly opticians had considerable trouble in deciding the quality of their newly-ground specula or object-glasses4 ,they found it expedient to mount them temporarily1 and then1 by actual trial on difficult objects1 to judge of their efficiency4 ,this involved labour and occasioned delay1 especially in the case of large instruments4 ,foucault showed that crucial tests might be applied in the workshop1 and that glasses could be turned out of hand without any misgivings as to their perfection of figure4 ,foucault's early experiments in parabolizing glass led him to important results4 ,by depositing a thin coating of silver on his specula he obtained a reflective power far surpassing that of metal4 ,thereafter metal was not thought of as a suitable material for reflecting-telescopes4 ,silver-on-glass mirrors immediately came into great request4 ,the latter undoubtedly possess a great superiority over metal1 especially as regards light-grasping power1 the relative capacity according to ,sir ,j4 ,herschel being as #hbd to #dcf4 ,glass mirrors have also another advantage in being less heavy than those of metal4 ,it is true the silver film is not very durable1 but it can be renewed at any time with little trouble or expense4 ,with of ,hereford1 and after him ,calver of ,chelmsford1 became noted for the excellency of their glass mirrors4 ,they were found nearly comparable to refractors of the same aperture4 ,a tendency of the times was evidently in the direction of large instruments4 ,one of #dgb-;inches aperture 7for which a sum of #aij1jjj francs was paid7 was completed by ,martin in #ahge for the ,paris ,observatory1 but its employment since that year has not furnished a very successful record4 ,the largest instrument of the kind yet made has a speculum #e feet in diameter and #bg-;feet focal length4 ,it was placed in position in ,september #ahhh1 and was made by the owner1 ,mr4 ,common1 of ,ealing1 whose previous instrument was a #cg-;inch glass reflector by ,calver4 ,the #e-;foot telescope is undoubtedly of much greater capacity than the colossal reflector of ,lord ,rosse1 though it is not so large4 ,mr4 ,calver has recently figured a #ej-;inch mirror for ,sir ,h4 ,bessemer1 but the mounting is not completed2 and he is expecting to make other large reflectors1 viz4 one over #e feet in diameter and another over #c feet4 ,the late ,mr4 ,nasmyth also erected some fine instruments1 and adopted a combination of the ,cassegrainian and ,newtonian forms to ensure greater convenience for the observer4 ,instead of permitting the rays from the small convex mirror to return through the large mirror1 he diverted them through the side of the tube by means of a flat mirror1 as in ,newtonians4 ,but this construction is not to be commended1 because much light is lost and defects increased by the additional mirror4 ,smaller telescopes of the kind we have been referring to have become extremely popular3 and deservedly so4 ,they are likely to maintain their character in future years2 for the ,newtonian form of instrument1 besides being thoroughly effective in critical work1 is moderate in price and gives images absolutely achromatic4 ,moreover1 it is used with a facility and ease which an experienced observer knows how to appreciate4 ,whatever may be the altitude of the objects under scrutiny1 he is enabled to retain a perfectly convenient and natural posture1 and may pursue his work during long intervals without any of the fatigue or discomfort incidental to the use of certain other forms of instrument4 ,returning now to refractors3 many years elapsed after ,dollond patented his achromatic object-glass before it was found feasible to construct these instruments of a size sufficient to grasp faint and delicate objects4 ,opticians were thwarted in their efforts to obtain glass of the requisite purity for lenses1 unless in small disks very few inches in diameter4 ,it is related that ,dollond met with a pot of uncommonly pure flint glass in #agfj1 but even with this advantage of material he admitted that1 after numerous attempts1 he could not provide really excellent object-glasses of more than #c-c_/d-;inches diameter4 ,it may therefore be readily imagined that a refractor of #d or #e-;inches aperture was an instrument of great rarity and expense4 ,towards the latter part of the #ahth century ,tulley's price was #bge for a #e-;inch equatoreally mounted4 ,illustration3 ,fig4 #i4 #aj-;inch ,reflecting-,telescope on a ,german ,equatoreal1 by ,calver4 ,in later years marked improvements were effected in the manufacture of glass4 ,a sign of this is apparent in the fact that1 in #ahbi1 ,sir ,james ,south was enabled to purchase a #ab-;inch lens4 ,four years before this the ,dorpat telescope1 having an objective of #i inches1 had created quite a sensation4 ,as time went on1 still larger glasses were made4 ,in #ahfb ,alvan ,clark ,sons1 of ,new ,york1 ,u4,s4,a41 finished an instrument of #ah-;inches aperture1 at a cost of #cgjj2 and in #ahfi ,cooke ,sons mounted a #bdf-;inch object-glass for the late ,mr4 ,newall1 of ,gateshead4 ,the latter instrument was much larger than any other refractor hitherto made1 but it was not long to maintain supremacy4 ,one of #beh inches and #bi-;feet focus was finished in #ahgb by ,alvan ,clark ,sons for the ,naval ,observatory1 ,washington1 at a cost of #ijjj4 ,another1 of similar size1 was supplied by the same firm to ,mr4 ,mc,cormick1 ,u4,s4,a4 ,several important discoveries1 including the satellites of ,mars1 were effected with the great ,washington telescope4 ,a few years later a #bg-;inch was completed by ,grubb for the ,vienna ,observatory1 and quite recently the four largest refractors ever made have been placed in position and are actively employed in various departments of work4 ,these include a #bi-;inch by ,martin for the ,paris ,observatory1 a #cj-;inch by ,henry ,bros4 for ,nice1 a #cj-;inch by ,a4 ,clark ,sons for ,pulkowa1 and a #cf-;inch1 also by ,a4 ,clark ,sons1 for the ,lick ,observatory on ,mount ,hamilton in ,california4 ,the latter has no rival in point of size1 though rumours are current that still larger lenses are in contemplation4 ,the tube of the #cf-;inch is #ef feet long and #c feet in diameter at the ends1 but the diameter is greater in the middle4 ,it is placed within a great dome #ge feet in diameter4 ,the expense of the entire apparatus is given as follows3--,cost of the dome1 #ef1hej2 of the visual objective1 #ec1jjj2 of the photographic objective1 #ac1jjj2 of the mounting1 #db1jjj4 ,total1 #afd1hej4 ,this noble instrument--due to the munificence of one individual1 the late ,mr4 ,james ,lick1 of ,chicago1 who bequeathed #gjj1jjj for the purpose--may be regarded as the king of refracting-telescopes4 ,placed on the summit of ,mount ,hamilton1 where the atmosphere is exceptionally favourable for celestial observations1 and utilized as its resources are by some of the best observers in ,america1 we may confidently expect it to largely augment our knowledge of the heavenly bodies4 ,the great development in the powers of both refracting and reflecting-telescopes1 as a means of astronomical discovery1 exemplifies in a remarkable degree the ever-increasing resources and refinements of mechanical art4 ,in #afaj ,galilei1 from his window at ,padua1 first viewed the moon and planets with his crude instrument having a power of #c1 and he achieved much during the remaining years he lived1 by increasing it tenfold1 so that at last he could magnify an object #cj times4 ,huygens laboured well in the same field2 and others who succeeded him formed links in the chain of progress which has almost uninterruptedly run through all the years separating ,galilei's time from our own4 ,the primitive efforts of the ,florentine philosopher appear to have had their sequel in the magnificent telescope which has lately been erected under the pure sky of ,mount ,hamilton4 ,the capacity of this instrument relatively to that of earlier ones may be judged from the fact that a power of about #ccjj times has lately been employed with success in the measurement of a close and difficult double star4 ,could ,galilei but stand for a few moments at the eyepiece of this great refractor1 and contemplate the same objects which he saw1 nearly three centuries ago1 through his imperfect little glasses at ,padua1 he would be appalled at the splendid achievements of modern science4 ,,footnotes3 #a ,galileo ,galilei is very generally called by his christian name1 but ,i depart from this practice here4 #b #8,observatory1' vol4 ii4 p4 #cfd4 #c ,reproduced1 by permission1 from ,cassell's #8,new ,popular ,educator4' #d ,reproduced1 by permission1 from ,cassell's #8,new ,popular ,educator4' ,,chapter ,,ii4 ,,relative ,,merits ,,of ,,large ,,and ,,small ,,telescopes4 ,the number of large telescopes having so greatly increased in recent years1 and there being every prospect that the demand for such instruments will continue1 it may be well to consider their advantages as compared with those of much inferior size4 ,object-glasses and specula will probably soon be made of a diameter not hitherto attained2 for it is palpably one of the ambitions of the age to surpass all previous efforts in the way of telescopic construction4 ,there are some who doubt that such enormous instruments are really necessary1 and question whether the results obtained with them are sufficient return for the great expense involved in their erection4 ,large instruments require large observatories2 and the latter must be at some distance from a town1 and in a locality where the atmosphere is favourable4 ,nothing can be done with great aperture in the presence of smoke and other vapours1 which1 as they cross the field1 become ruinous to definition4 ,moreover1 a big instrument is not to be manipulated with the same facility as a small one3 and when anything goes wrong with it1 its rectification may be a serious matter1 owing to the size4 ,such telescopes need constant attention if they would be kept in thorough working order4 ,on the other hand1 small instruments involve little outlay1 they are very portable1 and require little space4 ,they may be employed in or out of doors1 according to the inclination and convenience of the observer4 ,they are controlled with the greatest ease1 and seldom get out of adjustment4 ,they are less susceptible to atmospheric influences than larger instruments1 and hence may be used more frequently with success and at places by no means favourably situated in this respect4 ,finally1 their defining powers are of such excellent character as to compensate in a measure for feeble illumination4 ,in discussing this question it will be advisable to glance at the performances of certain instruments of considerable size4 ,the introduction of really large glasses dates from a century ago1 when ,sir ,w4 ,herschel mounted his reflector1 #d feet in aperture1 at ,slough4 ,he discovered two of the inner satellites of ,saturn very soon after it was completed2 but apart from this the instrument seems to have achieved little4 ,herschel remarked that on ,august #bh1 #aghi1 when he brought the great instrument to the parallel of ,saturn1 he saw the spots upon the planet better than he had ever seen them before4 ,the night was probably an exceptionally good one1 for we do not find this praise reiterated4 ,indeed1 ,herschel appears to have practically discarded his large instrument for others of less size4 ,he found that with his small specula of #g-;ft4 focus and #fc-;in4 aperture he had 8light sufficient to see the belts of ,saturn completely well1 and that here the maximum of distinctness might be much easier obtained than where large apertures are concerned40 ,even in his sweeps for nebul he employed a speculum of #bj-;ft4 focus and #ah-;in4 aperture in preference to his #d-;ft4 instrument1 though on objects of this nature light-grasping power is essentially necessary4 ,the labour and loss of time involved in controlling the large telescope probably led to its being laid aside for more ready means1 though ,herschel was not the man to spare trouble when an object was to be gained4 ,his life was spent in gleaning new facts from the sky2 and had the #d-;foot served his purpose better than smaller instruments1 no trifling obstacle would have deterred him from its constant employment4 ,but his aim was to accomplish as much as possible in every available hour when the stars were shining1 and experience doubtless taught him to rely chiefly upon his smaller appliances as being the most serviceable4 ,the ,le ,mairean form1 or 8,front view10 which ,herschel adopted for the large instrument may quite possibly have been in some degree responsible for its bad definition4 ,illustration3 ,fig4 #aj4 ,lord ,rosse's #f-;foot ,reflecting-,telescope4 ,lord ,rosse's #f-;ft4 reflector has now been used for nearly half a century1 and its results ought to furnish us with good evidence as to the value of such instruments4 ,it has done important work on the nebul1 especially in the re-observation of the objects in ,sir ,j4 ,herschel's ,catalogues of #ahcc and #ahfd4 ,to this instrument is due the discovery of spiral nebul2 and perhaps this achievement is its best4 ,but when we reflect on the length of its service1 we are led to wonder that so little has been accomplished4 ,for thirty years the satellites of ,mars eluded its grasp1 and then fell a prize to one of the large ,american telescopes4 ,the bright planets#e have been sometimes submitted to its powers1 and careful drawings executed by good observers2 but they show no extent of detail beyond what may be discerned in a small telescope4 ,this does not necessarily impugn the figure of the large speculum1 the performance of which is entirely dependent upon the condition of the air4 ,the late ,dr4 ,robinson1 of ,armagh1 who had the direction of the instrument for sometime1 wrote in #ahga3--8;,a stream of heated air passing before the telescope1 the agitation and hygrometric state of the atmosphere1 and any differences of temperature between the speculum and the air in the tube are all capable of injuring or even destroying definition1 though the speculum were absolutely perfect4 ,the effect of these disturbances is1 in reflectors1 as the cube of their apertures2 and hence there are few hours in the year when the #f-;foot can display its full powers40 ,another of the regular observers1 ,mr4 ,g4 ,j4 ,stoney1 wrote in #ahgh3--8,the usual appearance of the double star #b ,andromed with the best mirrors was a single bright mass of blue light some seconds in diameter and boiling violently40 ,on the best nights1 however1 8the disturbance of the air would seem now and then suddenly to cease for perhaps half a second1 and the star would then instantly become two very minute round specks of white light1 with an interval between which1 from recollection1 ,i would estimate as equal to the diameter of either of them1 or perhaps slightly less4 ,the instrument would have furnished this appearance uninterruptedly if the state of the air had permitted40 ,the present observer in charge1 ,dr4 ,boeddicker1 wrote the author in #ahhi3--8,there can be no doubt that on favourable nights the definition of the #f-;foot is equal to that of any instrument1 as is fully shown by ,dr4 ,copeland's drawings of ,jupiter published in the #8,monthly ,notices' for ,march #ahgd4 ,it appears to me1 however1 that the advantage in going from the #c-;foot to the #f-;foot is not so great in the case of planets as in the case of nebul2 yet1 as to the ,moon1 the detail revealed by the #f-;foot on a first-class night is simply astounding4 ,the large telescope is a ,newtonian mounted on a universal joint4 ,for the outlying portions of the great drawing of the ,orion nebula it was used as a ,herschelian4 ,as to powers profitably to be used1 ,i find no advantage in going beyond #fjj2 yet formerly on short occasions 7not longer than perhaps #a hour a night7 very much higher powers 7over #ajjj7 have been successfully employed by my predecessors40 ,mr4 ,lassell's #d-;foot reflector was taken to ,malta1 and while there its owner1 assisted by ,mr4 ,marth1 discovered a large number of nebul with it1 but it appears to have done nothing else4 ,his #b-;foot reflector1 which he had employed in previous years1 seems to have been his most effective instrument2 for with this he discovered ,ariel and ,umbriel1 the two inner satellites of ,uranus1 ,hyperion1 the faintest satellite of ,saturn1 and the only known satellite of ,neptune4 ,he also was one of the first to distinguish the crape ring of ,saturn4 ,mr4 ,lassell had many years of experience in the use of large reflectors2 and in #ahga he wrote3--8,there are formidable and1 ,i fear1 insurmountable difficulties attending the construction of telescopes of large size4444 ,these are1 primarily1 the errors and disturbances of the atmosphere and the flexure of the object-glasses or specula4 ,the visible errors of the atmosphere are1 ,i believe1 generally in proportion to the aperture of the telescope4444 ,up to the size referring to an #h-;in4 ,o4-,g4 in question1 seasons of tranquil sky may be found when its errors are scarcely appreciable2 but when we go much beyond this limit 7say to #b feet and upwards71 both these difficulties become truly formidable4 ,it is true that the defect of flexure may be in some degree eliminated1 but that of atmospheric disturbance is quite unassailable4 ,these circumstances will always make large telescopes proportionately less powerful than smaller ones2 but notwithstanding these disadvantages they will1 on some heavenly objects1 reveal more than any small ones can40 ,mr4 ,lassell's last sentence refers to 8delineations of the forms of the fainter nebul10 to 8seeing the inner satellites of ,uranus1 the satellite of ,neptune1 and the seventh satellite of ,saturn40 ,he mentions that1 when at ,malta1 he 8saw1 in the #b-;foot equatoreal1 with a power of #ajbg1 the two components of #b ,andromed distinctly separated to the distance of a neat diameter of the smaller one4 ,now1 no telescope of anything like #h-;inches diameter could exhibit the star in this style40 ,the large ,cooke refractor of #bdh-;inches aperture1 which has been mounted for about twenty years at ,gateshead1 has a singularly barren record4 ,its atmospheric surroundings appear to have rendered it impotent4 ,the owner of this fine and costly instrument wrote the author in #ahhe3--8;,atmosphere has an immense deal to do with definition4 ,i have only had one fine night since #ahgj6 ,i then saw what ,i have never seen since40 ,the ,melbourne reflector of #d-;feet aperture performed very indifferently for some years1 and little work was accomplished with it4 ,latterly its performance has been more satisfactory2 excellent photographs of the ,moon have been taken1 and it has been much employed in observations of nebul4 ,the speculum having recently become tarnished1 it has been dismounted for the purpose of being repolished4 ,the silver-on-glass reflector of #dgb-;in4 diameter1 at the ,paris ,observatory1 was used for some years by ,m4 ,wolf1 who has also had the control of smaller telescopes4 ,he was in a favourable position to judge of their relative effectiveness4 ,in a lecture delivered at the ,sardonne on ,march #f1 #ahhf1 he said3--8,during the years ,i have observed with the great ,parisian telescope ,i have found but one solitary night when the mirror was perfect40 ,further on1 he adds3--8,i have observed a great deal with the two instruments both reflectors of #aeg inches and #dgb inches4 ,i have rarely found any advantage in using the larger one when the object was sufficiently luminous40 ,m4 ,wolf also avers that a refractor of #ae inches or reflector of #aeg inches will show everything in the heavens that can be discovered by instruments of very large aperture4 ,he always found a telescope of #aeg-;inch aperture surpass one of #gi inches1 but expresses himself confidently that beyond about #ae inches increased aperture is no gain4 ,the ,washington refractor of #beh inches effected a splendid success in ,prof4 ,hall's hands in #ahgg1 when it revealed the two satellites of ,mars4 ,but immediately afterwards these minute bodies were shown in much smaller instruments2 whence it became obvious that their original discovery was not entirely due to the grasp of the #beh-;inch telescope1 but in a measure to the astuteness displayed by ,prof4 ,hall in the search4 ,a good observer had been associated with a good telescope2 and an inviting research having been undertaken1 it produced the natural result--an important success4 ,the same instrument1 in the same hands1 enabled the rotation-period of ,saturn to be accurately determined by means of a white spot visible in ,december #ahgf on the disk of the planet1 and which was subsequently seen by other observers with smaller glasses4 ,good work in other directions has also been accomplished at ,washington1 especially in observations of double stars and faint satellites4 ,but notwithstanding these excellent performances1 ,prof4 ,hall expressed himself in rather disparaging terms of his appliances1 saying 8the large telescope does not show enough detail40 ,he gave a more favourable report in #ahhh2 for we find it stated that 8the objective retains its figure and polish well4 ,by comparison with several other objectives which ,prof4 ,hall has had an opportunity of seeing during recent years1 he finds that the glass is an excellent one40 ,prof4 ,young1 who has charge of the #bc-;inch refractor at ,princeton1 has also commented on the subject of the definition of large telescopes4 ,he says3--8,the greater susceptibility of large instruments to atmospheric disturbances is most sadly true2 and yet1 on the whole1 ,i find also true what ,mr4 ,clark told me would be the case on first mounting our #bc-;inch instrument1 that ,i can almost always see with the #bc-;inch everything ,i see with the #i-;inch under the same atmospheric conditions1 and see it better1--if the seeing is bad only a little better1 if good immensely better40 ,prof4 ,young also mentioned that a power of #abjj on the #bc-;inch 8worked perfectly on ,jupiter on two different evenings in the spring of #ahhe in bringing out fine details relating to the red spot and showing the true forms of certain white dots on the ,s4 polar belt40 ,the #bf-;inch refractor at the ,leander ,mc,cormick ,observatory1 ,u4 ,s4 ,a41 is successfully engaged in observations of nebul1 and many new objects of this character have been found4 ,it does not appear that the telescope is much used for other purposes2 so that we can attach no significance to the fact that important discoveries have not been made with it in other departments4 ,the great ,vienna refractor of #bg-;inches aperture 8does not seem to accomplish quite what was expected of it10 according to ,mr4 ,sawerthal1 who recently visited the ,observatory at ,whring1 ,vienna4 ,the ,director1 ,dr4 ,weiss1 states in his last report that 8the #bg-;inch ,grubb refractor has only been occasionally used1 when the objects were too faint for the handier instruments40 ,the still larger telescopes erected at the ,observatories at ,pulkowa and ,nice have so recently come into employment that it would be premature to judge of their performance4 ,in the ,annual ,report from ,pulkowa 7#ahhg7 it is stated that ,dr4 ,h4 ,struve was using the #cj-;inch refractor 8in measuring those of ,burnham's double stars which are only seldom measurable with the #8old #ae-;inch1' together with other stars of which measures are scarce4 ,he made #dfj measures in eight or nine months1 as well as #aff micro metric observations of the fainter satellites of ,saturn and #ae of that of ,neptune40 ,at ,nice the #cj-;inch refractor was employed by ,m4 ,perrotin in physical observations of ,mars in ,may and ,june #ahhh4 ,the canal-shaped markings of ,schiaparelli were confirmed1 and some of them were traced 8from the ocean of the southern hemisphere right across both continents and seas up to the north polar ice-cap40 ,the #cj-;inch also showed some remarkable changes in the markings2 but these were not confirmed at other observatories4 ,the telescope evidently revealed a considerable amount of detail on this planet2 whence we may infer that its defining power is highly satisfactory4 ,the great ,lick refractor1 which appears to have been 8first directed to the heavens from its permanent home on ,mount ,hamilton on the evening of ,january #c1 #ahhh10 has been found ample work by the zealous astronomers who have it in charge4 ,prof4 ,holden1 in speaking of it1 says3--8,it needs peculiar conditions1 but when all the conditions are favourable its performance is superb40 ,mr4 ,keeler1 one of the observers1 writes that1 on ,january #g1 #ahhh1 when ,saturn was examined1 8he not only shone with the brilliancy due to the great size of the objective1 but the minutest details of his surface were visible with wonderful distinctness4 ,the outlines of the rings were very sharply defined with a power of #ajjj40 ,mr4 ,keeler adds3--8,according to my experience1 there is a direct gain in power with increase of aperture4 ,the #ab-;inch equatoreal brings to view objects entirely beyond the reach of the #f-;inch telescope1 and details almost beyond perception with the #ab-;inch are visible at a glance with the #cf-;inch equatoreal4 ,the great telescope is equal in defining power to the smaller ones40 ,this is no small praise1 and it must have been extremely gratifying1 not only to those who were immediately associated with the construction of the telescope1 but to astronomers everywhere who were hoping to hear a satisfactory report4 ,in its practical results this instrument has not yet1 it is true1 given us a discovery of any magnitude4 ,it has disclosed several very small stars in the trapezium of the ,orion nebula1 some difficult double stars have been found and measured1 and some interesting work has been done on the planets and nebul4 ,physical details have been observed in the ring nebula1 between and ,lyr1 which no other telescope has ever reached before4 ,mr4 ,common's #e-;foot reflector has been employed on several objects4 ,in the spring of #ahhi ,uranus was frequently observed with it1 and several minute points of light1 suspected to be new satellites1 were picked up4 ,evidence was obtained of a new satellite between ,titania and ,umbriel2 but bad weather and haze1 combined with the low altitude of ,uranus1 interfered with the complete success of the observations4 8,with only moderate powers1 ,uranus does not show a perfectly sharp disk4 ,no markings are visible on it1 and nothing like a ring has been seen round it40 ,mr4 ,common1 in a letter to the writer1 dated ,november #i1 #ahhi1 says3--8,the #e-;foot has only been tried in an unfinished state as yet1 the mirror not being quite finished when put into the tube last year4 ,this was in order to gain experience and save the season4 ,it performed much better than ,i had hoped1 and is greatly superior to the #c-;foot4 ,i took some very fine photographs with it last year4 ,it has been refigured1 or rather completed1 this summer1 and has just been resilvered40 ,from this it is evident that ,mr4 ,common's large instrument has not yet been fully tested2 but it clearly gives promise of successful results1 and encourages the hope that it will exert an influence on the progress of astronomy4 ,owing to the highly reflective quality of silvered glass1 the #e-;foot speculum has a far greater command of light 7space-penetrating power7 than the great objective mounted at the ,lick ,observatory4 ,mr4 ,common's mirror may therefore be expected to grasp nebul1 stars1 satellites1 and comets which are of the last degree of faintness and quite invisible in the ,lick refractor4 ,but we must not forget that the latter instrument is certainly placed in a better atmosphere1 and that its action is not therefore arrested in nearly the same degree by haze and undulations of the air4 ,with equal conditions1 the great reflector at ,ealing would probably far surpass the large refractor we have referred to1 the latter having less than one third of the light-grasping power of the former4 ,this rapid sketch of the performances of some of our finest telescopes must suffice for the present in assisting us to estimate their value as instruments of discovery4 ,and it must be admitted that1 on the whole1 these appliances have been disappointing4 ,the record of their successes is by no means an extended one1 and in some individual cases absolute failure is unmistakable4 ,we must judge of large glasses by their revelations2 their capacity must be estimated by results4 ,we often meet with glowing descriptions of colossal telescopes3 their advantages are specified and their performances extolled to such a degree that expectation is raised to the highest pitch4 ,but it is not always that such praise is justified by facts4 ,the fruit of their employment is rarely prolific to the extent anticipated1 because the observers have been defeated in their efforts by impediments which inseparably attend the use of such huge constructions4 ,our atmosphere is always in a state of unrest4 ,its condition is subject to many variations4 ,heat1 radiated or evolved from terrestrial objects1 rises in waves and floats along with the wind4 ,these vapours exercise a property of refraction1 with the result that1 as they pass in front of celestial objects1 the latter at once become subject to a rapid series of contortions in detail4 ,their outlines appear tremulous1 and all the features are involved in a rippling effect that seriously compromises the definition4 ,delicate markings are quite effaced on a disk which is thus in a state of ebullition2 and on such occasions observers are rarely able to attain their ends4 ,telescopic work is1 in fact1 best deferred until a time when the air has become more tranquil4 ,in large instruments these disturbances are very troublesome1 as they increase proportionately with aperture4 ,they are so pronounced and so persistent as to practically annul the advantage of considerable light-grasping power2 for unless the images are fairly well defined1 mere brightness counts for nothing4 ,reflectors are peculiarly susceptible to this obstacle2 moreover1 the open tube1 the fact that rays from an object pass twice through its length1 and that a certain amount of heat radiated from the observer must travel across the mouth of the tube all serve to impair the definition4 ,a speculum1 to act well1 must be of coincident temperature in every part4 ,this is not always the case1 owing to the variableness of the weather or to unequal exposure of the speculum4 ,large refractors1 though decidedly less liable to atmospheric influences1 are yet so much at the mercy of them that one of the first and most important things discussed in regard to a new instrument is that of a desirable site for it4 ,the great weight of large objectives and specula tends to endanger the perfect consistency and durableness of their figure1 and imposes a severe strain upon their cellular mounting4 ,the glasses must obviously assume a variety of bearings during active employment4 ,this introduces a possible cause of defective performance2 for in some instances definition has been found unequal1 according to the position of the glass4 ,specula are very likely to be affected in this manner1 as they are loosely deposited in their cells to allow of expansion1 and the adjustment is easily deranged4 ,the slightest flaw in the mounting of objectives immediately makes itself apparent in faulty images4 ,special precautions are of course taken to prevent flexure and other errors of the kind alluded to1 and modern adaptations may be said to have nearly eliminated them2 but there is always a little outstanding danger1 from the ease with which glasses may be distorted or their adjustment become unsettled4 ,another difficulty formerly urged against telescopes of great size was the trouble of managing them2 but this objection can scarcely be applied to the fine instruments of the present day1 which are so contrived as to be nearly as tractable as small ones4 ,a century ago1 glass of the requisite purity for large objectives could not be obtained2 but this difficulty appears also to have quite disappeared4 ,and the process of figuring lenses of considerable diameter is now effected with the same confidence and success as that of greatly inferior sizes4 ,let us now turn for a moment to the consideration of small instruments1 premising that in this category are included all those up to about #ab-;inches aperture4 ,modern advances have quite altered our ideas as to what may be regarded as large and small telescopes4 ,sixty-five years ago the ,dorpat refractor1 with a #i-;inch objective by ,fraunhofer1 was considered a prodigy of its class2 now it occupies a very minor place relatively to the #cj-;inch and #cf-;inch objectives at ,nice1 ,pulkowa1 and ,mount ,hamilton4 ,prof4 ,hall remarked1 in #ahhe3--8,there is too much scepticism on the part of those who are observing with large instruments in regard to what can be seen with small ones40 ,this is undoubtedly true2 but a mere prejudice or opinion of this sort cannot affect the question we are discussing1 as it is one essentially relying upon facts4 ,small instruments have done a vast amount of useful work in every field of astronomical observation4 ,even in the realm of nebul1 which1 more than any other1 requires great penetrating power1 ,d',arrest showed what could be effected with small aperture4 ,burnham1 with only a #f-;inch refractor1 has equally distinguished himself in another branch2 for he has discovered more double stars than any previous observer4 ,dawes was one of the most successful amateurs of his day1 though his instrumental means never exceeded an #h-;inch glass4 ,but we need not particularize further4 ,it will be best to get a general result from the collective evidence of past years4 ,we find that nearly all the comets1 planetoids1 double stars1 c4 owe their first detection to comparatively small instruments4 ,our knowledge of sun-spots1 lunar and planetary features is also very largely derived from similar sources4 ,there is no department but what is indebted more or less to the services of small telescopes3 the good work they have done is due to their excellent defining powers and to the facility with which they may be used4 ,illustration3 ,fig4 #aa4 ,refracting-,telescope1 by ,browning4 ,we have already said that the record of discoveries made with really large instruments is limited2 but it should also be remarked that until quite recently the number of such instruments has been very small4 ,and not always1 perhaps1 have the best men had the control of them4 ,virtually the observer himself constitutes the most important part of his telescope3 it is useless having a glass of great capacity at one end of a tube1 and a man of small capacity at the other4 ,two different observers essentially alter the character of an instrument1 according to their individual skill in utilizing its powers4 ,large telescopes are invariably constructed for the special purpose of discovering unknown orbs and gleaning new facts from the firmament4 ,but in attempting to carry out this design1 obstacles of a grave nature confront the observer4 ,the comparatively tranquil and sharply definite images seen in small instruments disappear1 and in their places forms are presented much more brilliant and expansive1 it is true1 but involved in glare and subject to constant agitation1 which serve to obliterate most of the details4 ,the observer becomes conscious that what he has gained in light has been lost in definition4 ,at times--perhaps on one occasion in fifty--this experience is different2 the atmosphere has apparently assumed a state of quiescence1 and objects are seen in a great telescope with the same clearness of detail as in smaller ones4 ,it is then the observer fully realizes that his instrument1 though generally ineffective1 is not itself in fault1 and that it would do valuable work were the normal condition of the air suitable to the exercise of its capacity4 ,those who have effected discoveries with large instruments have done so in spite of the impediment alluded to4 ,relying mainly upon great illuminating power1 bad or indifferent definition has been tolerated2 and they have succeeded in detecting minute satellites1 faint nebul1 clusters1 and small companions to double stars4 ,telescopes of great aperture are at home in this kind of work4 ,but when we come to consider discoveries on the surfaces of the ,sun1 ,moon1 and planets1 the case is entirely different2 the diligent use of small appliances appears to have left little for the larger constructions to do4 ,there are some thousands of drawings of the objects named1 made by observers employing telescopes from #c up to #gb inches in diameter2 and a careful inspection shows that the smaller instruments have not been outdone in this interesting field of observation4 ,in point of fact they rather appear to have had the advantage1 and the reason of this is perhaps sufficiently palpable4 ,the details on a bright planetary object are apt to become obliterated in the glare of a large instrument4 ,even with a small telescope objects like ,venus and ,jupiter are best seen at about the time of sunset1 and before their excessive brilliancy on the dark sky is enabled to act prejudicially in effacing the delicate markings4 ,probably this is one of the causes which1 in combination with the undulations of the atmosphere1 have restricted the discoveries of large instruments chiefly to faint satellites1 stars1 and nebul4 ,prof4 ,young ascribes many of the successes of small instruments to exceptional cuteness of vision on the part of certain observers1 and to the fact that such instruments are so very numerous and so diligently used that it is fair to conclude they must reap the main harvest of discoveries4 ,we must remember that for every observer working with an aperture of #ah inches and more1 there are more than a hundred employing objectives or specula of from #e to #ab inches2 hence we may expect some notable instances of keen sight amongst the latter4 ,the success of men like ,dawes and others1 who outstrip their contemporaries1 and with small glasses achieve phenomenal results1 is to be ascribed partly to good vision and partly to that natural aptitude and pertinacity uniformly characteristic of the best observers4 ,these circumstances go far to explain the unproductiveness of large telescopes3 in the race for distinction they are often distanced by their more numerous and agile competitors4 ,the objections which applied to the large reflecting instruments of ,herschel1 ,lassell1 and ,rosse scarcely operate with the same force in regard to the great refractors of the present day1 and for these reasons3--,refractors are somewhat less sensitive to atmospheric disturbances than reflectors4 ,the modern instruments are mounted in much improved style1 and placed in localities selected for their reception4 ,in fact1 all that the optician's art can do to perfect such appliances has been done1 and ,nature herself has been consulted as to essentials2 for we find the most powerful refractor of all erected on the summit of ,mount ,hamilton1 where the skies are clear and ,urania ever smiles invitingly4 ,some observers who have obtained experience both with large and small telescopes aver that1 even on a bright planet1 they can see more1 and often see it much better1 with the larger glasses4 ,but we rarely1 if ever1 find them saying they can discern anything which is absolutely beyond the reach of small instruments4 ,it would be much more satisfactory evidence of the super-excellence of the former if definite features could be detected which are quite beyond the reach of telescopes of inferior size2 but we seldom meet with experiences of this kind1 and the inference is obvious4 ,there is undoubtedly a certain aperture which combines in itself sufficient light-grasping power with excellent definition4 ,it takes a position midway between great illuminating power and bad definition on the one hand1 and feeble illuminating power and sharp definition on the other4 ,such an aperture must form the best working instrument in an average situation upon ordinary nights and ordinary objects4 ,m4 ,wolf fixes this aperture at about #ae inches1 and he is probably near the truth4 ,the quaint ,dr4 ,kitchener1 who1 early in the present century1 made a number of trials with fifty-one telescopes1 entertained a very poor opinion of big instruments4 ,in his book on #8,telescopes1' he says3--8,immense telescopes are only about as useful as the enormous spectacles suspended over the doors of opticians40 444 8,astronomical amateurs should rather seek for perfect instruments than large ones4 ,what good can a great deal of bad light do80 ,we shall be in a better position a few years hence to estimate the value of great telescopes2 for the principal instruments of this class have only been completed a short time4 ,judging from the statements of some of the observers1 who are men of the utmost probity and ability1 certain of the large instruments are capable of work far in advance of anything hitherto done4 ,definition1 they say1 is excellent1 notwithstanding the great increase of aperture4 ,the old stumbling-block appears1 therefore1 to have been removed1 and astronomy is to be congratulated on the acquirement of such vastly improved implements of research4 ,even should the large telescopes continue to prove disappointing in certain branches1 they may certainly be expected to maintain their advantage in others4 ,they will always be valuable as a corrective to smaller and handier instruments4 ,for special lines of work in which very small or very faint objects are concerned1 considerable light-grasping power is absolutely required2 and it is chiefly in these departments that large instruments may be further expected to augment our knowledge4 ,in photographic and spectroscopic work they also have a special value1 which late researches have brought prominently to the fore4 ,the telescopes of the future will probably surpass in dimensions those of our own day4 ,the ,university of ,los ,angelos1 in ,california1 propose to erect a #db-;inch refractor on the summit of ,wilson's ,peak of the ,sierra ,madre mountains1 which is #fjjj feet high and about #be miles from ,los ,angelos4 ,in reference to this contemplated extension of size1 it may be opportune to mention that large objectives do not transmit light proportionately with their increased diameter1 owing to greater thickness of the lenses1 which increases the absorption4 ,the ,washington objective of #beh-;inch aperture is #bhg inches in thickness1 and more than half the light which falls upon it is lost by absorption4 ,on the other hand1 specula1 with every enlargement of aperture1 give proportionately more light-grasping power1 and their diameters might be greatly increased but for the mechanical obstacles in the way of their construction4 ,mr4 ,ranyard expresses the opinion that 8with the refractor we are fast approaching the practical limit of size40 ,after referring to the ,washington object-glass as above1 he says3--8,if we double the thickness1 more than three quarters of the light would be absorbed and less than one quarter would be transmitted4 ,the greatest loss of light is only for the centre of the object-glass2 but in all parts the absorption is quadrupled for a lens of double aperture40 ,if1 therefore1 future years see any great development in the sizes of telescopes1 it will probably be in connection with reflectors2 for the loss of light by absorption in the thick lenses of large refractors must ultimately determine their limits4 ,mr4 ,calver says3--8,the light of reflectors exceeding #ah inches in diameter is certainly greater than that of refractors of equal size1 and for anything like #c feet very much greater40 ,he nearly obtained the order for a monster reflector for the ,lick ,observatory1 the ,americans admitting that the reflector must be the instrument of the future for power and light because there were practically no limits to its size4 ,but the reflector has not been much used in ,america1 and therefore is little known4 ,for this reason the authorities decided to erect a large refractor1 and they appear to have been justified in their selection1 for the #cf-;inch objective has proved excellent4 ,,footnotes3 #e ,such objects show considerable glare in a very large instrument4 ,the advent of ,jupiter into the field of the #f-;foot has been compared to the brightness of a coach-lamp4 ,the outer satellite of ,mars was seen twice with this instrument in #ahgg1 8but the glare of the planet was found too strong to allow of good measures being taken40 ,,chapter ,,iii4 ,,notes ,,on ,,telescopes ,,and ,,their ,,accessories4 ,choice of ,telescopes4--,refractors and ,reflectors4--,observer's ,aims4--,testing ,telescopes4--,mounting4--,eyepieces4--, requisite ,powers4--,overstating ,powers4--,method of finding the ,power4--,field of ,eyepiece4--,limited ,means no obstacle4--,observing-,seats4-,advantage of ,equatoreals4--,test-,objects4--,cheapne ss and increasing number of ,telescopes4--,utility of ,stops4--,cleaning ,lenses4--,opera-,glasses4--,dewing of ,mirrors4--,celestial ,globe4--,observatories4 ,choice of ,telescopes4--,the subject of the choice of telescopes has exercised every astronomer more or less1 and the question as to the best form of instrument is one which has occasioned endless controversy4 ,the decision is an important one to amateurs1 who at the outset of their observing careers require the most efficient instruments obtainable at reasonable cost4 ,it is useless applying to scientific friends who1 influenced by different tastes1 will give an amount of contradictory advice that will be very perplexing4 ,some invariably recommend a small refractor and unjustly disparage reflectors1 as not only unfitted for very delicate work1 but as constantly needing re-adjustment and resilvering#f4 ,others will advise a moderate-sized reflector as affording wonderfully fine views of the ,moon and planets4 ,the question of cost is greatly in favour of the latter construction1 and1 all things considered1 it may claim an unquestionable advantage4 ,a man who has decided to spend a small sum for the purpose not merely of gratifying his curiosity but of doing really serviceable work1 must adopt the reflector1 because refractors of1 say1 #e inches and upwards are far too costly1 and become enormously expensive as the diameter increases4 ,this is not the case with reflectors2 they come within the reach of all1 and may indeed be constructed by the observer himself with a little patience and ingenuity4 ,refractors and ,reflectors4--,the relative merits of refractors and reflectors#g have been so frequently compared and discussed that we have no desire to re-open the question here4 ,these comparisons have been rarely free from bias1 or sufficiently complete to afford really conclusive evidence either way4 ,there is no doubt that each form of instrument possesses its special advantages3 aperture for aperture the refractor is acknowledged to be superior in light-grasping power1 but the ratio given by different observers is not quite concordant4 ,a silver-on-glass mirror of #h-;inches aperture is certainly equal to a #g-;inch objective in this respect1 while as regards dividing power and the definition of planetary markings1 the reflector is equal to a refractor of the same aperture4 ,the much shorter focal length of the reflector is an advantage not to be overlooked4 ,a century ago ,sir ,w4 ,herschel figured his specula to foci of more than a foot to every inch of aperture1 except in the case of his largest instruments4 ,thus he made specula of #ah-;inches and #bd-;inches diameter1 the former of which had a focal length of #bj feet and the latter of #be feet4 ,the glass mirrors of the present time are much shorter1 and the change has not proved incompatible with excellent performance4 ,calver has made two good mirrors of #ag-a_/d-;inches aperture1 and only #h ft4 #d in4 focus4 ,mr4 ,common's #e-;foot mirror is only #bg feet1 so that in these instances the length of the tube is less than six times the diameter4 ,illustration3 ,fig4 #ab4 8,the ,popular ,reflector0 by ,calver4 ,it has long been proved that refractors and reflectors alike are1 in good hands1 capable of producing equally good results2 and we may depend upon it that1 in spite of all argument and experiment1 both kinds of telescope will continue to hold their own until superseded by a new combination1 which hardly seems likely4 ,if the observer is free from prejudice1 he will have no cause to deplore the character of his instrument1 always supposing it to be by a good maker4 ,be it object-glass or speculum1 he will rarely find it lacking in effectiveness4 ,it happens only too often that the telescope or the atmosphere is hastily blamed when the fault rests with the observer himself4 ,let him be persistent in waiting opportunities1 and let the instrument be nicely adjusted and in good condition1 and in the great majority of cases it will perform all that can reasonably be expected of it4 ,in choosing appliances for observational purposes1 the observer will of course be guided by his means and requirements4 ,if his inclination lead him to enter a particular department of research1 he will take care to provide himself with such instruments as are specially applicable to the work in hand4 ,modern opticians have effected so many improvements1 and brought out so many special aids to smooth the way of an observer1 that it matters little in which direction he advances2 he will scarcely find his progress impeded by want of suitable apparatus4 ,in size1 as also in character1 the observer should be careful to discriminate as to what is really essential4 ,large instruments and high powers are not necessary to show what can be sufficiently well seen in a small telescope with moderate power4 ,of course there is nothing like experience in such matters1 and practice soon renders one more or less proficient in applying the best available means4 ,illustration3 ,fig4 #ac4 #c-;inch ,refracting-,telescope1 by ,newton ,co4 ,an amateur who really wants a competent instrument and has to consider cost1 will do well to purchase a ,newtonian reflector4 ,a #d-;inch refractor will cost about as much as a #aj-;inch reflector1 but1 as a working tool1 the latter will possess a great advantage4 ,a small refractor1 if a good one1 will do wonders1 and is a very handy appliance1 but it will not have sufficient grasp of light for it to be thoroughly serviceable on faint objects4 ,anyone who is hesitating in his choice should look at the cluster about ,persei through instruments such as alluded to1 and he will be astonished at the vast difference in favour of the reflector4 ,for viewing sun-spots and certain lunar objects small refractors are very effective1 and star-images are usually better seen than in reflectors1 but the latter are much preferable for general work on account of three important advantages1 viz41 cheapness1 illuminating power1 and convenience of observation4 ,when high magnifiers are employed on a refractor of small aperture1 the images of planets become very faint and dusky1 so that details are lost4 ,observer's ,aims4--,if the intending observer merely requires a telescope to exhibit glimpses of the wonders which he has seen portrayed in books1 and has no intention of pursuing the subject further than as an occasional hobby1 he will do well to purchase a small refractor between #c and #d inches in aperture4 ,such instruments are extremely effective on the ,sun and ,moon1 which are naturally the chief objects to attract attention1 and1 apart from this1 appliances of the size alluded to may be conveniently used from an open window4 ,the latter is an important consideration to many persons2 moreover1 a small telescope of this kind will reveal an astonishing number of interesting objects in connection with the planets1 comets1 c41 and it may be employed by way of diversion upon terrestrial landscape1 as such instruments are almost invariably provided with non-inverting eyepieces4 ,out-of-door observing is inconvenient in many respects1 and those who procure a telescope merely to find a little recreation will soon acknowledge a small refractor to be eminently adapted to their purposes and conveniences4 ,those who meditate going farther afield1 and taking up observation habitually as a means of acquiring practical knowledge1 and possibly of doing original work1 will essentially need different means4 ,they will require reflectors of about #h or #aj inches aperture2 and1 if mounted in the open on solid ground1 so much the better1 as there will be a more expansive view1 and a freedom from heated currents1 which renders an apartment unsuited to observations1 unless with small apertures where the effects are scarcely appreciable4 ,a reflector of the diameter mentioned will command sufficient grasp to exhibit the more delicate features of planetary markings1 and will show many other difficult objects in which the sky abounds4 ,if the observer be specially interested in the surface configuration of ,mars and ,jupiter he will find a reflector a remarkably efficient instrument4 ,on the ,moon and planets it is admitted that its performance is1 if not superior1 equal to that of refractors4 ,if1 however1 the inclination of the observer leads him in the direction of double stars1 their discovery and measurement1 he will perhaps find a refractor more to be depended upon1 though there is no reason why a well-mounted reflector should not be successfully employed in this branch2 and the cost of a refractor of the size to be really useful as an instrument of discovery must be something very considerable--perhaps ten times as great as that of a reflector of equal capacity4 ,as far as my own experience goes the refractor gives decidedly the best image of a star4 ,in the reflector1 a bright star under moderately high power is seen with rays extending right across the field1 and these appear to be caused by the supports of the flat4 ,testing ,telescopes4--,no amateur should buy an instrument1 especially a second-hand one1 without testing it1 and this is a delicate process involving many points to be duly weighed4 ,experience is of great service in such matters1 and is1 in fact1 absolutely necessary4 ,even old observers are sometimes misled as to the real worth of a glass4 ,in such cases1 there is nothing like having a reliable means of comparison1 i4 e4 another telescope of acknowledged excellence with which to test the doubtful instrument4 ,in the absence of such a standard judgment will be more difficult1 but with care a satisfactory decision may be arrived at4 ,the ,moon is too easy an object for the purpose of such trials2 the observer should rather select ,venus or ,jupiter4 ,the former is1 however1 so brilliant on a dark sky1 and so much affected with glare1 that the image will almost sure to be faulty even if the glass is a good one4 ,let the hour be either near sunrise or sunset1 and if the planet has a tolerably high altitude1 her disk ought to be seen beautifully sharp and white4 ,various powers should be tried1 increasing them each time1 and it should be noticed particularly whether the greater expansion of the image ruins the definition or simply enfeebles the light4 ,in a thoroughly good glass faintness will come on without seriously impairing the definite contour of the object viewed1 and the observer will realize that the indistinctness is merely occasioned by the power being relatively in excess of the light-grasp4 ,but in a defective telescope1 a press of magnifying power at once brings out a mistiness and confuses the details of the image in a very palpable manner4 ,try how he will1 the observer will find it impossible to get rid of this1 except1 perhaps1 by a 8stop0 which cuts off so much light that the instrument is ineffective for the work required of it4 ,the blurred image is thought1 at the moment of its first perception1 to be caused by the object being out of focus1 and the observer vainly endeavours to get a sharper image until he finds the source of error lies elsewhere4 ,a well-figured glass ought to come very sharply to a focus4 ,the slightest turn of the adjusting-screw should make a sensible difference4 ,on the other hand1 an inferior lens will permit a slight alteration of focusing without affecting the distinctness1 because the rays from the image are not accurately thrown to a point4 ,jupiter is also a good test4 ,the limbs of the planet1 if shown clean and hard1 and the belts1 if they are pictured like the finely cut details of an engraving1 will at once stamp a telescope as one of superior quality4 ,saturn can also be examined though not1 perhaps1 so severe a test4 ,the belts1 crape ring1 ,cassini's division1 ought to be revealed in any telescope of moderate aperture4 ,if1 with regard to any of these objects1 the details apparently run into each other and there is a 8fuzzy0 or woolly aspect about them which cannot be eliminated by careful focusing1 then either the atmosphere or the telescope is in fault4 ,if the former1 another opportunity must be awaited4 ,an observer of experience will see at a glance whether the cause lies in the air or the instrument4 ,the images will be agitated by obnoxious currents1 if the defects are due to the atmosphere1 but if the glass itself is in error1 then the objects will be comparatively tranquil but merged in hazy outlines1 and a general lack of distinctness will be apparent4 ,perhaps the best test of all as to the efficiency of a telescope is that of a moderately bright star1 say of the #bnd or #crd magnitude4 ,with a high power the image should be very small1 circular1 and surrounded by two or three rings of light lying perfectly concentric with each other4 ,no rays1 wings1 or extraneous appearance other than the diffraction rings should appear4 ,this1 however1 specially applies to refractors1 for in reflectors the arms of the flat occasion rays from any bright star2 ,i have also seen them from ,mars1 but of course this does not indicate an imperfect mirror4 ,if there is any distortion on one side of the image1 then the lenses are inaccurately centred though the instrument may be otherwise good1 and a little attention may soon set matters right4 ,when testing a glass the observer should choose objects at fairly high altitudes1 and not condemn a telescope from a single night's work unless the evidence is of unusually convincing character4 ,if false colour is seen in a silver-on-glass reflector it is originated by the eyepiece1 though not necessarily so in a refractor4 ,the object-glass of the latter will be sure to show some uncorrected colour fringing a bright object4 ,a good lens1 when exactly focused1 exhibits a claret tint1 but within the focus purple is seen and beyond the focus green comes out4 ,in certain cases the secondary spectrum of an object-glass is so inadequately corrected that the vivid colouring of the images is sometimes attributed by inexperienced observers to a real effect4 ,a friend who used a #c-;inch refractor once called on me to have a glimpse of ,jupiter through my #aj-;inch ,with-reflector4 ,on looking at the planet he at once exclaimed 8,but where are the beautiful colours1 ,mr4 ,denning80 ,i replied to his question by asking another1 viz41 8,what colours80 he answered1 8,why1 the bright colours ,i see round ,jupiter in my refractor80 ,i said1 8,oh1 they exist in your telescope only60 ,he looked incredulous1 and when he left me that night did not seem altogether pleased with the appearance of ,jupiter shorn of his false hues6 ,mounting4--,too much care cannot be given to the mounting of telescopes1 for the most perfectly figured glass will be rendered useless by an inefficient stand2 a faulty lens1 if thoroughly well mounted1 will do more than a really good one on a shaky or unmanageable mounting4 ,whatever form is adopted1 the arrangement should ensure the utmost steadiness1 combined with every facility for readily following objects4 ,a man who has every now and then to undergo a great physical exertion in bodily shifting the instrument is rendered unfit for delicate work4 ,the telescope should be provided with every requisite for carrying on prolonged work with slight exertion on the part of the observer4 ,unless the stand is firm there will be persistent vibrations1 especially if the instrument is erected in the open1 for there are very few nights in the year when the air is quite calm4 ,these contingencies should be provided against with scrupulous attention if the observer would render his telescope most effective for the display of its powers1 and avoid the constant annoyance that must otherwise follow4 ,illustration3 ,fig4 #ad4 ,huygens's negative eyepiece4 ,illustration3 ,fig4 #ae4 ,ramsden's positive eyepiece4 ,eyepieces4--,good eyepieces are absolutely essential4 ,many object-glasses and specula have been deprecated for errors really originated by the eyepiece4 ,again1 telescopes have not unfrequently been blamed for failures through want of discrimination in applying suitable powers4 ,a consistent adaptation of powers according to the aperture of the telescope1 the character of the object1 the nature of the observation1 and the atmospheric conditions prevailing at the time1 is necessary to ensure the best results4 ,if it is required to exhibit a general view of ,jupiter and his satellites to a friend1 we must utilize a low power with a large field2 if1 on the other hand1 we desire to show the red spot and its configuration in detail1 we must apply the highest power that is satisfactorily available4 ,the negative or ,huygenian eyepiece is the one commonly used1 and it forms good colourless images1 though the field is rather small4 ,the positive or ,ramsden eyepiece gives a flatter and larger field1 but it is not often achromatic4 ,a ,kellner eyepiece1 the feature of which is a very large field1 is often serviceable in observations of nebul1 clusters1 and comets4 ,telescopes are sometimes stated to bear #ajj to the inch on planets1 but this is far beyond their capacities even in the very best condition of air4 ,amateurs soon find from experience that it is best to employ those powers which afford the clearest and most comprehensive views of the particular objects under scrutiny4 ,of course when abnormally high powers are mentioned in connection with an observation1 they have an impressive sound1 but this is all1 for they are practically useless for ordinary work4 ,i find that #dj1 or at the utmost #ej to the inch1 is ample1 and generally beyond the capacities of my #aj-;inch reflector4 ,a ,barlow lens used in front of the eyepiece raises the power about one third1 and thus a whole set of eyepieces may be increased by its insertion4 ,it is said to improve the definition1 while the loss of light is very trifling4 ,i formerly used a ,barlow lens in all planetary observations1 but finally dispensed with it1 as ,i concluded the improved distinctness did not compensate for the fainter image4 ,a great advantage1 both in light and definition1 results from the employment of a single lens as eyepiece4 ,true1 the field is very limited1 and1 owing to the spherical aberration1 the object so greatly distorted near the edges that it must be kept near the centre1 but1 on the whole1 the superiority is most evident4 ,by many careful trials ,i find it possible to glimpse far more detail in planetary markings than with the ordinary eyepiece4 ,dawes1 and other able observers1 also found a great advantage in the single lens1 and ,sir ,w4 ,herschel1 more than a century ago1 expressed himself thus3--8,i have tried both the double and single lens eye-glass of equal powers1 and always found that the single eye-glass had much the superiority in light and distinctness40 ,requisite ,powers4--,for general purposes ,i believe three eyepieces are all that is absolutely requisite1 viz41 a low power with large field for sweeping up nebul and comets2 a moderate power for viewing the ,moon and planets2 and a high power for double stars and the more delicate forms on the planets4 ,for a #c-;inch refractor1 eyepieces of about #ae1 #ge1 and #aej would be best1 and for a #aj-;inch reflector #dj1 #aej1 and #cjj4 ,for very difficult double stars a still higher power will be occasionally useful1 say #bej for the refractor1 and #ejj for the reflector4 ,the definition usually suffers so much under high powers1 and the tremors of the atmosphere are brought out so conspicuously1 that the greater expansion of the image of a planet does not necessarily enable it to present more observable detail4 ,the features appear diluted and merged in hazy outlines1 and there is a lack of the bright1 sharply determinate forms so steadily recognized under lower magnifiers4 ,in special cases great power may become essential1 and1 under certain favourable circumstances1 will prove really serviceable1 but1 in a general way1 it is admitted that the lowest power which shows an object well is always the best4 ,i have occasionally obtained very fair views of ,saturn with a power of #hfe1 but find that ,i can perceive more of the detail with #beb4 ,some daylight observations of ,venus were also effected under very high power1 and1 though the definition remained tolerably good1 ,i found as the result of careful comparison that less power answered more satisfactorily4 ,but it would be absurd to lay down inviolable rules in such cases4 ,special instruments1 objects1 and circumstances require special powers1 and observers may always determine with a little care and experience the most eligible means to support their endeavours4 ,one thing should be particularly remembered1 that the power used must not be beyond the illuminating capacity of the instrument1 for planetary features appear so faint and shady under excessive magnifiers that nothing is gained4 ,to grasp details there must be a fair amount of light4 ,i have seen more with #beb on my #aj-;inch reflector than with #cej on a #e-a_/d-;inch refractor1 because of the advantage from the brighter image in the former case4 ,overstating ,powers4--,it seems to be a fashionable imposition on the part of opticians to overstate magnifying powers4 ,eyepieces are usually advertised at double their true strength4 ,my own #aj-;inch reflector was catalogued as having four eyepieces1 #ajj to #fjj1 but on trial ,i found the highest was no more than #ccj4 ,this custom of exaggerating powers seems to have long been a privileged deception1 and persons buying telescopes ought to be guarded against it4 ,dr4 ,kitchiner says it originated with the celebrated maker of reflectors1 ,james ,short1 and justly condemns it as a practice which should be discontinued4 ,i suppose it is thought that high powers advertised in connection with a telescope have an exalted sound and are calculated to attract the unwary purchaser2 but good instruments need no insidious trade artifices to make them saleable4 ,the practice does not affect observers of experience1 because it is well understood1 and they take good care to test their eyepieces directly they get them4 ,but the case is different with young and inexperienced amateurs1 who naturally enough accept the words of respectable opticians1 only to find1 in many cases1 that they have been misleading and a source of considerable annoyance4 ,method of finding the ,power4--,the magnifying power of a telescope may be determined by dividing the focal length of the object-glass or mirror by the focal length of the eye-lens4 ,thus1 if the large glass has a focus of #gj inches and the eye-lens a focus of one inch1 then the power is #gj4 ,if the latter is only #a_/d-;inch focus1 the resulting power will be #bhj4 ,but this method is only applicable to single lens eyepieces4 ,we may1 however1 resort to several other means of finding the powers of the compound eyepieces of ,huygens or ,ramsden4 ,let the observer fix a slip of white cardboard1 say #a inch wide1 to a door or post some distance off1 and then 7with a refractor7 view it1 while keeping the disengaged eye open1 and note the exact space covered by the telescopic image of the card as projected on the door seen by the other eye4 ,the number of inches included in the space alluded to will represent the linear magnifying power4 ,a brick wall or any surface with distinct1 regularly marked divisions will answer the same purpose1 the number of bricks or divisions covered by the telescopic image of one of them being equivalent to the power4 ,but it should not be forgotten that a telescope magnifies slightly less upon a celestial object than upon a near terrestrial one owing to the shorter focus1 and a trifling allowance will have to be made for this4 ,another plan may be mentioned4 ,when the telescope is directed to any fairly bright object or to the sky1 and the observer removes his eye about #aj inches from the eyepiece1 a sharply defined1 bright little disk will be perceived in the eye-lens4 ,if the diameter of this disk is ascertained and the clear aperture of the object-glass or mirror is divided by it1 the quotient will be the magnifying power4 ,thus1 if the small circle of light is #b inch diameter and the effective aperture of the large glass #e inches1 then the power is #be4 ,if the former is #jb inch diameter and the latter #ge inches1 the power will be #cge4 ,the dynamometer is a little instrument specially designed to facilitate this means of fixing the magnifying power4 ,it enables the diameter of the small luminous circle in the eye-lens to be very accurately measured1 and this is a most important factor in deriving the power by this method4 ,illustration3 ,fig4 #af4 ,,berthon',s ,,dynamometer4 ,,horne ,,thornthwaite ,,london4 ,field of ,eyepiece4--,observers often require to know the diameter of the fields of their eyepieces4 ,those engaged in sweeping up comets1 nebul1 or other objects requiring large fields and low powers1 find it quite important to have this information4 ,they may acquire it for themselves by simple methods4 ,a planet1 or star such as ,orionis1 or ,virginis1 or ,aquil1 close to the equator1 should be allowed to run exactly through the centre of the field1 and the interval occupied in its complete transit from ingress to egress noted several times4 ,the mean result in min4 and sec4 of time must then be multiplied by #ae1 and this will represent the diameter required in min4 and sec4 of arc on the equator4 ,a planet or star near the meridian is the best for the purpose4 ,if the object occupies #a min4 #bg sec4 of time in passing from the ,e4 to the ,w4 limit of the field1 then #hg sec4 #ae #acje1 or #ba #de4 ,a more accurate method of deriving the angle subtended by the field is to let a star1 say ,regulus1 pass through the centre1 and fix the time which lapses in its entire passage by a sidereal clock2 then the interval so found #ae cosine of the declination of ,regulus will indicate the diameter of the field4 ,suppose for instance1 that the star named occupies #b min4 #ad sec4 #acd sec4 in its passage right across the whole and central part of the field3 then #acd log #babgaje #ae log #aagfjia ,dec4 of ,regulus #ab #cj log cos #iihieha ---------------- #aifb log #cbibggg so that the diameter of the field of the eyepiece must be #cb #db1 nearly corresponding with the diameter of the ,moon4 ,limited ,means no ,obstacle4--,there are many observers who1 having limited means1 are apt to consider themselves practically unable to effect good work4 ,this is a great illusion4 ,there are several branches of astronomy in which the diligent use of a small instrument may be turned to excellent account4 ,perseverance will often compensate for lack of powerful appliances4 ,many of the large and expensive telescopes1 now becoming so common1 are engaged in work which could be as well performed with smaller aperture1 and when the manifold advantages of moderate instruments are considered1 amateurs may well cease to deplore the apparent insufficiency of their apparatus4 ,it is1 however1 true that refractors have now attained dimensions and a degree of proficiency never contemplated in former times1 and that the modern ingenuity of art has given birth to innumerable devices to facilitate the work of those engaged in observation4 ,in many of our best appointed observatories the arrangements are so very replete with conveniences1 and so sedatory in their influences1 that the observer has every inducement to fall asleep1 though we do not find instances of 8nodding0 recorded in their annals4 ,further progress in the same direction leads us to joyfully anticipate the time when1 instead of standing out in the frost1 we may comfortably make our observations in bed4 ,this will admirably suit all those who1 like ,bristol people1 are reported to sleep with one eye open6 ,but1 to be more serious1 the work of amateurs is much hindered by lack of means to construct observatories wherein they may conduct researches without suffering from all the rigours of an unfavourable climate4 ,many of them have1 like ,william ,herschel a century ago1 to pursue their labours under no canopy but the heavens above1 and are exposed to all the trying severity of frost and keen winds1 which keep them shivering for hours together1 and very much awake6 ,illustration3 ,fig4 #ag4 ,cooke and ,son's ,educational ,telescope4 ,observing-,seats4--,as to observing-seats1 many useful contrivances have been described from time to time in the #8,astronomical ,register' and #8,english ,mechanic4' ,some of these answer their design admirably1 but ,i believe a good chair1 embodying all the many little requirements of the observer1 yet awaits construction4 ,those ,i have seen1 while supplying certain acknowledged wants1 are yet deficient in some points which need provision4 ,with my reflector ,i find an ordinary step-ladder answers the purpose very well4 ,it is at once light1 simple1 and durable1 and enables observations to be secured at any altitude4 ,it may be readily placed so that the observer can work in a sitting posture1 and the upper shelves1 while convenient to lean upon1 may be so arranged as to hold eyepieces1 and are to be further utilized when making drawings at the telescope4 ,i find it possible to obtain very steady views of celestial objects in this way4 ,everyone knows that during a critical observation it is as essential for the observer to be perfectly still as it is for the instrument to be free from vibration4 ,a person who stands looking through a telescope feels a desire to ensure a convenient stability by catching hold of it4 ,the impression is no doubt correctly conveyed to his mind that he may obtain a better view in this way2 and so he would1 were it not for the dancing of the image which instantly follows the handling of the instrument4 ,for this reason it is absolutely necessary that no part of the observer touch the telescope while in use4 ,he must ensure the desired steadiness1 which is really a most important consideration1 by other means2 and an observer who provides for this contingency will have taken a useful step in the way of achieving delicate work4 ,advantage of ,equatoreals4--,those who employ equatoreal mounting and clock-work will manifestly command an advantage in tracing features on a planet or other object requiring critical scrutiny4 ,common stands1 though often good make-shifts1 require constant application on the part of the observer1 when his undivided attention should be concentrated on the object4 ,with an alt-azimuth stand nearly one half the observer's time is occupied in keeping the object near the middle of the field4 ,though good views are obtainable1 they are very fugitive4 ,just as the delicate features are being impressed on the retina they are lost in the ill-defined margin of the field1 or from the necessity of suddenly shifting the object back4 ,a succession of hurried views of this kind1 during which the observer is frantically endeavouring to grasp details which only require a steady view to be well displayed1 are often tantalizing and seldom satisfactory in their issues4 ,this is especially the case when a single lens and high powers are used1 and if the night is windy the difficulty is intensified4 ,it is1 therefore1 evident that a clock-driven telescope possesses marked advantages in delicate work on faint objects1 because the prolonged view better enables the eye to gather in the details which are all but lost in the elusive glimpses afforded by inferior means4 ,still we must not forget that rough appliances do not present an effectual barrier to success4 ,the very finest definition comes only in momentary glimpses4 ,the sharply-cut outlines of planetary configuration cannot steadily be held for long together4 ,only now and then the image acquires the distinctness of an engraving1 when the air and the focus of eye and telescope severally combine to produce a perfect picture4 ,observers1 therefore1 whose instruments are simply1 though perhaps substantially mounted in handy fashion1 must profit by these moments of fine seeing1 and1 when drawing1 will find it expedient to fill in1 little by little1 the delicate forms which reach the eye4 ,this will take much time owing to the drawbacks alluded to1 but the outcome will more than justify its expenditure1 and the observer will gain patience and perseverance which will prove a useful experience in the future4 ,lenses out of centre or misplaced are1 like other defects1 calculated to give rise to errors as numerous as they are various4 ,but the most striking of these apparently belong to a period when telescopes were far less perfect and popular than at the present day4 ,indeed1 it is surprising that so very few false or imaginary discoveries are announced when we consider the vast array of instruments that are now employed4 ,it is true we occasionally hear that a comet has been discovered close to ,jupiter1 that several companions have been seen to ,polaris1 or that some other extraordinary 8find0 has been effected1 but the age is dead when such announcements were accepted without suitable investigation4 ,the satellite of ,venus has long since ceased to exist4 ,the active volcanoes on the ,moon have become extinct4 ,even ,vulcan will have to be set aside1 and1 like many another sensation which caused quite a furre in its day1 must soon be altogether expunged from the category of 8suspects40 ,test-objects4 ,opticians sometimes advertise lists of objects--generally double stars--which may be seen with their instruments1 but it does not appear to be sufficiently understood that the character of a telescope is dependent in a great degree upon the ability of the observer1 who can either make or mar it1 according to the skill he displays in its management4 ,some men will undoubtedly see more with #e inches of aperture than others will with #aj4 ,certain observers appear to excel in detecting delicate planetary markings1 while others possess special aptitude for glimpsing minute objects such as faint satellites1 or comites to double stars1 and the explanation seems to be that partly by experience and partly by differences in the sensitiveness of vision1 exceptional powers are sometimes acquired in each of these departments4 ,the various test-objects which have been given by reliable authorities1 though representing average attainments1 are not applicable to the abnormal powers of vision possessed by certain observers4 ,in fact1 the capacity of a telescope cannot be correctly assigned and its powers circumscribed by arbitrary rules1 because1 as already stated1 the character of the observer himself becomes a most important factor in this relation4 ,climatic influences have also considerable weight1 though less so than the personal variations referred to1 for one man will succeed1 where another meets with utter failure4 ,this is unquestionably due to differences in eyesight1 method1 and experience4 ,but whatever the primary causes may be1 everyone knows they induce widely discordant results1 and occasion many of the contradictions which become the subjects of controversy4 ,and1 as a rule1 amateurs should avoid controversy1 because it very rarely clears up a contested point4 ,there is argument and reiteration1 but no mutual understanding or settlement of the question at issue4 ,it wastes time1 and often destroys that good feeling which should subsist amongst astronomers of every class and nationality4 ,in cases where an important principle is involved1 and discussion promises to throw light upon it1 the circumstances are quite different4 ,but paltry quibblings1 fault-finding1 or the constant expression of negative views1 peculiar to sceptics1 should be abandoned1 as hindering rather than accelerating the progress of science4 ,let observers continually exercise care and discretion and satisfy themselves in every legitimate way as to the accuracy of their results1 and they may fearlessly give them expression and overcome any objections made to their acceptance4 ,they should accord one another an equal desire for the promotion of truth4 ,competition and rivalry in good spirit increase enthusiasm1 but there is little occasion for the bitterness and spleen sometimes exhibited in scientific journals4 ,there are some men whose reputations do not rest upon good or original work performed by themselves1 but rather upon the alacrity with which they discover grievances and upon the care they will bestow in exposing trifling errors in the writings of their not-infallible contemporaries4 ,such critics would earn a more honourable title to regard were they to devote their time to some better method of serving the cause of science4 ,cheapness and increasing number of ,telescopes4--,a marked feature of optical instruments is their increasing cheapness4 ,little more than half a century ago ,tulley charged #cae for a #aj-;inch ,newtonian reflector4 ,at the present time ,calver asks #ej for an instrument of the same aperture1 and sometimes one may be picked up1 second-hand1 for half of that amount4 ,not only have telescopes become cheaper1 but they have greatly improved in performance since silvered glass superseded the metallic speculum4 ,hence we find moderately-powerful instruments in the hands of a very large number of observers4 ,astronomical publications have proportionately increased1 so that amateurs of to-day can boast of facilities1 both of making and recording observations1 which were scarcely dreamt of a century ago4 ,it must be admitted1 however1 that the results hardly do justice to the means available4 ,such an enormous number of telescopes are variously employed that one cannot avoid a feeling of surprise at the comparative rarity of new discoveries1 and1 indeed1 of published observations generally4 ,it is certain that the majority of existing telescopes are either lying idle or applied in such a desultory fashion as to virtually negative the value of the results4 ,others1 again1 are indiscriminately employed upon every diversity of object without special aim or method1 and with a mere desire to satisfy curiosity4 ,now it is to be greatly deplored that so much observing strength is either latent or misdirected4 ,the circumstances obviously demand that an earnest effort should be made to utilize and attract it into suitable channels4 ,to do this effectually1 the value of collective effort should be forcibly explained1 the interest and enthusiasm of observers must be aroused in a permanent manner1 and they must be banded together according to their choice of subjects4 ,an effort in this direction has been made by the ,liverpool ,astronomical ,society1 and the results have proved distinctly favourable2 a considerable amount of useful work has been effected in several branches and it forms the subject of some valuable reports which have been annually published in the #8,journal4' ,utility of ,stops4--,there are a good many details connected with observation which1 though advice may be tendered in a general way1 are best left to the discrimination of observers1 who will very soon discover their influences by practical trial and treat them accordingly4 ,the employment of stops or diaphragms to contract the aperture of telescopes is a question on which a diversity of opinion has been expressed4 ,it is often found1 on nights of indifferent seeing1 that the whole aperture1 especially of a faulty instrument1 gives bad images1 and that1 by reducing it1 definition becomes immensely improved4 ,but ,mr4 ,burnham1 the double star observer1 records his opinion that a good glass needs no contraction1 and that the whole aperture shows more than a part unless there is defective figuring at the outer zone of the lens1 which will be cut off by the stop and its performance thereby greatly improved4 ,he seems to think that a glass requiring contraction is essentially defective1 but this is totally opposed to the conclusions of other observers4 ,it is almost universally admitted that1 on bad nights1 the advantages of a large aperture are neutralized by unsteady definition1 and that1 by reducing the diameter1 the character of the images is enhanced4 ,as regards instruments of moderate calibre the necessity is less urgent4 ,with my #aj-;inch reflector ,i rarely1 if ever1 employ stops1 for by reducing the aperture to #h inches the gain in definition does not sufficiently repay for the serious loss of light4 ,but in the case of large telescopes the conservation of light is not so important1 and a #ad-;inch or #af-;inch stop may be frequently employed on an #ah-;inch glass with striking advantage4 ,the theory that only defective lenses improve with contraction is fallacious1 for in certain cases where stops are regularly employed it is found that1 under circumstances of really good seeing1 the whole aperture gives images which are as nearly perfect as possible4 ,it is clear from this that the fault lies with the atmosphere1 and that under bad conditions it becomes imperative to limit its interference consistently with the retention of sufficient light to distinguish the object well4 ,in large reflectors1 particularly1 the undulations of the air are very active in destroying definition1 and the fact will be patent enough to anyone who compares the images given in widely different apertures4 ,the hard1 cleanly cut disks shown by a small speculum or object-glass offer an attractive contrast to the flaring1 indefinite forms often seen in big telescopes4 ,cleaning ,lenses4--,as to wiping objectives or mirrors1 this should be performed not more often than absolute necessity requires2 and in any case the touches should be delicate and made with materials of very soft texture4 ,the owner of a good objective should never take the handkerchief out of his pocket and1 in order to remove a little dust or dew1 rub the glass until the offensive deposit is thought to be removed4 ,yet this is sometimes done1 though frequent repetition of such a process must ultimately ruin the best telescope notwithstanding the hardness of the crown glass forming the outer lens of the objective4 ,it will not bear such 8rough and ready0 usage and in time must show some ugly scratches which will greatly affect its value though they may not seriously detract from its practical utility4 ,good tools deserve better treatment4 ,when the glass really wants cleaning1 remove it from the tube and sweep its whole surface gently with a dry camel's-hair brush1 or when this is not at hand get a piece of linen and 8flick0 off the dust particles4 ,then wipe the lens1 as soon as these have been dislodged1 with an old silk1 or soft cambric handkerchief2 fine chamois leather is also a good material1 and soft tissue paper1 aided by the breath1 has been recommended4 ,but whatever substance may be adopted it must be perfectly clean and free from dust4 ,when not in use it should be corked up in a wide-necked bottle where it will be safe from contact with foreign particles4 ,in the case of mirrors there is an obvious need that1 when being repolished1 the material used should be perfectly dry and that the mirror also should be in the same state4 ,it is unnecessary to say here that in no case must the silver film be touched when it is clouded over with moisture4 ,this must first be allowed to evaporate in a free current of air or before a fire2 the former is to be preferred4 ,a suitable polishing-pad may be made with a square piece of washleather or chamois in which cotton-wool is placed and then tied into a bag4 ,this may be dipped into a little of the finest rouge1 and its employment will often restore a bright surface to the mirror4 ,but the latter should be left 8severely alone0 unless there is urgent occasion to repolish it1 as every application of the rouged pad wears the film and may take off minute parts of it1 especially when dust has not been altogether excluded4 ,the precarious nature of the silvered surface undoubtedly constitutes the greatest disadvantage of modern reflectors4 ,the polish on the old metallic mirrors was far more durable4 ,some of ,short's1 figured #aej years ago1 still exist and are apparently as bright as when they were turned out of the workshop6 ,i have a #d-;inch ,gregorian by ,watson which must be quite a century old1 and both large and small specula seem to have retained their pristine condition4 ,with regard to the duration of the silver-on-glass films1 much of course depends upon the care and means taken to preserve them4 ,calver says that sometimes the deposit does not last so long as expected1 though he has known the same films in use for ten years4 ,a mirror that looks badly tarnished and fit for nothing will often perform wonderfully well4 ,with my #aj-;inch in a sadly deteriorated state ,i have obtained views of the ,moon1 ,venus1 and ,jupiter that could hardly be surpassed4 ,the moderate reflection from a tarnished mirror evidently improves the image of a bright object by eliminating the glare and allowing the fainter details to be readily seen4 ,when not in use a tight-fitting cap should always be placed over the mirror1 and if a pad of cotton wadding of the same diameter is made to inlay this cap it tends to preserve the film by absorbing much of the moisture that otherwise condenses on its surface4 ,the #8,hints on ,reflecting-,telescopes1' by ,w4 ,h4 ,thornthwaite and by ,g4 ,calver1 and the #8,plea for ,reflectors1' by ,j4 ,browning1 may be instructively consulted by all those who use this form of instrument4 ,the latter work is now1 however1 out of print1 and ,mr4 ,browning tells me that he has quite relinquished the manufacture of reflecting-telescopes4 ,mr4 ,g4 ,with of ,hereford1 who formerly supplied the mirrors for his instruments1 has recently disposed of his reserve stock and entered an entirely different sphere of labour4 ,in the publications above alluded to amateurs will find a large amount of practical information on the value and treatment of glass mirrors4 ,opera-,glass4--,a very useful adjunct1 and often a really valuable one to the astronomical amateur1 is the ,opera-,glass1 or rather the larger form of this instrument generally known as the ,field-,glass4 ,of certain objects it gives views which cannot be surpassed1 and it is especially useful in observations of variable stars and large comets4 ,whenever the horizon is being scanned for a glimpse of the fugitive ,mercury1 or when it is desired to have a very early peep at the narrow crescent of the young ,moon1 or to pick up ,venus at midday1 or ,jupiter before sunset1 all one has to do is to sweep over the region where the object is situated1 when it is pretty sure to be caught1 and the unaided eye will probably reach it soon afterwards4 ,the opera-glass has the dignity of being the first telescope invented1 for even its binocular form is not new2 it is virtually the same pattern of instrument that was introduced at ,middleburg in #afji1 though its compound object-glasses are of more modern date4 ,anyone who entertains any doubts as to the efficacy of the opera-glass or has had little experience in its use will do well to look at the ,pleiades and compare the splendid aspect of that cluster1 as it is there presented1 with the view obtained by the naked eye1 and he will acknowledge at once that it constitutes a tool without which the observer's equipment is by no means perfect4 ,the object-glasses should have diameters of #b or #b inches1 and the magnifying power lie between #d and #f4 ,there is a large field of view and the images are very bright4 ,the observer is enabled to enjoy the luxury of using both his eyes1 and when he directs the instrument upon a terrestrial landscape he will be gratified that it does not turn the world upside down6 ,it is not surprising that an appliance1 with recommendations so significant1 is coming more into favour every day1 and for those branches suitable to its means it is doing much useful work4 ,a volume has been recently published dealing expressly with the use of the opera-glass in ,astronomy2 and in the #8,journal of the ,l4,a4,s4' vol4 vii4 p4 #abj1 there is an excellent paper by ,major ,markwick on the same subject4 ,this instrument will never1 of course1 by the nature of its construction1 be comparable to a modern telescope in regard to power1 for ,galilei1 when he augmented his magnifiers to #cj1 appears to have practically exhausted the resources of this appliance4 ,but in all those departments requiring an expansive field and little power with a brilliant and distinct image1 the larger form of opera-glass is a great desideratum1 and its portability is not one of the least of its advantages4 ,dewing of ,mirrors4--,the disposition of mirrors to become clouded over upon rises of temperature is a point meriting comment4 ,when permanently left in a telescope1 fully exposed out of doors1 the speculum undergoes daily transitions4 ,the heat generated in the interior of the tube by the sun's action causes a thick film of moisture to form upon the silvered surface of the mirror1 which remains in this state for a considerable time1 though the moisture evaporates before the evening4 ,the flat is similarly affected1 and the result of these frequent changes is that the coating of silver becomes impaired and presents a crackly appearance all over the surface4 ,sometimes when a marked increase of temperature occurs towards evening the speculum is rendered totally unserviceable until it has been submitted to what ,dr4 ,kitchiner terms a process of 8roasting40 ,the vapour will soon disappear when the mirror is brought indoors and placed before a fire2 but it is not till some time after it has been remounted in the tube that it will perform satisfactorily4 ,those who keep their mirrors in more equable temperatures will not experience these inconveniences1 which may also in some measure be obviated by regularly placing a tight-fitting cap1 inlaid with cotton-wool1 over the speculum at the conclusion of work4 ,this also protects the silver from the yellow sulphurous deposit which soon collects upon it if used in a town4 ,all sudden variations of temperature act prejudicially on the performance of specula1 and their best work is only accomplished when free from such disturbing elements4 ,i have rarely found the flat to become dewed in a natural way during the progress of observation4 ,if on a cold night the observer puts his hand upon its supports in order to alter its adjustment it instantly becomes dewed1 or if he stands looking down the tube it is almost sure to be similarly affected2 but in the ordinary course of work the flat is little liable to become dewed in sensible degree4 ,with refractors dew-caps are very necessary1 though they do not always prevent the deposition of moisture on the object-glass1 and this occasions frequent wiping or drying1 which in either case is very objectionable4 ,celestial ,globe4--,this forms another extremely useful addendum to the appliances of the amateur4 ,it enables a great many problems to be solved in a very simple manner1 and helps the young student to a lucid comprehension of the apparent motions and positions of the fixed stars4 ,with #8,keith on the ,globes' as a reference-book he may soon acquire the method of determining the times of rising1 southing1 and setting of any celestial object the place of which is known4 ,he can also readily find the height 7altitude7 and bearing 7azimuth7 at any time4 ,the distance in degrees between any two stars or between a star and the ,moon1 a planet1 or a comet may be found at a glance by laying the quadrant of altitude on the pair of objects and reading off the number of degrees separating them4 ,if a new comet has been discovered1 its position should be marked in pencil upon the globe2 and the observer1 after having noted its exact place relatively to neighbouring stars1 may proceed to identify the object with his telescope4 ,if a large meteor is seen1 its apparent path amongst the constellations should be projected on the globe and the points1 in ,r4,a4 and ,dec41 of beginning and ending of the flight read off and entered in a book4 ,in many other practical branches of astronomy this instrument will prove highly serviceable1 and is far preferable to a star-atlas4 ,but the latter is the most useful to the beginner who is just learning the names of the stars and the configuration of the chief groups1 because on the globe the positions are all reversed east and west4 ,the surface of the globe represents the entire star-sphere reduced to a common distance from the earth1 and as seen from outside that sphere4 ,the observer1 therefore1 must imagine his eye to be situated in the centre of the globe1 if he would see the stars in the same relative places as he sees them in the heavens4 ,the reversion of the star-positions to which we have been alluding is very confusing at first1 and no doubt it provokes mistakes1 but a little experience will practically remove this objection4 ,the one great recommendation to a star-atlas is that it displays the stars in the natural positions in which they are discerned by the eye1 thus enabling the student to become readily acquainted with them1 whereas the celestial globe affords no such facility4 ,but in other respects the latter possesses some valuable functions1 and the amateur who devotes some of his leisure to mastering the really useful problems will attain a knowledge that will be of great benefit to him in after years4 ,a globe of #ab-;inches diameter will be large enough for many purposes1 but one of #ah-;inches will be the most effective size4 ,it should be mounted on a tall stand with single body and tripod base4 ,the stands1 fitted with three parallel legs1 in which the globe is supported in the middle by weak connections from them1 are not nearly so durable4 ,i have used several #ah-;inch globes mounted in this manner1 and the supports have quite given way under the pressure of constant use2 but this is impossible with the strong single body1 which is capable of withstanding any strain4 ,globes are frequently to be obtained second-hand1 and at trifling cost2 but the observer must allow for precession if he uses an old article4 ,many of the stars will be #a or #b east of the positions in which they are marked on the globe2 and it will be necessary to remember this if the appliance is to be employed for exact results4 ,observatories4--,massive and lofty buildings have long gone out of fashion1 and lighter1 drier structures have properly supplanted them4 ,instruments of size are generally placed on or near the ground and solidly supported to ensure stability1 while the other erections are made consistent with the necessity for pretty equable temperature and freedom from damp4 ,amateurs will ordinarily find that a simple wooden enclosure for the telescope1 with suitable arrangements for opening the top in any direction1 is sufficient for their purpose and very inexpensive4 ,some observers have1 indeed1 secured the desired shelter for themselves and their telescopes by means of a canvas tent provided with ready means for obtaining sky-room4 ,berthon has given a good description of an amateur's observing-hut in #8,the ,english ,mechanic' for ,october #acth and #bjth1 #ahga2 and ,chambers supplies some information about amateur observatories in #8,nature' for ,november #aith1 #ahheh4 ,mr4 ,thornthwaite's4 #8,hints on ,telescopes' may be usefully consulted for details of the ,romsey ,observatory1 which1 like the ,berthon model1 seems peculiarly adapted to the necessities of the amateur4 ,the great requirements in such structures are that they should be dry and not obstruct any region of the firmament4 ,they should also be large enough to allow the observer perfect freedom in his movements and during the progress of his observations4 ,they are then decided advantages1 and will materially add to that comfort and convenience without which it is rarely possible to accomplish really good work4 ,when an observatory is to be dispensed with it becomes necessary to erect a small wooden house near the instrument1 especially if placed at the far end of a garden1 in which the observer may keep certain appliances1 such as a lantern1 celestial globe1 step-ladder or observing-seat1 oil1 c4 ,here also he may record his seeings1 complete his sketches1 and consult his working-list1 star-charts1 and ephemerides4 ,a shelter of this sort1 apart from its practical helpfulness1 avoids any necessity for the observer to go in and out of doors1 up and down stairs1 c41 to the annoyance of the rest of his family1 who1 on a frosty night1 are decidedly not of an astronomic turn1 and vastly prefer house-warming to stargazing6 ,,footnotes3 #f ,my #aj-;inch reflector by ,with-,browning was persistently used for four years without being resilvered or once getting out of adjustment4 #g ,in this and future references to reflectors the ,newtonian form is alluded to4 ,the direct-vision reflectors of ,gregory and ,cassegrain have gone out of use1 and the present popularity of ,newtonians may be regarded as a case of the 8survival of the fittest40 #h ,chambers's #8,descriptive ,astronomy1' #dth ed4 vol4 ii41 also contains some useful references and diagrams4 ,,chapter ,,iv4 ,,notes ,,on ,,telescopic ,,work4 ,preparation4--,working-,lists4--,wind4- -,vision4--,records4--,drawing4--,friend ly ,indulgences4--,open-,air ,observing4--,method4--,perseverance4--, definition in ,towns4--,photography4--,publications4-- ,past and ,future4--,attractions of ,telescopic ,work4 ,preparation4--,an observer in commencing work in any department of astronomy will find it a very great assistance to his progress if he carefully reads and digests all that has been previously effected in the same line4 ,he will see many of the chief difficulties and their remedies explained4 ,he will further learn the best methods and be in the position of a man who has already gained considerable experience4 ,if he enter upon a research of which he has acquired no foreknowledge he will be merely groping in the dark1 and must encounter many obstacles which1 though they may not effectually turn him from his purpose1 will at least involve a considerable expenditure of time and labour4 ,on the other hand1 a person who relies upon guidance from prior experimentalists will probably make rapid headway4 ,he will be fortified to meet contingencies and to avoid complications as they arise4 ,he will be better enabled to discriminate as to the most eligible means and will confidently endeavour to push them to the furthest extent4 ,by adopting existing instructions for his direction and familiarizing himself with the latest information from the best authorities he will in a great measure ensure his own success or at least bring it within measurable distance4 ,the want of this foreknowledge has often been the main cause of failure1 and it has sometimes led to misconceptions and imaginary discoveries2 for after much thought and labour a man will overcome an impediment or achieve an end in a way for which he claims credit1 only to find that he has been anticipated years before and that had he consulted past records1 his difficulties would have been avoided and he might have pressed much nearer the goal4 ,too much importance cannot be attached to the acquisition of foreknowledge of the character referred to1 though we do not mean that former methods or results are to be implicitly trusted4 ,let every observer judge for himself to a certain extent and let him follow original plans whenever he regards them as feasible2 let him test preceding results whenever he doubts their accuracy4 ,we recommend past experiences as a guide1 not as an infallible precept4 ,it would be as much a mistake to follow the old groove with a sort of credulous infatuation as it would be to enter upon it in utter ignorance of theoretical knowledge4 ,an observer should take the direction of his labours from previous workers1 but be prepared to diverge from acknowledged rules should he feel justified in doing so from his new experiences4 ,illustration3 ,fig4 #ah4 ,refracting-,telescope on a ,german ,equatoreal4 ,working-,lists4--,full advantage should be taken of good observing weather4 ,sir ,john ,herschel most aptly said that no time occupied in the preparation of working-lists is ill-spent4 ,in our climate the value of this maxim cannot be overrated4 ,if the #ajj hours of exceptionally good seeing1 available in the course of the year1 are to be profitably employed1 we must be continually prepared with a scheme of systematic work4 ,the observer should compile lists of objects it is intended to examine1 and their places must be marked upon the globe or chart so as to avoid all troublesome references during the actual progress of observation4 ,if he has to consult ephemerides and otherwise withdraw attention from the telescope he loses valuable time3 moreover the positions hurriedly assigned in such cases are frequently wrong and entail duplicate references1 involving additional waste of time2 all this may be avoided by careful preparation beforehand4 ,if he has a series of double or variable stars to observe he must tabulate their places in convenient order so as to facilitate the work4 ,if he intend hunting up nebul or telescopic comets he must carefully mark their positions relatively to adjoining stars4 ,in the case of selenographical objects or planetary markings he may equally prepare himself by previous study4 ,adopting these precautions1 objects may be readily identified and the work expedited4 ,when no such preparation is made much confusion and loss of time result4 ,on a cloudy1 wet day observers often consider it unnecessary to make such provision and they are taken at a great disadvantage when the sky suddenly clears4 ,a good observer1 like a good general1 ought to provide1 by the proper disposition of his means1 against any emergency4 ,in stormy weather valuable observations are often permissible if the observer is prompt1 for the definition is occasionally suitable under such circumstances4 ,the most tantalizing weather of all is that experienced during an anti-cyclone in winter4 ,for a week or two the barometer is very steady at a high reading1 the air is calm1 and the sky is obscured with an impenetrable mass of clouds4 ,wind4--,the influence of wind on definition has been much discussed in its various aspects1 but it is scarcely feasible to lay down definite rules on the subject4 ,the east wind is rarely favourable to good seeing1 but the law is far from absolute4 ,we must remember that several distinct currents sometimes prevail1 and the air strata at various elevations are of different degrees of humidity and therefore exercise different effects upon telescopic definition4 ,a mere surface breeze from the east may underlie an extensive and moist current from the south-west1 and telescopic definition may prove very fair under the combination4 ,calm nights when there is a little haze and fog1 making the stars look somewhat dim1 frequently afford wonderfully good seeing4 ,as a rule1 when the stars are sparkling and brilliant1 the definition is bad2 planetary disks are unsteady and the details obliterated in glare4 ,but this is not always so4 ,i have sometimes found in windy weather after storms from the west quarter1 when the air has become very transparent1 that exceptionally sharp views may be obtained2 but unfortunately they are not without drawbacks1 for the telescope vibrates violently with every gust of wind and the images cannot be held long enough for anything satisfactory to be seen4 ,the tenuous patches of white cirrous cloud which float at high altitudes will often improve definition in a surprising manner1 especially on the ,moon and planets4 ,of course this does not apply to nebul or comets1 which are objects of totally different character and essentially require a dark night rather than good definition before they may be seen under the best conditions4 ,as a rule1 a steady1 humid atmosphere is highly conducive to good seeing1 and it is rather improved than impaired by a little fog or thin1 white cloud4 ,some unique effects of peculiar definition1 such as oval or triangular star disks1 have been occasionally recorded1 but we must content ourselves with a bare reference to these phenomena4 ,with regard to the general question it may1 however1 be added that the character of the seeing often varies at very short intervals in this climate4 ,in the course of a night's work the definition will sometimes fluctuate in a most remarkable manner4 ,an observer who comes to the telescope and finds it impossible to obtain satisfactory images should not entirely relinquish work at the first trial4 ,after an interval he should again test its performance1 for it frequently happens that a night ushered in by turbulent vapours1 improves greatly at a later period1 and in the morning part becomes so fine that it is worthy to be included in the select #ajj hours assigned by ,sir ,w4 ,herschel as the annual limit4 ,those who reside in towns will usually get the best definition after midnight1 because there is less interference then from smoke and heated vapours4 ,it would greatly conduce to our knowledge of atmospheric vagaries as affecting definition1 if observers1 especially those employing large aperture1 preserved records as to the quality of the seeing1 also direction of wind and readings of the barometer and thermometer4 ,vision4--,there are perhaps differences quite as considerable in powers of vision as in quality of definition4 ,it is not meant by this that the same person is subject to great individual variations1 though some people are certainly liable to fluctuations1 according to state of health and other conditions4 ,some eyes1 as already stated1 are less effective in defining planetary markings than in detecting minute stars or faint satellites of distant planets4 ,of course the natural capacity is greatly enhanced by constant practice1 for the human eye has proved itself competent to attain a surprising degree of excellence by habitual training4 ,frequent efforts1 if not overpressed so as to unduly strain the optic nerves1 are found to intensify rather than weaken the powers of sight4 ,thus a distinguishing trait among astronomers has been their keenness of vision1 which1 in many cases1 they have retained to an advanced age4 ,it is true ,dr4 ,kitchiner said his 8eye at the age of forty-seven became as much impaired by the extreme exertion it had been put to in the prosecution of telescope trials1 as an eye which has been employed only in ordinary occupations usually is at sixty years of age6--to cultivate a little acquaintance with the particular and comparative powers of telescopes requires many extremely eye-teasing experiments40 ,but the ,doctor's opinion is not generally confirmed by other testimony1 the fact being that the eye is usually strengthened by special service of this character4 ,to unduly tax or press its powers must result in injury2 but it is well known that the capacities of our sight and other senses are enhanced by their healthy exercise1 and that comparative disuse is a great source of declining efficiency4 ,before the observer may hope to excel as a telescopist it is clear that a certain degree of training is requisite4 ,many men exhibit very keen sight under ordinary circumstances1 but when they come to the telescope are hopelessly beaten by a man who has a practised eye4 ,on several occasions the writer was much impressed with evidences of extraordinary sight in certain individuals1 but upon being tested at the telescope they were found very deficient1 both as regards planetary detail and faint satellites4 ,objects which were quite conspicuous to an experienced eye were totally invisible to them4 ,i believe it is a good plan for habitual observers to employ method in exercising their sight4 ,in my own case ,i invariably use the right eye on the markings of planets and the left on minute stars and satellites4 ,practice has given each eye a superiority over the other in the special work to which it has been devoted1 and ,i fancy the practice might be more generally followed with success4 ,it is an advantage to keep both eyes open when in the act of observing1 especially when surrounding objects are perfectly dark and there is no distracting light from neighbouring windows or lamps4 ,the slight effort required to keep the disengaged eye closed interferes with the action of the other1 and though this is but trivial1 critical work is not efficiently performed under such conditions4 ,whenever light interferes the observer may exclude it by a shade so arranged as to afford complete protection to the unoccupied eye4 ,if faint objects are to be examined the observer should remain in a dark situation for some little time previously1 so that the pupil of the eye may be dilated to the utmost extent and in a state most suitable for such work4 ,after coming from a brilliantly lit apartment1 or after viewing the ,moon or a conspicuous planet1 the eye is totally unfit to receive impressions from a difficult object1 such as a minute star or faint nebula or comet2 some time must be allowed to elapse so that the eye may recover its sensitiveness4 ,as a rule amateurs will find it best to confine their attention to one class of objects only on the same evening1 for if the ,moon is first examined and then immediately afterwards the telescope is directed upon double stars and nebul1 the latter objects are little likely to be seen with good effect4 ,if faint objects generally are persistently studied night after night and the observer refrains from solar and lunar work1 his eye will acquire greater sensitiveness and he will readily pick up minute forms which are utterly beyond the reach of a man who indiscriminately employs his eye and telescope upon bright and faint objects4 ,records4--,with regard to records1 every observer should make a note of what he sees1 and at the earliest possible instant after the observation has been effected4 ,if the duty is relegated to a subsequent occasion it is either not done at all or done very imperfectly4 ,the most salient features of whatever is observed should be jotted down in systematic form1 so as to permit of ready reference afterwards4 ,it is useful to preserve these records in a paged book1 with an index1 so that the matter can be regularly posted up4 ,the negligence of certain observers in this respect has resulted in the total loss of valuable observations4 ,even if the details appear to possess no significance1 they should be faithfully registered in a convenient1 legible form1 because many facts deemed of no moment at the time may become of considerable importance4 ,the observer should never refrain from such descriptions because he attributes little value to them4 ,some men keep voluminous diaries in which there is scarcely anything worth record2 but this is going to the other extreme4 ,all that is wanted is a concise and brief statement of facts4 ,some persons have omitted references to features or objects observed because they could not understand them1 and rather distrusted the evidence of their eyes2 but these are the very experiences which require careful record and reinvestigation4 ,drawing4--,few observers are good draughtsmen2 but it is astonishing how seldom we meet with real endeavours to excel in this respect4 ,every amateur should practise drawing1 however indifferent his efforts may be4 ,delineations1 even if roughly executed1 are often more effective than whole pages of description4 ,pictorial representations form the leading attraction of astronomical literature1 and are capable of rendering it more interesting to the popular mind than any other influence4 ,they induce a more apt conception of what celestial objects are really like than any amount of verbal matter can possibly do4 ,for this reason it becomes the obvious duty of every observer to cultivate sketching and drawing1 at least in a rudimentary way4 ,he will frequently find it essential to illustrate his descriptions1 so as to ensure their ready comprehension4 ,in fact1 a thoroughly efficient observer must of necessity become a draughtsman4 ,it should1 however1 be his invariable aim to depict just what he sees and in precisely the form in which it impresses his eye4 ,mere pictorial embellishments must be disregarded1 and he should be careful not to include doubtful features1 possibly existing in the imagination alone1 unless he intends them simply for his own guidance in future investigations4 ,if he sees but little1 and it is faithfully delineated1 it will be of more real value than a most elaborate drawing in which the eye and imagination have each played a part4 ,it is an undoubted fact that some of the most striking illustrations in astronomical handbooks are disfigured by features either wrongly depicted or having no existence whatever4 ,there is very great need for caution in representing such markings only as are distinctly and unmistakably visible4 ,in all cases where the object is new or doubtful the observer should await duplicate observations before announcing it4 ,it is better that new features should evade discovery than that delusive representations should be handed down to posterity4 ,as regards selenographical drawings ,i would refer the reader to what ,mr4 ,eiger advises on p4 #ba and #bb of volume v4 of the #8,journal of the ,liverpool ,astronomical ,society4' ,my own plan in sketching at the telescope is to first roughly delineate the features bit by bit as ,i successively glimpse them1 assuring myself1 as ,i proceed1 as to general correctness in outline and position2 then1 on completion1 ,i go indoors to a better light and make copies while the details are still freshly impressed on the mind4 ,to soften details a small piece of blotting-paper must be wrapped round the pointed end of the pencil1 and the parts requiring to be smoothed gently touched or rubbed until the desired effect is attained4 ,this simple method1 properly applied1 will enable delicate markings to be faithfully reproduced1 and it certainly adds in no small degree to the merit of a drawing4 ,friendly ,indulgences4--,every man whose astronomical predilections are known1 and who has a telescope of any size1 is pestered with applications from friends and others who wish to view some of the wonders of the heavens4 ,of course it is the duty of all of us to encourage a laudable interest in the science1 especially when evinced by neighbours or acquaintances2 but the utility of an observer constituting himself a showman1 and sacrificing many valuable hours which might be spent in useful observations1 may be seriously questioned4 ,the weather is so bad in this country that we can ill spare an hour from our scanty store4 ,is it therefore desirable to satisfy the idle curiosity of people who have no deep-seated regard for astronomy1 and will certainly never exhibit their professed interest in a substantial manner8 ,assuredly not4 ,the time of our observers is altogether too valuable to be employed in this fashion4 ,yet it is an undisputed fact that some self-denying amateurs are unwearying in their efforts to accommodate their friends in the respect alluded to4 ,my own impression is that1 except in special cases1 the observer will best consult the interests of astronomy1 as well as his own convenience and pleasure1 by declining the character of showman2 for depend upon it a person who appreciates the science in the right fashion will find ways and means to procure a telescope and gratify his tastes to the fullest capacity4 ,some years ago ,i took considerable trouble on several evenings in showing a variety of objects to a clerical friend1 who expressed an intention to buy a telescope and devote his leisure to the science4 ,i spent many hours in explanations c42 but some weeks later my pupil informed me his expenses were so heavy that he really could not afford to purchase instruments4 ,yet ,i found soon after that he afforded #cj in a useless embellishment of the front of his residence1 and it so disgusted me that ,i resolved to waste no more precious time in a similar way4 ,open-,air ,observing4--,night air is generally thought to be pernicious to health2 but the longevity of astronomers is certainly opposed to this idea4 ,those observers who are unusually susceptible to affections of the respiratory organs must of course exercise extreme care1 and will hardly be wise in pursuing astronomical work out of doors on keen1 wintry nights4 ,but others1 less liable to climatic influences1 may conduct operations with impunity and safety during the most severe weather4 ,precautions should always be taken to maintain a convenient degree of warmth2 and1 for the rest1 the observer's enthusiasm must sustain him4 ,a 8wadded dressing-gown0 has been mentioned as an effective protection from cold4 ,i have found that a long1 thick overcoat1 substantially lined with flannel1 and under this a stout cardigan jacket1 will resist the inroads of cold for a long time4 ,on very trying nights a rug may also be thrown over the shoulders and strapped round the body4 ,during intense frosts1 however1 the cold will penetrate 7as ,i have found while engaged in prolonged watches for shooting-stars7 through almost any covering4 ,as soon as the observer becomes uncomfortably chilly he should go indoors and thoroughly warm his things before a fire4 ,he may then return fortified to his work and pursue it for another period before the frost again makes its presence disagreeably felt4 ,on windy nights a knitted woollen helmet to cover the head1 and reaching to the shoulders1 is an excellent protection2 but an observer had better not wear it more often than is imperative1 or it becomes a necessity on ordinary nights4 ,it is a great mistake to suppose that 8a glass of something hot0 before going into the night air is a good preventive to catching cold4 ,it acts rather in the contrary way4 ,the reaction after the system has been unduly heated only renders the observer more sensitive1 and the inhalation of cold air is then very liable to induce affections of the throat4 ,a telescope permanently erected in the open1 and exposed to all weathers1 must soon lose its smart and bright appearance1 but it need lose none of its efficiency1 which is of far more importance2 for it is intended for service1 not for show4 ,the instrument should be kept well painted and oiled4 ,i find vaseline an excellent application for the screws and parts controlling the motions1 as it is not congelative like common oils4 ,the observer1 before a night's work and before darkness sets in1 will do well to examine his instrument and see that it is in the best condition to facilitate work4 ,whole tribes of insects take up their habitation in the base or framework1 and even in the telescope itself if they can effect a lodgment2 and ,i have sometimes had to sweep away a perfect labyrinth of spiders' webs from the interior of the main tube4 ,on one occasion ,i could not see anything through the finder1 try how ,i would4 ,i afterwards discovered that a mason-wasp 7,odynerus murarius7 had adopted the vacuity in front of the eye-lens as a suitable site for her nest2 and here she had formed her cells1 deposited her eggs1 and enclosed the caterpillars necessary for the support of the young when hatched4 ,on another night ,i came hurriedly to the telescope to observe ,jupiter with my single-lens eyepiece1 power #beb1 but could make nothing out of it but a confused glare1 subject to sudden extinctions and other extraordinary vagaries4 ,i supposed that the branches of a tree1 waving in the wind1 must be interposed in the line of sight1 but soon saw this could not possibly be the explanation4 ,looking again into the eyepiece1 ,i caught a momentary glimpse of what ,i interpreted for the legs of an insect magnified into gigantic proportions and very distinct on the bright background formed by ,jupiter much out of focus4 ,on detaching the eyepiece and carrying it indoors to a light1 an innocent-looking sample of the common earwig crawled out of it4 ,the gyrations of the insect in its endeavours to find a place of egress from its confinement had clearly caused the effects alluded to4 ,telescopic observers are thus liable to become microscopic observers before they are conscious of the fact1 and perhaps also in opposition to their intention4 ,other experiences might be narrated1 especially as regards nocturnal observing in country or suburban districts1 where the 8serious student of the skies0 may1 like myself1 find diversion to his protracted vigils by the occasional capture of a too-inquisitive hedgehog or some other marauding quadruped4 ,illustration3 ,fig4 #ai4 ,the ,author's ,telescope3 a #aj-;inch ,with-,browning ,reflector4 ,method4--,nearly all the most successful observers have been men of method4 ,the work they took in hand has been followed persistently and with certain definite ends in view4 ,they recognized that there should be a purpose in every observation4 ,some amateurs take an incredible amount of pains to look up an object for the simple satisfaction of seeing it4 ,but seeing an object is not observing it4 ,the mere view counts for nothing from a scientific standpoint1 though it may doubtless afford some satisfaction to the person obtaining it4 ,a practical astronomer1 with his own credit at stake and the interests of the science at heart1 will require something more4 ,in observing a comet he will either fix its position by careful measurement with reference to stars near1 or critically examine its physical peculiarities1 or perhaps both4 ,in securing these data he will have accomplished useful work1 which may quite possibly have an enduring value4 ,in other branches of observation his aim will be similar1 namely to acquire new materials with regard to place or to physical phenomena1 according to the nature of the research upon which he happens to be engaged4 ,such results as he gathers are neatly tabulated in a form convenient for after comparisons4 ,there have been instances1 we know1 where sheer carelessness has resulted in the loss of important discoveries4 ,lalande must have found ,neptune 7and mathematical astronomy would have been robbed of its greatest triumph7 half a century before it was identified in ,galle's telescope1 but his want of care enabled it to elude him just when he was hovering on the very verge of its discovery4 ,numerous other instances might be mentioned4 ,failure may either arise from imperfect or inaccurate records1 from a want of discrimination1 from neglect in tracing an apparent discordance to its true source1 or from hesitation4 ,i may be pardoned for mentioning a case within my own experience4 ,on ,july #aa1 #ahha1 just before daylight1 ,i stood contemplating ,auriga1 and the idea occurred to me to sweep the region with my comet eyepiece1 but ,i hesitated1 thinking the prospect not sufficiently inviting4 ,three nights later ,schberle at ,ann ,arbor1 ,u4,s4,a41 discovered a bright telescopic comet in ,auriga6 ,before sunrise on ,october #d of the same year ,i had been observing ,jupiter1 and again hesitated as to the utility of comet-seeking1 but1 remembering the little episode in my past experience1 ,i instantly set to work1 and at almost the first sweep alighted upon a suspicious object which afterwards proved itself a comet of short period4 ,these facts teach one to value his opportunities4 ,they cannot be lightly neglected1 coming as they do all too rarely4 ,the observer should never hesitate4 ,he must endeavour to at least effect a little whenever an occasion offers2 for it is just that little which may yield a marked success--greater1 perhaps1 than months of arduous labour may achieve at another time4 ,perseverance4--,persistency in observation1 apart from the value derived from cumulative results1 increases the powers of an observer to a considerable degree4 ,this is especially the case when the same objects are subjected to repeated scrutiny4 ,a first view1 though it may seem perfectly satisfactory in its conditions and results1 does not represent what the observer is capable of doing with renewed effort4 ,let us suppose that a lunar object with complicated detail is to be thoroughly surveyed4 ,the observer delineates at the first view everything that appears to be visible4 ,but a subsequent effort reveals other features which eluded him before1 and many additional details are gradually reached during later observations4 ,ultimately the observer finds that his first drawing is scarcely more than a mere outline of the formation as he sees it at his latest efforts4 ,details which he regarded as difficult at first have become comparatively conspicuous1 and a number of delicate structures have been exhibited which were quite beyond his reach at the outset4 ,the eye has become familiarized with the object1 and its powers fairly brought out by training and experience4 ,this training is very serviceable1 but is seldom appreciated in the degree of its influence4 ,many a tyro has abandoned a projected series of observations on finding that his initiatory view falls wofully short of published drawings or descriptions4 ,he considers himself hopelessly distanced1 and regards it as impossible to attain--much less excel--the results achieved by his predecessors4 ,he does not realize that their work is the issue of years of close application1 and that it represents the collective outcome of many successive nights4 ,i need hardly say that it is a great mistake to anticipate failure in this way4 ,no telescopic work has been done in the past that will not be done better in the future4 ,no observer can rate his capacity until he has rigorously tested it by experience4 ,the eye must become accustomed to an object before it is able to do itself justice4 ,those who have been sedulously engaged in a certain research will1 as a rule1 see far more than others who are but just entering upon it--not from a natural superiority of vision1 but because of the aptitude and power acquired by practice4 ,no matter how meagre an observer's primary attempts may be1 he should by no means relax his efforts1 but rather feel that his want of success must be remedied by experience4 ,it is a common fault with observers that they leave too much to their instruments1 and rely upon them for the results which really depend entirely upon their personal endeavours4 ,a skilled workman will do good work with indifferent tools2 for after all it is the character of the man that is evident in his results1 and not so much the resources which art places in his hands4 ,much also depends upon the feelings by which the amateur is actuated when he commences work4 ,a few enter into it with a degree of energy and determination that knows no wearying and will accept no defeat4 ,others display a half-hearted enthusiasm1 and are constantly doubting either their personal ability or their instrumental means4 ,many others1 again1 when the circumstances appear a little against them regard failure as inevitable4 ,it need hardly be said1 however1 that every difficulty may be surmounted by perseverance1 and that a man's enthusiasm is often the measure of his success1 and success is rarely denied to him whose heart is in his work4 ,definition in ,towns4--,the astronomical journals contain some interesting references to the definition of telescopes in large towns4 ,of course the purer the air the better for observational purposes4 ,but observers who reside in populous districts need not despair of doing really useful work4 ,the vapours hanging over a large city are by no means so objectional as is commonly supposed4 ,when they are circulating rapidly across the observer's field of view they will prove very troublesome at times2 but in a comparatively tranquil state of the air definition is excellent4 ,i have frequently found planetary markings very sharp and steady through the smoke and fog of ,bristol4 ,the interposing vapours have the effect of moderating the bright images and improving their quality4 ,when there is a driving wind1 and these heated vapours from the city are rolling rapidly past1 objects at once appear in a state of ebullition1 and the work of observation may as well be postponed4 ,smoke from neighbouring chimneys is utterly ruinous to definition3 a bright star is transformed into a seething1 cometary mass1 and the planets undergo contortions of the most astonishing character4 ,large instruments being more susceptible to such influences--and1 indeed1 to atmospherical vagaries of all kinds--are chiefly affected by the drawbacks we have alluded to2 but there are many opportunities when their powers may be fully utilized4 ,in sweeping for faint comets1 or in other work 7such as the observation of nebul7 where a dark sky is the first essential1 a town station has a manifest disadvantage because of the artificial illumination of the atmosphere4 ,but for general telescopic work the conditions do not offer a serious impediment1 especially if the observer is careful to seize the many suitable occasions that must occur4 ,the direction of the wind relatively to his position and the central part of the city1 will occasion considerable differences to an observer who uses a telescope in a suburban locality4 ,photography4--,upon this branch of practical astronomy not much will be said in this volume1 as it is rather beyond its scope1 and possibly also beyond the resources of ordinary amateurs1 so far as really valuable work is concerned4 ,a reference must1 however1 be made to an innovation which has deservedly assumed a very prominent place1 and is clearly destined to exert an accelerating influence on the progress of exact astronomy4 ,at present it is impossible to foretell how far it may be employed and extended1 but judging from recent developments its applications will be as manifold as they will be valuable4 ,photographic records possess a great advantage over others1 because they are more accurate and therefore more reliable4 ,they are pictures from ,nature taken by means free from the bias and error inseparable from mere eye-estimations or hand-drawings4 ,the latter are full of discordances when compared one with another1 and can seldom be implicitly trusted2 but in the photograph a different state of things prevails4 ,here we have a faithful portrayal or reproduction of the object impressed by itself upon the plate4 ,hence it can be depended upon1 because there has been no intermediate meddling either with its position or features by what may be termed artistic misrepresentation4 ,true1 there may be imperfections in the process2 trifling flaws and obstructions will invariably creep in wherever comparatively new and novel work is attempted1 but these will but little detract from the value of its results4 ,photography is obviously a means of discovery as well as a means of accurate record2 for nebul and faint stars quite invisible to the eye have been distinguished for the first time upon the negatives4 ,those of our amateurs who intend working in this branch will find it a productive one1 and not decaying in interest2 but the necessary outfit will be expensive if thoroughly capable instruments are to be employed in the service4 ,illustration3 ,,london ,,stereoscopic ,,co4 ,,photomezzotype ,,stanmore ,,observatory4 ,,outside ,,view ,publications4--,the observer of to-day may esteem himself particularly fortunate in regard to the number and quality of the astronomical journals within his reach4 ,discoveries and current events receive prompt notice in these1 and readers are fully informed upon the leading topics4 ,among the best of the periodicals alluded to are #8,the ,observatory' 7,taylor ,francis1 ,london71 #8,the ,sidereal ,messenger' 7,northfield1 ,minn41 ,u4,s4,a471 and ,l',astronomie 7,gautier-,villars1 ,paris74 ,the ,astronomische ,nachrichten 7,kiel1 ,germany7 is a very old and valued serial1 and #8,the ,astronomical ,journal' 7,cambridge1 ,mass41 ,u4,s4,a47 may also be favourably mentioned4 ,the #8,monthly ,notices' of the ,royal ,astronomical ,society and the #8,journals' of the ,liverpool and ,british ,astronomical ,societies contain many interesting materials4 #8,nature1' #8,the ,english ,mechanic1' and #8,knowledge' are among the ,english journals which devote part of their space to the science2 and the beautiful illustrations in the latter entitle it to special recognition4 ,it is evident1 from this short summary1 the amateur will find that his literary appetite may be amply satisfied1 and should he desire a channel for recording his own work or ideas the publications referred to offer him every facility and encouragement4 ,as to almanacks1 the #8,nautical' which has been termed 8,the ,astronomer's ,bible10 includes a mass of tabular matter1 some portion of which is of utility to the amateur1 but it does not give data which are to be found in some other publications4 ,i refer particularly to ephemerides of the satellites of ,mars1 ,saturn1 ,uranus1 and ,neptune1 to the dates of max4 and min4 of variable stars1 to the times of rising and setting of the ,sun1 ,moon1 and planets1 to the epochs and positions of meteor-showers1 c4 ,the annual #8,companion to the ,observatory' furnishes most of these details1 and #8,whitaker's ,almanack' and ,brown ,sons' #8,nautical ,almanack' each contain a large amount of serviceable information4 ,the latter1 however1 is chiefly devoted to topics connected with ,navigation1 while #8,whitaker's ,almanack' is an extensive repertory of general facts4 ,with respect to handbooks much depends upon the direction of the observer's labours1 for he will obviously require works dealing expressly with his special subject4 ,as a reliable companion to the telescope1 ,webb's #8,celestial ,objects for ,common ,telescopes' 7#dth edit41 #ahha7 is indispensable2 as a work of reference1 and one forming an exhaustive conspectus of astronomical facts1 ,chambers's #8,descriptive ,astronomy' 7#dth edit41 in #c vols41 #ahhi7 may be recommended4 ,ledger's #8,the ,sun1 its planets and their satellites' is another good descriptive work4 ,the beginner will find ,noble's #8,hours with a #c-;inch ,telescope' full of very instructive and agreeable material2 while the more experienced astronomer1 requiring a masterly exposition of the principles of the science1 must procure ,sir ,j4 ,herschel's #8,outlines' 7#aath edit41 #ahga74 ,in departmental work books of more exclusive character will be necessary4 ,thus1 students of solar physics will want ,young's volume on #8,the ,sun2' observers of our satellite will need ,neison's #8,moon4' ,those who find double stars interesting should get ,crossley1 ,gledhill1 ,wilson's #8,handbook' and ,chambers's revised edition of ,admiral ,smyth's #8,cycle2' others working on variable stars will need the ,catalogues of ,chandler and ,gore4 ,jovian phenomena are well represented in ,stanley ,williams's #8,zenographic ,fragments4' ,comets have been fully treated of in works by ,cooper1 ,hind1 and ,guillemin2 while to the observer of eclipses ,johnson's #8,eclipses ,past and ,future' is a valuable guide4 ,everyone interested in nebul will of course require ,herschel-,dreyer's #8,general ,catalogue1' containing #ghdj objects and published by the ,royal ,astronomical ,society in #ahhh4 ,as to planetary observations1 the several works of ,webb1 ,chambers 7vol4 i471 and ,ledger1 first cited1 supply a large amount of detail1 almost obviating the necessity for further books4 ,past and ,future4--,observers and telescopes go on increasing day by day1 and the future of astronomy has a most brilliant outlook4 ,photography has latterly effected a partial revolution in observation1 though it can never entirely supersede old methods4 ,spectrum analysis1 too1 has formed a valuable acquisition during the last quarter of a century4 ,with the new and refined processes1 and with the gigantic instruments which have been erected1 we may confidently anticipate many additions to our knowledge1 especially in regard to very small and faint bodies which the inferior appliances of previous years have failed to grasp4 ,and it is certain that some of the presumed discoveries of past times must be expunged1 because not verified by the more perfect and powerful researches of a later date4 ,let us place in parallel columns 7#a7 a few of the suspected objects thus to be erased1 and 7#b7 some of those which the future will probably add to our store3- 7#a47 7#b47 ,satellite of ,venus4 ,satellites of ,uranus and ,neptune4 ,vulcan4 ,ultra-,neptunian ,planet4 ,active ,volcanoes on the ,moon4 ,changes on the ,moon4 ,detached cusps of ,venus and ,mercury ,rotation of ,mercury1 ,venus1 indicating high mountains4 ,uranus1 and ,neptune4 ,rings of ,uranus and ,neptune4 ,minor ,planets4 ,multiple companions to ,polaris ,periodical ,comets4 and ,vega4 ,nebul and ,double ,stars4 ,whatever may be the direction of future enquiries or the departures from old and tried methods1 ordinary amateurs with small instruments1 though handicapped more heavily as regards the prospect of effecting discoveries1 may yet always be expected to accomplish useful work4 ,even to him who simply makes the science a hobby and a source of recreation in a leisure hour after the cares of business1 the sky never ceases to afford a means of agreeable entertainment4 ,he may neither achieve distinction nor seek it2 but this he will assuredly do--gain an instructive insight into the marvellous works of his ,creator1 and acquire a knowledge which can only exercise an elevating tone to his life4 ,the observer who quietly1 from his cottage window1 surveys the evening star or the new ,moon through his little telescope often finds a deeper pleasure than the proficient astronomer who1 from his elevated and richly appointed observatory1 discovers new orbs with one of the most powerful instruments ever made4 ,attractions of ,telescopic ,work4--,in concluding our comments we may briefly refer to the importance and pleasure attached to telescopic work1 and the growing popularity of observation in the attractive and diverse field of astronomy4 ,a telescope may either be employed as an instrument of scientific discovery and critical work1 or it may be made a source of recreation and instruction4 ,by its means the powers of the eye are so far assisted and expanded that we are enabled to form a clearer conception of the wonderful works of the ,creator than could be obtained in any other way4 ,objects which appear to natural vision in dim and uncertain characters are resolved1 even in telescopes of the smallest pretentions1 into pictures of well-defined outlines containing details of configuration far exceeding what are expected4 ,and it is entirely owing to the exact measurements obtained under telescopic power that many of the most important problems of astronomy have been satisfactorily solved4 ,to this instrument we are indebted1 not only in a great measure for our knowledge of the physical features of many celestial bodies1 but also for the accurate information we have gained as to their motions1 distances1 and magnitudes4 ,apart from this it is capable of affording ample entertainment to all those who are desirous of viewing for themselves some of the absorbing wonders of astronomy as described in our handbooks4 ,and a demonstration of this practical kind is more effective than any amount of description in bringing home to the comprehension of the uninitiated the unique and picturesque side of astronomy4 ,,chapter ,v4 ,,the ,,sun4 ,solar ,observations4--,early notices of ,spots4--,difficulties of the old observers4--,small instruments useful4--,tinted glass4--,solar ,diagonal4--,structure of a ,spot4--,methods of ,drawing4--,ascertaining ,dimensions4--,observer's aims4--,eclipses of the ,sun4--,periodicity of ,spots4--,crateriform structure4--8,willow-,leaves40--,rotatio n of the ,sun4--,planetary bodies in transit4--,proper motion of ,sun-spots4--,rise and decay of ,spots4--,black ,nuclei in the umbr4--,bright objects near the ,sun4--,cyclonic action4--,sudden outbursts of ,facul4--,shadows cast by ,facul4--,veiled ,spots4--,recurrent disturbances4--,recurrent forms4--,exceptional position of ,spots4--,the ,solar prominences4 8,along the skies the ,sun obliquely rolls1 ,forsakes1 by turns1 and visits both the poles2 ,diff'rent his track1 but constant his career1 ,divides the times1 and measures out the year40 ,the ,sun is not an object comprehended in the title of this volume4 ,but to have omitted reference to a body of such vast importance1 and one displaying so many interesting features to the telescopic observer1 would have been inexcusable4 ,we may regard the ,sun as the dominant power1 the controlling orb1 and the great central luminary of our system4 ,the phenomena visibly displayed on his surface assume a particular significance1 as affecting a body occupying so high a place in the celestial mechanism4 ,the mean apparent diameter of the ,sun is #cb #cf1 and his real diameter #hff1jjj miles4 ,the apparent diameter varies from a minimum of #ca #cb at the end of ,june to a maximum of #cbcf2 at the end of ,december2 and the mean value is reached both at the end of ,march and ,september4 ,the ,sun's mean distance from the ,earth is about #ib1ijj1jjj miles1 computed from a solar parallax of #hh1 which appears to agree with the best of recent determinations4 ,at this distance the linear value of #a of arc is #ddg miles4 ,the ,sun's apparent diameter is as follows on the first day of each month3-- ,jan4 #a #cb #cfj ,feb4 #a #cb #cah ,mar4 #a #cb #bjd ,april #a #cb #ch ,may #a #ca #dhj ,june #a #ca #cfd ,july #a #ca #cbj ,aug4 #a #ca #ceh ,sept4 #a #ca #dgj ,oct4 #a #cb #bf ,nov4 #a #cb #aib ,dec4 #a #cb #caf ,solar observations may be pursued with a facility greater than that attending work in some other departments of practical astronomy4 ,the ,moon1 planets1 and stars have to be observed at night1 when cold air1 darkness1 and other circumstances are the cause of inconvenience2 but the student of the ,sun labours only in the light and warmth of genial days1 when all the incidentals to observation may be agreeably performed4 ,there are1 however1 some drawbacks even in this pleasant sphere of work4 ,the light of the ,sun is so great that much persistent observation is apt to have an injurious effect on the eye1 and will certainly deaden its sensitiveness on faint objects4 ,in the summer months the observer experiences discomfort during a lengthy observation from remaining so long in the powerful rays of the ,sun1 some of which must fall upon his face unless measures are adopted to shield it4 ,during the progress of solar work the student should always provide for himself as much shelter as possible from the glare1 which must otherwise disturb that equanimity of feeling in the absence of which no delicate research is likely to be successfully conducted4 8,spots on the ,sun0 were remarked long before the telescope came into service4 ,in the early ,chinese annals many references are made to these objects2 thus1 in ,a4,d4 #ahh1 ,february #ad1 it is recorded--8,the colour of the ,sun reddish-yellow2 a fleckle in the ,sun 7bird-shaped740 ,other ancient notices compare the spots to a flying bird1 an apple1 or an egg4 ,many spots were seen in later years1 especially in #cba1 #hjg1 #hdj1 #ajif1 c4 ,in #hjg a large black spot upon the ,sun was watched during a period of eight days4 ,it reflects much credit upon observers of a past age that they performed so many useful feats of observation1 though relying simply upon the powers with which ,nature alone had endowed them4 ,they anticipated the telescope in some important discoveries4 ,large sun-spots are not1 it is true1 difficult features to perceive with the naked eye under certain circumstances2 for whenever there is a fog or haze sufficiently dense to veil the lustre of the ,sun in suitable degree1 they can be readily seen1 presuming1 of course1 that such spots are in existence at the time4 ,they are sometimes observed1 in a purely casual way1 by people who may happen to glance at the ,sun when he is involved in fog and looks like a dull1 red ball suspended in the firmament4 ,on one occasion1 near sunset1 in the autumn of #ahgj1 ,i saw four large spots on different parts of the ,sun1 and these phenomena were very numerous at about this time4 ,when spots attain a diameter of #ej or more they may be detected by persons of good sight2 but if the ,sun is high and clear1 coloured glass must be used to defend the eye4 ,doubt hangs over the question as to the first telescopic observer of the spots4 ,it is certain that ,fabricius1 ,galilei1 ,harriot1 and ,scheiner all remarked them in about the year #afaa2 and of these ,fabricius perhaps deserves the chief praise1 as the first who published a memoir on the subject4 ,galilei appears undoubtedly to have had priority in recognizing the bright spots1 or facul4 ,scheiner discovered that the black spots1 or macul1 are composed of a dark umbra and a fainter outlying shade1 called the penumbra4 ,arago quotes him as having also described the ,sun as 8covered over its whole surface with very small1 bright1 and obscure points1 or with lively and sombre streaks of very slender dimensions1 crossing each other in all directions40 ,he announced1 too1 that the spots were confined to a narrow zone on the north and south sides of the equator1 and this he termed the 8,royal ,zone40 ,some grave difficulties appear to have marked the attempts of the earlier observers2 for they did not all use coloured glasses1 and the dazzling light of the ,sun1 intensified by their lenses1 often overpowered the sight1 and so we find them awaiting opportunities when fog partly obscured the ,sun near his rising or setting4 ,thus ,harriot1 who seems to have noticed and figured three sun-spots as early as #afaj1 ,dec4 #h1 says3--8,the altitude of the ,sonne being #g or #h degrees1 and it being a frost and a mist1 ,i saw the ,sonne in this manner40 ,his drawing followed4 ,on another occasion he says3--8,a notable mist3 ,i observed the ,sonne at sundry times1 when it was fit40 ,fabricius advised other observers to commence their observations by admitting only a small portion of the ,sun into the field1 so that the eye might be prepared to receive the light of the entire disk4 ,galilei was equally unaware of the advantage of tinted glass1 and adopted the expedient of scanning the ,sun when placed in the vicinity of the horizon4 ,he remarks that 8the spot of #afab1 ,april #e appeared at sunset20 and his writings contain other references of similar import4 ,scheiner1 however1 appears to have been more alive to the requirements of the work1 and employed a plain green glass placed in front of the object-lens of his telescope4 ,under the various circumstances we have been alluding to1 the views obtained of the solar surface must necessarily have been of a very defective character1 and the old observers at least deserve our sympathy in their exertions4 ,no such obstacles confront the observer now4 ,he has everything provided for him4 ,instrumental devices rob the ,sun of his noonday brilliancy1 and the eye serenely scans the details of his expansive image without the slightest pain or effort4 ,small telescopes are peculiarly well adapted for solar observations4 ,a good #c-;inch refractor or #d-;inch reflector will reveal an astonishing diversity of structure in the spots1 and show something of the complicated minuti of the general surface4 ,if the aperture of either instrument is #b inches more than that stated1 so much the better2 but further than this it is rarely advisable to go4 ,when the objective or mirror exceeds a diameter of #e or #f inches a stop often improves the images1 and even smaller instruments will perform better when a little contracted4 ,definition is here the point to be desired2 of light we have a superabundance4 ,but if the observer meditates a critical analysis of the detail1 either of a single spot1 of a group of spots1 or of a small area of the luminous surface1 then a fair amount of aperture should be used1 because greater aperture means greater separating power1 and the latter will be useful in resolving the network of fibrous materials of which apparently the whole surface is composed4 ,but for the common requirements of the observer an instrument of #c or #d inches will be found very effective1 and it can either be used on a short tripod stand1 placed on a steady table near a window having a south aspect1 or it may be mounted on a tall garden stand and1 according to the owner's pleasure1 either fixed at his window or in his garden4 ,two powers will be really necessary--one of about #fj and a field of quite #cc to contain the entire disk and give a good general view1 and another of #aej to which the observer will have recourse when examining details4 ,additional eyepieces will be sometimes useful1 especially one of about #ajj2 but the power of #fj previously recommended will1 if a ,huygenian1 answer the same purpose1 for if the field-lens is removed it will be increased to about #ij4 ,and should the observer think that anything is to be gained by a higher magnifier than #aej1 let him use the eye-lens only of that power4 ,i have obtained many exquisite views of sun-spots with a single lens1 and1 instead of purchasing new eyepieces1 a real advantage will be derived in adopting the plan suggested4 ,there will be a smaller field and more colour about the image1 but the improvement in definition is considerable1 and more than balances these disadvantages4 ,tinted glass must always be employed1 unless a dense fog prevails1 in which case the example of the old observers may be emulated4 ,several coloured glasses1 of various depths1 are needed for use according as the occasion requires4 ,with a high ,sun on a bright ,june day a darker tint will be necessary than in the winter1 when the ,sun's rays are but feebly transmitted through the horizontal vapours4 ,red glass is unsatisfactory1 as there is much heat and glare with it2 but when used in combination with green the effect is excellent4 ,green alone is often used1 and answers well2 but it is not always thick and dense enough for the purpose4 ,the plan of ,sir ,w4 ,herschel1 to interpose a glass trough of diluted ink1 has never become popular1 though he found it to succeed admirably4 ,smoked glass is also adapted for solar work1 and recommends itself as being always obtainable at a minute's notice4 ,some observers use a ,barlow lens1 with a thin film of silver deposited on the surfaces4 ,it is then sufficiently transparent to give a neutral tint when held before a light1 and sharp definition is said to be obtained without additional protection4 ,mr4 ,thornthwaite has also employed a coloured ,barlow lens with effect4 ,a solar diagonal is a very necessary appliance if the observer would ensure perfect safety2 for any refractor exceeding #b-;inches aperture may1 when turned on the ,sun1 focus enough heat to fracture the tinted sun-glass4 ,the diagonal1 by preserving a part only of the solar rays which are transmitted by the object-glass1 enables observations to be made in security4 ,this little instrument is comparatively cheap1 and no telescope is complete without one4 ,dawes's solar eyepiece serves the same purpose in a different manner1 but it is an expensive luxury4 ,in the latter construction there is a perforated diaphragm fixed near the eyepiece and so arranged that the quantity of admitted light may be modified consistently with the observer's wishes4 ,in reflecting-telescopes with glass mirrors1 effective views of the ,sun are obtainable by employing unsilvered mirrors2 for sufficient light is reflected by the glass surfaces to form good images of solar detail4 ,what1 perhaps1 interferes more than any other circumstance with successful observation of the ,sun1 is the fact that the rays1 falling upon the telescope and objects near1 induce a good deal of radiation1 the direct tendency of which is to impair the definition and give a rippling effect to the disk4 ,this is sometimes present in such force that the spots are subject to an incessant commotion1 which serves to obliterate their more delicate features4 ,a shady place is best1 therefore1 for such work2 and if the observer leaves his telescope for a short time1 intending to resume observations1 it should never be placed broadside to the ,sun1 or the tube wall get hot1 and heated currents must be generated in the interior1 to the ruin of subsequent views4 ,a large sun-spot consists of an apparently black nucleus1 a brown umbra1 divided possibly by veins of bright matter or by encroachments of the penumbra which surrounds it4 ,the latter is of much lighter tone than the umbra1 though often similar in its general form4 ,the outer edges of the umbra are serrated or scalloped by rice-grain protuberances4 ,the inner region of the penumbra is much brighter than the outer1 and the latter often exhibits quite a dusky fringe1 induced by lines of dark material intervening with the brighter particles4 ,the filaments forming the penumbra--often grouped in a radial manner with reference to the centre of a spot--would appear to be more widely separated near the outer border of the penumbra1 and sufficiently so to allow sections of the umbral layer of the ,sun to be observed through the interstices4 ,the lighter tint of the interior part of the penumbra is stated to be due to contrast2 but this is a mistake4 ,the difference is too definite and distinct to permit such an explanation4 ,mr4 ,maunder says 8that usually 7not invariably7 the penumbra darkens towards the umbra1 and that the phenomenon as ordinarily described is merely an effect of contrast40 ,my own observations1 however1 appear to show that there is an actual difference of detail in the outer and inner portions of the penumbra1 which gives a darker tone to the former4 ,in drawing the forms of sun-spots the observer must be expeditious1 because of the variations which are quickly and constantly affecting them4 ,in concluding a sketch ,i find it essential to make several alterations in it1 owing to the changes which have occurred in the spots during the interval of a quarter of an hour or so since it was commenced4 ,the details must be filled in consecutively1 each one being the result of a careful scrutiny4 ,when finished1 the whole sketch should be compared with the object itself and amended if found necessary4 ,the observer should also mark upon the sheet the measured or estimated latitude and longitude of the spot1 and make a finished drawing from the basis of his sketch as soon as possible afterwards4 ,at ,stonyhurst ,observatory excellent delineations of solar phenomena are made2 and the late ,father ,perry1 who lost his life in the cause of science1 thus described the method3--8,on every fine day the image of the ,sun is projected on a thin board attached to the telescope1 and a drawing of the ,sun is made1 #aj inches in diameter1 showing the position and outline of the spots visible4 ,it is the first duty of the assistant who makes the drawings to note the position of the spots1 and sketch their outlines4 ,he then proceeds to shade in the penumbra and to draw the finer details1 comparing the drawing from time to time by placing it alongside the projected image of the spots4 ,the position of the facul is then filled in with a red pencil1 so that the eye can at once recognize their grouping with respect to sun-spots1 and the other details drawn with a black pencil40 ,the same astronomer also stated that1 8as a general rule1 careful drawings of the projected image of the ,sun give much more satisfactory pictures of the solar surface than the photographs taken even at our best observatories4 ,it is quite true that occasionally an exquisite photograph on an enlarged scale may be obtained1 which exhibits features such as no pencil could portray as accurately1 but rarely indeed will the photograph furnish all the details that a practised eye and hand1 kept patiently at the sketch-board1 will detect and faithfully describe4 ,and the reason is not far to seek2 for any experienced observer knows that1 even on the finest day1 the definition is continually changing with the sky1 and that it is only at comparatively rare moments we can expect those perfect conditions that enable the finest details to stand out sharply1 as ,schiaparelli expresses it1 like the faintest lines of a steel engraving4 ,a photograph may be accidentally taken during one of these exceptionally favoured moments2 but a patient draughtsman is almost sure to secure several of these best opportunities at each prolonged visit to his sketch-board4 ,what would1 therefore1 be a great acquisition at present is a series of careful solar drawings1 taken at short intervals of time1 on days when characteristic spots are visible upon the ,sun2 and this would be the surest way of adding much valuable information to that already possessed concerning the changes that take place in the solar photosphere40 ,with regard to ascertaining the dimensions of sun-spots1 very precise results require accurate means of measurement and some mathematical knowledge4 ,for the general purposes of the amateur1 who will only want round numbers1 simple methods may be adopted with success4 ,i have used1 on a #d-;inch refractor1 a graduated piece of plane glass1 mounted suitably for insertion in the focus of the eyepiece1 and marked with divisions #a_/bjj of an inch apart4 ,with power #fe ,i find the ,sun's disk at max4 distance covers #hc divisions of the graduated lens2 so that one division #bbh1 the ,sun's min4 diameter being #ahib4 ,each division1 therefore1 is equal to #aj1dcd miles1 the ,sun's real diameter being #hff1jjj miles4 ,illustration3 ,fig4 #bj4 ,sun-spot of ,june #ai1 #ahhi1 #b;h ,p4,m4 ,i viewed a large spot on ,june #ai1 #ahhi1 and found its major axis covered #bf divisions1 #eici2 so that its apparent length was about #bg1jjj miles4 ,for #ahib 3 #hff1jjj miles 33 #eic 3 #bg1adc miles4 ,the same method may be adopted if the image is thrown upon a screen4 ,approximate values are to be obtained by means of fine cross wires fixed in the eyepiece4 ,note the exact interval occupied by the ,sun in crossing the vertical wire1 and also the interval occupied by the large spot or group4 ,if the ,sun is #acc seconds in passing the wire1 and the group #fe seconds1 then #acc seconds 3 #hff1jjj miles 33 #fe seconds 3 #db1cbc miles4 ,this plan is likely to be most successful when the ,sun is near its meridian passage2 but it may be applied at any hour1 if care is taken to adjust the eyepiece so that the ,sun's motion is precisely at right angles to the vertical wire4 ,one other plan may be mentioned4 ,draw on cardboard1 with compasses1 a circle about #aj or #ab inches diameter1 and divide this with #ca parallel lines4 ,subdivide each of the spaces into #e1 less prominently marked4 ,then1 during observation1 keep both eyes open1 and hold or fix the circular disk at a distance enabling it to coincide with the telescopic image of the ,sun4 ,by carefully noting how many divisions the group covers on the cardboard1 its dimensions may be readily found1 because one division will be equal to about #edaj miles4 ,of course these methods#aj are simply approximate1 and only strictly applicable to objects not far removed from the central regions of the ,sun1 because the spots are portions of a sphere1 and not angles subtended by a flat surface4 ,when close to the ,e4 or ,w4 limbs1 foreshortening is considerable1 though the polar diameter of a spot is not affected by it then4 ,presuming an observer to have his #c-or #d-;inch telescope duly fitted with a solar diagonal and tinted glass1 he may naturally ask1 after his curiosity has been satisfied by the contemplation of his first sun-spot1 what he can do further3 ,what special features is he to look for8 ,what changes ought to be recorded8 ,what are the doubtful points that require to be cleared up as regards the ,sun's physical appearance8 ,in what way are new and novel facts likely to be glimpsed8 ,in a word1 he desires to know in what manner he may employ his eyes and instrument usefully for science1 while also gaining pleasure for himself4 ,information like this is often needed by the young student1 and sometimes indeed by men who have already gained a little experience1 and who possess much larger instruments than we have intimated above4 ,in endeavouring to offer suggestions in response to such inquiries1 ,i would remark that the nature and direction of a research essentially depend upon several conditions1 viz4 the observer's inclination1 his instrumental equipment1 his place of observation1 and the amount of time he can devote to the pursuit of his object4 ,there are very few men who1 like ,schwabe of ,dessau1 will confront the ,sun on nearly every day for more than forty years in order to learn something of its secrets4 ,such extraordinary pertinacity is fortunately not required1 except in special cases4 ,amateurs may effect much valuable work in the short intervals which many of them steal either from business or domestic ties and offer at the shrine of astronomy4 ,there are quite a considerable number of attractive phenomena and features on which the solar observer will find ample employment1 and to the principal of these it may be as well to make individual references4 ,eclipses of the ,sun4--,these phenomena deservedly rank amongst the most important and impressive events displayed by the heavenly bodies1 and they are specially interesting to the possessors of small telescopes4 ,solar eclipses have been so often made the subject of observation and discussion1 that our knowledge of the appearances presented may be considered to be nearly complete4 ,the various aspects of ,nature on such occasions have been so attentively studied in their manifold bearings1 that virtually nothing remains for the ordinary observer but to reexamine and corroborate facts already well ascertained4 ,he can expect to glean few materials in a field where a plentiful harvest has just been reaped4 ,but the eclipsed ,sun1 if it has revealed most of its secrets to previous investigators1 has certainly not declined in attractiveness2 and the amateur will find the spectacle still capable of exhibiting features which1 though not full of the charms of novelty1 will be sufficiently striking and diversified to be remembered long after the event has passed4 ,illustration3 ,fig4 #ba4 #ahia1 ,june #f4 #ahii1 ,june #h4 #aijj1 ,may #bh4 #aije1 ,aug4 #cj4 #aijh1 ,june #bh4 #aiab1 ,april #ag4 #aiad1 ,aug4 #ba4 #aiaf1 ,feb4 #c4 ,at sunset4 #aiai1 ,nov4 #bb4 #aibj1 ,nov4 #aj4 #aiba1 ,april #h4 #aibb1 ,march #bh4 ,at sunset4 ,at sunset4 ,solar ,eclipses visible in ,england1 #ahia to #aibb4 ,illustration3 ,fig4 #bb4 ,total ,solar ,eclipse of ,august #ai1 #ahhg4 ,eclipses recur in cycles of #ah years and #aj days 7 #fehe days74 ,this period was determined by the ancients1 and called the saros4 ,by its means the times and magnitudes of eclipses were roughly computed long before astronomy became an exact science4 ,a solar eclipse is really an occultation of the ,sun by the ,moon2 for the word eclipse1 in its usual reference1 denotes the obscuration of one body by its immersion in the shadow of another4 ,during any single year there are never less than two eclipses1 nor more than seven4 ,whenever there are two only1 both are solar4 ,since the fine solar eclipse of ,december #bb1 #ahgj1 no large eclipse of the ,sun has been visible in ,england4 ,it is remarkable that during the thirty years from #ahgj to #aijj these phenomena are all of an unimportant1 minor character4 ,within the thirty years following #ahia there will be twelve solar eclipses1 for which the ,rev4 ,s4 ,j4 ,johnson has given projections 7as shown on p4 #ih7 for the period of greatest obscuration4 ,total eclipses are extremely rare as regards their visibility at a given station4 ,thus between #hgh and #agae not one was observed at ,london1 and during the next #ejj years there will be a similar absence of such a phenomenon4 ,the observer of total eclipses must perforce journey to those particular tracts of the earth's surface over which the band of totality passes4 ,on such occasions photography plays an important part2 and the corona1 the red flames1 the shadow-bands1 and numerous other features become the subjects of necessarily hurried observation and record1 for totality endures for very few minutes#aa4 ,as regards ordinary partial eclipses1 amateurs usually find ample entertainment in noting the serrated aspect of the ,moon's contour projected on the bright ,sun4 ,it is also interesting to watch the disappearance and reappearance of the solar spots visible at the time4 ,rather a low magnifying power1 with sufficiently expansive field to include the entire disk1 is commonly best for the purpose of these observations4 ,periodicity of ,spots4--,this detail may be said to have been fully investigated4 ,schwabe and ,wolf have accomplished much in this direction4 ,a work of this kind must1 by the nature of it1 extend over many years and entail many thousands of observations4 ,it is therefore more suited to the professional astronomer than to the amateur1 whose attention is more or less irregular owing to other calls4 ,the sun-spot cycle is one of about #aa years1 during which there are alternately few and many spots on the ,sun4 ,there appear to be some curious fluctuations1 disturbing the regular increase and decrease in the number of spots2 and these variations are worthy of more attention4 ,the following are the years of observed maxima and minima of sun-spot frequency3-- ,maxima4 ,minima4 #ahbh4 #ahcc4 #ahcg4 #ahdc4 #ahdh4 #ahed4 #ahfj4 #ahfg4 #ahgj4 #ahgh4 #ahhc-d4 #ahij 7874 ,these phenomena have been rare during the past few years4 ,the next maximum may be expected in about #ahid1 when solar observers will probably have an abundance of new materials to study4 ,crateriform ,structure4--,in #agfi ,prof4 ,wilson1 of ,glasgow1 while watching a sun-spot with a ,gregorian reflecting-telescope1 remarked that1 as it approached near the limb1 the penumbra became much foreshortened on the interior side4 ,he inferred from this that the spots were cavities1 and the idea has been generally accepted2 so that these objects are sometimes termed solar craters1 and commonly regarded as openings in the luminous atmosphere of the ,sun4 ,but the conclusion appears to be based on data not uniformly supporting it4 ,in #ahhf the ,rev4 ,f4 ,howlett published some observations which 8entirely militate against the commonly received opinion that the spots are to any extent sunk in the solar surface as to produce always those effects of perspective foreshortening of the inner side of the penumbra 7when near the limb7 which have been described in various works on astronomy40 ,in a number of instances the penumbra is wider on the side nearest the ,sun's centre1 whereas the converse ought to be the case on the cavity theory4 ,the fine sun-spot of ,july #ahhi offered an example of this2 for when it was near the ,w4 limb the ,w4 side of the penumbra was obviously much narrower than the ,e4 side1 so that the appearance would indicate the object as an elevation rather than a depression4 ,the observer should keep a register of the aspect of all pretty large spots near the limb1 and note the relative widths of the ,e4 and ,w4 sides of the penumbra4 ,an extensive table of such results would be interesting1 and certain to throw some light on the theory of spot-structure4 ,it is of course possible that occasionally the inner side of the penumbra is broader than the outer1 and thus appears wider even on the limb1 though really forming the side of a shallow depression4 8,willow-,leaves40--,in #ahfa the late ,mr4 ,nasmyth announced that the entire solar surface was composed of minute luminous filaments in the shape of 8willow-leaves10 which interlaced one another in every possible variety of direction4 ,this alleged discovery only met with doubtful corroboration4 ,the objects were stated by some authorities to be simply identical with the 8corrugations0 and 8bright nodules0 of ,sir ,w4 ,herschel4 ,mr4 ,stone called them 8rice-grains40 ,the eagle-eyed ,dawes thought 8granulations0 a more appropriate term1 as it implied no consistency of form and size4 ,secchi referred to them as oblong filaments1 and 8rather like bits of cotton-wool of elongated form40 ,the ,rev4 ,f4 ,howlett described the ,sun as presenting a granulated1 mottled appearance in a #c-;inch ,dollond refractor1 and mentioned that on the morning of ,june #i1 #ahfe1 the aspect of its surface was like that of new-fallen snow1 the objects 8being not rounded but sharply angular40 ,the opinions of observers were thus singularly diverse1 and the result of several animated discussions at the ,royal ,astronomical ,society was that little unanimity was arrived at1 except as to the fact that the ,sun's surface was crowded with small luminous filaments of elongated form1 and either rounded or angular at the ends4 ,there was no accord as to their precise forms or distinctive manner of grouping4 ,some of the observers averred that the 8willow-leaves0 or 8rice-grains0 had no title whatever to be regarded as a new discovery1 the same appearances having been recognized long before4 ,gradually the contention ceased1 and though more than a quarter of a century has passed since the discussion arose there has been little new light thrown on the subject4 ,amateurs will therefore do well to probe deeper into this promising branch of solar observation4 ,as ,mr4 ,nasmyth himself stated1 considerable telescopic power is required1 combined with a good atmosphere4 ,but comparatively small instruments will also be useful1 because of their excellent definition and efficacy in displaying details on a brilliant orb like the ,sun4 ,a power of #aej should be employed in examining small regions of the general surface1 and also the edges of the umbra and penumbra of sun-spots4 ,when definition is unusually sharp1 and the details very distinct1 the magnifying power should be increased if it can be done with advantage2 and the observer should utilize an occasion like this to the utmost extent4 ,on a really excellent day more may be sometimes detected than during several weeks when the atmosphere is only moderately favourable4 ,the observations1 being of a critical nature1 should not be attempted in winter1 when the ,sun is low4 ,i have frequently secured fine views of the delicate structure of the solar surface between about #h and #i ,a4,m4 in the summer months2 and this is often a convenient time for amateurs to snatch a glimpse1 before going to business4 ,with reference to the general question as to the existence of the 8willow-leaves10 my conception of the matter is that the features described by ,mr4 ,nasmyth are not new4 ,his drawing of a spot in ,sir ,j4 ,herschel's #8,outlines' and ,chambers's #8,descriptive ,astronomy' exhibits objects extremely uniform in shape and size1 and this uniformity ,i have never observed in the penumbra of spots4 ,as to the engraving in the #8,outlines1' showing the aspect of the interlaced 8willow-leaves0 on the general surface1 this is also not realized in observation4 ,the 8corrugations0 and 8bright nodules0 of ,sir ,w4 ,herschel aptly represent what is seen1 and they are possibly identical with the 8very small bright and obscure points0 and 8lively and sombre streaks0 of ,scheiner1 though seen much better and in more profusion of detail through the improved modern telescopes4 ,the so-called 8willow-leaves0 are rounded at the ends1 and are consistent neither in size nor shape4 ,they encroach upon the umbra of the spots1 and give a thatched appearance to the edges4 ,the penumbra also shows this in its outer limits1 where it is also fringed with lenticular particles4 ,drawings by ,capocci and ,pastorff seventy-five years ago1 and published in ,arago's #8,popular ,astronomy1' show the thatching at the edges of the umbra quite as palpably as it is represented in recent drawings4 ,illustration3 ,fig4 #bc4 ,belts of ,sun-spots1 visible ,october #bi1 #ahfh4 ,rotation of the ,sun4--,by noting when the same individual spots return to the same relative places on the disk1 the approximate time of rotation is easily deduced4 ,this varies according to the latitude of the spots#ab2 whence it is evident the solar atmosphere is affected by currents of different velocities1 causing the spots to vary in their longitudes with reference to each other4 ,the ,earth's motion round the ,sun causes the spots to travel apparently more slowly than they really do2 for observations prove that a spot completes a rotation in #bg days #e hours1 whereas the actual time1 after making allowance for the earth's orbital motion1 is about #be days #g-c_/d hours4 ,the period of rotation may be roughly found as follows1 supposing a spot to return to precisely the same part of the disk in #bg days #e hours3-- #cfe;d #e;h #dim #bg;d #e;h #cib #aj;h #dim4 ,then #cib;d #aj;h #dim 7 #efe1abim7 3 #cfe;d #e;h #dim 7 #ebe1idim7 33 #bg;d #e;h 7 #ci1ahjm7 3 #be;d #g;h #ddm 7 #cf1dfdm74 ,for exact results several circumstances have to be considered1 such as the direction of the spot-motions across the disk1 as the chords vary according to the season2 thus in ,june and ,december the spots traverse straight lines1 while in ,march and ,september their paths are curved1 like a belt on ,saturn when the planet is inclined4 ,some of the spots display considerable proper motion2 so that it is best to observe a number of these objects1 and reduce the times to a mean result4 ,they are not very durable1 rarely lasting longer than a few weeks2 but some of the more extensive disturbances are sustained for several months1 during which many singular changes are effected4 ,the period of rotation1 as determined by several observers1 is as follows3-- d h m #afgh4 ,cassini #be #ac #ee #agah4 ,bianchini #be #g #dh #agge4 ,delambre #be #j #ag #ahda4 ,laugier #be #h #aj #ahdf4 ,kysus #be #b #aj #aheb4 ,bhm #be #ab #bi #ahfc4 ,carrington #be #i #g #ahfe4 ,schwabe #be #e #j #ahfh4 ,sprer #be #e #ca #ahhh4 ,wilsing #be #e #dg ,the motion of rotation is similar in direction to that in which the planets move found the ,sun1 namely from west to east4 ,hence the spots come into view on the east limb of the ,sun1 and disappear at the west4 ,planetary ,bodies in transit4--,during observation the observer should particularly watch any very dark1 small spots that may be visible1 such as are isolated and pretty circular and definite in outline4 ,if an object of this character is seen it should be examined with a high power1 and its aspect critically noted4 ,should the observer entertain any suspicion of its being of a planetary nature1 he should carefully determine its position on the disk1 and1 after a short interval1 re-observe it for traces of motion4 ,if it remains stationary1 its true solar origin will be proved4 ,if motion is shown1 then the successive positions of the object during its transit1 and its place of egress1 with the time of each observation1 should be recorded4 ,in such a case it would be a good plan to project the ,sun's image1 and mark the place of the suspicious object and chief sun-spots at short intervals4 ,this would be more accurate than mere eye-estimation4 ,the observer who scans the solar surface for intra-,mercurial planets must remember that1 if any such bodies exist1 they will probably be very diminutive4 ,venus1 when on the ,sun in ,december #ahhb1 was a spot #fc in diameter1 and easily perceptible to the naked eye4 ,mercury1 at the transits of #ahfa1 #ahfh1 and #ahha1 was a little less than #aj1 but in #ahgh was #ab4 ,if 8,vulcan10 the suspected interior planet1 has any existence it may possibly be much smaller than ,mercury1 and will thus escape observation1 unless the observer exercises great care in the search4 ,the mobile1 planetary spots asserted to have been seen on the ,sun in past years prove nothing definite1 and appear to have been illusory4 ,proper ,motion of ,sun-spots4--,this feature is one deserving more investigation4 ,the distances separating individual spots should either be measured with a micrometer or determined by transits across a wire1 and the displacement recorded from hour to hour or from day to day4 ,spots in different latitudes will almost certainly exhibit some change of relative place2 and objects in the same latitude must be watched1 for similar variations probably affect them4 ,the physical peculiarities of such spots should be remarked1 and also the alterations of appearance they undergo during the time they approach or recede from each other4 ,rise and ,decay of ,spots4--,occasionally large spots are formed in an incredibly short time1 and the disappearance of others has been equally sudden4 ,schwabe found1 from many observations1 that the western spots of a group are obliterated first2 but authorities differ4 ,i have usually observed that the smaller1 outlying members of a group vanish before the larger spot1 which then contracts and is invaded by tongues of facul2 so that its effacement soon follows1 and nothing remains to indicate the disturbance but bright ridges of facul1 which are very conspicuous near the limb4 ,black ,nuclei in the ,umbr4--,dawes was the first to announce that the umbra sometimes included a much darker area or nucleus4 ,this is present in nearly all large spots4 ,a part of the umbra seems covered or veiled by a slightly luminous medium1 and the portion unaffected looks black by contrast4 ,on ,october #a1 #ahha1 with a #b-;inch refractor1 ,i saw a large sun-spot1 the umbra of which was broken up into #g fragments1 and the ,s4 preceding part appeared very black while the others showed a much lighter tint4 ,in the fine spot of ,june #ahhi a nucleus was also distinctly apparent2 and this feature is sometimes so obvious in large spots that it may be observed with an instrument of only #b-;inches aperture4 ,i have usually remarked the nucleus on one side of the umbra1 and abutting the penumbra4 ,it may be formed by light patches of transparent material floating over the umbra1 and leaving a part free where the ,sun's dark body is fully exposed4 ,this light material is possibly suspended far above the umbra and inconstant in its position2 so that the place and form of the nucleus should always be noted for traces of change4 ,it is necessary that such details should be closely watched during an entire day1 or several days2 for the variations could then be followed1 and perhaps reduced to some law4 ,this persistence is very necessary1 in order to solve many of the peculiarities of sun-spots1 which1 though pretty well known in appearance1 have not been thoroughly studied in their various developments4 ,bright ,objects near the ,sun4--,small1 rapidly moving bodies have been occasionally reported as seen passing over the ,sun4 ,in several cases these have been prematurely assigned a meteoric origin4 ,they have been described as luminous bodies of irregular shape1 as moving in a common direction1 and as being very distinct when projected on the dark sky just outlying the bright limb of the ,sun4 ,there is little doubt they are either the pappus of different kinds of seed1 or convolutions of gossamer1 which have been lifted to great heights in the air1 and are rendered bright by reflection from the bordering ,sun4 ,in this connection ,i may mention some observations of my own with a #d-;inch refractor3-- 8#ahhi1 ,,may #bj1 #j;h #cjm ,p4,m4--,bright points and little misty forms kept passing from the ,sun's limb1 at the average rate of #ac in a minute4 ,they moved in the same direction as the clouds and wind4 ,some of them were followed by tails1 which were far from straight4 ,i saw them best when ,i focused the telescope for an object much nearer than the ,sun4 ,one of these forms would occasionally halt and pursue an irregular flight4 ,it was evident they were terrestrial objects1 with motions controlled by the wind4 8#c;h ,p4,m4--,many bright objects still passing from the ,sun's limb40 8#ahhi1 ,,may #bb1 #i;h ,a4,m4--,observed vast numbers of luminous particles floating about contiguous to the ,sun's margin4 ,they were clearly carried along by the wind2 but this being very slight1 their motions were extremely slow1 and now and then many of them became nearly stationary4 ,their directions were far from uniform1 though the general tendency was obviously in a common line of flight4 ,i watched them for some time passing in a plentiful shower40 ,these objects are always noticed in summer-time1 and ,i believe they would much more frequently attract remark but for the fact that they require a longer focus than the ,sun and cannot be recognized when on the disk1 to which the observer is usually giving the whole of his attention4 ,those who are often employed in solar work will find it an interesting diversion to look for these bodies4 ,the instrument should be focused as for a distant terrestrial object1 and only a part of the ,sun's limb should be retained in the field of view of an eyepiece of moderately low power4 ,then1 looking intently at the dark sky near the limb1 the bright objects will be sometimes seen sailing past in considerable numbers4 ,cyclonic ,action4--,the appearance in detail of certain spots1 coupled with evidences of rotatory motion round their own centres1 has induced the belief that they are liable to action in some degree similar to the cyclonic storms#ac which disturb and rend the terrestrial atmosphere4 ,such indications should be looked for in fairly conspicuous spots1 and any peculiarities of the nature alluded to made the subject of close investigation4 ,a spot showing features having a spiral tendency may not1 however1 have a gyratory movement about its centre4 ,this can only be determined by critically noting the details1 and frequently reobserving them for traces of motion4 ,the penumbra always shows radiations converging on the umbra as a centre2 but this is merely a form of structure1 and proves nothing in evidence of a revolving storm4 ,sudden ,outbursts of ,facul4--,in ,september #ahei ,carrington and ,hodgson independently observed a striking outburst of facul in front of a large group of spots which they were examining4 ,it remained visible about five minutes1 during which interval several patches of light travelled over a region nearly #cd1jjj miles in extent4 ,an extraordinary magnetic disturbance was simultaneously recorded at the ,kew ,observatory1 and sixteen hours afterwards there followed a magnetic storm of unusual severity4 ,on another occasion ,dr4 ,peters observed flashes of light cross and recross the umbra of a prominent spot with electric velocity4 ,some other startling observations of solar phenomena have been effected1 and there is no question as to their having been matters of fact4 ,in the presence of effects so sudden1 so obvious1 and so unexpected1 no wonder the observers at first doubted the evidence of their eyes and suspected the cause to lie in a fractured glass or a fault of adjustment4 ,but the corroboration afforded the clearest proof as to the actuality of the events described4 ,they will doubtless occur again2 but these phenomena cannot be definitely predicted as to time1 so that students of the solar surface should be prepared for a repetition of them whenever they may occur4 ,illustration3 ,fig4 #bd4 ,shadows cast by ,facul4--,m4 ,trouvelot1 while examining a large sun-spot on ,may #bf1 #ahgh1 noticed that it was 8completely surrounded by very brilliant and massive facul40 8,on one part of the penumbra an extraordinary appearance was perceived1 which resembled so closely a shadow1 as it would have been cast by the overhanging faculous mass1 that it seemed useless to seek1 and it was impossible to admit1 any other explanation4 ,this shadow1 the outline of which was a little diffused1 had the same shape as1 and reproduced with great exactness1 the outline of the faculous mass situated above it4 ,it was not so black as the opening in spots called the umbra1 but of a very dark tint40 ,a similar feature was seen by ,kirk and ,maclean on ,may #b1 #ahhd1 and the #8,observatory1' vol4 vii4 pp4 #adf1 #agj1 and #aig1 contains some interesting particulars on this subject4 ,fig4 #bd is a drawing by ,kirk1 in which the shadow is represented by ,a1 ,b2 at ,c 8it accurately followed the outline of the intensely white margin of the spot40 ,veiled ,spots4--,the late ,father ,perry described these objects at the ,r4,a4,s4 meeting on ,may #i1 #ahhd1 and said they are to be seen all over the face of the ,sun4 ,they only exist for two or three minutes1 and then disappear4 ,in one instance he observed a train of these veiled spots stretching over 8a tenth part of the ,sun's diameter1 which was nearly as obvious to the eye as the penumbra of an ordinary spot2 it split into two throughout its whole length1 and disappeared in a minute4 ,the veiled spots seem to be of two classes3 the one appear like small greyish clouds1 which disappear after a few minutes1 as if they were formed and rapidly evaporated by the ,sun's heat1 and the others seem to be connected with the umbra of ordinary spots2 they appear about them1 and are more permanent than the ordinary veiled spots1 lasting sometimes two or three days1 but never longer40 ,these markings appear to have been first detected by ,trouvelot in #ahge1 and he gives some information as to this class of phenomena in the #8,observatory1' vol4 viii4 pp4 #bbh et seq4 ,recurrent ,disturbances#ad4--;,it is supposed1 and with good evidence affirming the idea1 that certain regions of the ,sun's surface are subject to frequent outbursts of spots1 which are possibly due to forces acting from below the ,sun's bright atmosphere4 ,after the disappearance of large groups or isolated spots it is therefore advisable to watch the same region for some time afterwards1 to find whether it remains perfectly quiescent1 or whether it soon again becomes a seat of activity and change4 ,recurrent ,forms4--,certain spots observed at different times have exhibited appearances so nearly resembling each other that it has been considered the likeness may be due to something more than mere accident4 ,whenever such suggestive coincidences are recognized the observer should note them particularly1 and secure drawings4 ,it should be his aim to determine the exact intervals elapsing between the presentation of spots or groups of this character1 and also whether they occupy the same latitude and longitude on the ,sun's disk4 ,exceptional ,position of ,spots4--,the ordinary spots are rarely seen more than #ce distant from the solar equator or within #h of it4 ,they usually appear in the zones from #h to #bj ,n4 and ,s4 of the equator4 ,a few exceptions may be mentioned#ae4 ,mechain saw a spot in ,july #aghj having a latitude of #dj-a_/c2 in ,april #ahbf ,capocci recorded one having #di of ,s4 latitude2 ,schwabe and ,peters observed spots #ej from the equator4 ,lahire1 in the last century1 described a spot as visible in a latitude of #gj2 but the accuracy of this observation has been questioned4 ,whenever a spot is seen near the equator1 or very far removed from it1 measures should be taken of its exact place2 for it is desirable to learn something more of those disturbances which occasionally affect the more barren regions of the solar envelope4 ,the ,solar ,prominences4--,those amateurs who have included a spectroscope in their instrumental outfit will find the study of the chromosphere and prominences a most productive one4 ,huggins and ,zllner were the first to apply the 8open-slit0 method2 and the study of the shape of the hydrogen prominences commenced in #ahfi4 ,tupman details 7#8,monthly ,notices ,r4,a4,s41' vol4 xxxiii4 p4 #ajf7 a series of observations which he secured in #ahgb with a refractor of #c-;inches aperture and a direct-vision spectroscope of five prisms4 ,he mentions the cost of the entire apparatus as only #ah1 and says he entertains 8no doubt that an equally effective instrument could be made for much less40 ,the prominences appear to be of different kinds1 and are known as 8cloud0- and 8flame0-prominences4 ,both are liable to rapid changes4 ,trouvelot1 in ,june #ahgd1 noticed 8a gigantic comma-shaped prominence1 #hb1jjj miles high1 which vanished from before his eyes by a withdrawal of light as sudden as the passage of a flash of lightning40 ,since the study of these remarkable forms was rendered feasible by using a greater dispersion to open the slit of the spectroscope wide enough to see them1 they have been made the subject of daily study and record4 ,the results1 so far as they have been investigated1 show that the region of the ,sun's limb in which the prominences are most frequent reaches to some #dj on either side of the equator1 which is somewhat greater than the area of sun-spot frequency4 ,the chromosphere itself is probably of much the same character as the erupted prominences1 and formed of little flames arranged thickly together like 8blades of grass40 ,in observing the ,sun with a telescope the amateur will soon notice that the surface is far more brilliant in the central parts than round the margin of the disk4 ,vgel has estimated that immediately inside the edges the brightness does not amount to one seventh that of the centre4 ,the difference is entirely due to the solar atmosphere1 which is probably very shallow relatively to the great diameter of the ,sun4 ,,footnotes3 #i ,the ,rev4 ,f4 ,howlett measured this spot on the following day1 ,june #bj1 and found it #fc in its largest diameter4 ,he used a small refractor1 and projected the ,sun's image on to a screen sufficiently distant for it to have a diameter of #c feet4 #aj ,on ,may #ac1 #ahij1 at #c;h1 ,i tested the three methods alluded to on a scattered train of small spots1 and derived the following measurements of length3-- ,by glass micrometer #gf1egj miles4 cross wires #gf1faj cardboard disk #ge1ggj ,in this comparison ,i used an excellent #d-;inch ,cooke refractor1 belonging to a friend4 #aa ,the maximum duration of totality1 under every favouring circumstance1 appears to be about #h minutes4 ,the great eclipse which occurred on ,august #ah1 #ahfh1 maintained the total phase for nearly #f minutes #ej seconds in the ,gulf of ,siam4 ,in reference to this eclipse1 ,dr4 ,weiss says3--8,in the records of ancient eclipses there are to be found only two which may be compared in size with that of ,august #ah1 #ahfh1 but none in which the totality lasted so long4 ,the first of these is the eclipse of ,thales 7#bh ,may1 #ehe ,b4,c471 which is said to have been the first predicted1 and to have terminated a bloody war between the ,lydians and the ,medes4 ,the second was visible on ,june #ag1 #adcc1 in ,scotland1 and the time of its occurrence was long remembered by the people of that country as #8the black hour4'0 #ab ,carrington found that spots near the equator gave a shorter rotation-period than those far removed from it4 ,this offers an analogy to the spots on ,jupiter1 which move with greater celerity near the equator1 though the rule is not absolute4 #ac ,in #aheb ,dawes observed and measured a rotatory motion affecting a spot at the rate of about #ag per day4 #ad ,lalande1 in #aggh1 asserted that 8there are spots of very considerable magnitude1 which1 reappear in the same physical points of the solar disk40 #ae ,a spot was visible on ,june #cj1 #ahhi1 in #dj ,south latitude4 ,its recorded duration was #b days4 ,this object was observed at the ,stonyhurst ,observatory and at a station in ,north ,america4 ,,chapter ,,vi4 ,,the ,,moon4 ,attractive aspect of the ,moon4--,absence of air and water4--,only one ,hemisphere visible4--,earthshine4--,telescopic observations of the lunar surface4--,eclipses4--,lunar changes4--,formations4--,plato and other objects described4--,table of ,moon's age and formations near terminator4--,occultations of stars4--,visibility of the new ,moon4 8,the western ,sun withdraws3 meanwhile the ,moon1 ,full orb'd1 and breaking through the scatter'd clouds1 ,shows her broad visage in the crimson'd east40 ,early in autumn1 when the evenings are frequently clear1 many persons are led with more force than usual to evince an interest in our satellite1 and to desire information which may not be conveniently obtained at the time4 ,the aspect of the ,moon at her rising1 near the time of the full1 during the months of ,august1 ,september1 and ,october1 is more conspicuously noticeable than at any other season of the year1 on account of the position she then assumes on successive nights1 enabling her to rise at closely identical times for several evenings together4 ,the appearance of her large1 ruddy globe at near the same hour1 and her increasing brilliancy as her horizontal rays give way under a more vertical position1 originated the title of 8,harvest ,moon10 to commemorate the facility afforded by her light for the ingathering of the corn preceding the time of the autumnal equinox4 ,it will be universally admitted that the ,moon possesses special attractions for us1 as being situated nearer than any other celestial body1 and forming the inseparable companion or tributary world to the ,earth4 ,the many important influences she exercises have led to her becoming the object of close investigation2 so that her motions and physical appearances have been ascertained with a remarkable degree of exactness and amplitude4 ,her movements regulate the tides2 her positions are of the utmost moment to the mariner2 her light is the welcome beacon of the wayfarer1 and its picturesque serenity has ever formed the theme of poets4 ,to the practical astronomer she constitutes an orb perfectly unique as regards extent and variety of detail2 and questions relating to the physical condition of her surface1 now and in past ages1 supply a fund of endless speculation to the theorist4 ,the mean apparent diameter of the ,moon is #ca #e1 and it varies from #bi #ba at perigee to #cc #ca at apogee4 ,her real diameter is #bafj miles1 and her mean distance slightly exceeds #bcg1jjj miles4 ,her revolution round the ,earth 7 sidereal period7 is performed in #bg;d #g;h #dcm #aas#df1 but the time from one new moon to another 7 synodical period7 is #bi;d #ab;h #ddm #cs4 ,the ,moon's motion through the firmament is at the rate of #ac #aj #ce per day and #cb #ef per hour4 ,thus she travels over a space slightly exceeding her own diameter in one hour4 ,the linear value of #a at the distance of our satellite is #aaf mile1 and of #a #fi miles4 ,when we critically survey the face of the ,moon with a good telescope1 we see at once that her surface is broken up into a series of craters of various sizes1 and that some very irregular formations are scattered here and there1 which present a similar appearance to elevated mountain-ranges4 ,the crateriform aspect of the ,moon is perhaps the more striking feature1 from its greater extent2 and we recognize in the individual forms a simile to the circular cavities formed in slag or some other hard substances under the action of intense heat4 ,in certain regions of the ,moon1 especially those near the south pole1 the disk is one mass of abutting craters1 and were it not for the obvious want of symmetry in form and uniformity of size1 the appearance would be analogous to that of a gigantic honeycomb4 ,these craters are commonly surrounded by high walls or ramparts1 and often include conical hills rising from their centres to great heights4 ,while the eye examines these singular structures1 and lingers amongst the mass of intricate detail in which the whole surface abounds1 we cannot but feel impressed at the marvellous sharpness of definition with which the different features are presented to our view4 ,it matters not to what district we direct our gaze1 there is the same perfect serenity and clearness of outline4 ,not the slightest indication can be discerned anywhere of mist or other obscuring vapours hanging over the lunar landscape4 ,absence of ,air and ,water4--,now it is palpable from this that the ,moon has no atmosphere of sufficient density to render itself appreciable2 for such an appendage1 if it existed in any visible form1 would at once obtrude upon the attention1 and we should probably recognize some of the characteristics common to the behaviour of our terrestrial clouds4 ,but nothing of the kind is apparent on the ,moon3 there is an unbroken transparency spread over the whole extent of the ,moon's scenery2 whence we conclude that if any air exists on the surface it is of extremely attenuated nature1 and possibly confined to the bottom of the craters and low-lying formations1 which are arranged in such prolific manner on our satellite4 ,nor is there any perceptible intimation of water upon the ,moon4 ,it is true that several dark grey patches have been given names1 leading one directly to the inference that lakes and seas comprise part of the surface phenomena4 ,thus there is the ,mare ,serenitatis 78the sea of serenity07 and many other designations of similar import1 which we cannot but insist are wrongly applied and calculated to lead to misapprehension4 ,before the invention of the telescope furnished us with the means of accurately determining the character of the lunar features1 such apellations may have been considered eligible2 but now that the non-existence of water in any extensive form is admitted1 the titles are rendered obsolete4 ,still their retention is in some respects advisable1 for any sweeping change in a recognized system of nomenclature must cause confusion1 and the names alluded to serve a useful end in facilitating reference2 so that1 under the circumstances1 it would perhaps be unwise to attempt reform1 or to introduce an innovation which must occasion many difficulties4 ,only one ,hemisphere visible4--,in discussing the nature and appearances of the lunar formations1 it must be distinctly understood that our remarks apply to those visible on the side invariably turned towards the ,earth4 ,for1 in point of fact1 there is a considerable expanse of the lunar disk never perceptible from the ,earth at all4 ,this is occasioned by the circumstance that the ,moon rotates upon her axis in precisely the same time as she revolves around the ,earth1 and is therefore enabled to present the same side towards us on all occasions4 ,a slight tilting 7called libration7 takes place1 so that we are allowed a glimpse of fragments of the side normally invisible1 and its analogous aspect leads us to suppose that there is no great distinction between the features of the ,moon's visible and invisible hemispheres4 ,from exact computations it appears that we are enabled to see a proportion of #ei_/ajj of the surface1 and that the remaining #da_/ajj are permanently beyond our reach4 ,earthshine4--,a few mornings before new moon1 and on a few evenings after it1 the whole outline of the dark portion of the lunar globe may be distinctly perceived4 ,a feeble illumination like twilight pervades the opaque part1 and this is really earthlight thrown upon our satellite1 for near the times of new moon the ,earth appears at her brightest 7her disk being fully illuminated7 as seen from the ,moon4 ,the ,french term for this light is la lumire cendre1 or 8the ashy light40 ,the appearance is often popularly referred to in our own country as 8the old ,moon in the new ,moon's arms40 ,some of the old observers remarked that the waning ,moon showed this earthlight more strongly than the new ,moon4 ,telescopic ,observations of the ,lunar ,surface4--,our telescopes give by far the most pleasing view of the ,moon when she is in a crescent shape4 ,at such a period the craters and mountains1 with their dark shadows1 are splendidly displayed4 ,a good view is also obtainable with the ,moon at first or last quarter1 or when the disk is gibbous4 ,but the full ,moon is decidedly less attractive2 for the shadows have all disappeared1 and the various formations have quite lost their distinctive character4 ,the disk is enveloped in a flood of light1 causing glare1 and though there is a large amount of detail1 including systems of bright rays1 many differences of tint1 and bright spots1 yet the effect is altogether less satisfactory than at the time of a crescent phase4 ,the nature of the work undertaken by the amateur must largely depend upon his opportunities and the capacity of his appliances4 ,it is evident that in the investigation of lunar details it is essential to be very particular in recording observations2 for unless the conditions of illumination are nearly the same1 lunar objects will present little resemblance4 ,he should therefore examine the formations at intervals of #ei;d #a;h #bhm1 when the terminator is resting on nearly identical parts of the surface4 ,in periods of #ddb;d #bc;h 7 #ae lunations7 there is another repetition of similar phase2 also in periods of #ejb;d #j;h #bhm 7 #ag lunations74 ,the observer1 in entering results into his note-book1 should state the ,moon's age to the nearest minute1 and give aperture and power of telescope and state of sky4 ,those objects which he has recorded at one lunation should be re-observed after an intervening lunation1 or at intervals of #ei;d #a;h #bhm4 ,he will then find his notes and drawings are comparable4 ,by the persistent scrutiny of special structures he will discern more and more of their details2 in other words1 he will find his eye soon acquires power with experience and familiarity with the object4 ,comparisons of his own work with the charts and records of previous observers will be sure to interest him greatly1 and the differences which he will almost certainly detect may exert a useful influence in inciting him to ascertain the source of them4 ,he must not be premature in attributing such discordances to actual changes on the ,moon2 for he must remember that perfect harmony is rarely to be found in the experiences of different observers4 ,but whenever his own results are inconsistent with those of others1 the fact should be carefully noted and the observations repeated and rediscussed with a view to reconcile them4 ,the charts and descriptions of former selenographers are excellent in their way1 and the outcome of much zealous labour2 but they contain omissions and inaccuracies which it has been impracticable to avoid4 ,the amateur who discovers a mountain1 craterlet1 or rill not depicted on his lunar maps must therefore neither regard it as a new formation or as a new discovery2 for it may have been overlooked by some of the previous observers1 and is possibly drawn or described in a work which he does not happen to have consulted4 ,such differences should1 however1 always be announced1 as they clear the way for others working in the same field4 ,a small instrument1 with an object-glass of about #b inches1 will reveal a large amount of intricate detail on the surface of our satellite1 and will afford the young student many evenings of interesting recreation4 ,but for a more advanced survey of the formations1 with the view to discover unknown objects or traces of physical change in known features1 a telescope of at least #h or #aj inches aperture is probably necessary1 and powers of #cjj1 #cej1 and more4 ,eclipses of the ,moon4--,these phenomena comprise a variety of interesting aspects4 ,they are less numerous1 in actual occurrence1 than solar eclipses in the proportion of about #b to #c2 but they are more frequently visible1 because they may be witnessed from any part of an entire hemisphere1 whereas eclipses of the ,sun are only observable from a tract of the ,earth's surface not exceeding #ahj miles in breadth4 ,the ,moon may remain totally eclipsed for a period of #b hours #d minutes1 and the whole duration1 including the penumbral obscuration from its first to its last projection1 is about #f hours4 ,sometimes the ,moon suffers total eclipse twice in the same year1 and both may be visible1 as in #ahdd1 #ahgg1 #aifd1 c4 ,it is possible for three such eclipses to occur within a single year1 as in #aedd4 ,in #aiag there will be three total lunar eclipses1 but not all visible in ,england4 ,in the latter year there will be no less than seven eclipses1 as in #aice4 ,on the last two occasions--,oct4 #d1 #ahhd1 and ,jan4 #bh1 #ahhh--when the ,moon was totally immersed in the ,earth's shadow1 the atmosphere was very clear2 and it is hoped equally favourable conditions will attend the similar phenomena of ,nov4 #ae1 #ahia1 ,sept4 #d1 #ahie1 and ,dec4 #bg1 #ahih4 ,one of the most interesting features during these temporary obscurations of our satellite is the occultation of small stars4 ,prof4 ,struve compiled a list of no less than #aaf of these objects that would pass behind the ,moon's shadowed limb during the eclipse of ,oct4 #d1 #ahhd4 ,another important effect is the variable colouring on the ,moon4 ,this differs considerably in relative intensity as seen during successive eclipses1 and the cause is not perhaps fully accounted for4 ,kepler thought it due to differences in humidity of those parts of the ,earth's atmosphere through which the solar rays pass and are refracted to the eclipsed ,moon4 ,the intense red hue which envelopes the lunar surface on such occasions is due to the absorption of the blue rays of light by our atmosphere4 ,the sky at sunset is often observed to be similarly coloured1 and from the operation of similar causes4 ,sometimes the ,moon entirely disappears when eclipsed1 but on other occasions remains distinctly obvious1 like a bright red ball suspended in the firmament4 ,on ,may #e1 #aaaj1 ,dec4 #i1 #afbj1 ,may #ah1 #agfa1 and ,june #aj1 #ahaf1 our satellite is said to have become absolutely imperceptible during eclipse4 ,wargentin1 who described the appearance in #agfa1 remarks3--8,the ,moon's body disappeared so completely that not the slightest trace of any portion of the lunar disk could be discerned1 either with the naked eye or with the telescope40 ,on ,oct4 #d1 #ahhd1 ,i noticed that the opacity was much greater than usual2 at the middle period of the eclipse the ,moon's diameter was apparently so much reduced that she looked like a dull1 faint1 nebulous mass1 without sharply determinate outlines4 ,the effect was similar to that of a star or planet struggling through dense haze4 ,yet1 on ,march #ai1 #ahdh1 the ,moon 8presented a luminosity quite unusual4 ,the light and dark places on the face of our satellite could be almost as well made out as on an ordinary dull moonlight night40 ,on ,july #ab1 #ahgj1 ,feb4 #bg and ,aug4 #bc1 #ahgg1 and ,jan4 #bh1 #ahhh1 the ,moon1 as observed at ,bristol1 was also fairly bright when totally immersed in the ,earth's shadow4 ,in explanation of these singular differences1 ,dr4 ,burder has suggested that ,kepler's views seem inadequate1 and that the solar corona is probably implicated in producing light and dark eclipses4 ,he concludes that1 as the corona sometimes extends to considerable distances from the ,sun1 and is very variable in brightness1 it may have sufficient influence to occasion the effects alluded to4 ,lunar ,changes4--,the question as to whether physical changes are occurring in the surface-formations of our satellite is one which offers attractive inducements to telescopic observers4 ,though the ,moon appears to have passed the active state1 it is very possible that trivial alterations continue to affect some of her features4 ,in ,april #aghg ,sir ,w4 ,herschel wrote3--8,i perceive three volcanoes in different places of the dark part of the new ,moon4 ,two of them are already nearly extinct1 or otherwise in a state of going to break out2 the third shows an eruption of fire or luminous matter40 ,schrter1 however1 was correctly of opinion that these appearances were due to reflected light from the ,earth falling upon elevated spots of the ,moon having unusual capacity to return it4 ,schrter himself thought he detected sudden changes in #agia4 ,he says that1 on the #cjth of ,december1 at #e;h ,p4,m41 with a #g-;foot reflector magnifying #afa times1 he perceived the commencement of a small crater on the ,s4,w4 declivity of the volcanic mountain in the ,mare ,crisium1 having a shadow of at least #b #e4 ,on the #aath of ,january1 #agib1 at #e;h #bjm ,p4,m41 on looking at the place again he could see neither the new crater nor its shadow4 ,in this case the disappearance was doubtless an apparent one1 merely due to the reversed illumination under which the object was examined in the interval of #ab days4 ,many other observers besides ,herschel have been struck with the brightness of certain spots situated in the opaque region of the lunar disk2 but there is no doubt the cause has been uniformly one and the same1 viz4 the highly reflective properties of some of the mountains 7notably of one named ,aristarchus71 which are distinctly visible as luminous spots amid the relatively dark regions surrounding them4 ,they afford no certain evidence of existing volcanic energy1 and in the light of modern researches such an idea cannot be entertained4 ,on ,june #aj1 #ahff1 ,temple noticed a remarkable light appearance1 agreeing with the position of ,aristarchus1 upon the dark side of the ,moon1 faintly illuminated by earthshine4 ,the object did not exhibit a faint white light analogous to that of other craters in the dark side1 but it was star-like1 diffused1 in colour reddish yellow1 and evidently dissimilar to other bright spots4 ,he wrote1 in reference to this matter3--8,of course ,i am far from surmising a still active chemical outbreak1 as such an outbreak supposes water and an atmosphere1 both of which are universally allowed not to exist on the ,moon1 so that the crater-forming process can only be thought of as a dry1 chemical1 although warm one40 ,on ,november #ag1 #ahff1 ,schmidt announced that the lunar crater ,linn1 about #e miles in diameter1 and situated in the ,mare ,serenitatis1 had disappeared6 ,he averred that he had been familiar with the object as a deep crater since #ahda1 but in ,october #ahff he found its place occupied by a whitish cloud4 ,this cloud was always visible1 but the crater itself appeared to have become filled up1 and was certainly invisible under its former aspect4 ,such a definite statement1 emanating as it did from a diligent and experienced student of selenography1 naturally aroused keen interest1 and ,linn at once became the object of wide-spread observation4 ,but a reference to ,schrter's results1 obtained in the latter part of the last century1 threw some doubt upon the alleged change4 ,this observer had figured ,linn on ,november #e1 #aghh1 as a round white spot1 and there is nothing in his drawing indicating a crateriform aspect4 ,his description of ,linn was3--8,a flat1 somewhat doubtful crater1 which appears as a round white spot40 ,mr4 ,huggins regarded ,schrter's observations as correctly expressing the appearance of this object in #ahfg under the same conditions of illumination4 ,on the other hand1 ,lohrmann 7#ahbc7 and ,mdler 7#ahca7 referred to ,linn as a deep crater1 and in terms inconsistent both with ,schrter's drawing and with the present aspect of the object4 ,the outcome of the many fresh observations that were collected was that ,linn appeared as a white cloud1 with a small black crater within a large shallow-ringed depression4 ,but as usual in such cases1 the observers were far from being unanimous as to the details of the formation2 and certainly in regard to a lunar object this need occasion no surprise1 for slight differences in the angle of illumination produce marked changes in the aspect of lunar features4 ,the fact of actual change could not be demonstrated1 and the negative view appears to have subsequently gained weight4 ,another instance of alleged activity on the ,moon was notified by ,dr4 ,klein in the spring of #ahgg4 ,he saw a deep black crater about #ah miles to the ,w4,n4,w4 of ,hyginus1 and in a particular place where he had previously recognized no such object1 though he had frequently examined the region and was perfectly familiar with it4 ,forthwith every telescope was directed to this part of the ,moon4 ,the maps of earlier observers were eagerly consulted1 and lunar photographs scanned for traces of the new object4 ,many drawings were made of the district near ,hyginus and of the remarkable rill or cleft connected with it2 but amongst both old and new records some puzzling discordances were detected4 ,many of the observers1 instead of finding ,dr4 ,klein's new formation a sharply-cut1 deep crater1 saw it rather in the character of a saucer-like depression2 and ,i drew it under this aspect on several occasions with a #aj-;inch reflector4 ,the fact1 therefore1 of its being a new feature admitted of no valid and convincing proofs1 and thus the same uncertainty remains attached to this object as to ,linn1 nothing being absolutely proved#af4 ,the problem as to whether the ,moon is still the seat of physical activity has yet to be solved4 ,many circumstances are antagonistic to the discovery of changes on the ,moon4 ,as the ,sun's altitude is constantly varying with reference to lunar objects1 they assume different aspects from hour to hour4 ,in a short interval the same formations become very dissimilar4 ,when the ,sun is rising above the more minute craters they are often distinguished in their true characters2 but near the period of full ,moon they are visible as bright spots1 and it is impossible to tell whether they represent craters or conical hills4 ,with a vertical ,sun1 as at the full1 all the shadows have disappeared--in fact1 the entire configuration has been transformed1 and many of the interesting lineaments displayed at the crescent phase are no longer seen4 ,the ,moon's libration also introduces slight differences in the appearance of objects4 ,and these are not the only drawbacks2 for observations1 in themselves1 are seldom accordant1 and it is found that drawings and descriptions are not always to be reconciled1 though referring to identical and invariable features4 ,the lunar landscape must be studied under the same conditions of illumination and libration1 with the same instrument and power1 and in a similar state of atmosphere1 if results are to be strictly comparable4 ,but it is very rarely that observations can be effected under precisely equal conditions2 hence discordances are found amongst the records4 ,the whole of the ,moon's visible sphere exhibits striking imprints of convulsions and volcanic action in past times1 though no such forces appear to operate now4 ,the surface seems to have become quiescent1 and to have assumed a rigidity inconsistent with the idea of present energy4 ,but we cannot be absolutely certain that minute changes are not taking place1 and1 being minute1 the prospect of their detection is somewhat remote4 ,students of lunar scenery will probably have to watch details with scrupulous care and for long periods before an instance of real activity can be demonstrated4 ,lunar ,formations4--,the ,moon abounds in objects of very diversified character1 and they have been classified according to peculiarities of structure4 ,the names of eminent astronomers have been applied to many of the more definite features--a plan of nomenclature which originated with ,riccioli1 who published a lunar map at the middle of the seventeenth century4 ,the following brief summary comprises many of the principal formations3-- ,mare4 ,a name applied by ,hevelius to denote the large and relatively level plains on the ,moon1 which present some similarity to terrestrial seas4 ,they are visible to the naked eye as dusky spots1 and in a telescope show many craters1 hills1 and mounds1 and some extensive undulations of surface4 ,palus 7,marsh7 and ,lacus 7,lake7 were titles given by ,riccioli to minor areas of a dark colour1 and exhibiting greater variety of detail and tint than the ,maria4 ,sinus 7,bay7 has been applied to objects like deep bays on the borders of the ,maria4 ,walled ,plains extend from #dj to #aej miles in diameter1 and are commonly surrounded by a terraced wall or mountain-ranges4 ,the interiors are tolerably level1 though often marked with crater-pits1 mounds1 and ridges4 ,mountain-,rings4 ,these represent rings of mountains and hills1 enclosing irregularities1 possibly furnished by the debris of the crumbling exterior walls1 which1 in certain instances1 appear to have fallen inwards4 ,ring-,plains are more circular and regular in type than the walled plains1 and consist of a moderately flat surface surrounded by a single wall4 ,crater-,plains are somewhat similar1 and seldom exceed #bj miles in diameter4 ,they 8rise steeply from the mass of debris around the foot of their walls to a considerable height1 and then fall precipitously to the interior in a rough curved slope1 whilst on their walls1 especially on the exterior1 craterlets and crater-cones often exist in considerable numbers40 ,craters1 ,craterlets1 and ,crater-,pits4 ,usually circular in form1 and severally offering distinctions as to dimensions and shape4 ,the craters are surrounded by walls1 rising abruptly to tolerable heights1 and pretty regular in their contour4 ,when the ,sun is rising the shadow of the walls falls upon the interior of the craters1 and many of these dark conspicuous objects are to be seen near the ,moon's terminator4 ,with a high ,sun some of the craters are extremely bright4 ,in proof of the large number of these objects1 it may be noted here that in ,mdler's lunar map 7#ahcg7 #ggce craters are figured1 while in ,schmidt's 7#ahgh7 there are no less than #cb1hef6 ,crater-,cones4 ,conical hills or mountains1 visible as small luminous spots about the period of full ,moon4 ,they are from #a_/b to #c miles in diameter1 and show deep central depressions4 ,it is somewhat difficult to distinguish them from the ordinary mountain-peaks and white spots1 and they are not unlike the cones of terrestrial volcanoes4 ,rills or ,clefts4 ,these are very curious objects4 ,they were first discovered by ,schrter in #aghg1 and some of them are to be traced over a considerable extent of the lunar surface1 their entire length being #bjj or #cjj miles4 ,they have the appearance of cuttings or canals1 and are sometimes straight1 sometimes bent1 and not unfrequently develop branches which intersect each other4 ,they apparently run without interruption through many varieties of lunar objects4 ,the bottoms of these rills are nearly flat1 and look not unlike dried riverbeds4 ,some observers have regarded them as fractures or cracks in the ,moon's surface2 but their appearance and circumstances of arrangement are opposed to such a view4 ,our present knowledge includes more than #ajjj of these rills4 ,mountain-,ranges are chains of lofty peaks and highlands1 sometimes divided by rills and numerous ravines and cross valleys4 ,some of these ranges are of vast magnitude1 and the summits of the mountains reach altitudes between #ae1jjj and #bj1jjj feet1 and sometimes even more4 ,mountain-,ridges are to be found scattered in the greatest abundance in the most disturbed localities of the lunar surface4 ,they sometimes connect several formations1 or surmount ravines or depressions of large extent4 ,peaks attaining altitudes of more than #ejjj feet rise from them1 and they range in several cases over #ajj miles4 ,ray-,centres4 ,systems of radiating light-streaks1 having a mountain-ring as the centre of divergence1 and stretching to distances of some hundreds of miles round4 ,tycho1 ,copernicus1 ,kepler1 ,anaxagoras1 ,aristarchus1 and ,olbers are pronounced examples of this class4 ,in ,beer and ,mdler's chart of the ,moon the names are attached to the various formations1 as they are also in ,neison's maps and in some other works4 ,one of these will be absolutely necessary to the student in prosecuting his studies4 ,he will then have a ready means of acquainting himself with the various formations1 and making comparisons between his new results and the drawings of earlier selenographers4 ,i would refer the reader to ,neison's and ,webb's books for many references in detail to lunar features1 and must be content here with a brief description of a few leading objects3-- ,plato is an extensive walled plain1 #fj miles in diameter1 and situated on the ,n4,e4 boundary of the ,mare ,imbrium4 ,nasmyth and ,carpenter describe the wall as 8serrated with noble peaks1 which cast their black shadows across the plateau in a most picturesque manner1 like the towers and spires of a great cathedral40 ,it has received a large amount of attention1 with a view to trace whether changes are occurring in the numerous white spots and streaks lying in its interior4 ,in #ahfi-ga ,mr4 ,birt collected many observations1 and on discussing them was led to believe that 8there is strong probability that activity1 of a character sufficient to render its effects visible1 had been manifested40 ,the inquiry was renewed by ,stanley ,williams in #ahhb-hd1 and he concluded that the results were strongly confirmatory of actual change having occurred since #ahfi-ga4 ,the relative visibility of several of the bright spots had altered in the interim1 and the curious intermingling bright streaks also exhibited traces of variation4 ,at sunrise the interior of ,plato is pure grey2 but with the sun at a considerable height above it1 the plain becomes a dark steel-grey4 ,the change is an abnormal one1 and difficult to explain4 ,south of ,plato there is a fine example of an isolated peak1 named ,pico1 which is about #hjjj feet high4 ,illustration3 ,fig4 #be4 ,light-spots and streaks on ,plato1 #ahgi-hb4 7,a4 ,stanley ,williams47 ,great ,alpine ,valley4 ,this object1 supposed to have been discovered by ,bianchini in #agbg1 and having a length1 according to ,mdler1 of #hc miles and a breadth varying from #c to #f miles1 is a very conspicuous depression situated near ,plato1 and running from the ,mare ,frigoris to the ,mare ,imbrium4 ,it exhibits at its southern extremity an oval formation1 and a narrow gorge issues from it to the northward1 opening out further on1 and imparting to the whole appearance a shape which ,webb likened to a ,florence oil-flask4 ,elger has fully described this singular structure4 8,it is only when far removed from the terminator that its ,v-shaped outlet to the ,mare ,imbrium flanked on either side by the lofty ,alps can be traced to advantage1 or the flask-like expansion with the constricted gorge leading up to it from the ,n4,w4 satisfactorily observed4 ,at other times these features are always more or less concealed by the shadows of neighbouring heights4 ,the details of the upper or more attenuated end of the valley are1 however1 best seen under a setting sun1 when many striking objects come to light1 of which few traces appear at other times40 ,archimedes4 ,one of the most definite and regular of the walled plains4 ,it is #fj miles in diameter1 with a wall rising about #dbjj feet above the surface4 ,some small craters and various streaks diversify its centre4 ,tycho4 ,a grand ring-plain1 #ed miles in diameter and about #ag1jjj feet 7 nearly #c miles7 deep1 and forming the centre of the chief ray-system of the ,moon4 ,the light-radiations stretch over one fourth of the visible hemisphere at the full1 but they are imperceptible with the ,sun's altitude below #bj4 ,these remarkable radiations from ,tycho form a striking aspect of lunar scenery1 and any small telescope reveals them4 ,webb has termed ,tycho 8the metropolitan formation of the ,moon20 and the idea embodied in the expression must strike observers as very apposite4 ,this object is visible to the naked eye at the time of full4 ,a fine hill rises from its centre to a height of #eejj feet4 ,copernicus4 ,a magnificent ring-plain1 #ef miles in diameter1 and surrounded by a wall 7in which there are terraces and lofty peaks1 separated by ravines7 attaining an elevation of #aa1jjj feet4 ,there is a central hill of nearly #bejj feet4 ,from ,copernicus light-streaks are plentifully extended on all sides1 and apparently connect this object with the many others of similar character which are situated in this region4 ,neison says that near ,copernicus the light-streaks unite and form a kind of nimbus or light-cloud about it4 ,the streaks are most conspicuous towards the ,n41 where they are from #e to #ad miles in width4 ,to the ,n4,w4 of ,copernicus1 about halfway in the direction of the neighbouring ring-plain ,eratosthenes 7and ,n4 of ,stadius71 there is a considerable number of crater-pits4 ,mdler figured sixty-one of these1 and regarded that number as certainly less than half the total number visible4 ,they appear to be ranged in rows or streams1 and are so close together in places as to nearly form crater-rills4 ,schmidt saw the ground hereabout pierced like a honeycomb1 and managed to count about #cjj little craters2 but they are so thickly strewn in this district that exact numbers or places cannot be assigned4 ,they are best observable when the ,sun is rising on the ,e4 wall of ,copernicus4 ,the interior of this fine object shows six or seven peaks1 which are often capped with sunshine1 and very brilliant amid the black shadow thrown from the surrounding wall4 ,theophilus4 ,another ring-plain1 and one of the deepest visible4 ,its terraced lofty wall1 #fd miles in diameter1 rises in a series of peaks to heights varying between #ad1jjj and #ah1jjj feet4 ,there is a central mountain1 broken by ravines2 but from one of the masses a peak ascends to a height of about #fjjj feet4 ,petavius4 ,a large walled plain1 surrounded by a double wall or rampart1 which rises to #aa1jjj feet on its ,e4 side4 ,there are hills and ridges in the interior1 and a central peak1 ,a1 reaching to #eejj feet above the ,e4 part of the floor1 which is convex in form4 ,a smaller peak1 of nearly #djjj feet1 lies ,w4 of ,a4 ,several small craterlets have been seen in the interior4 ,newton4 ,the deepest walled plain known upon the ,moon's surface4 ,in form it is elliptical2 its length is #adc miles1 while its breadth is only #fi miles4 ,the walls show the terracing so common in these objects1 and one lofty peak reaches the unusual height of #bd1jjj feet above the floor4 ,the interior includes some small craters1 mountain protuberances1 and other irregularities4 ,neison says that1 owing to 8the immense height of the wall1 a great part of the floor is entirely lost in shadow1 neither ,earth nor ,sun being ever visible from it40 ,illustration3 ,fig4 #bf4 ,petavius and ,wrottesley at sunset4 #ahhe1 ,dec4 #bc1 #i;h to #aj;h #cjm4 7,t4 ,gwyn ,elger47 ,grimaldi4 ,an immense walled plain1 extending over #adh miles from ,n4 to ,s4 and about #acj miles from ,e4 to ,w4 ,its interior is very dark4 ,clavius is another grand example of this class of object1 and is rather larger than ,grimaldi1 but unfavourably placed near the ,s4 pole4 ,schickard may also be mentioned as a large formation of similar type1 and situated near the ,s4,e4 limb of the ,moon4 ,illustration3 ,fig4 #bg4 ,birt1 ,birt ,a1 and the ,straight ,wall4 #ahhc1 ,feb4 #ae1 #f;h to #h;h #djm4 7,t4 ,gwyn ,elger47 ,rill or ,cleft of ,hyginus4 ,a conspicuous example of the lunar rills1 and one which yields to very moderate instruments4 ,neison notes that it is readily visible in a #b-;inch telescope2 while ,webb remarks that a power of only #dj1 in a good instrument1 is enough to show it under any illumination4 ,the rill is about #aej miles long4 ,it cuts through a number of crater-pits1 and ,mdler found so many widenings in it that it appeared like a confluent train of craters4 ,the rill traverses the large crater-pit ,hyginus1 which is #c-c_/d miles in diameter and moderately deep4 ,other fine examples of rill-systems will be found between ,rheita and ,metius and near ,triesnecker and ,ramsden4 ,straight ,wall4 ,a singular structure on the ,e4 side of the ring-plain ,thebit4 ,it is a ridge or wall1 which looks regular enough for a work of art1 according to ,webb4 ,its average height is #dej feet 7,schrter71 #ajjd feet 7,mdler71 or #hhj feet 7,schmidt74 ,these several determinations are given to show the discordances sometimes found in the measures of good observers4 ,this object is about #fj miles long2 at one extremity lies a small crater1 at the other there is a branching mountain nearly #bjjj feet high4 ,elger has drawn this object1 under both a rising and a setting sun1 in the ,liverpool ,astronomical ,society's #8,journal1' vol4 v4 p4 #aef1 and remarks that it may be well observed at from #bj to #cj hours after the ,moon's first quarter4 ,valley near ,rheita4 ,south of the ring-plain ,rheita1 on the ,s4,w4 limb1 there is an enormous valley1 which extends in its entire length over #ahg miles1 with a width ranging from #aj to #be miles4 ,there are several fine valleys in this particular region4 ,leibnitz ,mountains4 ,these are really situated on the further hemisphere of the ,moon1 but libration brings them into view1 and they are sometimes grandly seen in profile on the ,s4 margin4 ,four of the peaks ascend to elevations of #bf1jjj or #bg1jjj feet1 and one mass1 towering far above the others1 is fully #cj1jjj feet in height1 and is unquestionably the most lofty mountain on the ,moon4 ,drfel ,mountains4 ,visible on the ,moon's ,s4,s4,e4 limb4 ,they exhibit three peaks1 which1 on the authority of ,schrter1 rise to more than #bf1jjj feet above the average level of the limb4 ,the loftiest mountains on the ,earth are in the ,himalayas--a range of immense extent to the ,n4 of ,india4 ,the three highest peaks are ,mount ,everest 7#bi1jjb feet71 ,kunchinjinga 7#bh1aef feet71 and ,dhawalagiri 7#bh1jjj feet74 ,the only lunar mountain more elevated than these is that of the ,leibnitz range1 which1 as we have already stated1 ascends to fully #cj1jjj feet4 ,illustration3 ,fig4 #bh4 ,aristarchus and ,herodotus at sunrise4 #ahhd1 ,jan4 #i1 #h;h #cjm to #aj;h #cjm4 7,t4 ,gwyn ,elger47 ,apennines4 ,a vast chain of mountains1 extending over more than #dej miles of the lunar surface4 ,huygens is the most elevated peak1 rising to more than #ah1jjj feet1 and on its summit it shows a small crater4 ,there are several other very lofty peaks in this range4 ,the ,sun rises upon the westerly region of these mountains at the time of first quarter1 and the peaks and ridges1 with their contrasting shadows1 create a gorgeous effect just within1 and projecting into the darkness beyond1 the terminator4 ,there is an immense amount of detail to be studied here1 and much of it is within the reach of small instruments4 ,as the lunar mountains and craters are best seen near the terminator1 it may be useful to give a table of objects thus favourably placed between the times of new and full ,moon4 ,the summary may assist the student1 though it does not aim at exactness1 only even days being given4 ,objects near the ,terminator4 ,moon's age in days4 #b ,mare ,crisium1 ,messala1 ,sunrise on the ,mare ,humboldtianum1 ,langrenus1 ,vendelinus1 ,condorcet1 ,hansen1 ,gauss771 ,hahn1 ,berosus4 #c77 ,craters in ,mare ,crisium1 ,taruntius1 ,picard1 ,fraunhofer1 ,vega1 ,pontcoulant1 ,cleomedes771 ,furnerius1 ,petavius1 ,endymion1 ,messier771 ,vlacq4 #d ,mare ,nectaris1 ,macrobius771 ,proclus1 ,sunrise on ,fracastorius1 ,rheita and ,metius with the intervening valley1 ,guttemberg1 ,colombo1 ,santbech1 ,mountainous region ,w4 of ,mare ,serenitatis1 ,hercules1 ,atlas4 #e ,palus ,somnii1 ,plana1 ,capella1 ,isidorus1 ,polybius1 ,piccolomini1 ,vitruvius1 ,littrow1 ,fabricius1 ,posidonius1 ,le,monnier1 ,theophilus1 ,cyrillus1 ,catharina1 ,hommel4 #f ,tacitus1 ,maurolycus1 ,barocius1 ,dionysius771 ,sosigenes1 ,abulfeda1 ,descartes1 ,almamon1 ,gemma ,frisius1 ,plinius1 ,ross1 ,arago1 ,delambre1 ,aristoteles1 ,eudoxus1 ,julius ,csar1 ,linn1 ,menelaus4 ,the objects for observation when the ,moon's age is from #b to #d days may be suitably re-examined a few days after the full4 ,an extensive walled plain1 #aaj miles in length4 ,a large walled plain containing a small crater1 ,cleomedes ,a4 ,a curious double crater1 with comet-like rays crossing the ,mare ,fcunditatis4 ,a circular ring-plain1 #db miles in diameter4 ,the interior of this crater exhibits some interesting features as the ,sun rises higher above it4 #g ,ptolemus1 ,albategnius1 ,manilius#ag1 ,hyginus and its rill-system1 ,hipparchus1 ,autolycus1 ,aristillus1 ,cassini1 ,alpine ,valley1 ,w4 ,c4 ,bond1 ,walter1 ,miller1 ,la,caille1 ,apennines1 ,triesnecker and the rills ,w4 of it4 #h ,mare ,frigoris1 ,arzachel1 ,alphonsus1 ,alpetragius1 ,bode1 ,pallas1 ,archimedes1 ,plato1 ,maginus#ah1 ,msting#ai1 ,thebit1 ,saussure1 ,moretus1 ,straight ,wall1 ,lalande1 ,kirch4 #i ,tycho1 ,clavius1 ,eratosthenes#bj1 ,stadius and the craters running to ,n4,e41 ,timocharis1 ,pitatus1 ,gruemberger1 ,teneriffe ,mountains1 ,straight ,range#ba1 ,formation ,w4 of ,fontenelle#bb1 ,gambart4 #aj ,sinus ,iridum1 ,copernicus1 ,hesiodus and the rill to ,e41 ,wilhelm ,i41 ,longomontanus#bc1 ,heinsius1 ,pytheas1 ,lambert1 ,helicon1 ,wurzelbauer4 #aa ,bullialdus1 ,campanus1 ,mercator1 ,reinhold1 ,riphan ,mountains1 ,hippalus1 ,capuanus1 ,blancanus1 ,tobias ,mayer4 #ab ,mare ,imbrium1 ,gassendi#bd1 ,aristarchus and sinuous valley to the ,n4,e41 ,herodotus1 ,marius1 ,flamsteed1 ,letronne1 ,schiller1 ,mersenius1 ,doppelmayer4 #ac ,schickhard1 ,wargentin1 ,grimaldi1 ,byrgius1 ,phocylides1 ,hevelius1 ,seleucus1 ,crger1 ,briggs1 ,segner1 ,sirsalis4 #ad ,mare ,smythii1 ,bailly1 ,inghirami1 ,bouvard1 ,riccioli1 ,olbers1 ,hercynian ,mountains1 ,cardanus1 ,krafft1 ,cordilleras#be1 ,pythagoras#bf4 ,occultations of ,stars4--,among the various phenomena to which the lunar motions give rise none are more pleasing to the possessors of small telescopes than occultations of stars4 ,several of these occurrences are visible every month4 ,if the amateur has the means of obtaining accurate time1 he will engage himself usefully in noting the moments of disappearance and reappearance of the stars occulted4 ,this work is efficiently done1 it is true1 at some of our observatories1 and therefore little real necessity exists for amateurs to embark in routine work which can be conveniently undertaken at establishments where they have better appliances and trained observers to use them4 ,the mere watching of an occultation1 apart from the registry of exact results1 is interesting2 and there are features connected with it which have proved exceedingly difficult to account for4 ,the stars do not always disappear instantaneously4 ,on coming up to the edge of the ,moon they have not been suddenly blotted out1 but have appeared to hang on the ,moon's limb for several seconds4 ,this must arise from an optical illusion1 from the action of a lunar atmosphere1 or the stars must be observed through fissures on the ,moon's edge4 ,the former explanation is probably correct2 for it has happened that two observers at the same place have received different impressions of the phenomenon4 ,one has seen the star apparently projected on the ,moon's limb for about #e seconds1 while the other has witnessed its sudden extinction1 in the usual manner1 as it met the ,moon's edge4 ,new observations1 made with good instruments and reliable eyes1 and fully described1 will doubtless throw more light on the peculiar effects sometimes recorded4 ,visibility of the new and old ,moon4--,it is an interesting feature of observation to note how soon after conjunction the ,moon's thin crescent is observable with the naked eye4 ,a case has been mentioned in which the old ,moon was seen one morning before sunrise and the new ,moon just after sunset on the next day4 ,at ,bristol1 on the evening of ,march #cj1 #ahha1 ,i saw the new ,moon at #g;h #ajm1 the horizon being very clear in the west4 ,she was then only #bj;h #chm old4 ,on ,june #d1 #ahge1 ,i observed the ,moon's crescent at #i;h #ajm1 or #bb;h #dim after new ,moon4 ,dr4 ,degroupet1 of ,belgium1 saw the old ,moon on the morning of ,nov4 #bb1 #ahhi1 between #f;h #dgm and #g;h #bbm ,g4,m4,t41 or within #ah;h #bbm of the time of new ,moon4 ,,footnotes3 #af ,in ,september #ahhi ,prof4 ,thury1 of ,geneva1 reported a change in the centre of the crater ,plinius4 ,with a #f-;inch refractor he saw1 instead of the usual two hills in the interior1 a circular chalk-like disk 8with a dark spot in its centre like the orifice of a mud-volcano40 #ag ,a fine ring-plain1 #be miles in diameter4 #ah ,mdler says 8the full ,moon knows no ,maginus10 meaning that this object is invisible under a vertical ,sun4 #ai ,msting1 ,lalande1 and ,herschel form a fine triangle when the ,sun has attained a great altitude4 ,msting is a ray-centre4 #bj ,a ring-plain #cg miles in diameter1 with very irregular terraced walls4 #ba ,a range of mountains1 with intervening valleys4 #bb ,mdler describes this as a square enclosure with rampart-like boundaries1 which 8throw the observer into the highest astonishment40 #bc ,a great walled plain1 #ia miles in diameter4 #bd ,a walled plain1 #ee miles in diameter1 in which ,schrter suspected changes4 #be ,an extensive mountain-range on the ,e4 by ,s4 limb4 #bf ,a walled plain1 #ie miles in diameter1 and probably the deepest in the ,n4,e4 quadrant1 for the ,s4,e4 side of its wall rises to nearly #ag1jjj feet4 ,after the full the same objects should be re-examined under the reversed illumination4 ,,chapter ,,vii4 ,,mercury4 ,supposed planet1 8,vulcan40--,visibility of ,mercury4--,period c4--,elongations4--,amateur's first view4--,phases4--,atmosphere of ,mercury4--,telescopic observations4--,schiaparelli's results4--,observations of ,schrter and ,sir ,w4 ,herschel4--,transits of ,mercury4--,occultations of ,mercury4 8,come1 let us view the glowing west1 ,not far from the fallen ,sun2 ,for ,mercury is sparkling there1 ,and his race will soon be run4 ,with aspect pale1 and wav'ring beam1 ,he is quick to steal away1 ,and veils his face in curling mists1-- ,let us watch him while we may40 ,supposed planet 8,vulcan40--,mercury is the nearest known planet to the ,sun4 ,it is true that a body1 provisionally named ,vulcan#bg1 has been presumed to exist in the space interior to the orbit of ,mercury2 but absolute proof is lacking1 and every year the idea is losing strength in the absence of any confirmation of a reliable kind4 ,certain planetary spots1 observed in motion on the solar disk1 were reported to have been transits of this intra-,mercurial orb4 ,some eminent astronomers were thus drawn to take an affirmative view of the question1 and went so far as to compute the orbital elements and predict a few ensuing transits of the suspected planet4 ,but nothing was seen at the important times1 and some of the earlier observations have been shown to possess no significance whatever1 while grave doubts are attached to many of the others4 ,not one of the regular and best observers of the ,sun has recently detected any such body during its transits 7which would be likely to occur pretty frequently71 and there is other evidence of a negative character2 so that the ghost of ,vulcan may be said to have been laid1 and we may regard it as proven that no major planet revolves in the interval of #cf1jjj1jjj miles separating ,mercury from the ,sun4 ,visibility of ,mercury4--,copernicus1 amid the fogs of the ,vistula1 looked for ,mercury in vain1 and complained in his last hours that he had never seen it4 ,tycho ,brahe1 in the ,island of ,hueen1 appears to have been far more successful4 ,the planet is extremely fugitive in his appearances1 but is not nearly so difficult to find as many suppose4 ,whenever the horizon is very clear1 and the planet well placed1 a small sparkling object1 looking more like a scintillating star than a planetary body1 will be detected at a low altitude and may be followed to the horizon4 ,period c4--,mercury revolves round the ,sun in #hg;d #bc;h #aem #dds in an eccentric orbit1 so that his distance from that luminary varies from #dc1cej1jjj to #bh1egj1jjj miles4 ,when in superior conjunction the apparent diameter of the planet is #de2 at inferior1 conjunction it is #abi1 and at elongation #g4 ,his real diameter is #cjjj miles4 ,elongations4--,being situated so near to the ,sun1 it is obvious that to an observer on the ,earth he must always remain in the same general region of the firmament as that body4 ,his orbital motion enables him to successively assume positions to the ,e4 and ,w4 of the ,sun1 and these are known as his elongations1 which vary in distance from #ah to #bh4 ,he becomes visible at these periods either in the morning or evening twilight1 and under the best circumstances may remain above the horizon two hours in the absence of the ,sun4 ,the best times to observe the planet are at his ,e4 elongations during the first half of the year1 or at his ,w4 elongations in the last half2 for his position at such times being ,n4 of the ,sun's place1 he remains a long while in view4 ,it is unfortunate that when the elongation approaches its extreme limits of #bh the planet is situated ,s4 of the ,sun1 and therefore not nearly so favourably visible as at an elongation of only #ah or #bj1 when his position is ,n4 of the ,sun4 ,i have seen ,mercury on about sixty-five occasions with the naked eye4 ,in ,may #ahgf ,i noticed the planet on thirteen different evenings1 and between ,april #bb and ,may #aa1 #ahij1 ,i succeeded on ten evenings4 ,i believe that anyone who made it a practice to obtain naked-eye views of this object would succeed from about twelve to fifteen times in a year4 ,in a finer climate1 of course1 ,mercury may be distinguished more frequently4 ,occasionally he presents quite a conspicuous aspect on the horizon1 as in ,february #ahfh1 when ,i thought his lustre vied with that of ,jupiter1 and in ,november #ahhb1 when he shone brighter than ,sirius4 ,the planet is generally most conspicuous a few mornings after his ,w4 elongations and a few evenings before his ,e4 elongations4 ,amateur's ,first ,view4--,the first view of ,mercury forms quite an event in the experience of many amateurs4 ,the evasive planet is sought for with the same keen enthusiasm as though an important discovery were involved4 ,for a few evenings efforts are vain1 until at length a clearer sky and a closer watch enables the glittering little stranger to be caught amid the vapours of the horizon4 ,the observer is delighted1 and1 proud of his success1 he forthwith calls out the members of his family that they1 too1 may have a glimpse of the fugitive orb never seen by the eye of ,copernicus4 ,phases4--,in the course of his orbital round ,mercury exhibits all the phases of the ,moon4 ,near his elongations the disk is about half illuminated1 and similar in form to that of our satellite when in the first or third quarter4 ,but the phase is not to be distinctly made out unless circumstances are propitious4 ,galilei's telescope failed to reveal it1 and ,hevelius1 many years afterwards1 found it difficult4 ,this is explained by the small diameter of the planet and the rarity with which his disk appears sharply defined4 ,the phase is sometimes noted to be less than theory indicates2 for the planet has been seen crescented when he should have presented the form of a semicircle4 ,several observers have also remarked that his surface displays a rosy tint1 and that the terminator is more deeply shaded and indefinite than that of ,venus4 ,atmosphere4--,the atmosphere of ,mercury is probably far less dense than that of ,venus4 ,the latter being farthest from the ,sun might be expected to shine relatively more faintly than the former1 but the reverse is the case4 ,mercury has a dingy aspect in comparison with the bright white lustre of ,venus4 ,on ,may #ab1 #ahij1 when the two planets were visible as evening stars1 and separated from each other by a distance of only #b1 ,i examined them in a #aj-;inch reflector1 power #ade4 ,the disk of ,venus looked like newly-polished silver1 while that of ,mercury appeared of a dull leaden hue4 ,a similar observation was made by ,mr4 ,nasmyth on ,september #bh1 #ahgh4 ,the explanation appears to be that the atmosphere of ,mercury is of great rarity1 and incapable of reflection in the same high degree as the dense atmosphere of ,venus4 ,telescopic ,observations4--,as this planet is comparatively seldom to be observed under satisfactory conditions1 it is scarcely surprising that our knowledge of his appearance is very meagre1 or that amateurs consider the planet an object practically inaccessible as regards the observation of physical peculiarities1 and one upon which it is utterly useless to apply the telescope in the hope of effecting new discoveries4 ,former attempts have proved the extreme difficulty of obtaining good images of this planet4 ,the smallness of the disk1 and the fact that it is usually so much affected by the waves of vapour passing along the horizon as to be constantly flaring and moulding in a manner which scarcely enables the phase to be made out1 are great drawbacks1 which render it impossible to distinguish any delicate features that may be presented on the surface4 ,these circumstances are well calculated to lead observers to abandon this object as one too unpromising for further study2 but ,i think the view is partly induced by a misconception4 ,the planet's diminutive size is a hindrance which cannot be overcome2 but the bad definition1 resulting from low altitude1 may be obviated by those who will select more suitable times for their observations and not be dismayed if their initiatory efforts prove futile4 ,as a naked-eye object1 ,mercury must necessarily be looked for when near the horizon2 but there is no such need in regard to telescopic observation1 which ought to be only attempted when the planet surmounts the dense lower vapours and is placed at a sufficient elevation to give the instrument a fair chance of producing a steady image4 ,the presence of sunshine need not seriously impair the definition or make the disk too faint for detail4 ,i have occasionally seen ,mercury1 about two or three hours after his rising1 with outlines of extreme sharpness and quite comparable with the excellent views obtained of ,venus at the time of sunrise or sunset4 ,those who possess equatoreals should pick up the planet in the afternoon and follow him until after sunset1 when the horizontal vapours will interfere4 ,others who work with ordinary alt-azimuth stands will find it best to examine the planet at his western elongations during the last half of the year1 when he may be found soon after rising by the naked eye or with an opera-glass1 and retained in the telescope for several hours after sunrise if necessary4 ,he may sometimes also be brought into the field before sunset 7at the eastern elongations in the spring months71 by careful sweeping with a comet-eyepiece1 especially when either the ,moon1 ,venus1 or ,jupiter happens to be near1 and the observer has found the relative place of the planet from an ephemeris4 ,schiaparelli's ,results4--,mercury was displayed under several advantages in the morning twilight of ,november #ahhb1 and ,i made a series of observations with a #aj-;inch reflector1 power #bab4 ,several dark markings were perceived1 and a conspicuous white spot4 ,the general appearance of the disk was similar to that of ,mars1 and ,i forwarded a summary of my results to ,prof4 ,schiaparelli1 of ,milan1 who favoured me with the following interesting reply3-- 8,i have myself been occupied with this planet during the past year 7#ahhb74 ,you are right in saying that ,mercury is much easier to observe than ,venus1 and that his aspect resembles ,mars more than any other of the planets of the solar system4 ,it has some spots which become partially obscured and sometimes completely so2 it has also some brilliant white spots in a variable position4 ,as ,i observe the planet entirely by day and near the meridian ,i have been able to see its spots many times1 but not always with the necessary distinctness to make drawings sufficiently reliable to serve as a base for a rigorous investigation4 ,it is remarkable that the views taken near superior conjunction have been more instructive for me than those taken when the disk is near dichotomy1 the defect in diameter being compensated by the possibility of seeing nearly all the disk1 which1 under those conditions1 is more strongly illuminated4 ,i believe that by instrumental means1 such as our #h-;inch refractor at ,milan gives1 it is possible to prove the rotation-period of ,mercury and to gain a knowledge of the principal spots as regards the generality of their forms4 ,but these spots are really very complicated1 for1 besides the difficulties attending their observation1 they are extremely variable40 ,prof4 ,schiaparelli used an #h-;inch refractor in this work1 and was able1 under some favourable conditions1 to apply a power of #djj4 ,the outcome of his researches1 encouraged since #ahhb by the addition of an #ah-;inch refractor to the appliances of his ,observatory1 has been recently announced in the curious fact that the rotation of ,mercury is performed in the same time that the planet revolves round the ,sun6 ,if this conclusion is just1 ,mercury constantly presents one and the same hemisphere to the ,sun1 and the behaviour of the ,moon relatively to the ,earth has found an analogy4 ,but these deductions of the eminent ,italian astronomer require corroboration1 and this is not likely to be soon forthcoming owing to the obstacles which stand in the way4 ,observations of ,schrter and ,sir ,w4 ,herschel4--,schrter observed ,mercury with characteristic diligence between #aghj and #ahae4 ,in #ahjj he several times remarked that the southern horn of the crescent was blunted1 and fixed the planet's rotation-period at #bd;h #dm4 ,he also inferred the existence of a mountain #ab miles in height4 ,but elements of doubt are attached to some of ,schrter's observations2 and ,sir ,w4 ,herschel1 whose telescopic surveys of both ,mercury and ,venus were singularly barren of interesting results1 pointed out their improbability4 ,but the great observer of ,slough was not very amicably disposed towards his rival in ,germany4 ,his strictures appear1 however1 to have been not without justice if we consider them in the light of modern observations4 ,surface-markings4--,spots or markings of any kind have rarely been distinguished on ,mercury4 ,on ,june #aa1 #ahfg1 ,prince recorded a bright spot1 with faint lines diverging from it ,n4,e4 and ,s4 ,the spot was a little ,s4 of the centre4 ,birmingham1 on ,march #ac1 #ahgj1 glimpsed a large white spot near the planet's ,e4 limb1 and ,vgel1 at ,bothkamp1 observed spots on ,april #ad and #bb1 #ahga4 ,these instances are quoted by ,webb1 and they1 in combination with the markings seen by ,schiaparelli at ,milan and by the author at ,bristol in #ahhb1 sufficiently attest that this object deserves more attentive study4 ,illustration3 ,fig4 #bi4 #ahhb ,nov4 #e1 #ah;h #dim4 #ahhb1 ,nov4 #f1 #ah;h #eem4 ,mercury as a morning star4 7#aj-;inch ,reflector2 power #bab47 ,amateurs with moderately large instruments would be usefully employed in following this planet at the most opportune periods and making careful drawings under the highest powers that can be successfully applied4 ,mercury has been persistently neglected by many in past years1 and no doubt this 8swift-winged messenger of the ,gods0 has eluded some of his would-be pursuers2 but there is every prospect that a patient observer1 careful to utilize all available opportunities1 would soon gather some profitable data relating to his appearance4 ,transits of ,mercury4--,one of the most interesting phenomena1 albeit a somewhat rare event1 in connection with ,mercury1 is that of a transit across the ,sun4 ,the planet then appears as a black circular spot4 ,observers have noticed one or two very small luminous points on the black disk1 and an annulus has been visible round it4 ,these features are probably optical effects1 and it will be worth while to remember them on the occasion of future transits1 of which the subjoined is a list3-- #ahia1 ,may #i4 #ahid1 ,nov4 #aj4 #aijg1 ,nov4 #ab4 #aiad1 ,nov4 #f4 #aibd1 ,may #g4 #aibg1 ,nov4 #h4 #aicg1 ,may #aj4 #aidj1 ,nov4 #ab4 #aiec1 ,nov4 #ac4 #aifj1 ,nov4 #f4 #aigj1 ,may #i4 #aigc1 ,nov4 #i4 ,the first observer of a transit of ,mercury appears to have been ,gassendi1 at ,paris1 on ,nov4 #g1 #afca4 ,occultations of ,mercury4--,there was an occultation of ,mercury by the ,moon on ,april #be1 #ahch4 ,it occurred on the day of the planet's greatest elongation ,e41 and at a time in the evening when it might have been most suitably witnessed1 but cloudy skies appear to have frustrated the hopes of intending observers4 ,there was a repetition of the event on the morning of ,may #b1 #ahfg1 and it occurred1 curiously enough1 less than #bd hours after an occultation of ,venus4 ,,footnotes3 #bg ,chambers1 in his #8,descriptive ,astronomy1' #dth edition1 #ahhi1 devotes a chapter to the discussion of facts having reference to ,vulcan2 and the reader desiring full information will find it here4 ,,chapter ,,viii4 ,,venus4 ,beauty of ,venus4--,brilliancy4--,period c4--,venus as a telescopic object4--,surface-markings on the planet4--,rotation-period4--,faintness of the markings4--,twilight on ,venus4--,alleged ,satellite4--,further observations required4--,transits of ,venus4--,occultations of ,venus4 8,friend to mankind1 she glitters from afar1-- ,now the bright evening1 now the morning star40 ,beauty of ,venus4--,this planet has an expressive name1 and it naturally leads us to expect that the object to which it is applied is a beautiful one4 ,the observer will not be disappointed in this anticipation3 he will find ,venus the most attractive planet of our system4 ,no such difficulties are encountered in finding ,venus as in detecting ,mercury2 for the former recedes to a distance of #dg from the ,sun1 and sometimes remains visible #d hours after sunset1 as in ,february #ahhi4 ,but ,venus owes her beauty not so much to favourable position as to surpassing lustre4 ,none of the other planets can compare with her in respect to brilliancy4 ,the giant planet ,jupiter is pale beside her1 and offers no parallel4 ,ruddy ,mars looks faint in her presence1 and does not assume to rivalry4 ,this planet alternately adorns the morning and evening sky1 as she reaches her ,w4 and ,e4 elongations from the ,sun4 ,the ancients styled her ,lucifer 78the harbinger of day07 when a morning star and ,hesperus when an evening star4 ,brilliancy4--,her brightness is such as to lead her to occasionally become a conspicuous object to the naked eye in daytime1 and at night she casts a perceptible shadow4 ,this is specially the case near the epoch of her maximum brilliancy1 which is attained when the planet is in a crescent form1 with an apparent diameter of about #dj1 and situated some #e weeks from inferior conjunction4 ,though only a fourth part of the disk is then illuminated1 it emits more lustre than a greater phase1 because the latter occurs at a wider distance from the ,earth and when the diameter is much less4 ,her appearance is sometimes so striking that it is not to be wondered at that people1 not well informed as to celestial events1 have attributed it to causes of unusual nature4 ,when the planet was visible as a morning star in the autumn of #ahhg1 an idea became prevalent in the popular mind that the 8,star of ,bethlehem0 had returned1 and there were many persons who submitted to the inconvenience of rising before daylight to gaze upon a spectacle of such phenomenal import4 ,and they were not disappointed in the expectancy of beholding a star of extreme beauty1 though altogether wrong in surrounding it with a halo of mystery and wonder4 ,at intervals of eight years the elongations of ,venus are repeated on nearly the same dates as before1 and the planet is presented under very similar conditions4 ,this is because five synodical periods 7nearly #ac sidereal periods7 of ,venus are equal to eight terrestrial years4 ,thus very favourable ,e4 elongations occurred on ,may #i1 #ahfj1 ,may #g1 #ahfh1 ,may #e1 #ahgf1 and ,may #b1 #ahhd2 and on ,april #cj1 #ahib1 there will be a similar elongation4 ,period c4--,venus moves round the ,sun in an orbit of slight eccentricity1 and completes a revolution in #bbd;d #af;h #dim #hs4 ,her mean distance from that luminary is #fg1jjj1jjj miles4 ,the apparent diameter of the planet varies from #ie at superior to #fe at inferior conjunction1 and it averages #be at elongations4 ,her real diameter is #gejj miles4 ,the polar compression is very slight--in fact1 not sufficiently decided for measurement2 this is also true of ,mercury4 ,venus as a ,telescopic ,object4--,when the telescope is directed to ,venus it must be admitted that the result hardly justifies the anticipation4 ,observers are led to believe1 from the beauty of her aspect as viewed with the unaided eye1 that instrumental power will greatly enhance the picture and reveal more striking appearances than are displayed on less conspicuous planets4 ,but the hope is illusive4 ,the lustre of ,venus is so strong at night that her disk is rarely defined with satisfactory clearness2 there is generally a large amount of glare surrounding it1 and our instruments undergo a severe ordeal when their capacities are tested upon this planet4 ,observations should be undertaken in the daytime1 or near the times of sunrise or sunset1 when the refulgence of this object does not exert itself in extreme degree4 ,but putting aside the question of definition for the moment1 there are other circumstances which conspire to render the view a somewhat unattractive one4 ,there are no dark spots1 of bold outline1 such as we may plainly discern on ,mars1 visible on her surface4 ,there is no wonderful arrangement of luminous rings1 such as encircle ,saturn4 ,there are no signs of dark variegated belts1 similar to those which gird both ,jupiter and ,saturn2 nor is there any system of attendant satellites1 such as accompany each of the superior planets4 ,but though ,venus is wanting in these respects1 she may yet boast an attraction which the outer planets can never display to us1 namely1 the beautiful crescented phase1 which1 tradition says1 was predicted by ,copernicus1 and1 when afterwards observed in ,galilei's telescope1 justly considered a convincing fact in support of the ,copernican system4 ,the phases are best seen in strong twilight1 whenever ,venus is favourably situated4 ,it has been asserted that the crescent of this planet has been distinguished with the naked eye2 but the statement is undoubtedly erroneous4 ,any small glass will show it1 however1 as it is sometimes well visible when subtending an angle of #ej or #ee4 ,surface-markings4--,in #afff and the following year ,j4 ,d4 ,cassini observed several bright spots on ,venus and also two obscure markings2 but the latter were extremely faint and of irregular extent1 so that little could be gleaned from them4 ,he watched these forms closely and remarked certain changes in their positions1 which finally enabled him to determine the period of the planet's rotation4 ,in #agbf and #agbg ,bianchini1 at ,rome1 repeatedly observed dark spots1 and their outlines seem to have been so consistent that he depicted them on a chart and gave them names4 ,but ,j4 ,cassini1 at ,paris1 failed to confirm these results1 though he used telescopes of #hb-;and #aad-;feet focus2 and it was supposed the climate of ,paris was not suitable for such delicate observations4 ,schrter reviewed this planet in #aghh and later years1 and succeeded in detecting various markings and irregularities in the terminator and cusps4 ,he announced that he had seen the ,s4 horn of the crescent truncated1 so that a bright point was apparently isolated at its extremity4 ,from this he concluded there must be mountains of great altitude on the planet1 and the perpendicular height of one of these he computed at #bb miles1 which is four times the height of the most lofty mountain on the ,earth4 ,if the surface of ,venus were uniformly level1 then her cusps would taper gradually away to points1 and no such deformation as that described by ,schrter could possibly be produced4 ,and there is strong negative evidence among modern observations as to the existence of abnormal features2 so that the presence of very elevated mountains must be regarded as extremely doubtful1 if1 indeed1 the theory has not to be entirely abandoned4 ,the detached point at the ,s4 horn shown in ,schrter's telescope was probably a false appearance due to atmospheric disturbances or instrumental defects4 ,whenever the seeing is indifferent1 this planet assumes some treacherous features which are very apt to deceive the observer1 especially if his telescope is faulty4 ,spurious details are seen1 which quite disappear from the sharp images obtained in steadier air with a good glass4 ,i have never observed truncation in either of the horns of ,venus2 but on certain occasions1 when the planet has been ill-defined in passing vapours1 it was most easy to believe that a fragment became detached from the extremity of the cusp1 just in the manner described by ,schrter4 ,but close attention has showed the effect to be false1 and revealed its cause4 ,it was the rippling of the image that gave rise to the apparently dissevered cusp1 in the same way that passing air-waves and resulting quivers in the image of ,saturn's ring will sometimes produce displacements1 so that the observer momentarily sees several black divisions1 and the edges are multiplied and superimposed one on another4 ,refraction1 exercised by heated vapours in crossing objects1 is obviously the source of all this4 ,sir ,w4 ,herschel frequently examined this planet between #aggg and #agic1 but could not discern spots sufficiently definite and durable to enable him to fix the time of rotation4 ,he dissented from ,schrter as to the alleged mountains1 and said1 8,no eye which is not considerably better than mine1 or assisted by much better telescopes1 will ever get a sight of them40 ,mdler effected some observations of this planet in #ahcc and some subsequent years4 ,he detected spots on two occasions only1 but noticed irregularities in the terminator and cusps4 ,di ,vico and others at ,rome1 in #ahdj-a1 devoted much attention to this object1 and secured a large number of observations4 ,they appear to have recovered the spots charted by ,bianchini1 and described them as of the last degree of faintness4 ,the observers who saw the spots most readily were those who had the most difficulty in detecting the faint companion of a close double star4 ,in the spring of #ahda ,di ,vico saw a marking on the northern cusp involved in an oval luminosity1 and he likened it to a crater on the ,moon viewed obliquely4 ,this spot had a diameter of at least #d1 and it was seen to advance even into the obscure part of the disk4 ,rotation-,period4--,the following are the periods of rotation as given by the different authorities whose observations we have mentioned3-- #afff-g4 ,cassini #bc hrs4 #ba min4 #agbf-h4 ,bianchini #bd days #h hrs4#bh #ahaa4 ,schrter #bc hrs4 #ba min4 #h sec4#bi #ahdj-a4 ,di ,vico #bc hrs4 #ba min4 #bb sec4 ,schiaparelli has recently discussed a large number of observations of this planet1 and concludes that1 like ,mercury1 she rotates on her axis in the same time that she completes a sidereal revolution round the ,sun1 viz4 in #bbdg days6 ,i merely mention this remarkable deduction1 without quoting any facts in opposition to it4 ,from observations by ,perrotin at ,nice in #ahij1 including #gd observations1 the rotation of this planet is very slow1 and is made in such a way that the relative positions of the spots and terminator do not experience any notable change during many days4 ,illustration3 ,fig4 #cj4 #ahha1 ,mar4 #bb1 #f;h4 #ahha1 ,mar4 #bf1 #g;h4 #ahha1 ,mar4 #bh1 #f;h4 ,venus as an evening star4 7#aj-;inch ,reflector2 power #bab47 ,faintness of the ,markings4--,several observers have noticed a slight blunting of the ,s4 horn of ,venus1 and in recent years dusky spots have not unfrequently been seen1 notably by ,buffham1 ,langdon1 and others4 ,the only markings distinguishable with my #aj-;inch reflector are faint grey areas1 without definite boundaries4 ,these are sometimes so delicate that it is difficult to assign exact form and position to them1 and occasionally ,i have regarded their very existence as of doubtful character4 ,they appear to be mere inequalities in brightness of the surface1 and may be due to different reflective power in parts of the dense atmosphere of this planet4 ,certainly the spots are nothing like those seen on the disks of ,mars and ,jupiter1 many of which are extremely distinct and show sharply terminated outlines4 ,dawes1 an observer endowed with very keen sight1 could never succeed in finding any markings on ,venus1 and many others have failed4 ,but the evidence affirming their reality is too weighty and too numerously attested to allow them to be set aside4 ,occasionally the disk appears speckled with minute shadings1 and some observers have noticed crateriform objects near the terminator2 but these are uncertain4 ,brilliant spots have also been recorded quite recently at the cusps4 ,perhaps it may be advisable here to add a word of caution to observers not to be hastily drawn to believe the spots are visible in very small glasses4 ,accounts are sometimes published of very dark and definite markings seen with only #b or #c inches aperture4 ,such assertions are usually unreliable4 ,could the authors of such statements survey the planet through a good #aj-or #ab-;inch telescope1 they would see at once they had been deceived4 ,some years ago ,i made a number of observations of ,venus with #b-1 #c-1 and #d-a_/d-;inch refractors and #d-;and #aj-;inch reflectors1 and could readily detect with the small instruments what certainly appeared to be spots of a pronounced nature1 but on appealing to the #aj-;inch reflector1 in which the view became immensely improved1 the spots quite disappeared1 and there remained scarcely more than a suspicion of the faint condensations which usually constitute the only visible markings on the surface4 ,i believe1 also1 the serrated terminator is not a real feature of the object1 but rather an effect either of the rippling contour of the image or of an imperfect or inadequate telescope4 ,an atmosphere of considerable density probably surrounds this planet1 for at the limb the brightness of the disk is much intensified4 ,a medium like this1 that reflects and refracts light in extreme degree1 is brighter under oblique vision1 as at the limb of ,venus4 ,twilight on ,venus4--,when ,venus is a slender crescent1 near inferior conjunction1 a feeble luminosity pervades the dark part of the disk similar to the 8ashy light0 or earthshine observed on the crescented ,moon4 ,on such occasions the unilluminated surface appears to be involved in a phosphorescence4 ,several observers have1 however1 described the unilluminated limb of ,venus as darker than the background of sky4 ,zenger1 at ,prague1 has noticed a brownish-red ring surrounding the planet1 and he attributes the appearance to much the same cause as that which occasions the coppery colour of the ,moon in a total eclipse4 ,alleged ,satellite4--,cassini1 ,short1 ,montaigne1 and others1 in the #agth and #ahth centuries1 observed small crescents near ,venus and inferred the existence of a satellite2 but no such object has presented itself in more recent times4 ,it is extremely probable that the observers were mistaken4 ,in some cases the duplicate image may have been formed by reflection in the eyepiece2 in others a small star or planet situated near ,venus gave rise to the deception4 ,m4 ,stroobant has fully investigated this astronomical myth1 and disposed of many of the observations1 without having recourse to the apocryphal satellite named 8,neith0 by ,m4 ,niesten1 who has discussed the question from an affirmative point of view4 ,further ,observations required4--,from the foregoing summary amateurs will notice that several difficult and more or less evanescent features on this brilliant member of our system stand in need of confirmation4 ,certain disputed forms require also to be looked for4 ,the faint dusky patches1 the bright spots at the horns1 and the inequalities in the curve of the terminator will sure to be re-observed in future years2 and it is necessary that such details should be precisely noted in regard to their positions and outlines as often as possible4 ,a series of reliable observations of this character might enable a fresh value of the rotation-period to be deduced from them2 and this is desirable1 for though ,cassini1 ,schrter1 and ,di ,vico give periods which are in close harmony1 there are elements of uncertainty attached to their results4 ,a new determination of the period would be valuable1 and especially so if based on really trustworthy data obtained by one of the best modern telescopes4 ,with the planet situated near inferior conjunction1 the crescent 7reduced at such a time to a mere thread of light7 should be brought into the field1 and the observer should look for the extension of a faint glow over the interior parts of the surface1 and make comparisons between the relative brightness of the planet's dark limb and of the sky on which it is projected4 ,the telescopic images of ,venus are often excellent in daylight1 and those who possess means of readily finding the planet at such times will be very likely to gain some useful materials4 ,as to the presumed satellite1 that may be relegated to the care of observers who have the leisure and inclination to pursue an ignis fatuus2 but should any doubtful object appear in the field with ,venus at any time1 it ought to be fully recorded and identified1 if possible4 ,transits of ,venus4--,those who were prevented by circumstances of weather or otherwise from witnessing either of the transits of ,venus which occurred in #ahgd and #ahhb lost a spectacle of great rarity1 and one which they can never have another chance to behold4 ,the next transit occurs in the year #bjjd1 and its phenomena will doubtless be watched with avidity by the astronomers of a future generation4 ,the transit of #ahhb was seen by many observers in ,england1 though in some parts of the country the ,sun was obscured by clouds4 ,the planet was distinctly visible to the naked eye as a black circular spot in gradual motion across the solar disk4 ,the most important result of the telescopic observations was of course the re-determination of the ,sun's distance2 but amongst the physical features noted1 one of the most interesting was the appearance of a silver arc of light on that portion of the planet's edge which was outside the ,sun4 ,this is assumed to have been caused by the refraction of an atmosphere on ,venus4 ,the phenomenon was seen by several observers1 including ,prof4 ,langley in ,america and ,messrs4 ,prince and ,brodie in ,england4 ,occultations of ,venus4--,an occupation of this planet by the ,moon appears to have been recorded by the ,chinese on ,march #ai1 #cfa ,a4,d4 ,tycho ,brahe witnessed a similar phenomenon on ,may #bc1 #aehg4 ,mstlin observed ,venus occult ,regulus on ,sept4 #af1 #aegd2 and on ,oct4 #b1 #aeij1 this planet appears to have passed over ,mars4 ,visible occultations of ,venus are somewhat rare2 they usually occur in daylight4 ,a phenomenon of this kind was witnessed on ,dec4 #h1 #ahgg1 over all the ,w4 part of the ,united ,states2 and ,prof4 ,pritchett1 of ,missouri1 says3--8,the interest taken in it was shared alike by the educated and the illiterate1 and even by children40 ,the evening was cloudless1 and many persons noted the time of disappearance of ,venus as seen by the unassisted eye4 ,with a #ab-;inch refractor1 power #bge1 ,prof4 ,pritchett noted that 8when the bright limb of ,venus was within #h or #aj of the ,moon's dark limb1 a border of wavering light1 several seconds in width1 seemed to precede the planet4 ,its general effect was such as to place in doubt the moment of external contact40 ,a full description of this event1 and of the partial occultation of ,venus on ,oct4 #ab1 #ahgi1 is given in ,no4 #a of the #8,publications' of the ,morrison ,observatory1 ,missouri1 ,u4,s4,a4 ,venus is said1 by the ,arabian astronomer ,ibn-,jounis1 to have occulted ,regulus on ,sept4 #i1 #hhe ,a4,d42 and ,hind has examined the observations1 by means of ,le ,verrier's tables of the ,sun and planets4 ,he finds that on ,sept4 #i in the year mentioned1 at #af;h #dcm mean time1 ,venus approached the star within #ag2 so that to the naked eye the latter would appear to be occulted1 being overpowered in the glare of the planet4 ,,footnotes3 #bh ,this period was probably derived erroneously by ,bianchini4 ,it includes #be periods of #bc;h #bbm1 which corresponds with the times of rotation by ,cassini and others given in the table4 #bi ,schrter's final result4 ,in #aghh he had derived a period of #bc;h #bhm from observations of faint dark spots1 and in #aghi-ia irregularities in the ,s4 horn of ,venus gave him a period of #bc;h #bjm #eis4 ,,chapter ,,ix4 ,,mars4 ,appearance of the planet4--,period c4--,phase4--,surface ,configuration4--,charts and ,nomenclature of ,mars4--,discovery of two ,satellites and of ,canal-shaped markings4--,summary of ,observations4--,rotation of ,mars4--,further ,observations required4--,changes on ,mars4--,the two ,satellites4--,occultations of ,mars4 ,appearance of the ,planet4--,mars is the fourth planet in the order of distance from the ,sun4 ,he revolves in an orbit outside that of the ,earth1 and is the smallest of the superior planets4 ,his brilliancy is sometimes considerable when he occupies a position near to the ,earth1 and he emits an intense red light#cj1 which renders his appearance all the more striking4 ,ordinarily his lustre does not equal that of ,jupiter1 though when favourably placed he becomes a worthy rival of that orb4 ,in #agai he shone so brightly and with such a fiery aspect as to cause a panic4 ,the superstitious notions and belief in astrological influences prevailing at that time no doubt gave rise to the popular apprehension that the ruddy star was an omen of disaster1 and thus it was regarded with feelings of terror4 ,fortunately the light of science has long since removed such ideas from amongst us1 and celestial objects1 in all their various forms1 are contemplated without misgiving4 ,they are rather welcomed as affording the means of advancing our knowledge of ,god's wonderful works as displayed in the heavens4 ,period c4--,mars revolves round the ,sun in #fhf;d #bc;h #cjm #das1 and his mean distance from that luminary is #ada1ejj1jjj miles4 ,the orbit is one of considerable eccentricity1 the distance varying between #aed1gjj1jjj and #abh1cfj1jjj miles4 ,the apparent diameter of the planet when in conjunction with the ,sun is only #d2 but this may augment to #cjd at an opposition1 when the ,earth and ,mars occupy the least distant parts of their orbits4 ,the real diameter of ,mars is nearly #ejjj miles4 ,phase4--,at opposition the disk of ,mars is round1 but when in quadrature he appears distinctly gibbous and resembles the ,moon three days from full4 ,the phase is so palpable that ,galilei glimpsed it at the end of #afaj4 ,in delineations of ,mars the disk is generally drawn circular1 the compression being very slight and the phase too trivial to be regarded4 ,surface ,configuration4--,this planet being singularly variable in his position relatively to the ,earth1 presents at times a diameter so small that the most powerful instruments are ineffective to deal with him4 ,but at certain epochs he becomes an excellent object1 with a much expanded disk1 on which are displayed a number of bright and dark markings4 ,this happens1 however1 with comparative rarity2 for only during two months or so near every opposition1 occurring at intervals of #ghj days1 can the planet be well seen4 ,generally the apparent size of ,mars is very inconsiderable1 and the disk not sharply defined1 especially when the altitude is low4 ,reliable observations are seldom made at a time far removed from the date of opposition4 ,when the planet was badly placed1 in ,july #ahhb1 an observer secured some observations of position11 and published them1 thinking he had seen ,wells's ,comet1 which happened to be in the same quarter of the sky6 ,mars1 in nearer degree than any other member of our system1 shows a configuration which may be likened to that of the ,earth as regards its permanency2 and in some of its outlines a general resemblance also exists1 though in detail there is evidently much that is dissimilar4 ,it is fortunate that the atmosphere of ,mars is so rarefied that observers can look upon his real surface-lineaments with satisfactory perspicuity4 ,for more than #bej years now1 the telescope has been engaged in perfecting our knowledge of ,martian features1 and these have exhibited no mobility of form or place 7apart from that due to rotation or varying inclination of the planet7 so far as may be judged from a comparison of drawings4 ,plenty of differences exist in the latter1 it is true1 though similar objects are represented2 but the explanation obviously lies in the inaccuracies of amateur artists1 and has little if anything to do with physical changes on the planet4 ,when the spots were discovered in #afcf by ,fontana they were1 of course1 very dimly glimpsed in the incompetent appliances available at that time4 ,huygens1 in #afei1 saw them better by means of his long telescopes1 but still very imperfectly4 ,cassini1 in #afff1 effected a further advance in the same field1 and gathered data from which he was able to announce the period of rotation4 ,his value has proved remarkably correct1 considering the means he employed to obtain it and the very short interval over which his inquiries were conducted4 ,huygens had previously1 in #afei1 witnessed the returns of a certain spot to the same approximate place on the planet1 and was led to infer rotation in either #ab;h or #bd;h4 ,but this was little better than a guess1 and not nearly of the same precision as that which marked ,cassini's subsequent determination4 ,illustration3 ,fig4 #ca4 ,mars1 #ahcf1 ,april #ac1 #i;h #ejm2 long4 #ccb4 7#aj-;inch reflector2 power #beb47 ,near the poles of ,mars are intensely bright patches1 which have been considered to be vast areas of snow-crowned surface or fields of ice4 ,these 8polar snows0 are not situated exactly at the poles1 nor are they opposite to each other4 ,changes affect their aspect4 ,occasionally these or other bright markings1 when on the limb1 appear to protrude beyond the disk1 and this curious effect of irradiation distorts the limb in a striking manner4 ,charts and ,nomenclature of ,mars4--,it is not desirable to trace with any detail the successive labours of those who have chiefly contributed to our knowledge of areographic features4 ,maraldi1 ,w4 ,herschel1 ,schrter1 ,mdler1 ,schmidt1 and ,dawes were foremost amongst the observers of the past2 while ,schiaparelli and ,green are the most successful observers of to-day4 ,as telescopes improved in effectiveness the true forms and characteristics of the markings were discerned1 and at the present time some thousands of delineations of this planet must be in existence4 ,charts of the leading and best-assured features have been formed1 and the regions of light and shade 7supposed to represent land and sea7 have received proper names to distinguish them4 ,thus there is 8,fontana ,land10 8,maraldi ,sea10 8,herschel ,continent10 and others of similar import4 ,schiaparelli has framed a chart in which the spots are furnished with ,latin names taken from classical geography4 ,mdler's plan was to designate the markings by capital letters of the alphabet1 and to divide these by small letters in necessary cases4 ,but the charts of ,proctor1 ,green1 and others1 in which the names of past and present astronomers are applied1 seem to find most favour1 though it is admitted that this method of nomenclature is not free from objections4 ,in some instances the names have not been wisely selected4 ,a few years ago1 when christening celestial formations was more in fashion than it is now1 a man simply had to use a telescope for an evening or two on ,mars or the ,moon1 and spice the relation of his seeings with something in the way of novelty1 when his name would be pretty certainly attached to an object and hung in the heavens for all time6 ,a writer in the #8,astronomical ,register' for ,january #ahgi humorously suggested that 8the matter should be put into the hands of an advertizing agent0 and 8made the means of raising a revenue for astronomical purposes40 ,some men would not object to pay handsomely for the distinction of having their names applied to the seas and continents of ,mars or to the craters on the ,moon4 ,but it is all very well to disparage a system3 can a better one be found8 ,probably not2 but the lavish use of undeserving names is calculated to bring any system into contempt4 ,illustration3 ,fig4 #cb4 ,orbits of the ,satellites of ,mars4 ,discovery of ,satellites and of ,canal-shaped markings4--,the interest in this planet has been accentuated in recent years by several circumstances4 ,the discovery of two satellites in #ahgg by ,prof4 ,hall1 with the #beh-;inch ,washington refractor1 caused the directors of large instruments to test their capacity upon these minute objects4 ,schiaparelli's observations of the canal-shaped markings have afforded another attractive feature in connection with this planet4 ,he detected a network of dark straight lines stretching generally from ,n4 to ,s4 across the planet2 and in the winter of #ahha found these objects duplicated1 i4e4 the lines ran in pairs so close together that they were separated with difficulty4 ,the study of the topography of ,mars had never previously revealed structures like these2 yet the ,italian astronomer appears to have observed them with 8comparative ease whenever the air was still40 ,other observers have not wholly confirmed the appearances alluded to1 but no favourable opposition has occurred since #ahgg1 and no surprise need be felt that the delicate features visible in the pellucid sky of ,italy should elude detection in less genial climes4 ,in #ahhf ,m4 ,perrotin1 at ,nice1 using a #ae-;inch equatoreal1 saw a number of the 8canals10 and some of them were double4 ,in #ahhh the observers having charge of the #cf-;inch refractor at ,mount ,hamilton re-observed the 8canals0 as broad bands1 but none of them appeared to be duplicated4 ,the conditions were unfavourable1 the planet being more than three months past opposition4 ,prof4 ,schiaparelli re-observed the duple 8canals0 in ,june #ahij with a refractor by ,merz of #ah inches aperture1 powers #cej and #ejj4 ,his observations are supported by ,mr4 ,a4 ,s4 ,williams1 of ,brighton1 who informs me that he detected forty-three of the 8canals10 and seven of them were 8clearly and certainly seen to be double40 ,mr4 ,williams's instrument is a #f-;inch reflector by ,calver1 and powers of #cbj and #dcj were successfully employed on it2 magnifiers under #cjj were found of little use4 ,summary of ,observations4--,from observations at ,bristol ,i have drawn up the following summary as to the configuration of ,mars3-- #a4 ,that the 8,hour-glass0 or 8,kaiser ,sea10 and some other markings of analogous character1 present very bold1 dark1 and clearly defined outlines1 enabling them to be visible in very small telescopes4 ,in #ahgc ,i saw certain spots with a refractor of only #a-c_/d-;inch aperture4 ,mr4 ,grover1 in #ahfg1 8made a set of pencil-drawings1 with a #b-;inch telescope1 which gave the general markings of the planet very well40 ,in #8,recreative ,science' it is mentioned that on ,june #g1 #ahfj1 a semi-circular dark spot on the ,n4,w4 part of the disk of ,mars was distinctly seen with a #a-;inch telescope1 power #abj4 #b4 ,there is an intricate mass of surface-markings on the planet1 which1 in its main features1 is capable of being satisfactorily delineated1 and which in its general aspect is similar to the canals depicted by ,schiaparelli1 though not nearly so pronounced1 straight1 and uniform as he has shown in his charts4 #c4 ,the detail is visible in the form of irregular streaks1 condensations1 and veins of shading1 very faint and delicate in some parts4 ,the veins apparently connect many of the larger spots1 and here and there show condensations1 which have sometimes been drawn as isolated spots4 ,a night of good definition1 however1 reveals the feeble ligaments of shade connecting them4 #d4 ,that there exists on the immediate borders of many of the darker patches and veins a remarkable brightness or shimmering1 which reminds one of the bright spots merging out of the dark belts on ,jupiter4 ,just contiguous to the 8,kaiser ,sea10 and on its eastern limits1 this brightness was so striking in ,march #ahhf as to compare with that exhibited by the ,n4 polar cap4 ,in drawings by many observers these regions of special luminosity have no place1 but there is little doubt they occupy a leading position in the physical configuration of ,mars4 #e4 ,that there is no trace of a dense atmosphere on ,mars1 as some of the text-books infer4 ,the pronounced aspect of the chief markings1 their durableness and continuity of form1 the ease with which they may be traced up to the limb1 the absence of phenomena indicating dense cloud-bearing air-strata1 and other observed facts verify the conclusion that the planet's surface is comparatively free of vapours1 and in a totally different condition to that of ,jupiter and ,saturn4 ,rotation of ,mars4--,the diurnal period of this planet is known with far greater certainty and precision than that of any other planet1 the ,earth excepted4 ,it will be useful to quote the values derived since ,cassini's time3-- h m s #afff4 ,j4 ,d4 ,cassini #bd #dj #agjd4 ,j4 ,p4 ,maraldi #bd #ci #agha4 ,w4 ,herschel #bd #ci #bagca #aghd4 ,w4 ,herschel #bd #cg #bg #ahch4 ,j4,h4 ,mdler #bd #cg #bch #ahde4 ,o4 ,m4 ,mitchell #bd #cg #bjf #ahei4 ,a4 ,secchi #bd #cg #ce #ahfd4 ,f4 ,kaiser #bd #cg #bbfb #ahff4 ,r4 ,wolf #bd #cg #bbi #ahfi4 ,r4 ,a4 ,proctor #bd #cg #bbgce #ahgc4 ,f4 ,kaiser #bd #cg #bbeia #ahgc4 ,j4 ,f4 ,j4 ,schmidt #bd #cg #bbeg #ahhc4 ,a4 ,marth #bd #cg #bbfbf #ahhd4 ,w4 ,f4 ,denning #bd #cg #bbcdcb #ahhe4 ,h4 ,g4 v4 de ,s4 ,bakhuyzen #bd #cg #bbff ,the last of these1 by ,prof4 ,bakhuyzen of ,leyden1 is probably the best4 ,it was based on a large number of observations extending over #bbj years1 viz4 from those of ,huygens in #afei to those of ,schiaparelli in #ahgi4 ,in a terrestrial day ,mars rotates through #cejhibb1 according to ,mr4 ,marth's period4 ,in one hour the axial motion is #adf1 whereas on ,jupiter the horary rate of rotation is #cfg4 ,at intervals of #dj days 7during which ,mars completes #ci rotations7 the various features on the disk are presented at very nearly the same times as before4 ,mr4 ,marth's ephemerides of this planet are extremely useful to those who study the markings2 and these1 in combination with the charts and memoirs of ,schiaparelli1 ,green1 ,terby1 and others1 greatly facilitate and encourage the renewed study of this object4 ,further ,observations required4--,favourable oppositions of ,mars occur every #ae years1 as in #ahgg and #ahib4 ,it is at such periods that this planet should be sedulously interrogated for new features1 or for corroboration of those already known4 ,rather a high power must be employed--certainly more than #bjj2 and if the telescope has an aperture of at least #h inches1 the observer will be sure to discern a considerable extent of detail4 ,he should compare his views with the various charts previously alluded to1 and note any inconsistencies4 ,fresh drawings should also be made2 and if the forms are not well assured on one night1 he may confirm them by coming #cg minutes later to his instrument on the following night4 ,or the collective issue of several nights' work may be included in the same drawing4 ,the bright spots on the planet should be as attentively studied as the darker regions1 and given a place in every drawing2 for it is probably in connection with these luminous objects that active changes may be recognized4 ,the 8canals0 and their duplication form the principal markings to be looked for2 though the successful elucidation of these appearances can only be expected in a case where a powerful telescope1 a keen eye1 and a good atmosphere operate together4 ,something of them may be seen under ordinary conditions1 and they ought to be very generally sought for by amateurs2 for it is not always that success is found where the best conditions prevail4 ,the great telescopes at ,mount ,hamilton1 ,nice1 and other observatories may be expected to command some advantages of light1 power1 and position2 but this need not prevent competition1 or induce the idea that common appliances are practically of no avail4 ,everyone should strive to achieve as much as is consistent with his means and opportunities2 indeed there is all the more need for effort and energy in the observer when his tools are seemingly inadequate to a research1 and he should endeavour to find1 in his own eye and understanding1 that power which shall compensate in a great measure for lack of instrumental capacity4 ,mr4 ,proctor1 in his #8,old and ,new ,astronomy1' has justly remarked3--8,the directors of ,government observatories have usually been much less successful in studying planetary details than those zealous amateurs who take delight in the study of the heavenly orbs and are ready to wait and watch for favourable opportunities40 ,changes on ,mars4--,changes have been confidently reported in some of the ,martian spots4 ,instances have been quoted in which particular markings1 though very plain at certain times1 have scarcely been perceptible at others4 ,variations in outline as well as in visibility appear to have been witnessed1 and the subject is one which merits more extended notice4 ,it has been asserted that the origin of such variations probably lies in the aerial envelope of ,mars4 ,in ,april and ,may #ahhh ,m4 ,perrotin1 with the great refractor at ,nice1 failed to re-observe the feature known as the continent 8,libya0 on ,schiaparelli's chart1 and stated that though this formation was plainly visible in #ahhf1 it had ceased to exist in #ahhh4 ,he suggested that the obscuration was really produced by clouds or mists circulating in the atmosphere of ,mars4 ,but ,prof4 ,holden reported1 from the ,lick ,observatory1 that the object alluded to was distinctly visible with the #cf-;inch refractor there at the end of ,july1 and in the same form in which it was drawn by ,prof4 ,schiaparelli in #ahgg-h4 ,it is to be assumed1 therefore1 that if any change occurred it was one of transient nature4 ,there are other questions relating to the physical aspect of this planet which future observers should be able to answer4 ,do the markings retain their distinctness right up to the limb8 ,is the opaque crescent of the disk 7when ,mars is in quadrature7 involved in any phosphorescence or glow indicating an atmosphere8 ,are the bright spots and luminous borders to the continents equally as stable as the dark spots1 and do they maintain an equable brilliancy8 ,the ,n4 hemisphere of ,mars needs much further study1 as it is not so familiarly known as the ,s4 hemisphere4 ,this is due to the circumstance that1 at favourable oppositions1 the region of the ,s4 pole is suitably presented for observation4 ,it is only when the planet is comparatively distant1 and small in diameter1 that his ,n4 hemisphere comes into view4 ,the difference of inclination under which the features are seen at successive oppositions gives rise to many apparent changes of figure4 ,when the ,s4 hemisphere is exposed to the ,earth numerous objects are seen which are quite invisible when the opposite hemisphere is displayed to us4 ,these altering conditions have to be considered in their influences by every student of areography4 ,satellites of ,mars4--,after evading the keen and searching eyes of ,sir ,w4 ,herschel1 and the power of his #dj-;foot telescope--after eluding the grasp of ,lord ,rosse's #f-;foot speculum1 and the frequent scrutiny of ,lassell with his #b-;and #d-;foot mirrors1 the two satellites of ,mars were ultimately revealed to ,prof4 ,hall in the #beh-;inch refractor at ,washington4 ,these tiny orbs had been enabled to avoid previous discovery by their minuteness and by their close proximity to ,mars4 ,yet as soon as they were known to exist many observers saw them1 and in certain cases success was undoubtedly attained with comparatively small instruments4 ,the late ,dr4 ,erck picked up the outermost satellite with a #g-a_/c-;inch objective1 and ,mr4 ,pratt saw it with an #h-a_/g-;inch mirror by ,with4 ,but the effect of this eye-straining may just possibly1 in one or two instances1 have drawn the imagination out of its normal repose4 ,mr4 ,pratt's instrument shows stars in the group ,lyr which are invisible in the great ,washington telescope and in the #cf-;inch mirror formerly used by ,mr4 ,common2 so that it may well have produced a spectral satellite of ,mars4 ,but the satellites are certainly within the occasional reach of moderate means2 for they were repeatedly seen with a #i-;inch refractor at the ,observatory of ,princeton1 ,u4,s4,a41 in ,october and ,november #ahgi4 ,they 8were decidedly more easy to see than ,mimas10 the innermost satellite of ,saturn4 ,phobos1 the inner satellite1 revolves round the planet in #g;h #cim1 in an orbit #fjjj miles from the centre of ,mars4 ,at max4 elongation the satellite is about #ab distant from its primary1 and its opposition magnitude is #aa4 ,deimos1 the outer satellite1 revolves in #cj;h #ahm1 and its orbit is #ae1jjj miles distant from ,mars4 ,its elongations extend to #cb1 and its opposition mag4 is #ac4 ,these diminutive objects are probably not more than #aj miles in diameter4 ,they are obviously too faint for common instruments1 nor are they objects on which ordinary amateurs may occupy themselves with advantage4 ,of course it forms a highly interesting spectacle to glimpse1 just for once1 it may be1 the small bodies which resisted telescopic power for more than two and a half centuries2 but for really useful observations1 large aperture and means of accurate measurement are required4 ,occultations of ,mars4--,the most ancient account of a planetary occultation is probably that given by ,aristotle1 who refers to a lunar obscuration of ,mars that occurred on ,april #d1 #ceg ,b4,c41 according to the calculations of ,kepler4 ,another occultation of ,mars appears to have been recorded by the ,chinese on ,feb4 #ad1 #fi ,b4,c4 ,tycho ,brahe observed a repetition of the event on ,dec4 #cj1 #aeie4 ,mr4 ,baily describes a phenomenon of this kind which occurred on ,feb4 #ah1 #ahcg1 when 8the planet appeared of a fine yellow colour both at its ingress and egress4 ,no projection was observed40 ,mr4 ,snow1 of ,ashhurst1 saw the occultation of ,march #ab1 #ahed1 and he states the planet 8was of almost precisely the same colour as the ,moon1 and he could not help comparing it to a spangle on the face of the sky4 ,whilst it was slowly and solemnly vanishing1 it gave for several seconds the notion of its being the summit of a lunar mountain1 but melted gradually away40 ,as ,mars emersed1 8nothing whatever was to be seen of the two bodies1 clinging together1 as it were1 by threads of light2 nothing of the pear-shaped appearance often recorded as put on by planets under similar circumstances40 ,mr4 ,j4 ,tebbutt1 of ,windsor1 ,n4 ,s4 ,w41 watched an occultation of ,mars in full daylight on ,aug4 #ab1 #ahge1 when 8the rapid disappearance of the planet's disk was an exceedingly interesting phenomenon1 its extinction taking place at a considerable distance from the ,moon's illuminated disk4 ,the line marked by the ,moon's dark limb across the disk was well defined40 ,at the reappearance clouds were prevalent1 and 8the planet was observed as a small projection on the bright limb20 but he found it difficult to fix the exact time of last contact1 owing to the ill-defined character of the planet's gibbous limb4 ,an occultation of ,mars was also seen by ,prof4 ,grant at ,glasgow on ,june #c1 #ahgh4 ,,footnotes3 #cj ,this was believed by ,sir ,j4 ,herschel to be due to 8an ochrey tinge in the general soil1 like what the ,red-,sandstone districts on the ,earth may possibly offer to the inhabitants of ,mars1 only more decided40 #ca ,herschel's earlier observations were made in #aggg-gi1 and his period1 like that of his predecessors1 is about #b min4 in excess of the correct value2 but ,mdler pointed out that1 by giving ,mars an additional rotation on his axis1 ,herschel's value will agree within #b sec4 of his own4 ,herschel appears to have adopted #gfh rotations instead of #gfi1 and may have been led to this by the excessive periods of ,cassini and ,maraldi and by the want of intermediate data between his own observations in ,april #aggg and ,may-,june #aggi4 ,his second determination1 made in #aghd1 is more correct4 #cb ,deduced from observations extending over #ae years only1 at ,bristol4 ,,chapter ,x4 ,,the ,,planetoids4 ,number4--,history of their ,discovery4--,dimensions and ,brightness4--,occultation of ,vesta4 ,number4--,these bodies1 also called minor planets1 and1 formerly1 asteroids1 comprise a very numerous class1 and they are extremely small1 being quite invisible to the naked eye except in one or two special cases4 ,they all revolve in orbits situated between ,mars and ,jupiter4 ,the total number discovered is about #cjj1 of which ,prof4 ,j4 ,palisa of ,vienna has found more than #gj1 and the late ,dr4 ,c4 ,h4 ,f4 ,peters of ,clinton1 ,n4,y41 #di4 ,i have not given exact numbers in the two former cases1 because these discoveries are still rapidly progressing4 ,history of their ,discovery4--,the first known planetoid 7,ceres7 was sighted by ,piazzi on ,jan4 #a1 #ahja4 ,the following year1 on ,march #bh1 ,olbers found another 7,pallas74 ,in #ahjd1 on ,sept4 #a1 ,harding discovered a third 7,juno72 and in #ahjg1 ,march #bi1 ,olbers was a second time successful 7,vesta74 ,then for thirty-eight years no additions were made to the number4 ,the host of planetoids circulating between ,mars and ,jupiter preserved their incognito without disturbance from the prying and wakeful eyes of astronomers4 ,but in #ahde ,hencke1 of ,driessen1 after years of watching1 at length broke the spell of tranquillity by finding another small planet2 and his example was emulated by many other observers in subsequent years4 ,hind1 ,de ,gasparis1 and ,goldschmidt were amongst the earliest and most successful of those who gathered new planets from amongst the stars of the zodiacal constellations4 ,in later years ,luther1 ,watson1 and ,borrelly further extended the list2 but ,palisa and ,peters have distanced all competitors1 and shown a zeal in the work which has yielded an astonishing aggregate of discoveries4 ,charlois1 at ,nice1 has latterly earned distinction in the same field4 ,since #ahde new planetoids have been found at the rate of more than six per annum1 and a rich harvest yet remains to be gathered by the planet-seekers of the future4 ,a very large proportion of those already detected are between the tenth and twelfth magnitudes1 and are therefore only to be discerned in good instruments4 ,they present no distinction from small star-like points1 and are to be identified by their motions alone4 ,the mythological dictionary has furnished names for them1 and they are numbered in the order of their discovery as well4 ,dimensions and ,brightness4--,vesta is the largest and brightest of the group1 while ,ceres and ,pallas rank as second and third in the same respect4 ,vesta is about #bad miles in diameter2 but the more insignificant members of this family are probably not more than about #ae or #bj miles in diameter4 ,pallas has the most inclined orbit of all1 the inclination amounting to #cj #dd2 so that its position is by no means confined to the planet-zone of the ecliptic4 ,vesta is sometimes brighter than a #fth mag4 star2 while ,ceres1 ,pallas1 and ,juno vary between about the #gth and #hth magnitudes1 according to their distances from the ,earth4 ,a real variation of light has been assumed to occur1 but this is not fully proved4 ,in ,march #ahhg ,mr4 ,backhouse1 of ,sunderland1 saw an apparently new1 yellowish-white star near #ajc ,piscium1 and it was just visible to the naked eye4 ,this proved to be ,vesta1 though the identity of the object was not known at first1 and it formed the subject of two ,dun ,echt circulars4 ,formerly1 hazy indefinite outlines were attributed to some of the planetoids2 but the appearance probably arose from instrumental defects4 ,the search for these bodies is not a work likely to engage amateurs4 ,professional observers are best able to grapple with the difficulties attending this kind of observation1 where large telescopes1 means of exact measurement1 and ample data1 such as star-charts and ephemerides of the planetoids previously discovered1 are requisite4 ,the #8,nautical ,almanack' annually contains ephemerides of ,ceres1 ,pallas1 ,juno1 and ,vesta2 and observers wishing to pick up any one of them may readily ascertain positions by reference to this work4 ,occultation of ,vesta4--,an occultation of ,vesta occurred on ,dec4 #cj1 #ahga1 and it was observed by ,mr4 ,c4 ,g4 ,talmage at ,leyton with a #aj-;inch refractor1 power #hj4 ,he says the planet was exceedingly bright right up to the ,moon's limb4 ,,chapter ,,xi4 ,,jupiter4 ,an interesting ,object4--,brightness and ,position4--,period c4--,belts and ,spots on the ,planet4--,observations of ,hooke1 ,cassini1 and others4--,the 8,ellipse0 of #ahfi-gj4--,the ,red ,spot1 its appearance1 dimensions1 and rotation-period4--,bright equatoreal ,spots4--,dark ,spots in ,n4 hemisphere4--,rotation-period4--,nature of the ,red ,spot and of the bright and dark equatoreal ,spots4--,new ,belts4--,changes on ,jupiter4--,further ,observations required4--,occultations of ,jupiter4--,the four ,satellites1 and their phenomena4--,occultation of a star by ,jupiter4 8,beyond the sphere of ,mars1 in distant skies1 ,revolves the mighty magnitude of ,jove1 ,with kingly state1 the rival of the ,sun40 ,of all the planets1 ,jupiter is the most interesting for study by the amateur4 ,it is true that ,saturn forms an exquisite object1 and that his wonderful ring-system is well calculated to incite admiration as a feature unique in the solar system4 ,but when the two planets come to be repeatedly observed1 and the charm of first impressions has worn away1 the observer must admit that ,jupiter1 with his broad disk and constantly changing markings1 affords the materials for prolonged study and sustained interest4 ,with ,saturn the case is different4 ,his features are apparently quiescent2 usually there are no definite spots upon the belts or rings4 ,there is a sameness in the telescopic views2 and this ultimately leads to a feeling of monotony1 which causes the object to be neglected in favour of another where active changes are in visible progress4 ,brightness and ,position4--,jupiter is a brilliant object in the heavens1 his lustre exceeding that of ,mars or ,saturn1 though not equal to that of ,venus4 ,i have occasionally seen the planet with the naked eye in the daytime1 about half an hour after sunrise2 and it has been frequently observed by ,bond1 in ,america1 with the ,sun at a considerable altitude4 ,humboldt and ,bonpland1 at ,cumana1 #aj ,n4 lat41 saw ,jupiter distinctly with the naked eye1 #ah minutes after the ,sun had appeared in the horizon1 on ,sept4 #bf1 #ahcj4 ,the planet is favourably visible for a considerable time every year1 and is only beyond reach near the times of his conjunctions with the ,sun1 when he usually evades observation for about three months4 ,as regards his altitude1 ,jupiter becomes exceptionally well placed at intervals of #ab years2 thus in #ahei1 #ahgj-a1 and #ahhb his declination was #bb or #bc ,n41 and his height therefore very great when passing the meridian4 ,in #ahid he will occupy a similarly auspicious region to observers in the ,n4 hemisphere4 ,in #ahfe1 #ahgg1 and #ahhi his declination was #bc ,s41 and he was favourably presented to southern astronomers4 ,the image of ,jupiter as seen in a telescope is involved in a slight yellow tinge1 and with the naked eye the same colour is often apparent4 ,but when observed through a very pure transparent atmosphere1 his light nearly approaches the silvery lustre of ,venus or the ,moon4 ,the planet shines with unusual splendour1 considering his great distance from the ,sun1 and his atmosphere must be highly reflective and possibly intensified by inherent light from the planet himself4 ,the central parts of ,jupiter's disk are usually the brightest1 as there is a faint shading-off and indefiniteness at the limbs4 ,these and other facts support the view that ,jupiter is still incalescent and sufficiently self-luminous to emit a small amount of light4 ,period c4--,this planet revolves round the ,sun in #dccb;d #ad;h #bm1 which is equal to more than #aa-c_/d years4 ,his orbit is somewhat eccentric1 so that his distance from the ,sun varies from #ejf1ejj1jjj to #dfj1jjj1jjj miles1 and the mean is #dhc1cjj1jjj miles4 ,his apparent diameter ranges from a max4 of #ej at a good opposition to #cjd in conjunction4 ,the planet's diameter measured along the equator is #hh1jjj miles1 and the polar compression is very marked1 amounting to #a_/af1 or1 more exactly1 to #a_/aehb1 according to ,engelmann1 from a mean derived from eleven observers4 ,when ,jupiter is in quadrature there is a slight phase evident in the shading-off of the limb furthest from the ,sun4 ,belts and ,spots on the ,planet4--,from the time that the telescope became available as a means of astronomical research1 it may be readily surmised that an object coming so well within the reach of ordinary appliances1 and one displaying so many prominent and variable features1 should absorb a large share of attention1 and that many facts of interest should have been gleaned as to his physical peculiarities4 ,but it must be confessed that1 though something has been learned as to the visible behaviour of the markings1 there is much that is perplexing in their curious vagaries4 ,no doubt the vast changes affecting the ,jovian envelope1 the diversity of the markings1 and their proper motions result from the operations of a peculiarly variable atmosphere1 affected probably by a heated and active globe beneath it1 and by the very rapid movement of rotation to which it is subject4 ,the telescope1 on being turned towards ,jupiter1 reveals at once an array of dark and light stripes or belts stretching across the disk in a direction parallel to one another and to the equator of the planet4 ,these belts are supposed to have been first detected by ,zucchi in #afcj4 ,usually there are two broad and prominent dark belts1 one on either side of the equator2 while towards the poles other belts appear1 some of them very narrow1 partly by the effects of foreshortening4 ,the equatoreal zone of the planet is of a lighter tint1 and variegated with white and dark spots and streaks1 liable to rapid changes1 and indicating that this region is in a highly disturbed condition4 ,observations of ,hooke1 ,cassini1 and others4--,hooke and ,cassini were amongst the first to find definite spots on the surface of ,jupiter4 ,from #affd to #affg a particularly large and distinct spot was frequently seen in the planet's ,s4 hemisphere4 ,this object disappeared in the latter year1 but returned in #afgb1 and was seen until the close of #afgd1 when it again temporarily vanished1 to reappear at subsequent epochs4 ,cassini was enabled to determine the rotation-period from this spot4 ,he found that the markings in the immediate vicinity of the equator moved with greater celerity than those in higher latitudes1 the difference in their rotation-periods being nearly #f minutes4 ,a century later ,sir ,w4 ,herschel confirmed these results3 he saw a bright spot which completed a rotation in nearly #e minutes less time than several dark spots4 ,schrter also made many observations1 and noted frequent changes in the spots and differences in their rotation-periods4 ,he watched a bright object near the equator which had a period more than #e minutes less than some dark spots4 ,in later years ,mdler and others followed up the investigation of these markings1 and with nearly similar results4 ,the various spots were undoubtedly affected by proper motions1 enabling them to yield discordant rotation-periods4 ,bright forms near the equator moved with great rapidity and effected a rotation in about #i;h #ejm1 while dark spots on either side of it occupied between #i;h #eem and #i;h #efm4 ,the markings were evidently controlled by currents of different velocities in the planet's atmosphere4 ,dawes1 in #ahdi and following years1 noted luminous spots1 like satellites in transit1 on a belt in the planet's ,s4 hemisphere4 ,in ,october #aheg he observed a group of eleven of these objects2 and in #aheh ,lassell saw many similar appearances in a bright belt near the equator4 ,the ,ellipse of #ahfi-gj4--;,in #ahfi and #ahgj ,gledhill1 of ,halifax1 and ,prof4 ,mayer1 of the ,lehigh ,university1 saw a remarkable formation just south of the great belt lying on the ,s4 side of the equator4 ,it was in the form of a perfect ellipse1 ruddy in colour1 and very distinct in outline4 ,its major axis was parallel with the belts4 ,it was first observed on ,nov4 #ad1 #ahfi1 and had disappeared in ,july #ahgj1 though on ,dec4 #a1 #ahga1 a similar elliptic ring was seen resting on the ,s4 equatoreal dark band4 ,the ,red ,spot4--,in ,july #ahgh a large spot1 of oval form and intense red colour1 appeared in about the same latitude as the ellipse seen by ,gledhill and ,mayer in #ahfi-gj4 ,it was first announced by ,dennett of ,southampton1 though it appears to have been seen a few weeks earlier by ,prof4 ,pritchett1 of ,missouri1 ,u4,s4,a4 ,the object alluded to soon attracted general notice2 and as it continued visible during the oppositions of #ahgi1 #ahhj1 and #ahha under the same striking aspect1 it created a considerable stir among telescopists1 and the 8great red spot on ,jupiter0 became familiarly known both in appearance and in title4 ,no planetary marking in modern times has enlisted half the amount of attention that has been devoted to this object4 ,it has endured amid all the turmoils of the ,jovian atmosphere for twelve years1 and has preserved an integrity of form and size which prove it to have been singularly capable of withstanding disruption4 ,but its tint has varied greatly2 so that at times the oval outline of the spot could hardly be discerned amongst the contiguous belts4 ,in the winter of #ahha the interior of the ellipse began to lose tone1 and in #ahhb it faded rapidly1 so that the central region of the spot assumed nearly the same light tint as the outlying bright belts4 ,apparently the spot had either been filled up with luminous cloudy material or had been partially obscured by the interposition of matter situated higher in the ,jovian atmosphere4 ,the elliptical contour of the object was still intact1 however1 though it had quite lost its bold and prominent character4 ,only the skeleton of its former self remained1 and its entire disappearance seemed imminent4 ,but further decadence was fortunately averted by influences unknown to us1 and the spot has continued visible to this day1 though shorn of the attributes which roused so much enthusiasm amongst observers more than ten years ago4 ,from measures at ,chicago1 in the years from #ahgi to #ahhd1 ,prof4 ,hough found the mean dimensions of the spot to be3--,length #aage1 breadth #cga4 ,these figures represent a real length of #be1ijj miles and a diameter of #hbjj miles4 ,the latitude of the spot was #fig ,s4 ,this object has served an important end in attracting wide-spread observation1 not only to itself1 but to the general phenomena occurring on the surface of ,jupiter4 ,observers1 in studying the red spot1 were also led to study the bright equatoreal spots and other features so plentifully distributed over the disk4 ,it was most important this should be done2 for since the time of ,herschel and ,schrter not much progress had been made in elucidating the proper motions of the spots and finding an accurate rotation-period for the planet4 ,dawes1 ,lassell1 and many others had1 it is true1 secured some interesting observations and drawings1 but not of the special kind required1 and thus no fresh light had been thrown upon the vagaries in the behaviour of the spots1 as described by the old observers4 ,but a mass of new facts were now to be realized4 ,schmidt at ,athens1 ,prof4 ,hough at ,chicago1 ,a4 ,stanley ,williams at ,brighton1 and many others1 including myself at ,bristol1 began systematic observations of ,jupiter1 with a view to learn something more of the periods1 changes1 and general characteristics of the spots and other features4 ,the results were of an interesting nature1 though too extensive for more than bare mention here4 ,in #ahgi the red spot gave a rotation-period of #i;h #eem #cds#b1 but this increased to #i;h #eem #ces#f in #ahhj-a and to #i;h #eem #chs#b in #ahha-b4 ,during the ensuing three years the period was almost stationary at #i;h #eem #cis#a1 but in #ahhe-f it further augmented to #i;h #eem #das#a1 since which year it has ranged between #i;h #eem #djs and #das4 ,from ten years' observations1 the mean period of the red spot is as nearly as possible #i;h #eem #cis4 ,bright ,equatoreal ,spots4--,the bright spots near the equator rotated in #i;h #ejm #fs in #ahhj2 but in subsequent years the time slightly increased1 for in #ahhb ,i found it #i;h #ejm #hs#h1 and in #ahhc #i;h #ejm #aas#d4 ,the bright spots therefore perform a rotation in #e minutes less time than the red spot4 ,the former move so much more swiftly than the latter that they pass it at the rate of #bfj miles per hour1 and in #dd days have effected a complete circuit of ,jupiter relatively to it4 ,thus a brilliant white spot1 if noticed in the same longitude as the red spot on one night1 will1 on subsequent nights1 be observed to the ,w4 of it1 and1 after an interval of about #dd days1 the same objects will again occupy coincident longitude4 ,dark ,spots in ,n4 hemisphere4--,in the autumn of #ahhj there was a confluent outbreak of dark spots from a belt in about #be ,n4 latitude1 and these exhibited a rotation-period of only #i;h #dhm1 so that they travelled more rapidly than the white spots on the equator4 ,some short dusky belts were also remarked slightly ,s4 of the latitude of the red spot1 and these indicated a period of #i;h #eem #ahs4 ,it is clear from these various results that the motion of the ,jovian markings does not decrease according to their distance from the equator4 ,rotation-,period4--,below are given the times of rotation ascertained by some previous observers3-- h m s #affe4 ,j4 ,d4 ,cassini #i #ee #eh #afgb4 0 #i #ee #ej #afib4 0 7,a7#i #ej #agjh4 ,j4 ,p4 ,maraldi #i #ef #dh #agac4 0 #i #ef #aggc4 ,sylvabelle #i #ef #aggi4 7,b7,w4 ,herschel #i #ed #ec to #i #ee #dj #aggi4 0 7,a7#i #ej #dh to #i #ea #def #aghf4 7,c7,j4 ,h4 ,schrter #i #ee #ccf 0 0 #i #ee #agf 0 0 7,a7#i #ej #bg #ahce4 ,j4 ,h4 ,mdler #i #ee #bfe 0 ,g4 ,b4 ,airy #i #ee #bac #ahcf4 ,j4 ,h4 ,mdler #i #ee #bce #ahfb4 ,j4 ,f4 ,j4 ,schmidt #i #ee #beg #ahff4 0 #i #ee #dfc #ahgc4 ,o4 ,lohse #i #ee #aif #ahhj4 ,j4 ,f4 ,j4 ,schmidt #i #ee #cdd 0 0 7,a7#i #ej #ahha4 ,w4 ,f4 ,denning #i #dh 0 0 #i #ee #agi #ahhc4 0 7,a7#i #ej #hg #ahhe4 ,g4 ,w4 ,hough #i #ee #cgd 0 0 7,a7#i #ej #i #ahhf4 ,a4 ,marth #i #ee #djf #ahhg4 ,a4 ,s4 ,williams3-- ,spots in #ab ,n4 lat4 #i #ee #cfe 0 #d ,n4 lat4 7,a7#i #ej #dja 0 #h ,s4 lat4 7,a7#i #ej #bbd 0 #cj ,s4 lat4 #i #ee #aga #ahij4 7,d7,w4 ,f4 ,denning #i #ee #ci ,a3 ,bright spots near the equator of ,jupiter4 ,b3 ,herschel's observations embraced few rotations1 and the periods he derived differed considerably4 ,c3 ,schrter also alleges he saw spots return to the same part of the disk in #g;h #gm1 #g;h #cfm1 and #h;h #am6 ,d3 ,from ten years' observations of the red spot4 ,the foregoing list is by no means complete1 for1 owing to the large number of recent determinations1 ,i have thought it advisable to omit some of them4 ,it should be mentioned here that the above times of rotation are derived from atmospheric features more or less volatile in nature1 and that therefore the actual sphere of ,jupiter rotates in a period which we have not precisely discovered4 ,no doubt the motion of the real surface is not very different from that of the atmospheric markings above it4 ,there is reason to think that1 whatever the character of the planet's crust may be1 we have never yet obtained a glimpse of it4 ,a dense veil of impenetrable vapours appears to surround the globe on all sides1 and this is subject to violent derangement from the evolution of heated material or gaseous fluids from the surface below4 ,these disturbances seem to be very durable in some instances as to their observed effects4 ,the atmosphere would1 in fact1 appear to possess a singular capacity for retaining the impressions of its changes4 ,the permanency of certain spots can hardly be due to continued action from those parts of the disk immediately underlying them2 for their variable motions soon transport them far from the places at which they were first seen1 and prove their existence to be quite independent of their longitude4 ,nature of the ,red ,spot4--,there is much in connection with the red spot that remains in mystery4 ,its dimensions1 form1 and motion have severally been ascertained within small limits of error1 and the alterations in its tint and degree of visibility have been recorded with every care4 ,but we can only conjecture as to the origin1 character1 and end of this remarkable formation4 ,what agency produced it1 and moulded the definite elliptical outline it has always preserved--what forces control its oscillations of speed1 and keep it suspended so long in the aerial envelope of ,jupiter--are matters of pure theory4 ,when1 in ,july #ahgh1 it first came under notice it was a well-developed object1 and though ,russell in #ahgf1 ,lord ,rosse and others in #ahgc1 and ,gledhill and ,mayer in #ahfi-gj had delineated forms suspiciously like the red spot and situated in the same latitude1 yet the several features may not have been absolutely identical1 for nothing was seen of the spot in #ahgg or in some other years4 ,but there is a strong probability that the red ellipse of #ahfi-gj must have been the red spot in an incipient stage of its formation4 ,the object may have undergone temporary obscuration1 similarly to ,cassini's spot two centuries ago4 ,illustration3 ,fig4 #cc4 ,i4 #aheg1 ,nov4 #bg4 7,dawes47 ,,ii4 #ahei1 ,dec4 #bi4 7,huggins47 ,,iii4 #aheh1 ,mar4 #b4 7,huggins47 ,,iv4 #ahgj1 ,jan4 #bc4 7,gledhill47 ,v4 #ahgb1 ,feb4 #b4 7,gledhill47 ,,vi4 #ahhe1 ,feb4 #be4 7,denning47 ,my own opinion of the spot is that it represents an opening in the atmosphere of ,jupiter1 through which1 in #ahgh-hb1 we saw the dense red vapours of his lower strata1 if not his actual surface itself4 ,its lighter tint in recent years is probably due to the filling-in of the cavity by the encroachment of durable clouds in the vicinity4 ,parts of some of the more prominent belts display an intense red hue like that formerly shown by the red spot1 and they may be due to the same causes4 ,extensive fissures are probably formed in the atmosphere1 and quickly distended in longitude by the natural effect of the planet's tremendous velocity of rotation4 ,it is curious1 however1 that these rents1 after a certain distention1 assume a durable outline until they lose their colouring and are temporarily if not finally obliterated4 ,when the red spot was visible under its best conditions ,i frequently examined it1 hoping to detect some mark well in its interior which might serve as a clue to the true rotation-period of the sphere of ,jupiter4 ,for if the spot consisted of a clear patch in the planet's atmosphere1 ,i thought it possible some real object on the surface might be discerned through it1 in which case the difference in its motion and that of the red spot would enable the rate of motion of the globe to be found4 ,if the spot moves more slowly than the planet1 then a surface-marking must appear to pass from the ,e4 to the ,w4 side of the spot2 but no such evidence could be obtained1 owing to the absence of suitable markings4 ,the red tint of the great spot seemed very general over the entire area of the ellipse until its central regions paled in #ahhb4 ,there were two dark specks1 one at the ,e4 and another at the ,w4 extremity of the spot2 but these were unchangeable as regards position4 ,illustration3 ,fig4 #cd4 ,jupiter1 #ahhf1 ,april #i;d #aj;h #abm4 7#aj-;inch reflector2 power #beb47 ,the spot1 though placed very near the border of the great ,s4 belt1 has never been connected with it1 though in ,jan4-,feb4 #ahhd1 ,may #ahhe1 and ,march-,april #ahhf the spot became temporarily attached to a belt on its ,s4 side4 ,there was some controversy as to this feature1 ,prof4 ,hough1 from observations with the #ah-;inch refractor at ,chicago1 alleging that at no time had the spot coalesced with or been joined to any belt in its vicinity4 ,but in #ahhf many observers succeeded in detecting the junction of the markings alluded to1 and ,prof4 ,young gave a drawing of the appearance as seen with power #gij on the #bc-;inch objective at ,princeton 7see #8,sidereal ,messenger1' vol4 v4 p4 #bib74 ,the spot and belt were probably at different heights in the ,jovian atmosphere1 so that there was no commingling of material1 one object being simply projected on the other1 for the elliptical form of the red spot remained visible all the time4 ,the latter moves more slowly than the connecting belts1 and1 when clear of them1 is often seen with a white aureola fringing its environs4 ,bright ,equatoreal ,spots4--,these are affected by rapid changes of form1 brightness1 and motion4 ,sometimes they are exceedingly bright2 at other periods they are quite invisible4 ,this intermittency is not occasioned 7as ,i assured myself by many observations7 by the total extinction of spots and appearance of new ones1 but is due to the temporary obscuration of the same objects4 ,the variations are irregular1 and probably depend upon phenomena also irregular4 ,the motion of these objects often shows great deviations from their average rate2 they are sometimes much in advance of or behind their computed positions4 ,one fine spot of this class was closely watched in #ahhj and following years4 ,it was usually in the shape of a brilliant oval1 well defined1 and occasionally quite as large as the third satellite of ,jupiter2 but it was sometimes seen as a diffused white patch1 apparently emerging from the ,n4 edge of the belt4 ,whenever the spot was very bright1 there was a trail of light or luminous matter running eastwards from it1 as though there were an eruption of shining material from the spot1 which the rapid rotation of the planet from ,w4 to ,e4 caused to drift in an opposite direction4 ,dark ,equatoreal ,spots4--,closely contiguous to the white spots there are almost invariably seen very dark spots1 much deeper in tone than the dark belt upon which they appear to be projected4 ,it has been suggested that these dark spots are shadows from the white spots1 which may be elevated formations protruding through the envelope of ,jupiter4 ,this idea seems to me untenable2 for the dark spots have been distinguished under a vertical ,sun1 and sometimes they are found one on each side of a white spot4 ,again1 an intensely brilliant spot is occasionally seen without any outlying condensation of dark matter4 ,but though they are not shadows1 the dark equatoreal spots certainly have an intimate relation with the brighter markings near them and move with the same velocity4 ,it is proved from many observations that the longer an object is observed the slower becomes its rate of rotation4 ,sir ,w4 ,herschel found the converse4 ,in discussing his results of #aggh and #aggi1 he said3--8,by a comparison of the different periods it appears that a spot gradually performs its revolutions in less time than at first0 7,phil4 ,trans4 #agha1 p4 #abf74 ,but his periods were each based on less than fifty rotations1 so that no certain conclusions could be derived from them4 ,in recent years the rapidly moving bright spots have usually appeared in the equatoreal side of the great ,s4 dark belt4 ,the polar side of the great ,n4 belt also exhibits bright spots1 but these rotate in a period only a few seconds less than that of the red spot4 ,bright spots are also observed to the ,s4 of the latter object and on other portions of the disk4 ,as to the belts1 they are usually straight2 but cases are recorded of slant-belts1 in which the direction has been very oblique4 ,one of these was noticed in the planet's ,n4 hemisphere in ,mar4-,april #ahfj1 and another was seen in the ,s4 hemisphere in ,jan4 #ahgb4 ,i observed one near the ,n4 polar shading in ,dec4 #ahha4 ,new ,belts4--,the formation of the dark belts seems to be brought about gradually1 and they appear to be sustained in certain cases by eruptions of dark matter1 which gradually spread out into streams4 ,on ,oct4 #ag1 #ahhj1 two dark spots1 separated by #bj of longitude1 broke out on a belt some #be ,n4 of the equator4 ,other spots quickly formed on each side of the pair alluded to1 and distended themselves along the belt so that by ,dec4 #cj they covered three fourths of its entire circumference4 ,at the middle of ,january the spots formed a complete girdle round the planet2 but they became much fainter1 and were soon eradicated by combination with the belt on which they had appeared4 ,changes on ,jupiter4--,prof4 ,hough1 of ,chicago1 is adverse to the opinion that rapid changes occur on ,jupiter1 and mentions the stability of the red spot and other markings in support of his views4 ,he believes that the erroneous statements about sudden changes made by both ancient and modern astronomers are largely due to differences in the telescopic images due to atmospheric variations4 ,no doubt such an explanation will suffice to meet some instances1 and the swift rotation of the planet may also have been the unsuspected cause of some of the extraordinary changes described2 but there are real variations as well4 ,these are very frequent in the planet's equatoreal zone4 ,further ,observations required4--,drawings of ,jupiter obtained under the highest powers that may be employed with advantage1 and with a cautious regard to faithful delineation1 will probably throw much light on the phenomena occurring in this planet's atmosphere4 ,and it is most desirable to pursue the various markings year after year with unflagging perseverance2 for it is only by such means that we can hope to unravel the extraordinary problem which their visible behaviour offers for solution4 ,too much stress cannot possibly be laid on the necessity of observers being as precise as possible in their records4 ,the times when an object comes to the central meridian should be invariably noted2 for this affords a clue to its longitude1 and a means of determining its velocity4 ,its position1 ,n4 or ,s4 of the equator1 should be either measured or estimated2 and alterations in tone1 figure1 or tint described1 with a view to ascertain its real character4 ,the climate of ,england is very ill-adapted to an investigation of this sort1 where the most needful point consists in frequency of observation4 ,if the markings on ,jupiter could be re-examined every night1 and traced through their changes1 an explanation of certain phenomena exhibited by them would soon be forthcoming4 ,the interrupted character of previous observations destroys much of their value4 ,closely consecutive results are necessary to remove doubts as to the identity of the objects observed2 so that1 in such a research1 natural advantages of position are more desirable than instrumental advantages1 for the latter are impotent in a cloudy atmosphere4 ,the red spot must be watched as long as any vestiges of it remain4 ,its variations of speed may ultimately yield indications of periodicity#cc2 so may its alterations of tint4 ,the belts in the vicinity of the spot demand an equal share of attention2 for it may be possible to divine from their changes whether there are any links of association between them and the red spot4 ,in recent years the latter has apparently repulsed the belts on its ,n4 side1 though suffering encroachments from those on its ,s4 side4 ,the equatoreal spots also deserve continued vigilance on the part of observers4 ,it has already been stated that the bright spots vary rapidly2 their motions are not uniform in rate1 and what is now wanted is a large number of new observations4 ,does accelerated velocity occur with increased brilliancy of these objects8 ,are their alternating disappearances and revivals uniform in period8 and are they really due to transitory obscurations of the same durable forms8 ,are the dark spots which frequently border the white spots implicated in effacing the latter8 ,many other questions like these are suggested by the curious behaviour of the markings1 and the discriminating observer will know how to gather the materials likely to aid in answering them4 ,the rotation-period has been already found in regard to many features2 but this element may be re-investigated with profit1 for the velocity of the spots offers a very complex problem for solution4 ,do the markings generally exhibit a retardation of speed as long as they subsist8 ,abnormal spots1 such as those which made their apparition in the autumn of #ahhj1 should be traced through any vagaries they may present2 and peculiar shape or direction in the belts will also merit study1 as possibly supplying facts of consequence4 ,it will be important to learn whether objects in a certain latitude have a common rotation-period1 or whether different forms give different times4 ,the rate of motion shown by certain features may depend upon their character1 and not so much upon their position in latitude4 ,the altitudes of the various markings affords another promising line of research4 ,the appearances and changes of closely contiguous features may be expected to furnish useful data in this connection4 ,owing to their proper motions they apparently overlap each other at times1 and in their alterations of aspect the observer may discover the clue to their relative heights4 ,the subject is discussed in a practical and interesting way by ,mr4 ,green 7,memoirs ,r4 ,a4 ,s4 vol4 xlix4 p4 #bfd7 and by ,mr4 ,stanley ,williams 7#8,zenographic ,fragments1' i4 p4 #aab71 and these works should be consulted by everyone engaged in the study of ,jovian phenomena4 ,it is unfortunate that the observer1 in delineating this object1 must perforce adopt an extremely hurried method of representing what he sees at the telescope4 ,the planet turns so quickly upon his axis that forms near the central meridian become sensibly displaced in a few minutes2 indeed1 it has been stated that an interval of two minutes only is sufficient to introduce a change obvious to simple eye-estimation4 ,in order1 therefore1 to complete a sketch1 the utmost dispatch is requisite2 for this object cannot be depicted from the combined outcome of several evenings of observation4 ,the proper motions of the different features prevent this4 ,with ,mars1 or any orb exhibiting markings relatively constant1 collective results are extremely valuable1 and more trustworthy than pictures depending upon an isolated observation4 ,amateurs1 in entering upon these observations1 should be prepared for rapid changes in the apparent aspect of ,jupiter caused by his rotation1 and not hastily infer them to be real4 ,they should also hesitate before placing confidence in any anomalous results obtained under indifferent seeing2 for bad images have been directly responsible for many misleading announcements4 ,illustration3 ,fig4 #ce4 ,occultation of ,jupiter1 ,aug4 #g1 #ahhi4 ,occultations of ,jupiter by the ,moon4--,phenomena of this kind are always awaited with keen interest by the possessors of telescopes2 but it is rarely that all the circumstances are favourable4 ,the first recorded instance appears to have been in ,a4,d4 #hdg4 ,in #agib1 on ,april #g1 ,schrter observed an occultation of this planet1 with a desire to verify his suspicion of a lunar atmosphere4 ,he saw that 8some of the satellites became indistinct at the limb of the ,moon1 while others did not suffer any change of colour4 ,the belts and spots of ,jupiter appeared perfectly distinct when close to the limb of the ,moon40 ,on ,jan4 #b1 #aheg1 an occultation took place under conditions which rendered it visible to many observers in this country1 and the most interesting fact elicited was that at emersion a dark border was seen attached to the arc of the ,moon projected on the planet4 ,mr4 ,lassell described this dark border as 8a shadowy line1 in character1 magnitude1 and intensity extremely like ,saturn's obscure ring projected on the ball40 ,during the thirty years following #ahei only two occultations visible in ,england occurred1 and the last of these1 on ,august #g1 #ahhi1 was widely observed4 ,on this occasion ,capt4 ,noble and others redetected the shadowed edge of the ,moon seen by ,lassell in #aheg4 8,it was a strongly marked shading1 following the outline of the ,moon's limb40 ,at ,bristol ,i recorded that1 at the disappearance1 the outer margin of our satellite was fringed with light where it crossed the planet2 but at the reappearance this effect had vanished1 and the appearance was perfectly normal4 ,the disk of ,jupiter1 where it met the edge of the lunar disk1 looked dusky by the effects of contrast2 but ,i saw no marked shading with a sharply terminating boundary1 such as appears to have been remarked elsewhere4 ,as the planet emerged definition was superb1 the belts were lividly distinct1 and the spectacle was one of the prettiest that could be imagined4 ,the red spot was going off the ,w4 limb1 and the disk was covered with belts2 many of them near the poles were extremely narrow1 like fine lines drawn with a sharp lead pencil4 ,i used a #d-;inch refractor1 powers #fe and #ade1 with this instrument the foregoing sketch was made4 ,the exceptional distinctness of the ,jovian markings on this occasion shows that the proximity of the ,moon has certainly no tendency to efface planetary details1 but rather to intensify them#cd4 ,on ,sept4 #c1 #ahhi1 an occultation of ,jupiter was visible in ,america1 and observed by ,mr4 ,brooks at ,geneva1 ,n4,y41 with a #aj-a_/h-;inch equatoreal4 ,his drawing1 made from a photograph and eye-observations1 shows nothing of a dark fringe bordering the ,moon's limb4 ,illustration3 ,fig4 #cf4 ,jupiter and satellites seen in a small glass4 ,the four ,satellites4--,when ,galilei directed his telescope to ,jupiter on the evening of ,jan4 #g1 #afaj1 he saw three small star-like points near the planet2 so3-- ,illustration ,on ,jan4 #ac he discovered a fourth2 thus3-- ,illustration and ascertaining that these bodies followed ,jupiter in his course1 concluded them to be moons in attendance upon him4 ,at first the discovery was discredited by others2 but it soon had to be accepted as an incontestable fact of observation4 ,these satellites are usually among the very first objects which the amateur views in his telescope1 and they form1 in combination with their primary1 an exquisite picture1 the impression of which is not soon forgotten4 ,the periods1 distances1 c4 of the satellites are as follows3-- ---------------------------------------- ---------------------------------------- -------------------------------------- ,mean ,distance4 ,no4 and ,name4---------------------------------- -----,sidereal,mean ,real ,diameters ,miles4 ,period4 ,apparent ,diameter1 of ,jupiter4 ,diameter4in miles4 ---------------------------------------- ---------------------------------------- -------------------------------------- h m s ,i4 ,io #cjc #bfg1jjj #a #ah #bi #ajb #bcij ,,ii4 ,europa #dgb #dbe1jjj #c #ac #ah #jia #babj ,,iii4 ,ganymede #gga #fgh1jjj #g #d #j #adi #cdhj ,,iv4 ,callisto #acee #a1aic1jjjaf #ah #e #abg #bigj ---------------------------------------- ---------------------------------------- -------------------------------------- ,the third satellite is much the largest1 and its brightness is about equal to that of a star of the #fth mag4 ,the other three may be rated as generally #gth mag41 though their brightness is variable1 especially that of the fourth satellite1 which has been seen exceedingly faint4 ,it is customary to distinguish these objects1 not by their names1 as in the case of the moons of ,mars1 ,saturn1 and ,uranus1 but by the ,roman numbers affixed to them progressively according to their distances from ,jupiter4 ,the satellites are just visible to the naked eye when the conditions favour their detection2 but they are so much involved in the rays of the planet1 and often so near to him1 that it may be regarded as an exceptional feat to discern them without telescopic aid4 ,when ,,iii4 and ,,iv4 are near their max4 elongation and on the same side of the planet1 they have been occasionally observed separately4 ,i4 and ,,ii41 though much closer to ,jupiter and more within the influence of his glare and rays1 have been similarly seen4 ,when attempting such observations it is best to hide the bare disk of the planet behind some terrestrial object1 as this will cut off the obnoxious rays and prevent the brilliant light from dazzling the eye4 ,an opera-glass1 or any small portable telescope1 reveals the whole retinue of satellites1 and enables them to be traced through their revolutions4 ,the #8,nautical ,almanack' gives diagrams of their diurnal positions1 and with this work as a reference observers will find no difficulty in identifying them apart4 ,sir ,w4 ,herschel1 in the years #agid to #agif1 found that the satellites revolve on their axes in the same time that they revolve about the planet4 ,he was led to this conclusion by a study of the variations in the light emitted by the satellites in different parts of their orbits1 and described ,i4 as 8of a very intense bright1 white1 and shining light1--brighter than ,,ii4 or ,,iv4 7not larger74 ,,iv4 inclines to red1 and nearly as bright as ,,ii4 ,the latter is of a dull ash-colour4 ,,iii4 is very white40 ,modern observers have selected ,,ii4 as relatively the most highly reflective1 while ,,iv4 is the least4 ,spots exist on the surfaces of these objects1 and probably occasion many of the differences observed4 ,the eclipses1 occultations1 and transits of the satellites afford a very fertile and attractive series of phenomena for telescopic review4 ,the exact times of occurrence are tabulated in the #8,nautical ,almanack' and asterisks are affixed to such as are visible in this country4 ,prior to the date of opposition of ,jupiter the eclipses occur of course on the ,w4 side of the disk1 while after opposition they take place on the ,e4 side4 ,the durations are as follow for the several satellites3--,i4 #b;h #bjm1 ,,ii4 #b;h #efm1 ,,iii4 #c;h #dcm1 ,,iv4 #d;h #efm4 ,in reference to ,,iii4 and ,,iv4 the entire phenomenon may be generally observed2 but this is not so in regard to ,,ii41 as the emersions are frequently effected behind the planet4 ,only the immersions of ,i4 are visible before opposition1 from the same cause2 for the satellite enters the cone of shadow close to the planet's limb1 and only comes out of it when the globe of the planet is interposed in the line of sight4 ,in such cases the satellite emerges soon after from the limb of ,jupiter2 so that its obscuration has been compounded of two separate phenomena1 viz4 an eclipse and an occultation4 ,after opposition this satellite is first occulted and then eclipsed4 ,,iv4 sometimes escapes eclipse altogether1 by passing above or below the shadow4 ,the motion of light was discovered1 and its velocity determined1 by means of the eclipses of ,jupiter's satellites4 ,these phenomena are also useful in ascertaining longitudes4 ,a spectator on ,jupiter himself would see a vast number of solar and lunar eclipses--about #dejj of each--during the ,jovian year of #dccbf days1 because the three inner satellites exhibit these phenomena at every revolution1 their orbits being very slightly inclined to ,jupiter's equator1 and the latter being but little inclined to the plane of the ecliptic4 ,the occultations of the satellites are comparatively frequent1 and may be well observed in a good telescope4 ,a tolerably high magnifier is required to witness these occurrences with the best effect1 the disks of the satellites being small and not clearly traceable through the various stages of their disappearances unless much amplified4 ,with considerable telescopic power the disks are well seen1 and it then becomes feasible to watch the satellites1 first as they come into contact with the limb1 then as the globe of the planet overlaps more and more of their diminutive forms1 and finally as they reach last contact and withdraw their narrow unobscured segments behind the expansive sphere of their primary4 ,both the beginning and end phase of these occultations is generally observable in regard to ,sat4 ,,iv41 and frequently also in the case of ,,iii4 ,but with reference to ,,ii4 and ,i4 it often happens that only the disappearance or reappearance can be witnessed4 ,these occultations have furnished some singular and unexplained facts of observation4 ,on meeting the limb of ,jupiter ,sats4 ,i4 and ,,ii4 have not always disappeared in a normal way4 ,on ,april #bf1 #ahfc1 ,wray1 with an #h-;inch objective1 saw ,,ii4 distinctly projected within the limb for nearly #bjs4 ,other similar cases are recorded4 ,the satellites have been seen apparently 8through the edge of the disk40 ,one observer mentions that ,,ii4 appeared and disappeared several times before occultation4 ,the explanation appears to be that there is so much irradiation round the disk of ,jupiter that it produces a false limb1 and it is through this the satellites have been seen4 ,a very tremulous image1 in bad air1 may also be responsible for some of the anomalies recorded4 ,the transits of the ,jovian moons offer the most attractive phenomena of all1 and they come well within the reach of small telescopes4 ,on entering upon the planet they are visible as bright round spots projected on the dusky limb1 and subsequently present some eccentric features4 ,,ii4 is invisible1 except on the limbs2 ,i4 is often seen as a grey spot threading along the belts2 ,,iii4 appears as a large dark spot#ce1 nearly as black as its shadow2 ,,iv4 seems to be black1 and scarcely to be recognized from its shadow4 ,the appearances are certainly to some extent variable4 ,mr4 ,stanley ,williams has seen ,,iii4 as a brilliant disk at mid-transit4 ,i4 sometimes crosses the whole disk as a white spot2 at certain other times it is invisible2 at others1 again1 it is seen as a faint grey spot4 ,,iv4 is not always black1 its aspect depending upon the chord it traverses4 ,thus1 on the evening of ,sept4 #ab1 #ahhi1 ,mr4 ,williams1 ,mr4 ,g4 ,t4 ,davis of ,reading1 and myself were observing ,jupiter when ,,iv4 was in transit on a belt in the ,n4 hemisphere1 but not a vestige of the satellite was seen by any of us4 ,on the morning of ,may #bc1 #ahij1 at #c;h #cjm ,a4,m41 however1 while observing the red spot on ,jupiter1 ,i noticed a black circular spot on the great ,n4 equatoreal belt2 and this proved to be ,,iv4 in transit4 ,these peculiarities have been accounted for as partly due to contrast and partly to dusky spots on the surfaces of the satellites4 ,dr4 ,spitta has made a number of experiments to elucidate this subject1 and concludes that 8the perpetual whiteness of the second satellite1 and the darkened tints of the others during transit1 are due to differences in their relative albedo reflective power as compared with that of ,jupiter1 and are not dependent upon the relative quantity of light reflected by one or the other1 or upon any physical peculiarities of the ,jovian system40 ,the shadows of the satellites transit the disk as dark spots larger than the satellites themselves1 owing to the penumbral fringes4 ,before opposition these shadows precede the satellites2 after opposition the latter come first4 ,the shadow of ,,ii4 appears to be much lighter than the others1 and is usually of a pale chocolate-colour2 and ,i saw it thus at the opening of the year #ahhe3-- ,illustration3 ,fig4 #cg4 ,shadows of ,jupiter's ,satellites ,,ii4 and ,,iii4 near an equatoreal white spot 7,jan4 #a1 #ahhe1 #g;h #bjm ,a4,m474 ,sat4 ,,ii4 is probably involved in an atmosphere sufficiently dense to enable it to present undue luminosity relatively to the others2 and if so1 the feeble shadow it transmits on ,jupiter may be partly explained by the effects of refraction4 ,on the day of opposition both satellites and shadows are projected on the same part of the disk1 and the latter are occulted by the former4 ,on ,jan4 #ad1 #ahgb1 ,mr4 ,f4 ,m4 ,newton saw ,i4 centrally placed on its shadow2 so that the satellite was apparently surrounded with a ring of shade4 ,on ,may #ac1 #ahgf1 ,mr4 ,g4 ,d4 ,hirst saw ,sat4 ,i4 partly occulting its own shadow2 a black crescent was seen in the bright zone ,n4 of the equator4 ,on ,feb4 #ah1 #ahhe1 ,dr4 ,r4 ,copeland1 at ,dun ,echt1 saw the shadow of ,i4 8almost totally occulted by the satellite itself2 as the satellite approached ,jupiter's limb it came out quite bright and large1 with a mere crescent of the shadow showing on its southern edge40 ,this phenomenon was also observed at ,bristol4 ,occasionally all the satellites become invisible at the same time1 being either eclipsed1 occulted1 or in transit4 ,an instance of this kind was recorded by ,molyneux on ,nov4 #b1 #afha 7,o4,s474 ,sir ,w4 ,herschel observed a similar occurrence on ,may #bc1 #ahjb2 also ,wallis on ,april #ae1 #ahbf1 and ,dawes and others on ,sept4 #bg1 #ahdc1 and ,aug4 #ba1 #ahfg4 ,a visible repetition of the event was narrowly avoided on the morning of ,oct4 #ae1 #ahhc4 ,on this occasion the planet should1 according to the #8,nautical ,almanack1' have been denuded of his satellites for a period of #ai minutes2 but this disappearance did not occur1 for at no time were all the satellites included within the margin or shadow of ,jupiter4 ,i observed that ,sat4 ,,iii4 entered upon the disk just as ,,iv4 released itself1 and the two formed a curious configuration at #d;h ,a4,m41 hanging close upon the planet's limbs4 ,spots have been seen on the satellites both in transit and while shining on the dark sky4 ,this particularly refers to ,,iii4 and ,,iv4 ,,ii4 has never given indications of such markings on its bright uniformly clear surface4 ,dawes1 ,lassell1 and ,secchi frequently observed and drew the spots4 ,secchi described ,,iii4 as similar in aspect to the mottled disk of ,mars as seen in a small telescope2 his drawings exhibit no analogy1 however1 to those by ,dawes of the same object4 ,,iii4 has been remarked of a curious shape1 as if dark spots obliterated part of the limbs4 ,sat4 ,i4 was observed in transit on ,sept4 #h1 #ahij by ,barnard and ,burnham1 and it appeared to be double1 being divided by a bright interval or belt4 ,they used a #ab-;inch refractor1 powers #ejj and #gjj1 and the seeing was very fine4 ,many other curious points have been noticed in the various aspects and phenomena of the ,jovian satellites4 ,further observations will doubtless throw new light on some of the puzzling records of the past4 ,occultation of a ,star4--,an occultation of the #gth mag4 star #d ,geminorum by ,jupiter took place on ,nov4 #g1 #ahhb1 and it was observed by ,prof4 ,pritchett1 of ,glasgow1 ,missouri1 with a #ab-a_/d-;inch equatoreal1 power #bjj4 8,the images of both planet and star were very steady4 ,the margin of ,jupiter's disk was very sharply defined4 ,the immersion was very near the ,n4 border of the broad ,s4 equatoreal belt4 ,at #aa;h #bhm #ajs#fe local mean time the star was apparently within the dark outline of the disk1 apparent geometric contact having occurred at #aa;h #bjm #bds#di4 ,for a moment the star seemed to disappear1 but a moment later was plainly seen1 as if through a well-defined notch in the otherwise continuously even margin4 ,this notch lasted #dfs#bf1 and at #aa;h #bhm #efs#ia it vanished1 and the light of the star was entirely extinguished40 ,the emersion of the star could not be observed1 as clouds supervened4 ,,footnotes3 #cc ,the question of periodicity is an extremely interesting one as affecting the disposition1 form1 and colours of the markings on ,jupiter4 ,certain features visible in #ahfi-gj were unmistakably reproduced in #ahhj1 and it has been suspected that the cycle of these changes accords with the length of the ,jovian year4 ,future observations must be compared with old drawings and records for the identification of similar features if they are recurrent4 #cd ,on the morning of ,dec4 #e1 #ahhg1 ,i made a drawing of ,saturn1 the image of the planet being remarkably well defined1 though the ,moon was only #a distant4 #ce ,amongst the first observers of these dark transits were ,cassini 7,sept4 #b1 #affe71 ,romer 7#afgg71 and ,maraldi 7#agjg74 ,,chapter ,,xii4 ,,saturn4 ,apparent lustre4--,grand spectacle afforded by the ,rings4--,period c4--8,square-shouldered0 aspect4--,early ,observations4--,belts and ,spots on the ,planet4--,rotation-,period4--,the ,rings4--,divisions in the outer ,ring4--,the transparent or ,crape-ring4--,discordant ,observations4--,eccentric position of the ,rings4--,aspect4--,further ,observations required4--,occultations of ,saturn4--,the ,satellites4--,occultations of ,stars by ,saturn4 8,muse1 raise thy voice1 mysterious truth to sing1 ,how o'er the copious orb a lucid ring1 ,opaque and broad1 is seen its arch to spread ,round the big globe1 at stated periods led40 ,this planet shines brighter than an ordinary first-magnitude star1 and is a pretty conspicuous object1 though less luminous than either ,venus1 ,jupiter1 or ,mars4 ,he emits a dull yellowish light1 steadier than the sparkling lustre of ,mercury or ,venus4 ,the globe of ,saturn is surrounded by a system of highly reflective rings1 giving to the planet a character of form which finds no parallel among the other orbs of our system4 ,his peculiar construction is well calculated to be attractive in the highest degree to all those who take delight in viewing the wonders of the heavens4 ,saturn is justly considered one of the most charming pictures which the telescope unfolds4 ,a person who for the first time beholds the planet1 encircled in his rings and surrounded by his moons1 can hardly subdue an exclamation of surprise and wonder at a spectacle as unique as it is magnificent4 ,even old observers1 who again and again return to the contemplation of this remarkable orb1 confess they do so unwearyingly1 because they find no parallel elsewhere2 the beautifully curving outline of the symmetrical image always retains its interest1 and refreshes them with thoughts of the ,divine ,architect who framed it6 ,the luminous system of rings attending this planet not only gratifies the eye but gives rise to entertaining speculations as to its origin1 character1 and purposes with regard to the globe of ,saturn4 ,why1 it has been asked1 was this planet alone endowed with so novel an appendage8 and what particular design does it fulfil in the economy of ,saturn8 ,it cannot be regarded as simply an ornament in the firmament1 but must subserve important ends1 though these may not yet have been revealed to the eye of our understanding4 ,period c4--,saturn revolves round the ,sun in #aj1gei days #e hrs4 #af min41 which is equal to nearly #bi years4 ,his mean distance from the ,sun is #hhf1jjj1jjj miles1 but this interval varies from #hda to #ica millions1 owing to the eccentricity of his orbit4 ,when in opposition his apparent diameter reaches #bjg1 and declines to #ae at the time of conjunction4 ,the planet's actual diameter is #ge1jjj miles1 and his polar compression very considerable1 viz4 about #a_/aj1 which exceeds that of any other planet4 ,his synodic period is equal to #cgh days2 so that he comes into opposition with the ,sun thirteen days later every year4 ,the oblate figure of his disk is very noticeable when the rings are turned edgeways to the ,earth and practically invisible2 but when they are inclined the complete contour of the globe is lost1 and the polar flattening becomes scarcely obvious4 8,square-shouldered0 ,aspect4--,sir ,w4 ,herschel1 from observations in ,april #ahje1 said3--8,there is a singularity which distinguishes the figure of ,saturn from that of all the other planets40 ,on ,april #ai of the year named he described the planet as 8like a parallelogram with the four corners rounded off deeply1 but not so much as to bring it to a spheroid40 ,this gave the globe a 8square-shouldered0 aspect4 ,but this curious figure appears to have been very rarely observed in subsequent years2 and accurate measures with the micrometer were adduced in #ahcc-dh in proof that no such anomaly had a real existence4 ,dr4 ,kitchiner1 commenting on ,herschel's remarks1 said3--8,i have occasionally observed this planet during thirty years1 and ,i do not remember to have seen the body of it of this singular form except for a few months about ,september #ahah40 ,but there is no doubt that occasionally the planet does assume an apparent form similar to that attributed to it by ,herschel4 ,in the autumn of #ahhj ,i studied the visible appearance of ,saturn by means of a #aj-;inch reflector1 and recorded as follows3--8,the ,s4 pole1 over which the dark belts lay1 seemed compressed in the most remarkable manner2 but where a bright belt intervened1 in about lat4 #de1 the contrary effect was produced4 ,here the limbs were apparently raised 7by irradiation7 above the spherical contour2 so that the distorted image gave the planet that distinctly #8square-shouldered' aspect sometimes mentioned in text-books40 ,the explanation appears to me very simple4 ,the singular figure is due to the contrasting effects of the belts4 ,while the bright belt in lat4 #de causes a very evident shouldering-out of the limbs at its extremities1 the dark belts nearer the pole and the equator act with opposite effect1 for they apparently compress the disk where they meet the limbs1 and thus the eye discerns a figure to all appearance distorted into the 8square-shouldered0 form4 ,mr4 ,j4 ,l4 ,mc,cance confirmed these remarks by independent observations at the same period with a #aj-;inch reflector by ,calver 7#8,monthly ,notices1' vol4 xli4 pp4 #hd1 #bhb74 ,early ,observations4--,the appearance of ,saturn offered a considerable difficulty to observers soon after the invention of the telescope4 ,galilei became greatly perplexed4 ,he saw the planet1 not as a circular globe like ,jupiter1 but distinctly elongated in shape1 and conceived the appearance to be due to a central globe with smaller spheres hanging on the sides6 ,he continued his observations1 without1 however1 arriving at the solution of the mystery1 until the malformation began to disappear2 and in #afab he was astonished to find the disk spherical4 ,in his surprise1 he asked--8,were the appearances indeed illusion and fraud1 with which the glasses have so long deceived me1 as well as many others to whom ,i have shown them8444 ,the shortness of the time1 the unexpected nature of the event1 the weakness of my understanding1 and the fear of being mistaken1 have greatly confounded me40 ,gassendi1 in #afcc1 also announced that ,saturn appeared to him to be closely attended by two globes of the same colour as the planet4 ,riccioli alleged that the planet was surrounded by a thin1 plain1 elliptic ring1 connected with the sphere by two arms4 ,none of ,galilei's contemporaries possessed the instrumental means to extricate him from his doubts2 and it remained for ,huygens1 in #afed 7twelve years after the death of ,galilei71 to discover that ,saturn 8is surrounded by a slender flat ring1 which in no part coheres with the body of the planet1 and is inclined to the ecliptic0#cf4 ,the same observer showed that the disappearance which had so puzzled ,galilei arose from the varying inclination in the ring3 at times it would become invisible1 when presenting its narrow edge to the ,earth1 and this actually occurred again in #afga1 as ,huygens had predicted4 ,in #afgf ,cassini detected a belt upon the planet1 and also a dark division in the ring4 ,dr4 ,smith's #8,optics' 7#agch7 thus alludes to these discoveries3-- ,illustration3 ,fig4 #ch4 ,saturn1 as observed by ,cassini in ,august #afgf4 8,in the year #afgf1 after ,saturn had emerged from the ,sun's rays1 ,sig4 ,cassini saw him in the morning twilight with a darkish belt upon his globe1 parallel to the long axis of his ring as usual4 ,but what was most remarkable1 the broad side of the ring was bisected right round by a dark elliptical line1 dividing it1 as it were1 into two rings1 of which the inner ring appeared brighter than the outer one1 with nearly the like difference in brightness as between that of silver polished and unpolished--which1 though never observed before1 was seen many times after with tubes of #cd and #bj feet1 and more evidently in the twilight or moonlight than in a darker sky40 ,from the time when ,galilei's inadequate glass revealed the 8threefold0 aspect of ,saturn1 and led up to ,huygens's solution of the mystery in #afed1 this planet has been successively interrogated with the improved telescopes which every generation has produced4 ,cassini1 ,w4 ,herschel1 ,encke1 ,bond1 ,lassell1 ,dawes1 and ,hall are names familiar to us as having materially advanced our knowledge of this unique orb1 both as to his surface-configuration and as to his numerous retinue of satellites4 ,belts and ,spots on the ,planet4--,parallel belts are seen on the surface of ,saturn1 but they are much fainter than those on ,jupiter1 and they seldom display the spots and other irregularities interspersed with the belts of the latter planet4 ,well-bounded spots have rarely been distinguished on the disk of ,saturn2 the belts normally appear equal in tone1 without breaks1 condensations1 abrupt curves1 or branches1 so that the rotation-period has only been accurately determined by ,herschel and ,hall4 ,and in these cases the markings were certainly atmospheric1 and probably affected by proper motions similar to those operating on ,jupiter4 ,cassini and ,fatio remarked two bright streaks on the planet as early as #afhc4 ,sir ,w4 ,hershel1 in #agij1 observed a very dark spot near the margin of the limb1 and a few modern observers have been successful in distinguishing either bright or dark spots or patches1 though no continuous and useful observations appear to have been secured4 ,in the winter of #agic ,herschel noticed a very distinct quintuple belt1 which consisted of three dusky and two intervening light zones4 ,the dark belts presented a dusky yellow hue1 while the spaces separating them were white4 ,he recognized the evidences of rotation in the quintuple belt2 for on the same nights1 after a few hours' interval1 it exhibited considerable variation4 ,though seen with great precision at first1 it became indistinct at a later hour1 and the individual belts were placed at unequal distances4 ,rotation-,period4--,prof4 ,a4 ,hall1 at ,washington1 discovered on ,dec4 #g1 #ahgf1 a well-defined white spot1 #b or #c in diameter1 and situated just below the ring of ,saturn4 ,he watched this object till ,jan4 #b following1 when it had become faint and indistinct1 and the planet being low and the weather unfavourable no further observations were made4 ,the spot had fortunately been seen at four other observatories in the ,united ,states1 ,prof4 ,hall having notified its existence to them2 and on discussing the results1 a rotation-period was found not differing largely from ,herschel's value derived from the quintuple belt in #agic4 ,these are1 in fact1 the only two determinations on which we may place confidence4 ,they are as below3-- h m s ,probable error4 #agic4 ,sir ,w4 ,herschel #aj #af #jd #b min4 #ahgg4 ,prof4 ,a4 ,hall #aj #ad #bch #bc sec4 ,schrter1 from different spots1 computed periods of #aa;h #djm #cjs1 #aa;h #eam1 and more than #ab;h2 but these are probably excessive4 ,the difference of #am #cgs between the values of ,herschel and ,hall is relatively a trivial one1 as the markings observed were doubtless atmospheric and subject to irregularities of motion4 ,as to the rotation of the ring1 ,herschel1 in #aghi1 detected some bright marks on it1 and deduced the period as #aj;h #cbm #aes#dcg4 ,many astronomical works give the rotation-period of ,saturn as #aj;h #bim #afs#h2 and this is adopted in ,chambers's #8,descriptive ,astronomy1' #dth edit4 vol4 i4 p4 #fec4 ,the mistake has its origin in ,laplace's ,systme du ,monde1 where it is stated that ,saturn rotates in #jdbh of a day1 and the ring in #jdcg1 which1 reduced to hours1 minutes1 and seconds1 give #aj;h #afm #ags#b and #aj;h #bim #afs#h4 ,the equator of ,saturn is usually the brightest part of the disk4 ,on its ,s4 side1 in recent years1 it has been bounded by a very dark narrow belt4 ,further ,s4 the whole disk seems involved in a faint shading1 of a decidedly yellowish hue4 ,sometimes a considerable number of belts are visible2 but they are evidently liable to changes1 so that the same number and arrangement are not preserved from year to year4 ,the ,rings4--,as to the luminous rings1 the extreme diameter of the outer one is about #dj1 or more than #agj1jjj miles2 and the black division1 separating it from the inner one1 is #jd1 or #agjj miles4 ,the outer ring has a breadth of #bd1 or #aj1jjj miles2 while the inner one measures #ci1 or #ag1jjj miles4 ,the outer ring is less luminous than the inner2 the latter1 round its outer edges1 is extremely brilliant1 and has sometimes been described as the brightest part of the ,saturnian system4 ,the inner part of this ring is much shaded-off1 and offers a strong contrast to the silvery whiteness of the other portion4 ,illustration3 ,fig4 #ci4 ,saturn1 #ahhe1 ,dec4 #bc1 #g;h #edm4 7#aj-;inch reflector1 power #beb47 ,divisions in the ,outer ,ring4--,in the middle of the eighteenth century ,short1 the optician1 using one of his excellent reflectors1 thought he saw the outer ring divided by several dark lines2 but no other observer confirmed his suspicion4 ,in the third decade of the present century ,quetelet and ,capt4 ,kater appear to have observed ,short's divisions1 but ,sir ,j4 ,herschel and ,struve looked for them in vain4 ,in #ahcg ,encke fully satisfied himself1 by several observations and measurements1 as to the objective existence of the divided outer ring4 ,the division was not central1 cutting the ring into equal parts1 but situated in the inner part of the ring1 so that the wider part was outermost4 ,in subsequent years this division has been sometimes seen and placed nearest the outer edge of the ring4 ,certain observers1 provided with ample means1 have seen nothing of it2 others regard the division as variable4 ,it is sometimes described as a narrow black line2 while others refer to it as a faint pencillike shading1 and not a real division at all4 ,one observer occasionally sees it with considerable distinctness at the very same time that another observer1 with a more powerful telescope1 cannot glimpse it though looking specially for such an appearance6 ,it is difficult to reconcile such discordant experiences1 and unsafe to accept results of such a contradictory nature4 ,the 8,crape0-,ring4--,a far more certain feature was discovered in the autumn of #ahejch1 and one in reference to which there is unanimity of testimony4 ,on ,nov4 #aa ,g4 ,p4 ,bond1 in ,america1 and ,dawes1 in ,england1 on ,nov4 #be1 saw a nebulosity or faint luminous appearance like twilight1 fringing the interior margin of the inner ring4 ,later observations showed this to be occasioned by a transparent ring situated immediately within the inner luminous ring4 ,dawes considered the new ring to be divided into two parts2 but ,lassell1 with his large reflector1 subsequently negatived this supposition4 ,both limbs of ,saturn may be readily perceived through the transparent ring where it crosses the globe of the planet4 ,some irregularities have been suspected in it at different times by various observers4 ,in #ahhg dark condensations were reported to disturb its normal aspect2 but these were not seen at many observatories where such features1 if real1 could hardly have escaped detection4 ,illustration3 ,fig4 #dj4 ,saturn1 as observed by ,f4 ,terby1 ,february #ahhg4 ,it is strange to reflect that this transparent ring avoided discovery for so long a period4 ,it forms a feature distinctly to be recognized in relatively small telescopes--in fact1 ,grover has seen it1 where it crosses the globe of ,saturn1 with only #b inches of aperture4 ,yet1 though ever on the alert to detect new formations1 and exercising constant vigilance in their pursuit1 ,sir ,w4 ,herschel1 ,schrter1 and many others allowed this ring to escape them6 ,there is no reason to suppose that it is variable1 and that it was not so plain a century ago as now4 ,it affords another instance of how easily an unknown object may elude recognition1 though everyone sees it readily enough when attention is called to it4 ,in ,march #ahhi a white spot was detected on the rings by ,dr4 ,terby1 at ,louvain1 and it was seen by other observers with comparatively small instruments4 ,the spot was stationary1 and placed near the apparent junction of the globe and rings1 in the ,e4 ansa4 ,but with large telescopes nothing of this object could be detected3 it was shown to be an optical effect4 ,discordant ,observations4--,it is curious that the details of ,saturn have occasioned more dissension amongst observers than those of any other planet4 ,this may have partly arisen from the great distance of ,saturn1 the comparative feebleness of his light1 and complexity of his structure4 ,the planet is usually better defined than either ,mars or ,jupiter2 but with tolerably high powers on small instruments the image is faint1 and the features so diluted that the impressions received cannot always be depended upon1 especially when the air is unsteady4 ,a fluttering condition of the object is sufficient in itself to cause deception4 ,prof4 ,hall1 in speaking of the work done by the #beh-;inch refractor at ,washington in #ahhc1 says3--8,saturn's ring has been observed1 but many of the strange phenomena noted by other observers have not been seen even on the best nights40 ,the evidence afforded by this large instrument may not always be conclusive1 but in this case there can be no doubt it properly failed to show 8phenomena0 which had no existence4 ,eccentric ,position of the ,rings4--,the rings are slightly eccentric with regard to the ball2 in other words1 the ball is not situated in the centre of the rings4 ,differences have been observed denoting this1 though the observations are not altogether satisfactory4 ,it has been shown theoretically that the eccentricity referred to is necessary to maintain the stable equilibrium of the system2 for were the rings perfectly concentric with the planet1 they must coalesce with the ball4 ,the preservation of so complicated a structure must evidently require judicious and nicely balanced conditions4 ,with the great #bc-;inch refractor at ,princeton1 ,u4,s4,a41 the ball of ,saturn was seen through the division in the ring in ,november #ahhc--;an observation which had previously been made by ,lassell in #aheb4 ,aspect of the ,rings4--,in different years the rings present a varying outline1 owing to the fact of their inclination 7#bh #aj7 and to changes in the relative positions of the ,earth and ,saturn4 ,at intervals of about fifteen years the rings are widely open1 as they were in #ahee1 #ahfi1 and #ahhe1 and will be in #ahii4 ,at similar intervals they are rendered invisible1 being turned edgeways to the ,earth1 as in #ahdh1 #ahfb1 #ahgg1 and #ahia4 ,since #ahgg the ,s4 side of the rings has been presented to terrestrial observers2 but in #ahic the ,n4 side will come under inspection1 and remain in view until #aijg4 ,the ,s4 side of the rings is obviously more favourably visible to observers in ,england and other ,n4 latitudes1 because the planet is always above the equator and attains a fair altitude when it is presented4 ,the ,n4 side of the rings is exposed when ,saturn is in ,s4 declination1 and therefore more liable to our atmospheric disturbances owing to his comparatively low altitude4 ,the extreme narrowness of the rings is apparent at the periods when the planet crosses the node and they are situated in the plane of the line of sight4 ,in small telescopes they become invisible1 and the finest instruments only exhibit them as thread-like extensions from the equator of the planet4 ,sir ,j4 ,herschel says that on ,april #bi1 #ahcc1 the disappearance of the ring was complete when observed with a reflector of #ah inches aperture and #bj feet focal length4 ,it remained visible in #ahfb as a broken line of light4 ,at such times the satellites are seen as bright beads1 threading their way along the narrow wavering line of the belts4 ,inequalities have been observed at such times2 for the line of light into which the rings are then resolved is not uniform in breadth1 but appears broken and undulatory1 as though indicating a very rugged character of surface4 ,sir ,j4 ,herschel estimated the thickness of the rings as #bej miles1 but ,bond thought it far less--about #dj miles4 ,there are great obstacles in the way of ascertaining the exact proportions of a structure so distant and offering such an extremely slender form to our view4 ,further ,observations required4--,the globe and rings of ,saturn offer an encouraging prospect for additional discoveries4 ,though the more prominent details have already been descried1 there remain other features1 probably of more delicate outline and intermittent visibility1 which will be glimpsed in future years4 ,small instruments will scarcely be competent to deal efficiently with this object3 observers who can command at least a moderate grasp of light may1 however1 enter upon the work with every assurance of interesting results4 ,in this1 as in other sections of observational astronomy1 the student will realize that in oft-repeated observation and comparison of records and drawings he acquires a familiarity with the appearance of the object which will enable him to discern more and more of its configuration1 until ultimately he feels confident he has progressed as far as the utmost capacity of his instrument will permit4 ,it is in the sedulous application of his powers that the observer will find the key to success4 ,partial devotion to a subject offers a prospect far less encouraging2 for observations of a disconnected character are seldom valuable4 ,changes are unquestionably occurring both in connection with the ball and rings of ,saturn#ci4 ,some of the discrepancies between the observations published from time to time are only to be explained on this assumption4 ,it should therefore be the aim of observers to obtain further evidence of such variations1 and this may be best accomplished by assiduously watching the lineaments of the planet during the most favourable periods of each opposition4 ,the collection of a number of reliable materials through a series of years would undoubtedly possess weight in removing some of the anomalies of past observation1 and afford us a more thorough knowledge of the delicate markings4 ,the rotation-period of ,saturn is probably not much different from that given by the atmospheric markings seen by ,herschel and ,hall4 ,but additional determinations are very desirable for many reasons4 ,the spots which are so plentiful on ,mars and ,jupiter have furnished observers with a valid and concise means of ascertaining the rate of axial motion of those planets4 ,saturn1 however1 has far more sparingly provided the data for such an investigation2 for if we disregard ,schrter's uncertain figures1 we have but two values for the rotation-period4 ,these were fortunately effected by observers of exceptional ability1 and the periods may be accepted without reservation2 but other independent determinations are much required4 ,by multiplying results of this nature1 we have a prolific source of comparison2 and comparisons1 apart from being interesting1 are of importance in denoting erratic results and indicating those entitled to credence4 ,moreover1 a reliable mean value may be sometimes deduced from multiple records2 hence it becomes advisable to secure as many as possible4 ,the planet should be frequently examined during every opposition with the highest powers that are consistent with a perfectly distinct image2 and the observer should closely scan the various parts of the disk1 with an endeavour to trace spots1 breaks1 or other irregularities in the belts4 ,certain inequalities of tone have been occasionally apparent in past years1 and they will doubtless reappear4 ,the recovery of these features will form a welcome addition to our knowledge1 and1 if adequately observed1 will enable the rotation-period of the planet to be rediscussed4 ,in an enquiry of this kind many observations are needful1 and the longer the interval over which they extend the more accurate the results derived from them are likely to be4 ,if a broken belt should appear on ,saturn1 the time of its passing the planet's central meridian should be recorded1 either by measurement or careful estimation1 and an ephemeris computed based on a rotation-period of #aj-a_/d;h1 which is equal to a daily rate of nearly #hdc4 ,then it should be carefully looked for on subsequent evenings at the times given in the ephemeris1 and on every occasion when re-observed its time of transit should be noted as at first4 ,as long as the break continues visible1 so long ought it to be kept in view and the times of its central passages tabulated4 ,it would be advisable in such a case to secure cooperation from other observers1 as more numerous observations would be sure to accrue1 so that1 on the appearance of a marking such as that alluded to1 the discoverer will do well to announce it immediately to other amateurs who are engaged upon planetary work and most likely to assist him4 ,a white or dark spot1 or any condensation on the belts1 would of course serve the same purpose as a broken belt4 ,the nature of the object is not necessarily to be considered1 the main requirement being that it is one of which the longitude admits of determination4 ,markings on the belts1 if they are ever discernible1 must be watched with corresponding assiduity for traces of motion2 and if such motion should betray itself1 the object of the observer will be to ascertain its rate4 ,with reference to the narrow division in the outer ring1 usually termed 8,encke's division10 astronomers would regard it as a gratifying advance could the doubts overhanging this feature be removed4 ,is it a real division in the ring1 or simply a pencil-line of shading on the flat surface8 ,is it constant in place and appearance1 or does it frequently exhibit changes both as to intensity and position8 ,judging from prior experiences1 this particular object would appear to be extremely fugitive1 and incapable of being assigned either a definite place or aspect4 ,yet the more pronounced and well-attested details of ,saturn show no such vagaries3 ,cassini's division seems invariable4 ,are we therefore to surmise that the curious behaviour of ,encke's division is to be referred to errors of observation arising from the effects of unsteady air upon a very delicate object8 ,it is for future observers to answer these questions1 and this will entail no ordinary effort1 for the same impediments will be encountered in the future as in the past4 ,but fortunately our science is rapidly progressive1 and there is no doubt the mystery of ,encke's division will find-its solution before long4 ,a powerful telescope1 and a keen and continuous study of the outer ring1 will enable some discriminating observer to tell us the true story of its phenomena4 ,many other points in the ,saturnian system require renewed attention1 but some of them appear to be so doubtful as to scarcely deserve mention4 ,possibly the student had better commence his review of the planet without any of the bias or prejudice which former observations might occasion4 ,but it is as well to know the true state of the case2 for the judgment of a careful observer is not likely to be warped by preconception1 and of course some of the doubtful observations may be amply verified at a future time4 ,several of these have already been briefly referred to1 and a few others may here be noted4 ,the form of the shadow thrown on the rings from the ball has been observed of a curious shape1 and ,m4 ,trouvelot supposes it to be variable and occasioned by changes on the level surface of the rings4 ,the same observer has noticed transverse notches in the edges of the inner bright ring4 ,evidence of variation is not entirely wanting in regard to the chief division1 and observers should notice whether it appears uniformly black1 as it has been suggested that a gauze ring fills the interval4 ,exterior to the outer ring a faint luminosity has also been suspected1 as though the phenomenon of the inner ring had its counterpart here4 ,the colour of the belts on the ball should be ascribed by careful estimates1 as many such observations may give an insight into the variations occurring4 ,some observers have alleged that the transparent ring of ,bond and ,dawes is subject to very perceptible alterations4 ,it must be remembered1 however1 that the visible aspect of this exceedingly delicate structure is much affected by the condition of the atmosphere1 and that the inclination of the ,saturnian system must obviously introduce changes4 ,when the inclination is considerable1 the globe of the planet may be discerned through this ring with greater effect than at other times1 because we have to look through a thinner stratum of its material4 ,the observer1 in seeking to elucidate some of the anomalies of former researches1 will possibly himself gain a knowledge of features not hitherto recognized4 ,of the real existence of these he should assure himself by many critical observations before venturing to announce them4 ,we have hinted that further discoveries upon ,saturn may be considered as practically beyond the reach of small telescopes2 but the gratifying fact remains that some of the more noteworthy of the known features are visible in glasses of little pretention as regards size4 ,with a #b-;inch refractor1 power about #ij1 not only are the rings splendidly visible1 but ,cassini's division is readily glimpsed1 as well as the narrow dark belt on the body of the planet4 ,this sufficiently proves that a very small and portable instrument is capable of affording some excellent views of one of the most wonderful objects in the heavens4 ,grover has seen1 with an aperture similar to that named1 not only the belts and the shadow of the ball on the rings1 but two of the satellites as well2 and others may be equally successful4 ,occultations of ,saturn by the ,moon4--,phenomena of this kind were well observed in ,england on ,may #h1 #ahei1 ,april #bj and ,sept4 #cj1 #ahgj4 ,those of #ahei and ,sept4 #cj1 #ahgj1 were observed by the ,rev4 ,s4 ,j4 ,johnson1 who noted that 8the dull hue of the planet contrasted strikingly with the brilliant yellow of the ,moon40 ,dawes witnessed the occultation in #ahei1 and saw the opaque edge of our satellite sharply defined on the ball and rings of ,saturn1 without the slightest distortion of form4 ,no dark shading was remarked by him contiguous to the ,moon's bright edge at the reappearance1 such as he and others had observed on ,jupiter on the occasion of his occultation1 ,jan4 #b1 #aheg4 ,saturn was described as of a pale greenish hue1 and offered a strong contrast to the brilliant yellow lustre of the ,moon4 ,on the early morning of ,april #bj1 #ahgj1 several observers were on the qui vive for this interesting occurrence2 and their experiences are reported in the #8,monthly ,notices ,r4 ,a4 ,s4' vol4 xxx4 p4 #age et seq41 from which the following are brief extracts3-- ,mr4 ,ellis3--8,the light of the planet1 by contrast with the ,moon1 was very faint40 ,mr4 ,carpenter3--8,there was not the least alteration in the planet's form40 ,capt4 ,noble3--8,saturn appeared of a richly-greenish yellow when compared with the brilliant white light of the ,moon40 ,mr4 ,g4 ,c4 ,talmage3--8,the difference in colour between ,saturn and the ,moon was most marked1 the planet appearing of a yellow tint40 ,mr4 ,j4 ,carpenter3--8,at disappearance the planet was a very dull object when in contact with the ,moon2 its light probably a twentieth as bright4 ,at reappearance the planet was rather tremulous2 no distortion was noticed40 ,on ,june #ac1 #ahgj1 the ,rev4 ,j4 ,spear1 of ,bengal1 watched the ,moon pass 8steadily over the planet without causing any change of form or giving any indication of the planet's light passing through an atmospheric medium4 ,when near the ,moon's limb ,saturn assumed a sickly green hue40 ,i observed the occultation of ,sept4 #cj1 #ahgj1 at ,bristol1 with a #d-a_/d-;inch refractor2 but the event offered no novel traits1 the most prominent feature being the difference of brightness in the ,moon and ,saturn4 ,mr4 ,c4 ,l4 ,prince observed this event with a ,tulley refractor of #fh inches aperture1 power #bej4 ,he says there was not the slightest distortion of either body1 but he noticed that 8the edge of the ring lingered somewhat upon the ,moon's limb about the time of disappearance40 ,another occultation occurred soon after new ,moon on ,april #i1 #ahhc1 and one of the observers1 ,mr4 ,loomis1 described the disappearance of the rings as a spectacle of great interest1 and said the impression was forcibly conveyed to his mind that the ,moon was very much nearer to the eye than ,saturn4 ,the ,satellites4--,the discovery of the eight moons of this planet ranged over the long period of #aic years4 ,five different observers share the honours between them4 ,our knowledge of the ,saturnian satellites may almost be said to furnish us with a history of improvements in the telescope2 for they were severally detected at epochs corresponding to instrumental advances4 ,the following are the periods1 distances1 c4 of the satellites3-- ---------------------------------------- ---------------------------------------- ---------------- ,mean ,distance4 ---------------------------------------- ,sidereal ,real ,no4 and ,name4 ,diameters ,period4 ,diam4 of ,saturn4 ,miles4 ---------------------------------------- ---------------------------------------- ---------------- d h mmiles4 #gth4 ,mimas #aec #aae1jjj #j #bb #cg #ajjj #fth4 ,enceladus #aig #adh1jjj #a #h #ec 444 #eth4 ,tethys #bdd #ahc1jjj #a #ba #ah #ejj #dth4 ,dione #cab #bcd1jjj #b #ag #da #ejj #crd4 ,rhea #dcf #cbg1jjj #d #ab #be #abjj #ast4 ,titan #ajab #gei1jjjae #bb #da #ccjj #hth4 ,hyperion #abbc #iag1jjjba #g #g 444 #bnd4 ,iapetus #bifa #b1bba1jjjgi #g #ec #ahjj ---------------------------------------- ---------------------------------------- ---------------- ---------------------------------------- ---------------------------------------- -------- ,date of ,no4 and ,name4 ,discovery4 ,discoverer4 ---------------------------------------- ---------------------------------------- -------- #gth4 ,mimas #aghi1 ,sept4 #ag4,w4 ,herschel4 #fth4 ,enceladus#aghi1 ,aug4 #bh4,w4 ,herschel#dj4 #eth4 ,tethys #afhd1 ,mar4 #ba4;,j4 ,d4 ,cassini4 #dth4 ,dione #afhd1 ,mar4 #ba4;,j4 ,d4 ,cassini4 #crd4 ,rhea #afgb1 ,dec4 #bc4;,j4 ,d4 ,cassini4 #ast4 ,titan #afee1 ,mar4 #be4;,c4 ,huygens4 #hth4 ,hyperion #ahdh1 ,sept4 #ai4;,bond ,lassell4 #bnd4 ,iapetus #afga1 ,oct4 #be4;,j4 ,d4 ,cassini4 ---------------------------------------- ---------------------------------------- -------- ,the numbers in the first column refer to the order of discovery4 ,illustration3 ,fig4 #da4 ,apparent ,orbits of the ,five ,inner ,satellites of ,saturn1 as seen in an ,inverting ,telescope4 7,the arrows in the diagram show the direction of the motion of the satellites4 ,the figures indicate the interval1 in hours1 from the time of last ,east elongation47 ,titan is by far the largest satellite1 being equal to a star of the #hth mag4 and visible in any small telescope4 ,iapetus ranks next1 ordinarily about #ith mag41 but there are variations at different parts of the orbit similar to the variations which affect the satellites of ,jupiter2 a variegated surface1 and the effects of rotation1 originate the changes observed and give strong support to the inference that this satellite rotates in the same period that it revolves round its primary4 ,tethys1 ,dione1 and ,rhea are fainter1 and the difficulty of seeing them is intensified by their proximity to the planet2 but a good #d-;inch refractor will reveal them on a clear dark night4 ,the others are objects for powerful instruments and pellucid skies2 but ,enceladus is sometimes seen with moderate aperture4 ,the planet being usually much inclined1 his satellites are dispersed round about the rings1 and are not easy of identification4 ,minute stars lying near the path of ,saturn are very liable to be mistaken for them4 ,but the ephemerides drawn up by ,mr4 ,marth1 and published annually by the ,royal ,astronomical ,society1 are of the utmost service to amateurs engaged in these observations4 ,by simple reference they may readily identify the individual satellites on any night2 and these ephemerides are additionally useful as giving the times of conjunctions of some of the satellites with the ends of the ring and ,n4 and ,s4 points of the ball4 ,when the thin side of the rings is presented to the ,earth1 transits and other phenomena may be observed in connection with the ,saturnian moons2 but they appear to have been rarely recorded4 ,sir ,w4 ,herschel describes a 8beautiful observation of the transit of the shadow of ,titan over the disk in #aghi1 ,november #b40 ,it was also seen in #ahcc and #ahfb4 ,the late ,mr4 ,capron re-observed it on ,dec4 #aj1 #ahgg1 with a #h-a_/d-;inch reflector1 power #add1 and made the following sketch3-- ,illustration3 ,fig4 #db4 ,these shadow-transits admit of easy observation with appliances of very moderate capacity4 ,mr4 ,banks witnessed a phenomenon of the kind with a refractor of only #b-g_/h inches1 and says it was watched with the same facility and ease as the shadow of ,sat4 ,i4 on ,jupiter4 ,in looking for ,iapetus it must be remembered that it is commonly situated at a great distance from the planet4 ,titan is relatively much nearer1 and will always be recognized without trouble4 ,enceladus1 ,tethys1 ,dione1 and ,rhea hover near the outskirts of the ring2 while ,mimas is extremely close to it4 ,prof4 ,hall1 with the great ,washington refractor1 has effected many valuable measures of this system in recent years4 ,he finds the orbits of the five inner satellites are sensibly circular1 and that they are situated in the plane of the rings4 ,hyperion revolves in a very eccentric orbit1 and this satellite may approach very near to ,titan4 ,he obtained an observation on ,march #be1 #ahhe1 which seems pertinent to the question of variation in the light of the satellites4 ,he says3--8,mimas was remarkably bright1 and could not be missed even when the full light of the planet was admitted to the eye4 ,generally this satellite is a difficult object1 and from the ease with which it is occasionally seen one might think it variable2 but ,i think the difference is due to the quality of the image40 ,there is no doubt that this is the main cause of many assumed changes in celestial objects1 and especially in regard to those of a minute and delicate character4 ,occultations of ,stars4--,stars are rarely observed to be occulted by ,saturn4 ,webb mentions that1 in #agjg or #agjh1 ,dr4 ,clark noticed a star in the interval between the ball and rings2 and ,dawes once remarked a star of #he mag4 disappear behind the outer edge of the exterior ring4 ,it would be extremely interesting to watch a tolerably conspicuous star pass centrally behind the ,saturnian system1 and to trace it through ,cassini's division and the transparent ring1 noting any changes in magnitude or appearance as they occurred4 ,,footnotes3 #cf ,huygens appears to have used a refractor of #b-a_/c-;inch aperture and #bc-;feet focal length1 with a power of #ajj1 in effecting this discovery4 #cg ,schrter1 ,harding1 ,schwabe1 and others have observed luminous points on the rings1 but they have remained stationary1 so that the period of rotation announced by ,herschel has never been confirmed1 but rather disproved by counter-evidence4 ,herschel wrote1 in ,november #aghi3--8;,i formerly supposed the surface of the ring to be rough1 owing to luminous points like mountains seen on the ring1 till one of these supposed luminous points was kind enough to venture off the edge of the ring and appear as a satellite4 ,i have always found these appearances to be due to satellites40 #ch ,galle1 at ,berlin1 had1 twelve years previously1 made an observation which1 if it had been interpreted correctly1 would have given him priority4 ,in ,june #ahch he remarked1 on several nights1 that the inner boundary of the inner ring was very indistinct and 8gradually lost itself towards the body of the planet40 ,the space between the ring and ,saturn was half filled with a dim veil1 extending inwards from the ring4 ,these observations failed to attract the notice their importance deserved1 and ,galle himself did not appreciate their full significance until the announcements of ,bond and ,dawes in #ahej4 #ci ,struve wrote1 in #ahhc3--8,that changes do take place in the ring-system is sufficiently proved40 ,trouvelot1 ,schiaparelli1 and others have also remarked variations of a sufficiently decided character to be placed on record4 #dj ,herschel remarks that he saw this satellite in his #bj-;foot speculum two years before1 viz4 on ,aug4 #ai1 #aghg1 but he was then much engaged in observations of the satellites of ,uranus4 ,,chapter ,,xiii4 ,,uranus ,,and ,,neptune4 ,discovery of ,uranus4--,mistaken for a ,comet4--,true character revealed4--,period c4--,observations4--,belts on ,uranus4--,further ,observations required4--,the ,satellites4--,discovery of ,neptune4--,the planet observed in #agie4--,period c4--,observations4--,supposed ,ring4--,satellite4--,a trans-,neptunian ,planet4--,planetary ,conjunctions4 ,discovery4--,while ,sir ,w4 ,herschel was a musician at ,bath he formed the design of making a telescopic survey of the heavens4 ,when engaged in this he accidentally effected a discovery of great importance1 for on the night of ,march #ac1 #agha1 an object entered the field of his #fc-;inch reflector which ultimately proved to be a new major planet of our system4 ,the acute eye of ,herschel1 directly it alighted upon the strange body1 recognized it as one of unusual character1 for it had a perceptible disk1 and could be neither fixed star nor nebula4 ,he afterwards found the object to be in motion1 and its appearance being 8hazy and ill-defined0 with very high powers he was led to regard it as a comet1 and communicated his discovery to the ,royal ,society at its meeting on ,april #bf1 #agha4 ,his paper begins as follows3-- 8,on ,tuesday1 ,march #ac1 #agha1 between #aj and #aa in the evening1 while ,i was examining the small stars in the neighbourhood of ,h ,geminorum1 ,i perceived one that appeared visibly larger than the rest4 ,being struck with its uncommon magnitude1 ,i compared it to ,h ,geminorum and the small star in the quartile between ,auriga and ,gemini1 and finding it so much larger than either of them suspected it to be a comet4444 ,the power ,i had on when ,i first saw the comet was #bbg40 ,the supposed 8comet0 soon came under the observation of others1 including ,maskelyne the ,astronomer ,royal1 and ,messier1 the 8,comet ,ferret0 of ,paris4 ,the latter1 in a letter to ,herschel1 said3--8,nothing was more difficult than to catch it1 and ,i cannot conceive how you could have hit this star or comet several times1 for it was absolutely necessary for me to observe it for several days in succession before ,i could perceive that it was in motion40 ,true character revealed4--,as observations began to accumulate it was seen that a parabolic orbit failed to accommodate them4 ,ultimately the secret was revealed4 ,the only orbit to represent the motion of the new body was found to be an approximately circular one situated far outside the path of ,saturn1 and the inference became irresistible that the supposed 8comet0 must in reality be a new primary planet revolving on the outskirts of the solar system4 ,this conclusion was justified by facts of a convincing nature1 and its announcement created no small excitement in the scientific world4 ,every telescope was directed to that part of the firmament which contained the new orb1 and its pale blue disk1 wrapped in tiny proportions1 was viewed again and again with all the delight that so great a novelty could inspire4 ,from the earliest period of ancient history1 no discovery of the same kind had been effected4 ,the ,chaldans were acquainted with five major planets1 in addition to the ,earth1 and the number had remained constant until the vigilant eye of ,herschel enlarged our knowledge1 and ,saturn was relieved as the sentinel planet going his rounds on the distant frontiers of our system4 ,when the elements of the new body had been computed a search was instituted amongst the records of previous observers1 and it was found that ,herschel's planet had been seen on many occasions1 but it had invariably been mistaken for a fixed star4 ,flamsteed observed it on six occasions between #afij and #agae1 while ,le ,monnier saw it on #ab nights in the years from #agej to #agga1 and it seems to have been pure carelessness on the part of the latter which prevented him from anticipating ,herschel in one of the greatest discoveries of modern times4 ,the name ,uranus was applied to the new planet1 though the discoverer himself called it the ,georgium ,sidus1 and there were others who termed it 8,herschel10 in honour of the man through whose sagacity it had been revealed4 ,period c4--,uranus revolves round the ,sun in #cj1fhg days1 which very slightly exceeds #hd terrestrial years4 ,his mean distance from the ,sun is #a1ghb1jjj1jjj miles1 but the interval varies between #a1fii and #a1hfe millions of miles4 ,the apparent diameter of the planet undergoes little variation2 the mean is #cf1 but observers differ4 ,his real diameter is approximately #ca1jjj miles1 and the polar compression about #a_/ac1 though this value is not that found by all authorities4 ,observations4--,the planet near opposition shines like a star of the #fth magnitude1 and is observable with the naked eye4 ,he emits a bluish light4 ,while engaged in meteoric observations1 ,i have sometimes followed the planet with the naked eye during several months1 and noted the changes in his position relatively to the stars near4 ,it is clear from this that ,uranus admitted of detection before the invention of the telescope4 ,a luminous ring1 similar to that of ,saturn1 was at first supposed to surround ,uranus1 and ,herschel suspected the existence of such a feature on several occasions2 but it scarcely survived his later researches1 and modern observations have finally disposed of it4 ,lassell1 when working with his #b-;foot speculum at ,malta1 thought he saw a spot near the centre of the planet's disk1 but he considered this might possibly be due to an optical illusion4 ,in #ahfb1 ,jan4 #bi1 he said3--8,i received an impression which ,i am unable to render certain of an equatoreal dark belt40 ,in the early months of #ahgj1 ,mr4 ,buffham1 using a #i-;inch 8,with0 mirror1 powers #bab and #cbj1 saw bright spots and zones on the planet1 and inferred a rotation-period of about #ab hours4 ,on ,jan4 #af1 #ahgc1 when definition was very good1 no traces of any markings were visible in ,lord ,rosse's #f-;foot reflector4 ,in ,may and ,june #ahhc ,prof4 ,young1 having the advantage of the fine #bc-;inch refractor at the ,princeton ,observatory1 observed two faint belts1 one on each side of the equator1 and much like the belts of ,saturn4 ,on ,march #ah1 #ahhd1 ,messrs4 ,thollon and ,perrotin1 with the #ad-;inch equatoreal at ,nice1 remarked dark spots similar to those on ,mars1 towards the centre of the disk1 and a white spot was seen on the limb4 ,two different tints were perceived1 the colour of the ,n4,w4 hemisphere being dark1 and that of the ,s4,e4 a bluish-white colour4 ,in ,april observations were continued1 and the white spot was seen 8rather as a luminous band than a simple spot10 but it was most conspicuous near the limb4 ,the observers thought the appearances indicated a rotation-period of about #aj hours4 ,the brothers ,henry at ,paris1 in #ahhd1 invariably noticed two belts lying parallel to each other1 and including between them the brighter equatoreal zone of the planet4 ,their results apparently show that the angle between the plane of the ,uranian equator and that of the satellite-orbits is about #da4 ,illustration3 ,fig4 #dc4 ,uranus and his ,belts4 #ahhd4 ,m4 ,perrotin1 with the great #cj-;inch equatoreal at ,nice1 re-observed the belts in ,may and ,june #ahhi4 ,he wrote that dark parallel bands were noticed several times1 and they were very similar to the belts of ,jupiter4 ,on ,may #ca and ,june #a and #g the direction of the ,uranian belts was measured1 and the mean result showed that the plane of the equator of ,uranus differs little 7about #aj7 from the common plane of the orbits of the satellites4 ,this deduction is not1 it will be observed1 consistent with that of the ,brothers ,henry at ,paris1 who found a difference of #da4 ,m4 ,perrotin notes that the bands of ,uranus do not always present the same aspect4 ,they vary in size and number in different parts of their circumference4 ,this unequal distribution raises the hope that by an attentive study of these bands it will be possible to determine the duration of the planet's rotation4 ,further ,observations required4--,in the case of an object so faint and diminutive as ,uranus1 a powerful telescope is absolutely required to deal with it effectively4 ,a small instrument will readily show the disk1 and present the picture that caught the eye of ,herschel more than a century ago1 but considerable light and power must be at command if the observer would enter upon a study of the planet's surface-markings4 ,with my #aj-;inch reflector ,i have suspected the existence of the belts1 but under high powers the image is too feeble to exhibit delicate forms of this character4 ,it is to be hoped that with the large telescopes now available at various observatories1 some attention will be given to this planet1 more especially with regard to the study of the belts and determination of the rotation-period4 ,amateurs will have little trouble in picking up ,uranus2 his position can be learnt from an ephemeris and marked upon a star-map4 ,a little careful sweeping with a low power in the region indicated will soon reveal the object sought for1 and a higher power may then be applied to expand the disk and render identification certain4 ,it may be mentioned as an interesting point that some fifty years after the discovery of ,uranus by ,sir ,w4 ,herschel the planet was accidentally rediscovered by his son ,sir ,john ,herschel1 who mentioned the fact as follows in a letter to ,admiral ,smyth1 written on ,aug4 #h1 #ahcj3--8;,i have just completed two #bj-;foot reflectors1 and have got some interesting observations of the satellites of ,uranus4 ,the first sweep ,i made with my new mirror ,i rediscovered this planet by its disk1 having blundered upon it by the merest accident for #ai ,capricorni40 ,had the father failed to detect this planet in #agha1 the discovery might therefore have been made by the son half a century later4 ,some spectroscopic observations of ,uranus made in #ahhi with ,mr4 ,common's #e-;foot reflector1 appear to show that the planet 8is to a large extent self-luminous40 ,but ,mr4 ,huggins on ,june #c seems to have obtained a different result 7see #8,monthly ,notices1' xlix4 p4 #djd et seq474 ,the ,satellites4--,for many years it was supposed that ,uranus possessed six satellites1 all of which were discovered by ,sir ,w4 ,herschel1 but later observations proved that four of these had no existence4 ,they were small stars near the planet4 ,but two of ,herschel's satellites were fully corroborated1 and two new ones were discovered by ,lassell and ,struve4 ,the number of known satellites attending ,uranus is four1 and it is probable that many others exist1 though they are too minute to be distinguished in the most powerful instruments hitherto constructed4 ,the following are the periods1 distances1 c41 of the known satellites3-- ---------------------------------------- ---------------------------------------- ---------------------------------- ,mean distance4 ,number and ------------------------------------- ,max4 ,date of name4 ,diameters ,miles4 ,elonga- ,discovery4 of ,uranus4 tion4 ---------------------------------------- ---------------------------------------- ---------------------------------- #crd4 ,ariel #djc #abe1jjj #ab #ahdg1 ,sept4 #ad4 #dth4 ,umbriel #efa #agd1jjj #ae #ahdg1 ,oct4 #h4 #ast4 ,titania #iai #bhe1jjj #cc #aghg1 ,jan4 #aa4 #bnd4 ,oberon #abcb #chb1jjj #dd #aghg1 ,jan4 #aa4 ---------------------------------------- ---------------------------------------- ---------------------------------- ---------------------------------------- ----- ,discoverer4 d h m ---------------------------------------- ----- ,w4 ,lassell4 #b #ab #bi ,o4 ,struve4 #d #c #bg ,w4 ,herschel4 #h #af #eg ,w4 ,herschel4 #ac #aa #g ---------------------------------------- ----- ,titania and ,oberon are the two brightest satellites1 but none of them can be seen except in large instruments4 ,the two outer ones are said to have been glimpsed in a #dc-;inch refractor1 but this feat is phenomenal1 and certainly no criterion of ordinary capacity4 ,sir ,j4 ,herschel found them tolerably conspicuous in a reflector of #ah or #bj inches aperture1 and mentioned a test-object by which observers might determine whether their telescopes were adequate to reveal them4 ,this test is a minute double star lying between the stars and #b ,capricorni4 ,the magnitudes are #ae and #af1 and distance #c4 ,relatively to the satellites of ,uranus this faint double is a 8splendid object40 ,from observations with large modern instruments it appears highly probable that the four known satellites1 must be considerably larger than any others which may be revolving round the planet4 ,a curious fact in connection with these satellites is that their motions are retrograde4 ,illustration3 ,fig4 #dd4 ,apparent ,orbits of the ,satellites of ,uranus1 as seen in an ,inverting ,telescope4 7,the small circle in the above diagram represents the planet and is on the same scale as the orbits4 ,the arrows show the direction of the motion of the satellites1 and the figures indicate the number of days from the time of the last ,north elongation47 ,discovery of ,neptune4--,the leading incidents in the narrative of the discovery of ,uranus and ,neptune present a great dissimilarity--,uranus was discovered by accident1 ,neptune by design4 ,telescopic power revealed the former1 while theory disclosed the latter4 ,in one case optical appliances afforded the direct means of success1 while in the other the unerring precision of mathematical analysis attained it4 ,the telescope played but a secondary part in the discovery of ,neptune1 for this instrument was employed simply to realize or confirm what theory had proven4 ,certain irregularities in the motion of ,uranus could not be explained but on the assumption of an undetected planet situated outside the known boundaries of the system4 ,two able geometers applied themselves to study the problem of these irregularities1 and to deduce from them the place of the disturbing body4 ,this was effected independently by ,messrs4 ,le ,verrier and ,adams2 and ,dr4 ,galle1 of ,berlin1 having received from ,le ,verrier the leading results of his computations1 and the intimation that the longitude of the suspected planet was then #cbf1 found it with his telescope on the night of ,sept4 #bc1 #ahdf1 in longitude #cbf #eb4 ,the calculated place by ,prof4 ,adams was #cbi #ai for the same date and less accurate than the prediction of ,le ,verrier4 ,the former had priority both in attacking the problem and resolving it1 though unfortunately his efforts were not backed up in a practical way4 ,but for the supineness of certain officials1 there is little doubt that the planet would have been telescopically discovered in the autumn of #ahde1 when it was within #a #di of the place attributed to it by ,prof4 ,adams4 ,delays occurred owing to the doubts prevailing1 and in the meantime the planet was found elsewhere4 ,this circumstance does not rob ,prof4 ,adams of his hard-earned laurels1 though it shows how seriously official negligence can mar the character of a discovery4 ,observations in #agie4--,the name given to the new planet was ,neptune4 ,when the elements were computed it was found that they presented rather large differences with those theoretically computed by ,messrs4 ,le ,verrier and ,adams4 ,it was also found that the planet had been previously observed by ,lalande on ,may #h and #aj1 #agie1 but its true character escaped detection4 ,this astronomer had observed a star of the #hth mag4 on ,may #h2 but on ,may #aj1 not finding the same star in the exact place noted on the former evening1 he rejected the first observation as inaccurate and adopted the second1 marking it doubtful4 ,had ,lalande exercised a little discretion1 and confided in his work1 he would hardly have allowed the matter to rest here4 ,a subsequent observation would at once have exhibited the cause of the discrepancy1 and the mathematical triumph of ,le ,verrier and ,adams1 half a century later1 would have been forestalled4 ,lalande1 like ,le ,monnier1 the unsuspecting observer of ,uranus1 let a valuable discovery slip through his hands4 ,period c4--,neptune revolves round the ,sun in #fj1abf days1 which is equal to rather more than #afd of our years4 ,his mean distance from the ,sun is #b1gib1jjj1jjj miles1 and his usual diameter #bg4 ,he exceeds ,uranus in dimensions1 his real diameter being #cg1jjj miles4 ,observations4--,our knowledge of this distant orb is extremely limited1 owing to his apparently diminutive size and feebleness4 ,no markings have ever been sighted on his miniature disk1 and we can expect to learn nothing until one of the large telescopes is employed in the work4 ,no doubt this planet exhibits the same belted appearance as that of ,uranus1 and there is every probability that he possesses a numerous retinue of satellites4 ,in dealing with an object like this small instruments are useless2 they will display the disk1 and enable us to identify the object and determine its position if necessary1 but beyond this their powers are restricted by want of light4 ,supposed ,ring4--,directly the new planet was discovered1 ,mr4 ,lassell turned his large reflector upon it and sought to learn something of its appearance1 and possibly detect one or more of its satellites4 ,on ,october #c and #aj1 #ahdf1 he was struck with the appearance of the disk1 which was obviously not perfectly spherical4 ,he subsequently confirmed this impression1 and concluded that a ring1 inclined about #gj1 surrounded the planet4 ,prof4 ,challis supported this view1 but later observations in a purer sky led ,mr4 ,lassell to abandon the idea4 ,thus the ring of ,neptune1 like the ring of ,uranus1 though apparently obvious at first1 vanished in the light of more modern researches4 ,the ,satellite4--,but if ,mr4 ,lassell quite failed to demonstrate the existence of a ring1 he nevertheless succeeded in discovering a satellite belonging to the planet4 ,this was on ,oct4 #aj1 #ahdf4 ,the new satellite was found to have a period of #e;d #ba;h #cm1 and to be situated about #bbj1jjj miles distant from the planet4 ,its apparent star mag4 is #ad1 and at max4 elongation it extends its excursions to #ah on either side of its primary4 ,compared with the other satellites of our system the one attending ,neptune must be excessive in regard to size1 or it could not be discerned at the vast distance separating it from the ,earth4 ,illustration3 ,fig4 #de4 ,apparent ,orbit of the ,satellite of ,neptune1 as seen in an ,inverting ,telescope4 7,the small circle in the above diagram represents the planet1 the arrows show the direction of motion1 and the figures indicate the interval from the time of last ,north-east elongation47 ,a trans-,neptunian ,planet4--,is there a planet beyond ,neptune8 ,prof4 ,forbes wrote a memoir in #ahhj tending to prove that two such planets exist4 ,from the influences exerted by these bodies on certain comets of long period1 he approximately deduced the positions of the former1 and they were searched for with the great ,washington refractor1 but without success4 ,flammarion and ,todd have also arrived at conclusions affirming the existence of a planet outside ,neptune2 but the idea has not yet been realized by its telescopic discovery4 ,planetary ,conjunctions4--,before concluding this chapter1 an allusion should be made to a noteworthy class of events1 viz41 planetary conjunctions4 ,these include some of the most attractive aspects displayed by the heavenly bodies1 and they are sometimes witnessed by ordinary persons with the same amount of gratification as by the astronomical amateur4 ,in almanacks the times of such conjunctions are given1 so that intending observers may always be prepared for these events4 ,in a strict sense a conjunction occurs at the instant when two or more bodies have the same right ascension1 but the term is here intended to have a more general reference1 i4 e41 to denote the assembling together of two or more planets in the same region of the firmament4 ,historical records furnish us with a considerable number of planetary conjunctions1 and some of them were attentively observed long before the telescope came into use4 ,thus in #bjab ,b4,c41 ,feb4 #bf1 the ,moon1 ,mercury1 ,venus1 ,jupiter1 and ,saturn were in the same constellation1 and within #ad of one another4 ,in #aahf ,a4,d41 ,sep4 #ad1 the ,sun1 ,moon1 and all the known planets are said to have been situated in ,libra4 ,in #aebd ,venus1 ,mars1 ,jupiter1 and ,saturn were near together4 ,many similar instances might be quoted1 but this is unnecessary4 ,occasionally the conjunctions were so close that one planet appeared to occult another4 ,kepler refers to an occultation of ,jupiter by ,mars which he saw on ,january #i1 #aeia2 but this would really be a transit of ,mars across the disk of ,jupiter1 if contact actually occurred1 for the apparent diameter of ,jupiter always exceeds that of ,mars4 ,mstlin seems to have witnessed an occultation of ,mars by ,venus on ,oct4 #c1 #aeij4 ,it is probable1 however1 that these were near approaches only4 ,a genuine occultation of ,mercury by ,venus was telescopically observed on ,may #ag1 #agcg4 ,on the evening of ,march #c1 #ahha1 the new ,moon1 ,venus1 ,jupiter1 and ,saturn formed a brilliant quartet in ,pisces4 ,on the morning of ,july #ba1 #ahha1 ,i saw the ,moon1 ,venus1 ,mars1 ,jupiter1 ,saturn1 and ,aldebaran in the same region above the eastern horizon4 ,there was a very close conjunction of ,mars and ,saturn on the morning of ,sept4 #bj1 #ahhi4 ,mr4 ,marth computed that the nearest approach would occur at #h;h #gm ,a4,m41 when the distance between the centres would be #edh and less than that 7#gd7 observed at the time of the close conjunction of the same planets on ,june #cj1 #ahgi4 ,the interest centred in the conjunction of ,sept4 #bj1 #ahhi1 was enhanced by the fact that ,regulus was only #dg distant1 while ,venus was also in the same region4 ,i observed this phenomenon in my #aj-;inch reflector1 and with the help of a comet-eyepiece made the above sketch of the positions of the objects as they were presented in the field4 ,illustration3 ,fig4 #df4 ,mars1 ,saturn1 and ,regulus in same field1 ,sept4 #bj #ahhi1 #d;h #dem ,a4,m4 ,perhaps there is not much scientific importance attached to the observation of these conjunctions1 though comparisons of colour and surface-brilliancy are feasible at such epochs1 and are not wholly without value4 ,as spectacles merely1 they possess a high degree of interest to everyone who 8considers the heavens40 ,,chapter ,,xiv4 ,,comets ,,and ,,comet-,,seeking4 ,ideas concerning ,comets4--,appearance4--,large number visible4--,nature of ,apparition4--,tenuity of ,comets4--,differences of ,orbit4--,discoveries of ,comets4--,large ,comets4--,periodical ,comets4--,the ,comets of ,halley1 ,encke1 ,biela1 ,brorsen1 ,faye1 ,d',arrest1 ,pons-,winnecke1 and ,tuttle4--,grouping4--,further ,observations required4--,nomenclature of ,comets4--,curiosities of ,comets4--,naked-eye ,comets4--,comet-seeking4--,english weather4--,aperture and ,power required4--,annual rate of ,discovery4--,telescopic ,comets and ,nebul4--,ascertaining ,positions4--,dr4 ,doberck's hints4--,prizes4 ,superstitious ideas with regard to comets as the harbingers of disaster have long since been discarded for more rational opinions4 ,they are no longer looked upon as ill-omened presages of evil1 or as 8,from ,saturnius sent1 ,to fright the nations with a dire portent40 ,many references are to be found among old writings to the supposed evil influence of these bodies1 and to the dread which their appearance formerly incited in the popular mind4 ,shakespeare makes an allusion to the common belief3-- 8,hung be the heavens with black1 yield day to night6 ,comets1 importing change of time and states1 ,brandish your crystal tresses in the sky20 and in relation to the habit of connecting historical events with their apparition1 he further says3-- 8,when beggars die1 there are no comets seen2 ,the heavens themselves blaze forth the death of princes40 ,but1 happily1 the notions prevalent in former times have been superseded by the more enlightened views naturally resulting from the acquirement and diffusion of knowledge2 so that comets1 though still surrounded by a good deal of mystery1 are now regarded with considerable interest1 and welcomed1 not only as objects devoid of malevolent character1 but as furnishing many useful materials for study4 ,mere superstition has been put aside as an impediment to real progress1 and a more intelligent age has recognized the necessity of dealing only with facts and explaining them according to the laws of nature2 for it is on facts1 and their just interpretation1 that all true searchers after knowledge must rely4 ,comets are properly regarded as bodies which1 though far from being thoroughly understood in all the details of their physical structure and behaviour1 have yet a wonderful history1 and one which1 could it be clearly elucidated1 would unfold some new and marvellous facts4 ,under these circumstances we need evince no surprise that these visitors are invariably hailed with enthusiasm1 not only by scientific men1 who make them the special subjects of close observation1 but by everyone who regards celestial 8sights and signs0 with occasional attention4 ,appearance4--,from whatever point of view a large comet is considered1 it deserves all the interest manifested in it and all the labour expended in its investigation4 ,whilst its grand appearance in the firmament arrests the notice of all classes alike1 and is the subject of much curious speculation amongst the uninformed1 it merits1 apart from other considerations1 the most assiduous observation on account of the singular features it displays and the striking variations they undergo4 ,indeed1 the visible deportment of a comet during its rapid career near perihelion is so extraordinary as to form a problem1 the solution of which continues to defy the most ingenious theories4 ,the remarkable changes in progress1 the quickness and apparent irregularity of their development1 are the immediate result of a combination of forces1 the operations of which can neither be defined nor foreseen4 ,jets of flame and wreaths of vapour start from the brilliant nucleus2 while1 streaming away from the latter1 in a direction opposite to the ,sun1 is the fan-shaped tail1 often traceable over a large span of the heavens and commingling its extreme fainter limits with the star-dust in the background4 ,large number visible4--,the orbits of #djj comets have now been computed1 and more than #ejj others have been observed2 so that these bodies are extremely plentiful4 ,kepler described them to be as numerous as the fishes in the sea1 and no doubt the allegory is justly applied4 ,their vagaries of form1 size1 and place are equally noteworthy2 and those who enter upon the discussion of facts relating to these objects will find an endless store of interesting materials1 opening up a wide field for conjecture4 ,nature of ,apparition4--,the apparition of a comet may be either gradual or sudden4 ,usually the telescope gives us the earliest intimation that one of these bodies is approaching us#da4 ,it is first seen as a small round nebulosity1 with probably a central condensation or stellar nucleus of the #ajth or #aath mag4 ,the whole object brightens and expands as its distance grows less1 and it assumes an elongated form preparatory to the formation of a tail4 ,the latter varies greatly in different instances3 it may either be a narrow ray1 as shown in the southern comet of ,january #ahhg1 or a fan-shaped extension like that of the great comet of #agdd4 ,barnard's ,comet of ,december #ahhf exhibited a duple tail4 ,occasionally a fine comet bursts upon us suddenly1 like that of #ahdc or #ahfa4 ,the former was sufficiently bright to be discovered when only #d from the ,sun1 and the latter presented itself quite unexpectedly as a magnificent object even in the strong twilight of a ,june sky4 ,tenuity of ,comets4--,comets are noteworthy for the extreme thinness of their material4 ,the smallest stars may be discerned through the denser portions of the head1 without suffering any apparent diminution of light4 ,yet such stars would be quite obscured by the interposition of a minute speck of cloud or by a little fog or any vapour of trifling density4 ,comets are visible in the form of transparent nebulosities2 and their mass must be inconceivably small relatively to the enormous space over which they frequently extend4 ,sir ,j4 ,herschel has described the 8all but spiritual texture0 of comets2 and other authorities have referred to them as feeble wreaths of vapour1 which1 though obeying the laws of gravitation and suffering much perturbation1 are yet themselves incapable of exercising any disturbing influence upon the other bodies near which they pass4 ,it has been asserted that comets would show phases were they rendered luminous by reflected sunlight1 and that1 such features being absent1 these bodies must possess a phosphorescence of their own sufficient to cause the glow observed4 ,this idea1 however1 is hardly consistent with our present knowledge4 ,comets are not compact and coherent masses of matter2 they more likely represent vast groups of planetary atoms1 more or less loosely dispersed and sometimes forming streams4 ,the effect of sunshine upon such assemblages will be that the whole mass becomes illumined according to density1 and that no phase will be apparent1 inasmuch as the light is enabled to penetrate through its entirety4 ,differences of ,orbit4--,when three trustworthy observations of a comet's place have been made1 its orbit may be computed4 ,this may be either an ellipse1 a parabola1 or hyperbola4 ,if an ellipse the comet is periodical1 and the period depends upon the degree of eccentricity4 ,if a parabola the comet will not be seen again1 because this form of orbit does not reunite2 it consists of branches equally divergent and uniting at perihelion1 but extending outwards indefinitely in nearly parallel lines and without convergence4 ,if a hyperbola1 the comet is also not returnable2 the branches of the orbit are widely divergent1 and show no tendency to parallelism4 ,these several forms of orbit are somewhat different as applied to various comets1 but they are the same in effect4 ,thus ,tempel's ,comet of #ahfg revolves in an ellipse having an eccentricity of about #jdfcj1 while that of ,halley's ,comet is #jifgd4 ,no doubt some of the parabolic orbits applied to comets really represent very eccentric ellipses2 but the parabola is a convenient form of orbit for computation1 and unless ellipticity is very decided it indicates the path with sufficient accuracy4 ,discoveries of ,comets4--,in the latter part of the last century ,messier1 ,mechain1 and ,miss ,herschel shared nearly all the cometary discoveries between them4 ,then ,pons entered the field1 and he may be said to have monopolized this branch during the period from #ahjb to #ahbg1 for he was the first to announce thirty comets4 ,pons died in #ahca1 but the search was actively continued by others4 ,in about #ahdc a great rise became apparent in the rate of these discoveries2 and we find ,di ,vico1 ,mauvais1 and ,brorsen very successful at this period4 ,later on1 the work was sustained with the same prolific results by ,klinkerfues1 ,bruhns1 and ,donati1 and subsequently by ,winnecke1 ,tempel1 and ,coggia4 ,swift and ,borrelly also assisted materially to swell our knowledge2 while during the last few years ,barnard and ,brooks have exhibited a surprising amount of zeal in this department4 ,since #ahha no less than twenty-six comets are to be enumerated as the fruits of their endeavours1 and they are still engaged in nightly explorations of the sky with similar ends in view4 ,their diligent pursuit of these fugitive bodies will doubtless result in many further additions during ensuing years4 ,it is a curious circumstance that ,sir ,w4 ,herschel1 during all his star-gaugings and sweeps for nebul1 never discovered a comet4 ,he found a nebula on ,dec4 #ah1 #aghc1 near ,ceti1 which he described as 8small and cometic40 ,in ,sir ,j4 ,herschel's #8,general ,catalogue of ,nebul1' #ahfd1 p4 #ag1 this object is presumed to have been a comet1 as it could not be identified2 but at p4 #de the doubts are cleared up1 and ,sir ,w4 ,herschel's nebula1 the position of which was only roughly given1 is shown to be the same as another very near2 it is ,no4 #ajee of the new #8,general ,catalogue' published by the ,royal ,astronomical ,society in ,january #ahhh4 ,quite possibly ,sir ,w4 ,herschel's lists of nebul contain several comets1 as some of his objects are missing2 but errors of observation in ascribing positions may explain this4 ,herschel himself1 in speaking of a comet visible in the winter of #ahjg-h1 says3--8,if ,i had met the comet in one of my sweeps1 as it appeared between ,dec4 #f and ,feb4 #ba1 ,i should have put it down as a nebula4 ,perhaps my lists of nebul1 then1 contain some comets40 ,large ,comets4--,the most widely observed and attractive class of comets includes those of large proportions1 as they are not only visible to the naked eye1 but exhibit features having the lustre necessary to permit of their examination with high magnifying powers4 ,a brief summary of some of the finest comets of modern times is subjoined2 but1 to save space1 a few only of the more salient facts concerning them are given3-- #aegg1 ,nov4 and ,dec4--,observed by ,tycho ,brahe4 ,at the end of ,november it had a double tail2 the longest of the two branches was about #bj4 ,this comet was visible in the daytime4 #afah ,,ii41 ,nov4--8,the length of its tail equalled in extent one sixth part of the zodiac40 ,on ,nov4 #ah it was estimated as #dj4 ,longomontanus1 however1 described it as #ajd long1 and ,cysatus estimated it as #ge4 ,kepler referred to it as the largest comet that had appeared for a hundred and fifty years4 #afhj1 ,dec4--,a fine comet1 which on ,dec4 #ab had a narrow tail about #hj long4 ,the nucleus was equal to a #ast mag4 star4 ,hooke remarked jets of flame issuing from the nucleus4 ,at perihelion the comet approached very near the ,sun's surface1 similarly to the fine comets of #ahdc1 #ahhj1 and #ahhb4 #agdd1 ,jan4-,feb4--,probably the largest comet of the #ahth century4 ,at one time it displayed six tails1 each of which was #d in breadth4 ,the head was so bright that it was perceived with the naked eye in full sunshine4 ,at the middle of ,february the tail was #bd long1 and it was divided into two branches4 #agfi1 ,sept4--,discovered on ,aug4 #h by ,messier4 ,on ,aug4 #cj the comet had a trifid tail2 there was a central ray of #bd and two outlying ones of #d each4 ,on ,sept4 #ai the tail had increased to #ge1 and a few nights later ,pingre estimated it as #ij and #ig4 #ahaa ,i41 ,sept4-,oct4--,a very fine comet4 ,the tail was branched2 it did not1 however1 exceed #be in length and about #f in breadth4 ,sir ,w4 ,herschel found the nucleus to be #dbh miles in diameter4 ,this remarkable comet remained visible during a period extending over seventeen months4 ,its period is approximately #cjjj years4 #ahdc1 ,mar4--,visible in the daytime4 ,on ,mar4 #d its tail was #fi in length2 it was very narrow1 being only #a-a_/d in breadth throughout4 ,at perihelion this object passed very near to the ,sun1 like the great comet of #afhj4 it revolves in an elliptical orbit2 period about #cgf years4 ,this comet swept past perihelion with a velocity of #cff miles per second6 ,the real length of its tail was #bjj millions of miles6 #aheh ,,vi41 ,sept4-,oct4--,donati's ,comet3 one of the most brilliant comets of the #aith century4 ,early in ,october it displayed a tail about #dj long1 and on the #eth it passed over the star ,arcturus4 ,its period of revolution appears to be about #bjjj years4 #ahfa ,,ii41 ,june-,july4--,became suddenly visible at the end of ,june4 ,in the opinion of ,sir ,john ,herschel this comet surpassed in grandeur the comets of #ahaa and #aheh4 ,on ,june #cj the nucleus was equal to the brightness of ,venus1 and the tail was #hj long2 but early in ,july it increased to #ij4 ,one observer estimated its length as #ajj on ,july #b4 ,this comet remained visible during twelve months4 ,it appears to have an elliptical orbit1 with a period of #dji years4 #ahgd1 ,july4--,coggia's ,comet3 a fine object in the northern sky4 ,on ,july #ad the tail was #ce long1 and it remained visible several days after the nucleus had disappeared below the horizon4 ,the nucleus was about equal to a star of the #ast mag4 ,orbit probably elliptical1 with a period of about #egaa years4 #ahhj ,i41 ,jan4-,feb4--,a southern comet1 with a long narrow tail1 variously estimated from #cj to #dj in length4 ,it passed very near to the ,sun1 and presents an orbital resemblance to the fine comets of #afhj and #ahdc4 #ahha ,,iii41 ,june-,july4--,this large comet appeared in the northern heavens on ,june #bb1 and became generally visible to observers in ,england4 ,on the #bgth it had a tail #ae long4 ,its period of visibility extended over nine months4 #ahha ,,iv41 ,aug4--,this comet is scarcely entitled to rank as one of exceptional character2 but it was a conspicuous object for several weeks in ,august1 and had a tail #f long on the #aith4 #ahhb ,,iii41 ,oct4--,well visible in the morning sky1 with a tail #bb long4 ,the nucleus underwent remarkable changes1 and on ,oct4 #bc it showed four or five bright points or nuclei1 looking like 8a string of beads40 ,the comet threw off several small condensations1 which were observed as separate comets near the parent mass4 ,at perihelion this comet passed very close to the ,sun1 like the comets of #afhj1 #ahdc1 and #ahhj2 and these bodies were suspected to have an intimate relation1 if not an absolute identity4 ,but subsequent inquiries disproved this startling supposition2 for the comet of #ahhb was shown to have a period of about #gah years4 #ahhg ,i41 ,jan4--,a fine southern comet1 presenting many points of resemblance to that of #ahhj ,i4 ,on ,jan4 #bb1 as observed at ,adelaide1 the comet had a long narrow tail of about #cj1 but no well-defined nucleus4 ,on the same date1 at the ,cape of ,good ,hope1 the tail appeared as a narrow ribbon of light1 quite straight1 and of nearly uniform brightness throughout its length4 ,it was visible in the same region of the sky as the comet #ahhj ,i41 and came into view with equal suddenness4 ,periodical ,comets4--,on page #bce is a list of the periodical comets as at present known4 ,some of these1 marked with an asterisk1 have only been observed at one return1 and therefore await complete confirmation4 ,many other comets have shown indications of pursuing elliptical orbits4 ,amongst those of short period may be mentioned #agdc ,i41 #agff ,,ii41 #aghc ,i41 #ahai ,,iv41 #ahdd ,i41 and #ahgc ,,vii4 ,the following are examples of longer periods3-- ,comet4 ,period4 #ahfb ,,iii4 #aba years4 #aheg ,,iv4 #bcd 0 #ahfa ,i4 #dae 0 #ahfj ,,iii4 #ajhi 0 #ahhi ,,iv4 #eajj 0 #ahgg ,,ii4 #hcic 0 #ahdg ,,iii4 #aciah 0 #ahgg ,,iii4 #bh1jjj 0 #ahej ,i4 #bi1jjj 0 #aghj ,i4 #ge1cad 0 #ahdd ,,ii4 #ajb1jej 0 #agdd #abb1fhc 0 #ahdi ,i4 #chb1hja 0 #ahhb ,i4 #djj1jjj 0 ,these figures are to be regarded as approximations only4 ---------------------------------------- ---------------------------------------- ---------------------------- ,period1 ,perihelion ,long4 of ,long4 of ,name4 in ,passage4 ,perihelion4,ascending years4 ,node4 ---------------------------------------- ---------------------------------------- ---------------------------- ,encke #cbi #ahhh1 ,june #bh #aeh #cf #ccd #ci ,tempel 7#ahgc7 #ebj #ahgh1 ,sept4 #g #cjf #h #aba #a 99,barnard #edj #ahhd1 ,aug4 #af #cja #b #e #i ,brorsen #edf #ahgi1 ,mar4 #cj #aaf #ae #aja #ai ,pons-,winnecke #egc #ahhf1 ,sept4 #af #bgf #d #aja #ef ,tempel7#ahfg7 #eih #ahgi1 ,may #g #bch #aa #gh #df ,tempel-,swift #eii #ahhj1 ,nov4 #h #dc #j #bif #db 99,brooks 7#ahhf7 #fcj #ahhf1 ,june #g #bbi #df #ec #c 99,spitaler #fdj #ahij1 ,oct4 #bf #eh #bd #de #h ,biela #ffb #aheb1 ,sept4 #bc #aji #h #bde #eb ,d',arrest #ffd #ahij1 ,september #cai #i #adf #i 99,finlay #ffg #ahhf1 ,nov4 #bb #g #cd #eb #cj 99,wolf #fgh #ahhd1 ,sept4 #bg #ceb #ca #bjf #ah 99,swift #fia #ahhi1 ,nov4 #bi #fi #bi #cca #bg 99,brooks 7#ahhi7 #gjg #ahhi1 ,sept4 #cj #a #bf #ag #ei ,faye #geg #ahhh1 ,aug4 #ai #ej #ef #bji #db 99,denning #hfi #ahha1 ,sept4 #ac #cab #ca #fe #eg 99,peters #abhj #ahdf1 ,june #a #bdj #g #bfj #bh ,tuttle #acff #ahhe1 ,sept4 #aa #aaf #bh #bfi #db 99,tempel 7#ahff7 #ccah #ahff1 ,jan4 #aa #fj #bh #bca #bf 99,stephan #ccfb #ahfg1 ,jan4 #bj #ge #eb #gh #cf 99,westphal #fggg #aheb1 ,oct4 #ac #dc #ab #cdf #ac ,pons #gadh #ahhd1 ,jan4 #be #ic #ba #bed #f ,olbers #gbde #ahhg1 ,oct4 #h #adi #de #hd #cj 99,di ,vico #gcbe #ahdf1 ,mar4 #f #ij #ce #gg #cf 99,brorsen #gdig #ahdg1 ,sept4 #aj #gi #ac #cji #di ,halley #gfcg #ahce1 ,nov4 #ae #cjd #cb #ee #aj ---------------------------------------- ---------------------------------------- ---------------------------- ---------------------------------------- ----------------------- ,incli- ,mo- ,next ,name4 nation4tion4,return4 ---------------------------------------- ----------------------- ,encke #ab #ec ,d #ahia ,tempel 7#ahgc7 #ab #df ,d #ahid 99,barnard #e #bh ,d #ahie ,brorsen #bi #bc ,d #ahie ,pons-,winnecke #ad #bg ,d #ahib ,tempel7#ahfg7 #i #dg ,d #ahia ,tempel-,swift #e #ca ,d #ahib 99,brooks 7#ahhf7 #ab #ef ,d #ahib 99,spitaler #ab #eb ,d #ahig ,biela #ab #cc ,d 8 ,d',arrest #ae #dc ,d #ahig 99,finlay #c #b ,d #ahic 99,wolf #be #af ,d #ahia 99,swift #aj #c ,d #ahif 99,brooks 7#ahhi7 #f #d ,d #ahif ,faye #aa #bj ,d #ahif 99,denning #f #ea ,d #ahii 99,peters #cj #bd ,r 8 ,tuttle #ed #ai ,d #ahii 99,tempel 7#ahff7 #ag #ah ,r #ahii 99,stephan #ah #ac ,d #aijj 99,westphal #dj #ei ,d #aibj ,pons #gd #c ,d #aiee ,olbers #dd #ce ,d #aifj 99,di ,vico #hd #eg ,d #aiai 99,brorsen #ai #h ,d #aibb ,halley #ag #de ,r #aiab ---------------------------------------- ----------------------- ,halley's ,comet4--,a fine comet with a tail about #ae long appeared in the summer of #afhb1 and ,halley computed the orbit according to the method explained by ,newton4 ,he then consulted observations of previous comets1 and discovered a great similarity in the paths of large comets seen in #aeca and #afjg to that of the one he himself had observed in #afhb4 ,he thereupon suspected the three bodies to be one and the same1 and advised posterity to maintain a strict watch for the comet's return in about #ageh or #agei4 ,on pursuing his investigations still further1 he alighted upon records of comets in #acje1 #achj1 and #adef1 which greatly strengthened his opinion that the comet of #afhb moved in an elliptical path with a period of about #ge years4 ,he termed this body 8the ,mercury#db of comets1 revolving round the ,sun in the smallest orbit10 and said that1 should it reappear according to his prediction in about the year #ageh1 8impartial posterity must needs allow this to be the discovery of an ,englishman40 ,as the time drew near for the return of the comet1 interest became intensified1 and computations were made by ,clairaut with a view to determine the precise epoch when it would arrive at perihelion4 ,he found that the comet would be retarded by the action of ,jupiter and ,saturn1 but that perihelion would be reached at the middle of ,april #agei1 subject to an uncertainty of #cj days4 ,the comet was rediscovered on ,dec4 #be1 #ageh1 by ,palitzch1 an amateur astronomer at ,politz1 near ,dresden1 who employed a telescope of #h feet focal length1 and appears to have anticipated ,messier and others who were on the alert for it4 ,it arrived at perihelion on ,march #ab1 #agei1 and within a month of the date announced by ,clairaut4 ,early in ,may it had a tail nearly #ej long1 and presented a fine aspect in the heavens4 ,thus the sagacity of ,halley had revealed a periodical comet--the first known4 ,it duly returned again in #ahce1 and received all the attention which a body so replete with historical associations deserved4 ,illustration3 ,fig4 #dg4 ,comet #ahfb ,,iii4 7,aug4 #ai1 #ahfb74 ,illustration3 ,fig4 #dh4 ,sawerthal's ,comet1 #ahhh ,i4 7,march #be1 ,brooks74 ,encke's ,comet4--,until the year #ahai ,halley's ,comet was the only one certainly known to be periodical4 ,then the able deductions of ,encke presented us with a veritable 8,mercury#dc of comets40 ,he showed that a small comet1 discovered by the unwearying ,pons of ,marseilles on ,nov4 #bf1 #ahah1 was really identical with three previous comets--viz4 #aghf ,i4 7,mechain71 #agie 7,c4 ,herschel71 and #ahje 7,thulis71--and that its period was a very short one of about #c-a_/c years4 ,its return to perihelion was predicted to occur on ,may #bd1 #ahbb1 and this was observed in the southern hemisphere4 ,it returned again on ,sept4 #af1 #ahbe1 and on this occasion the circumstances were more favourable4 ,since #ahbe this object has effected nineteen returns to perihelion1 and one of the most singular facts noticed in connection with it is that its period is gradually shortening4 ,in #agie it was #abab days1 while in #aheh it was #abaj4 ,in order to explain this contraction of orbit1 it has been necessary to assume the existence of a thin medium in space capable of affording a slight resistance to the tenuous materials of a comet1 though not dense enough to appreciably affect the motions of planets4 ,if this closing-up of the orbit and shortening of period continue to operate through a vast interval of time1 ,encke's ,comet must be ultimately precipitated upon the ,sun6#dd ,biela's ,comet4--,this comet was discovered on ,feb4 #bg1 #ahbf1 by ,wilhelm von ,biela1 an ,austrian officer1 at ,josephstadt in ,bohemia1 and ten days later by ,gambart at ,marseilles4 ,it was found to be revolving in an orbit of short period1 and its elements presented an agreement with those of the comet of #aggb 7,montaigne7 and #ahjf ,i4 7,pons74 ,identity was inferred1 and the next return was fixed for ,nov4 #bg1 #ahcb1 when the object reappeared with great punctuality4 ,at the end of #ahde this comet displayed some startling phenomena2 for it divided into two portions1 apparently quite disconnected1 and which travelled side by side1 separated by an interval of more than #aej1jjj miles6 ,the double comet was observed again in #aheb1 when the interval separating them had1 however1 increased eightfold1 for the dark space between measured #a1bej1jjj miles4 ,this instance of a divided comet is by no means unique4 ,the great comet of #ahhb underwent a process of disruption1 by throwing off small masses of nebulosity1 which1 however1 survived the separation only a few days4 ,brooks's ,comet 7#ahhi ,v47 was found by ,barnard1 on ,aug4 #a1 #ahhi1 to be divided into four parts6 ,two of these had a brief existence2 but one of the minor fragments retained a very distinct appearance near the parent mass during the ensuing months of ,september and ,october4 ,the phenomena of ,biela's ,comet found an excellent counterpart here4 ,illustration3 ,fig4 #di4 ,brooks's double ,comet1 ,sept4 #ag1 #ahhi4 7#aj-;inch reflector1 power #fj4 ,w4 ,f4 ,denning47 ,since #aheb ,biela's ,comet has been lost4 ,the most assiduous observations have failed to recover it1 and the conclusion seems irresistible that further disintegrations have occurred and that its material has been dispersed beyond recognition4 ,the great meteoric storms of ,nov4 #bg1 #ahgb and #ahhe1 were derived from this comet1 and there is little reason to hope that as a comet it will ever be seen again4 ,brorsen's ,comet4--,a small comet was discovered in ,pisces by ,theodor ,brorsen1 at ,kiel1 on the evening of ,feb4 #bf1 #ahdf1 ,its observed path soon gave traces of an elliptical orbit2 and the period was found to be about #eeh years4 ,the comet was re-observed at its return to perihelion in #aheg1 #ahfh1 #ahgc1 and #ahgi2 but in #ahhd it was looked for in vain4 ,this comet was expected in ,february #ahij1 and several observers swept for it diligently1 but to no purpose4 ,are we1 therefore1 to regard this as another lost member of our system8 ,has the comet of ,brorsen1 like that of ,biela1 suffered dispersion in such degree as to be no longer within the reach of our powerful telescopes8 ,should negative results again attend observers in #ahie1 when the comet ought to return1 there will be no reason to doubt its actual disappearance4 ,it may be mentioned that owing to planetary perturbations1 the period of this body has rapidly become shorter since #ahdf4 ,it was then #bjcd days1 but in #ahgi was reduced to #aiie days4 ,faye's ,comet4--,first seen at the ,paris ,observatory on the night of ,nov4 #bb1 #ahdc1 when it was near the star ,bellatrix in ,orion4 ,the observations clearly proved the comet to be moving in an elliptical path1 and ,dr4 ,goldschmidt of ,gttingen determined its period as #g years4 ,it was re-observed in #ahea1 and also during each of its five subsequent returns1 the last of which occurred in ,august #ahhh4 ,the orbit of this body approaches nearer to the circular form than that of any other known comet1 except ,tempel's of #ahfg4 ,its perihelion distance is considerable1 for it never comes within the orbit of ,mars4 ,prof4 ,mller1 of ,lund1 has investigated the path with all the critical acumen of a profound mathematician1 and1 chiefly owing to his labours1 it is now regarded as one of the best known members of our system4 ,d',arrest's ,comet4--,discovered at the ,leipsic ,observatory on ,june #bg1 #ahea4 ,m4 ,villarceau discussed the orbit1 and announced it as an elliptic one with a periodic time of about #f years4 ,the comet was redetected at its return in #aheg-h1 #ahgj1 #ahgg1 and #ahij4 ,it is a very faint object4 ,pons-,winnecke's ,comet4--,discovered at ,bonn on ,march #h1 #aheh1 and on the elements being computed they were found nearly coincident with those of ,pons's ,comet1 #ahai ,,iii4 ,encke had assigned a period of #efb years for the latter1 but it managed to escape observation during the six returns that occurred in the #ci years between #ahai and #aheh4 ,its identity was fully established in #ahfi1 when it was again observed4 ,tuttle's ,comet4--,a faint1 diffused comet was discovered in the northern part of ,hercules by ,h4 ,p4 ,tuttle1 of ,cambridge1 ,u4,s4,a41 on ,jan4 #d1 #aheh4 ,its elements on being calculated were found by ,pape to be similar to those of a comet discovered by ,mechain on ,jan4 #i1 #agij1 and an elliptic orbit with a period of #acff years was derived from the new observations4 ,on the assumption that the two bodies were one and the same there must have occurred four unobserved returns to perihelion between #agij and #aheh4 ,the year #ahga was awaited in settlement of the question4 ,when it came the comet returned1 and the predictions received exact verification4 ,thus the comets of ,mechain and ,tuttle were placed in the inseverable bonds of identity4 ,of the other periodical comets it will be unnecessary to give details4 ,some of them are still without full corroboration1 only one return to perihelion having been observed4 ,the reappearance of ,pons's ,comet 7#ahab7 in #ahhc-d1 and of ,olbers's ,comet 7#ahae7 in #ahhg furnished two excellent examples of well-determined comets belonging to the same class as that of ,halley4 ,tempel's discoveries in #ahfg1 #ahfi1 and #ahgc afforded some interesting additions to the family of short-period comets1 and the list of these is continually extending owing to the assiduity of observers1 though the lost comets of ,biela and ,brorsen will have to be removed from it4 ,peters's ,comet of #ahdf is also doubtful1 as it escaped rediscovery in about #ahei1 #ahgb1 and #ahhd2 but this object may yet be captured at one of its succeeding apparitions4 ,these bodies often evade redetection when their periods and paths are not accurately known4 ,this has been fully exemplified in the case of the comets of ,pons-,winnecke and ,tuttle1 which were unseen at several consecutive returns4 ,it has been supposed1 and not without reason1 that the periodical comets are in process of wearing away4 ,they apparently grow fainter at each return4 ,halley's ,comet in #ahce was only moderately bright1 whereas in ancient times its appearance was magnificent4 ,illustration3 ,fig4 #ej4 ,pons's ,comet 7#ahab74 ,telescopic view4 #ahhd1 ,january #f1 #e;h #ejm4 7#aj-;inch reflector1 power #fj4 ,w4 ,f4 ,denning47 ,illustration3 ,fig4 #ea4 ,pons's ,comet 7#ahab74 ,telescopic view4 #ahhd1 ,january #ba1 #ac;h #ahm4 7#e-;inch refractor2 comet-eyepiece1 field #a-a_/d4 ,e4 ,e4 ,barnard47 ,grouping of ,periodical ,comets4--,it is a curious circumstance that these bodies are assorted into groups having their aphelia near the orbits of major planets4 ,the short-period comets comprised within the orbits of ,encke's 7#cbi years7 and ,denning's 7#hfi years7 have aphelia in the region of the path of ,jupiter1 hence they are occasionally referred to as ,jovian comets4 ,the next group is represented by the comets of ,peters and ,tuttle1 with aphelia near ,saturn4 ,the third group includes the comets of ,tempel and ,stephan1 with aphelia just outside the orbit of ,uranus4 ,the fourth group is shown by the comets of ,halley1 ,pons1 and ,olbers1 with three others less certainly ascertained1 with aphelia exterior to ,neptune4 ,there are unmistakable indications of other groups far outside the known boundaries of the solar system1 but these are not so well defined4 ,this clustering of cometary orbits has been ascribed to the attractive influences of the large superior planets1 which are so capable of disturbing the paths of comets passing near that the orbits become transformed1 and the aphelia henceforth lie near the points of extreme perturbation4 ,this has been called the 8capture theory20 and there is also an 8ejection theory10 which supposes the periodical comets to have had their birth in planetary ejections4 ,m4 ,hoek of ,utrecht has found cases in which the orbits of two or more comets exhibit a common point of intersection in distant space1 and infers their derivation from the same origin4 ,further ,observations required4--,one of the chief and essential features in cometary work is the accurate determination of positions4 ,but this entails the possession of expensive instruments1 and a knowledge which amateurs have not always acquired4 ,this department of labour can well be left to the trained hands at large observatories1 where1 fortunately1 it meets with every attention4 ,ordinary observers will merely require to know the approximate place1 and this is to be found by estimating the difference in ,r4,a4 and ,dec4 between a comet and a known star4 ,the position of the latter may be found in a good catalogue and corrected for precession2 then1 allowing for the observed differences1 the comet's place may be assigned to within very small limits of error4 ,a low power1 embracing a field of #a or more1 is best adapted for these observations1 as it is more likely to include a catalogued star1 and will exhibit the comet1 especially if a large one1 to the best effect4 ,the announcement of a new comet is always read with avidity by amateurs1 and their first desire is to see it for themselves4 ,this they may readily do by marking its place on a star-map or globe1 and noting its relative place amongst the stars near4 ,the telescope should then be directed towards the point indicated1 and if the comet is not presented in the field1 the instrument should be moved a little so that the surrounding region may be examined4 ,if failure still attends the effort1 the observer should point the telescope a few degrees ,e4 or ,w4 of the suspected point1 and then carefully sweep over the place of the comet4 ,it will then be picked up1 unless it is too faint for his aperture4 ,the first announcement of a comet generally gives the position at discovery1 and the daily rate and direction of motion4 ,the latter must of course be allowed for when the search is instituted4 ,the physical aspects of comets are as diversified as they are variable4 ,no two comets are exactly alike1 nor does the same comet exhibit a permanency of detail4 ,of course1 when these objects are enormously distant1 and barely visible1 many of them appear to present similar characteristics2 but under the closer and more expanded views obtainable near perihelion the resemblance vanishes1 and every comet is seen to possess features peculiar to itself4 ,to trace these features1 and to record them by delineation and description1 forms one of the most interesting branches in which amateurs may engage4 ,much has been learnt of previous comets by successively noting their transitions of form and brightness1 and the same scrupulous attention should be given to future comets4 ,the tails of comets are not always turned away from the ,sun4 ,indeed1 the contrary effect is sometimes produced4 ,occasionally there is a duple tail1 the largest branch of which follows the normal direction1 while the other is turned towards the ,sun4 ,forms of this character require close watching from night to night4 ,is the sunward tail developed suddenly8 and has it a fairly durable existence8 ,instances of singular curvature should also be noted4 ,the tails are seldom perfectly straight1 especially those attached to naked-eye comets1 and decided changes affect their visible outlines at very short intervals4 ,in large comets the space over which the tail extends should be sketched upon a star-map on successive evenings2 its changes of position and curve will then be manifested by comparisons1 and its increasing or decreasing length will also be apparent4 ,dark rifts1 like shadows1 often run lengthwise through the tail1 and occasion a fan-like appearance analogous to that which distinguished the great comet of #agdd and gave it a sextuple tail4 ,the light of comets sometimes fluctuates in a very extraordinary manner1 and too rapidly and irregularly to be consistent with theory4 ,in this respect1 ,pons's ,comet1 at its last return in #ahhc-d presented an eccentric behaviour4 ,bigourdan found that during the nineteen days from ,sept4 #e to #bd1 #ahhc1 the increase in the comet's brilliancy exceeded by thirty or forty times that resulting from reflected light alone6 ,this increase appears to have been due to a sudden outburst on ,sept4 #bb1 which occurred some time within the four hours preceding midnight4 ,dr4 ,mller1 of ,potsdam1 witnessed a further outburst on ,jan4 #a1 #ahhd1 within #a-c_/d hour2 and the extent of this was accurately determined by means of a photometer4 ,he found an augmentation of seven tenths of a magnitude in the brightness of the comet1 and an equally sudden fall to its previous lustre4 ,while these fluctuations were in progress1 he noticed variations in the shape of the nucleus not less remarkable than its variations in light4 ,those who observe future comets will do well1 therefore1 to be on the alert for similar phenomena4 ,the apparent brightness of the nuclei and alterations of shape or size should be recorded on every night when observations are feasible4 ,as a comet approaches the ,sun its material apparently contracts1 while with increasing distance from that luminary it expands4 ,usually the nucleus is extremely small and bright1 and it often looks like a star shining through nebulosity4 ,high powers must therefore be applied in its examination4 ,jets1 aigrettes1 luminous sectors1 and other appendages are often involved with the nucleus and outlying coma1 and they form a complicated structure well deserving further study4 ,a good deal of mystery still surrounds these appearances2 their curious forms and vagaries have yet to be explained4 ,stars are frequently observed through the head of a comet1 which apparently1 however1 exercises no influence in dimming their lustre4 ,but the stars are commonly seen behind the envelopes or com1 and very rarely through the nucleus4 ,nothing is better calculated to exhibit the transparent and tenuous character of comets than observations of this kind1 and observers should seek for further opportunities of making them4 ,if the motion of a comet is obviously carrying it in the direction of one of the stars in the field1 the observer may determine for himself the approximate time of conjunction by noting the distance between the star and comet and allowing for the motion of the latter4 ,he will then know when to come to his telescope and witness the phenomenon4 ,should it appear probable that the comet's nucleus will pass over the star1 he should commence his watch some time before it occurs2 he may then make comparisons before the star is involved in the outlying nebulosity1 and trace the whole event from beginning to end4 ,any changes in the light or aspect of either star or comet would then be manifested4 ,the comet of #ahdg is said to have passed centrally over a #eth mag4 star1 but the latter was unaffected4 ,encke's ,comet on one occasion interposed itself directly over one of a pair of #ajth mag4 stars1 but their relatively equal brilliancy suffered no change4 ,encke's ,comet1 however1 has no stellar nucleus4 ,the latter feature is so bright and compact as displayed in many other comets1 that its transit over a small star must have some effect either in obliterating it altogether1 or in detracting from its lustre4 ,visible evidences of rotation seem to have been suspected in certain comets1 but this has never been substantiated on sufficient grounds4 ,the circumstance is one1 however1 which should be remembered4 ,during a series of observations the observer who notes the details of structure with particular regard to position may discover similar traces1 and possibly learn something of the cause4 ,the nucleus of a bright comet should always be examined with a moderately high power1 so that any variations or peculiarities of form may be detected4 ,nomenclature of ,comets4--,it must be confessed that no perfectly satisfactory method has yet been devised as regards the naming of comets4 ,the plan of affixing ,roman numbers progressively for each year1 according to date of perihelion passage1 answers pretty well1 though a little confusion is sometimes caused by prematurely affixing the number1 especially when two comets are discovered successively1 the first of which is a long time before perihelion1 and the second considerably after it4 ,until a comet can be safely assigned its catalogue place1 it is preferable to refer to it by the name of the discoverer and date of discovery4 ,this is more distinctive than the common method of lettering comets according to the epochs of their detection4 ,as to periodical comets1 it is not difficult to find some inconsistencies in their names4 ,in the case of ,halley's ,comet 7#afhb1 discovered by ,flamsteed7 and ,encke's ,comet 7#ahai ,i41 discovered by ,pons71 it was most fitting that they should be known to posterity by the names of the two able computers whose investigations first revealed to us comets of long and short period respectively4 ,under ordinary circumstances the name of the discoverer is applied to a comet as a means of convenient reference1 and perhaps as a suitable recognition of the patient labours of the man who first announced it to the world4 ,the plan seems to have been to name comets after those fortunate persons who sighted them at the particular apparition during which periodicity was determined4 ,thus ,tuttle's ,comet 7#aheh ,i47 had been seen as long before as #agij by ,mechain1 and ,biela's 7#ahbf ,i47 was previously observed in #aggb by ,montaigne1 and in #ahje by ,pons4 ,it is1 however1 strange that a comet found by ,pons in #ahai 7,,iii4 of that year71 and which ,encke showed to be revolving in an ellipse with a periodic time of #e years1 should be called after ,winnecke1 who rediscovered it in #aheh4 ,to ,pons the real priority belongs1 though ,winnecke deserves much praise for redetecting and identifying this body after it had effected six unobserved returns to perihelion4 ,it is also curious to find that the comet of short period discovered by ,swift in #ahhj is called 8,tempel's #crd ,comet0 in ,galle's catalogue 7#ahhe71 from the fact that ,tempel found it at a previous return 7#ahfi71 when1 however1 its period was not ascertained4 ,there is little doubt that the title justly belongs to ,swift4 ,tempel himself called it 8,swift's ,comet40 ,one plan should in fairness to observers be consistently adhered to4 ,if comets are to be called after their original discoverers1 then ,biela's ,comet should be known as 8,montaigne's10 ,tuttle's as 8,mechain's10 c4 ,curiosities of ,comets4--,the comet of #agbi1 which was hardly visible to the naked eye1 has far the greatest perihelion distance 7#djdce7 of any comet known4 ,barnard's ,comet 7#ahhe ,,ii47 comes next with a perihelion distance of #bejfh4 ,pons's ,comet at its return in #ahhc-d remained visible for nine months4 ,when last seen1 on ,june #b1 #ahhd1 it was #dgj millions of miles from the ,earth1 and more remote in the depths of space than any other observed comet since that of #agbi4 ,barnard's ,comet 7#ahhi ,i471 though never visible to the naked eye1 was followed from ,sept4 #b1 #ahhh1 to ,aug4 #ah1 #ahij4 ,its distance from the ,sun was then #fbe 7,earth's distance #a71 or about #ehj millions of miles1 which is greater than that of many of the short-period comets at aphelia4 ,the most prolonged visibility of any previous comet was that of #ahaa ,i4 7#eaj days74 ,but this comet of ,barnard has been retained in view #gae days4 ,the great comet of #ahhb was watched right up to the ,sun's limb by ,messrs4 ,finlay and ,elkin at the ,cape of ,good ,hope on ,sept4 #af1 #ahhb4 ,the comet was actually seen to disappear at the margin1 and not a vestige of it could be traced during its transit across the solar disk4 ,the nucleus of the comet was #d0 in diameter1 and before transit it looked as bright as a part of the ,sun's surface2 but it was quite invisible when projected on the disk4 ,the alleged observations by ,pastorff and ,stark1 which were construed into visible transits of comets1 are therefore thoroughly disproved1 and will require another interpretation4 ,at the time of the total solar eclipse of ,may #ag1 #ahhb1 a bright comet was observed near the ,sun4 ,it was a striking object visible to the naked eye4 ,in the photographs which were taken of the eclipse the comet is well shown1 but this body escaped subsequent observation1 so that its orbit could not be determined4 ,naked-eye ,comets4--,arago mentions that twelve comets were visible to the naked eye during the period from #ahjj to #ahec1 but there appear to have been certainly thirty comets fulfilling this condition1 and ,i believe a careful search amongst cometary records would further augment the number4 ,during the ten years from #ahhj to #ahhi inclusive there were no less than sixteen comets perceptible to unaided vision1 and a considerable proportion of these were fine comets4 ,it is very rarely that two naked-eye comets are to be seen at the same epoch1 as in ,august #ahha and at the end of ,april #ahhf4 ,comet-seeking4--,for a long time after the invention of the telescope comet-seeking does not appear to have been undertaken in a methodical way1 and to have formed the habitual work of certain observers4 ,but the expected return of ,halley's ,comet in #agei roused observers to take the initiative in a branch of practical research which in after years was destined to prove remarkably productive4 ,messier1 ,palitzch1 and others began a system of sweeping the heavens for the predicted comet2 and it had a successful issue1 for ,palitzch1 who did not relax his labours even on ,christmas day1 alighted upon the coveted prize on ,dec4 #be1 #ageh4 ,since that time a regular search after comets has been maintained4 ,messier pursued it with indomitable energy through a long period of years1 and achieved many successes4 ,it is said of him that on one occasion he was anticipated in a discovery by ,montaigne1 and he appears to have deplored the loss of the comet more than the loss of his wife1 who was lying dead at the time4 ,a friend visited him1 and spoke a few words of sympathy in reference to his bereavement1 but ,messier1 in despair about the comet1 exclaimed3 8,i had discovered twelve--alas6 that ,i should be robbed of the thirteenth by ,montaigne60 and his eyes filled with tears4 ,recollecting himself1 and appreciating the loss he had sustained in his wife1 he added1 8,ah1 this poor woman60 ,messier encountered some serious obstacles to his favourite pursuit4 ,breen1 in his #8,planetary ,worlds1' mentions that ,messier1 while walking in ,president ,saron's garden1 fell into an ice-house1 and was disabled for a time4 ,later on 8the revolution deprived him of his little income and every evening he was wont to repair to the house of ,lalande to replenish the supply of oil for his midnight lamp4 ,the political storm necessitated his removal to another neighbourhood1 where he no longer heard the clocks of forty-two churches sounding the hours during his night-watchings40 ,messier discovered all his comets with a small #b-;foot telescope of #b inches aperture magnifying #e times and with a field of #d4 ,dr4 ,olbers1 of ,bremen1 was another diligent student in this field4 ,he did not effect many discoveries1 but1 from an upper apartment of his house1 he observed nearly all the comets which appeared during half a century4 ,during the first twenty-seven years of the present century1 ,pons discovered the majority of the comets that were seen4 ,he was a door-keeper at the ,observatory at ,marseilles1 and owing to the teaching and encouragement he received from ,thulis1 the director1 he achieved phenomenal success as a comet-hunter4 ,discoveries of comets have rarely been effected in ,england4 ,this is chiefly to be assigned to two circumstances4 ,first1 because the labour involved in seeking for these bodies has never perhaps been pursued to an equal degree and with the same tenacity as it formerly was in ,france1 and as it has recently been in the ,united ,states2 and second1 because the cloud-laden skies of ,england oppose the successful prosecution of a research in which a clear atmosphere is eminently desirable4 ,though comet-seeking does not always produce new discoveries1 it is certainly entertaining to those engaged in it2 for one of the most agreeable diversions of telescopic work is to scan the firmament with a large-field comet-eyepiece1 which exhibits the most pleasing views of star-groups1 coloured stars1 nebul1 and telescopic meteors4 ,the operation of sweeping for comets is attractive from other aspects1 though it undoubtedly needs close application1 patience1 and much caution4 ,the possibility of seeing a comet in the field at any time proves a constant source of allurement to the observer1 and sustains his enthusiasm4 ,the glimpsing of a nebulous object1 and the expectation 7before it has been identified7 that it may prove a comet1 induces a little excitement which pleasantly relieves the monotony that might otherwise be attached to a sedulous research of this nature2 and it is one in which amateurs may suitably engage with a fair prospect of success4 ,instruments of great power1 refinement1 and expense are not required4 ,it is rather a work calling for the exercise of patience and acute perception1 and for that tireless servitude which those only who have an inborn love for it can maintain4 ,english ,weather and ,comet-seeking4--,only two new comets having been discovered in ,england during the last forty years some people regard our climate as in a great measure responsible for this4 ,but the opinion seems to be erroneous4 ,the lack of discoveries has arisen from want of effort as much as from want of opportunity4 ,the best weather for comet-seeking is when the atmosphere is very transparent1 and the stars are lucid and sparkling4 ,haze1 fog1 or cloud of any kind offers a serious hindrance4 ,a thoroughly good night for planetary work is not usually good for cometary observation1 because sharp definition is not so requisite as a very clear sky4 ,a little fog or thin cloud1 which will often improve planetary images1 utterly obliterates a small telescopic comet4 ,the air is sometimes very pure and dark after storms1 and the stars remarkably bright2 it is then that the best opportunities are afforded for comet-hunting4 ,any systematic and regular work like this may be pursued in this country with every prospect of success by an observer who will persevere in it4 ,from some statistics printed in the #8,science ,observer1' ,boston1 it appears that during the seven months from ,may to ,november1 #ahhb1 ,lewis ,swift was comet-seeking during #cjj hours4 ,i have no ,english results of the same kind1 but my meteoric observations will supply a means of comparison4 ,from ,june to ,november1 #ahhg 7six months71 ,i was observing during #bag hours1 and for a nearly similar period during the last half of #ahgg1 though in each year work was only attempted with the ,moon absent4 ,my result for #ahhg averages #cf hours per month1 which is little less than the average derived from the comet-seeking records above quoted4 ,it is therefore fair to suppose that as much may be done here as in some regions of the ,united ,states4 ,mr4 ,w4 ,r4 ,brooks wrote me in #ahhi1 saying3 8,we have much cloudy weather in this part of ,america4 ,while in other portions of the country clear weather abounds1 it is not so in this section1 where much of my work has been done4 ,this is a most fertile section--the beautiful lake region of ,n4,y41--but it is for this reason a cloudy belt4 ,it is far different in ,colorado and ,california4 ,in the latter place1 at the ,lick ,observatory1 ,i hear they have #cjj clear nights in the year--a paradise for the astronomical observer6 ,my former site1 the ,red ,house ,observatory1 ,phelps1 ,n4,y41 is only six miles from ,geneva1 and hence in the same cloudy region40 ,prof4 ,swift also referred to the subject of weather in a letter to me dated ,july #cj1 #ahhi1 where he says3 8,i arrived home1 after a five weeks' visit to the ,lick ,observatory1 on ,march #a1 and have not had half a dozen first-class nights since--not in thirty years have ,i seen such prolonged rainy and cloudy weather40 ,now ,mr4 ,brooks has discovered #ac comets in #g years1 ,prof4 ,swift has found #h comets 7#ahfb-ahij71 and in addition to these has detected more than #gjj new nebul1 all of the latter since #ahhc4 ,from this it appears conclusively that if such extensive and valuable results can be obtained1 notwithstanding frequently bad weather1 then ,english observers may prove equally successful1 the important factor being that similar energy and ability direct their labours4 ,aperture and ,power required4--,opinions are divided as to the most suitable aperture and power for this work4 ,any telescope of from #d-to #aj-;inches aperture may be employed in it4 ,a low power 7#cj to #ej7 and large field 7#ej to #ij7 eyepiece are imperative2 and the instrument1 to be really effective1 should be mounted to facilitate sweeping either in a vertical or horizontal direction4 ,a reflector on an alt-azimuth stand is a most convenient form for vertical sweeps4 ,the defining-capacity of the telescope need not necessarily be perfect to be thoroughly serviceable1 the purpose being to distinguish faint nebulous bodies1 and not details of form4 ,far more will depend upon the observer's aptitude and persistency than upon his instrumental means1 which ought to be regarded as a mere adjunct to his powers and not a controlling influence in success1 for the latter lies in himself4 ,very large instruments are not often used1 because of their necessarily restricted fields4 ,moreover1 a small instrument1 apart from its advantage in this respect1 is worked with greater facility and expedition4 ,this is important1 especially when the observer is to examine the region in the immediate neighbourhood of the ,sun4 ,he has then a very brief interval for the attainment of his purpose1 and a small telescope must be used on account of its large field1 its ready manipulation1 and its general effectiveness on objects at low altitudes4 ,the case is somewhat different when the search is to be conducted in regions far removed from the ,sun's place2 for here the comets are in general faint1 and there is time for the work to be deliberately and critically performed4 ,large instruments are to be recommended for these districts as capable of revealing fainter objects1 though they are troublesome in several respects4 ,they show large numbers of nebul1 especially if the observer is exploring the region of ,virgo1 ,coma ,berenices1 or ,ursa ,major2 and he will have great difficulty in identifying them and in feeling his way with certainty4 ,these complications are inseparable from the work1 and1 though chiefly affecting large apertures1 should not always be shunned2 for a telescope capable of displaying very faint nebul is also capable of showing faint comets4 ,many comets have eluded discovery by the inadequate reach of the instruments in the hands of comet-seekers2 and the statement recently made that there are only about one hundred nebul liable to be mistaken for comets is not accurate1 because comets in certain positions are of the last degree of faintness1 and there is no identifying them from small nebul except by means of their motion4 ,mr4 ,brooks says3--8,medium magnifying powers1 with necessarily moderate-sized fields1 are better than very low powers and large fields4 ,while with the latter a large amount of the sky can be swept over in a given time1 the work is not so well done1 and a faint comet would be easily swept over and not seen4 ,a small region1 thoroughly worked1 is far more likely to be successful4 ,this gives a feeling of satisfaction with the work performed1 even with negative results4 ,in support of this ,i may remark that1 during all the years ,i have engaged in comet-seeking1 not a single comet has been discovered by another astronomer in a region of the heavens that ,i had just previously searched2 so that ,i have never had occasion to feel that ,i had swept over a comet and missed seeing it4 ,aside from the obvious requirement of good eyesight1 capable of detecting exceedingly faint objects1 a good telescope of at least moderate aperture1 and a familiarity attained by experience with the large number of nebul resembling telescopic comets1 the comet-seeker1 to be successful1 must possess in a high degree the qualities of patience1 perseverance1 energy1 and enthusiasm4 ,i have the highest admiration for the man or woman who discovers a comet1 because ,i know of the hard and thorough work which the success implies40 ,mr4 ,brooks's experience and success in this branch give weight to his suggestions1 and there can be little doubt that his commendation of moderate powers is fully justified4 ,i believe he usually sweeps with a power of #dj 7field of #a #bj7 on the #aj-a_/h-;inch equatoreal of his observatory4 ,speaking for myself1 ,i find powers of #cb 7field #a-a_/d7 and #dj 7field #a7 perform very satisfactorily on my #aj-;inch ,with-,browning reflector1 having frequently tried them on faint nebul and comets4 ,sometimes ,i employ a power of #fj1 field #ej2 but for ordinary purposes this is too high4 ,it is a good plan to sweep with a moderate power1 say of #dj1 and to keep a higher magnifier at hand to examine any suspicious objects that may be picked up4 ,with power #cb ,i often encounter forms1 the real character of which is uncertain4 ,in such cases ,i clamp the telescope and apply the power #fj1 which generally exhibits the objects as several minute stars grouped together1 or possibly nebul1 in which case ,i proceed to identify them4 ,with lower magnifiers than #cj there must always be considerable danger of sweeping over faint comets4 ,some of these are only of the #ajth1 #aath1 or #abth mag41 and less than #a diameter1 and must certainly elude detection unless adequate power is brought to bear upon them4 ,dr4 ,doberck mentioned in the ,l4 ,a4 ,s4 ,journal1 vol4 vi4 p4 #bcf1 an instrument for comet-seeking1 #c inches in aperture1 power about #aj1 and field of #e1 which was bought in #ahdb by the late ,mr4 ,cooper at ,markree4 ,but though with such a telescope a very large portion of the firmament might be swept in one night1 there would be serious disadvantages2 for small faint comets would pass through the field unseen1 and render the work abortive4 ,the necessary conditions of the case go far to support the view that moderate powers and fields are best2 for a search1 to be thorough and satisfactory1 must be done critically1 and with a power capable of revealing the smallest specimens of comets4 ,annual ,rate of ,discovery4--,arranging cometary discoveries during the century from #aghb to #ahha into periods of #bj years1 and comparing the annual average with that during the last eight years1 we get the following numbers3-- ,comets ,annual ,period4 found4 average4 #aghb-ahja #be #abe #ahjb-ahba #bf #acj #ahbb-ahda #cf #ahj #ahdb-ahfa #hc #dae #ahfb-ahha #gi #cie #ahhb-ahhi #dj #ejj ,these discoveries seem to have been greatly accelerated about the year #ahde4 ,the yearly average between #ahdb and #ahha was about #d2 but between #ahhb and #ahhi it increased to #e1 owing mainly to the diligence of ,barnard and ,brooks4 ,the months in which the largest number of cometary discoveries have been effected are ,july and ,august1 the figures since #aghb being-- ,comets ,month4 found4 ,percentage4 ,january #bb #gf ,february #bj #fi ,march #ah #fb ,april #be #hg ,may #ag #ei ,june #ba #gc ,july #cd #aah ,august #ch #acb ,september #bb #gf ,october #bj #fi ,november #bf #ij ,december #bf #ij ,of #bhi comets discovered during the last #ajh years1 #abc belonged to the first six months1 while no less than #aff belonged to the last half of the year4 ,though comets are not confined to any special region of the heavens1 there is no doubt that the vicinity of the ,sun is the spot to which the comet-seeker should direct his chief attention4 ,it is here where the majority of the discoveries have been made2 and theoretically this should be so1 seeing that the ,sun is the controlling influence of the cometary flights1 and that his position must be regarded as a sort of focus of their convergence and divergence4 ,hence the most likely spots are over the western horizon after sunset and the eastern horizon before sunrise4 ,the twilight and zodiacal light1 together with the mist at low altitudes1 are impediments which are inseparable from this work2 but they need not interfere to any serious extent if the observer is careful to make the best of his opportunities4 ,but though special attention is recommended to the neighbourhood of the ,sun1 other regions should not be altogether neglected1 for comets are occasionally found in nearly the opposite part of the heavens to the ,sun's place1 as1 for example1 ,zona's ,comet of ,november #ahij4 ,in order to save time1 and to prevent troublesome references during the progress of sweeping1 the brighter nebul should be marked upon a star-chart1 so that1 as they enter the field1 they may be instantly identified4 ,telescopic ,comets vary in size to a considerable degree4 ,in diameter they generally range from about #a to #g1 and are usually round1 with a bright centre like the globular clusters ,messier #b1 #c1 #ac1 #ae1 #di1 and #ib1 as seen with a low power2 but occasionally they are faint diffused masses1 like the planetary nebula near ,urs ,majoris1 ,m4 #ig1 or the large nebula ,s4 of ,cassiopei1 in the ,new ,general ,catalogue1 ,no4 #ahe1 ,r4,a4 #j;h #ccm1 ,dec4 #dg #dd ,n4 ,in brightness they range from being visible to the naked eye to objects of the last degree of faintness4 ,they average some #b or #c diameter1 but are sometimes less than #a2 so that the power of the sweeper should be capable of readily showing an object of this size as it passes through the field4 ,the observer should turn his instrument upon the small planetary nebula ,n4,g4,c4 #aeja1 ,r4,a4 #c;h #egm1 ,dec4 #fj #cg ,n4 in ,camelopardus4 ,it is about #a diameter4 ,he should also pick up ,n4,g4,c4 #ffed1 ,r4,a4 #ah;h #bgm1 ,dec4 #gc #f ,n41 which is a star of about #ab mag4 involved in a pretty conspicuous nebulosity4 ,swift describes the latter as looking just like a comet4 ,n4,g4,c4 #fbag1 ,r4,a4 #af;h #chm1 ,dec4 #gh #be ,n41 is also a small nebulosity which might easily be overlooked with a low power4 ,let the observer examine the three objects named1 and he will gather a good idea of a small telescopic comet1 especially from ,n4,g4,c4 #ffed1 which may be readily found1 as it is in the same field as ,draconis1 and visible at any time of the year and night4 ,n4,g4,c4 #ffdc1 ,r4,a4 #ah;h #bcm1 ,dec4 #gd #cb ,n41 is near the latter1 but it is a brighter object4 ,the observer will find two tolerably plain nebul in the same field at about ,r4,a4 #f;h #ebm1 ,dec4 #he #ef2 so that they are only #d from the pole4 ,they are ,n4,g4,c4 #bbgf and #bcjj4 ,these objects ought not to elude detection in any instrument properly adapted for comet-seeking4 ,ascertaining ,positions4--,no observer should be without the means of determining exact positions4 ,a ring-micrometer and comprehensive star-catalogues are most important accessories of the amateur4 ,when a suspicious object is found its precise position should be instantly measured2 but if no micrometer is at hand1 the observer should carefully note the place relatively to adjoining stars1 and then1 after a short interval1 re-observe it for traces of motion4 ,in these comparisons the low-power eyepiece should be exchanged for one of greater amplification1 because this will render a slight motion more readily sensible4 ,if the suspicious object proves to be a comet1 the extent and direction of its daily motion should be computed from the change in the observed places1 and the information telegraphed to the ,royal ,observatory1 ,greenwich4 ,a statement should also be given as to the diameter and brightness of the object2 we may then be satisfied that it will be readily picked up at some of the many stations where prompt attention is given to this class of observation4 ,amateurs who do not attempt to obtain exact positions are sometimes condemned for their negligence in this respect1 and most unjustly so4 ,by far the hardest part of the work falls to them1 and professional astronomers ought to be indebted to amateurs for leaving to their care an important feature of these observations4 ,if the latter are to undertake the labour of measuring as well as discovering comets1 then there will be nothing left in this line for the elaborate instruments of observatories to do4 ,yet1 while thus objecting to amateurs1 with their generally incomplete and inefficient appliances1 being expected to perform the work both of discovery and exact observation1 it cannot be denied that there is a great necessity for them to have the means of measurement1 and to utilize them during the first few observations1 which are usually made before the comet has been seen elsewhere1 and will therefore possess great value if precise4 ,dr4 ,doberck's ,hints4--,dr4 ,doberck has given some useful hints in connection with this subject3--8,in order to be as sure as possible of ultimate success it is not enough to sweep with the instrument and watch any suspicious object for proper motion4 ,it is better to procure a large map such as ,argelander's1 and1 comparing the image seen in the comet-seeker with the map1 to insert all the nebulous objects according as they are discovered4 ,at the end of the watch they are then compared with the catalogues of nebul and clusters of stars4 ,a general catalogue facilitates this1 but is never quite sufficient1 as there seems to be no limit to the number of objects in the sky1 and more are constantly being catalogued4 ,in the course of time an observer learns to remember the objects he has seen before in the seeker1 and at last he need not consult the map at all4 ,the subsequent observation of a newly-found comet is best made with the ring-micrometer if the telescope is not equatoreally mounted4 ,in the latter case it should be made by aid of a steel-bar micrometer4 ,as soon as three observations are available the first approximation to a parabolic orbit can generally be determined3 the calculation of which is quite elementary1 and would be enjoyed by many amateur astronomers who are fond of figures and would easily get used to ,olbers's method4 ,only the three positions must not be so near each other as to lie on a great circle40 ,prizes for ,discoveries4--,the ,vienna ,academy of ,sciences formerly gave a gold medal to the discoverer of every new comet4 ,these presentations were discontinued in about #ahhj2 and ,mr4 ,h4 ,h4 ,warner then offered a prize of #bjj for every unexpected comet found in the ,united ,states or in ,canada4 ,this prize was continued in subsequent years1 and the conditions were amended so as to include observers in ,europe4 ,many of these prizes were gained by ,barnard and ,brooks2 but they have not been re-offered during the past year or two4 ,mr4 ,warner1 however1 contemplates renewing them4 ,the ,astronomical ,society of the ,pacific now awards a bronze medal to all such discoverers4 ,,footnotes3 #da ,donati's ,comet of #aheh and ,coggia's ,comet of #ahgd may be mentioned as good examples of the gradual approach and development of these visitors witnessed by means of the telescope4 #db ,it ought1 perhaps1 in the present state of our knowledge1 to be termed 8the ,neptune of comets20 for it has the longest period of any comet whose path has been definitely ascertained by multiple returns to perihelion4 #dc ,encke's ,comet has the shortest period of all the known comets4 #dd ,newton conjectured that comets formed 8the aliment by which suns are sustained10 his opinion being that the former bodies finally coalesced with the suns round which they revolved4 ,he remarked3--8,i cannot say when the ,comet of #afhj will fall into the ,sun1--possibly after five or six revolutions2 but whenever that time shall arrive1 the heat of the ,sun will be raised by it to such a point that our globe will be burnt and all the animals upon it will perish40 ,,chapter ,,xv4 ,,meteors ,,and ,,meteoric ,,observations4 ,ancient ideas concerning ,meteors4--,meteoric ,apparitions4--,radiation of ,meteors4--,identity of ,meteors and ,comets4--,aerolites4--,fireballs4--,dif ferences of ,motion4--,nomenclature of ,meteor-,systems4--,meteor-,storms4--,te lescopic ,meteors4--,meteor-,showers4--,varieties of ,meteors4--,heights4--,meteoric ,observations4 8,as oft along the still and pure serene ,at nightfall1 glides a sudden trail of fire1 ,attracting with involuntary heed ,the eye to follow it1 erewhile it rest2 ,and seems some star that shifted place in heaven40 ,,dante4 ,no one can contemplate the firmament for long on a clear moonless night without noticing one or more of those luminous objects called shooting-stars4 ,they are particularly numerous in the autumnal months1 and will sometimes attract special attention either by their frequency of apparition or by their excessive brilliancy in individual cases4 ,for many ages little was known of these bodies1 though some of the ancient philosophers appear to have formed correct ideas as to their astronomical nature4 ,humboldt says that ,diogenes of ,apollonia1 who probably belonged to the period intermediate between ,anaxagoras and ,democritus1 expressed the opinion that1 8together with the visible stars1 there are invisible ones which are therefore without names4 ,these sometimes fall upon the ,earth and are extinguished1 as took place with the star of stone which fell at gos ,potamoi40 ,plutarch1 in the #8,life of ,lysander1' remarks3--8,falling stars are not emanations or rejected portions thrown off from the ethereal fire1 which when they come into our atmosphere are extinguished after being kindled3 they are1 rather1 celestial bodies which1 having once had an impetus of revolution1 fall1 or are cast down to the ,earth1 and are precipitated1 not only on inhabited countries1 but also1 and in greater numbers1 beyond these into the great sea1 so that they remain concealed40 ,in later times1 however1 opinions became less rational4 ,falling stars were considered to be of a purely terrestrial nature1 and originated by exhalations in the upper regions of the air4 ,shakespeare expressed the popular belief when he wrote3-- 8,i shall fall ,like a bright exhalation in the evening1 ,and no man see me more40 ,another theory1 attributed to ,laplace1 ,arago1 and others1 was that meteors were ejections from lunar volcanoes4 ,but these explanations were not altogether satisfactory in their application4 ,the truth is1 that men had commenced to theorize before they had begun to observe and accumulate facts4 ,they had learnt little or nothing as to the numbers1 directions1 and appearances of meteors1 and therefore possessed no materials on which to found any plausible hypothesis to account for them4 ,meteoric ,apparitions4--,the occasional apparition of brilliant detonating fireballs1 the occurrence of remarkable star-showers1 the precipitation upon the ,earth's surface of stony masses1 were facts which could be verified from many independent sources1 and they set men thinking how to account for the strange and startling freaks of nature as exhibited in such phenomena4 ,but though records existed of exceptionally large meteors and of meteor-showers1 the descriptions were imperfect and failed in the most important details4 ,the observers were usually unprepared for witnessing such events1 and gave exaggerated and inaccurate accounts of what they had seen4 ,the vivid brightness of a fireball 7overpowering the lustre of the stars1 and even vieing with the ,moon in splendour71 the flaming train left in its wake 7curling itself up into grotesque shapes1 as it drifted and died away71 the form of the nucleus with its jets and sparks1 and the final explosion1 with the reverberations it caused1 were all alluded to by the enthusiastic observer2 but it was only in rare cases that the more valuable features were placed on record4 ,the direction and duration of the meteor's flight amongst the stars were facts of greater significance than the mere visible aspect of the object2 but they were seldom regarded4 ,hence the early observations proved of little weight in inducing just conceptions as to the phenomena of meteors4 ,there is1 perhaps1 no celestial event which can compare1 as regards its striking aspect and interesting features1 with that of a meteoric display of the most brilliant kind4 ,a large comet1 a total solar eclipse1 a bright display of aurora1 have each their attractive and imposing forms2 but the effect produced is hardly equal to that during the ,earth's rencontre with a dense meteor-swarm4 ,the firmament becomes alive with shooting-stars of every magnitude2 their incessant flights are directed to every point of the compass for several hours2 and the scene is so animated1 and one of such peculiarly impressive and novel character1 that it can never be forgotten by those who have been among its fortunate spectators4 ,radiation of ,meteors4--,heis1 in ,germany1 was the pioneer in this branch of practical astronomy4 ,about half a century ago he began systematic observations1 and gathered many useful data4 ,schmidt1 at ,bonn and ,athens1 followed his example2 and in ,england ,prof4 ,alexander ,herschel and ,mr4 ,r4 ,p4 ,greg devoted themselves to the subject with highly successful results4 ,their collective labours revealed a large number of well-defined systems of meteors1 and enabled them to publish tables of the radiant-points4 ,the investigations were more precise than formerly1 and conducted on methods ensuring more accurate and plentiful materials4 ,the radiation of meteors from fixed points in the sky had been observed before in regard to the great display which occurred in ,november #ahcc2 but the meteors that fell on ordinary nights were regarded as sporadic1 until ,heis and his immediate successors showed they were reducible to an orderly arrangement and that every one of them had its radiant-point and its origin in a definite meteor-stream4 ,the apparently divergent flights from a common centre are simply due to the effects of perspective on bodies really moving in parallel directions and collected into groups more or less scattered4 ,illustration3 ,fig4 #eb4 ,radiation of ,meteors 7,shower of early ,perseids from #cbec1 ,july #bh-;,aug4 #a1 #ahgh47 ,identity of ,meteors and ,comets4--,the mystery concerning these fugitive objects and their vagaries of appearance was not always to remain concealed4 ,denison ,olmsted had1 in his work on #8,the ,mechanism of the ,heavens1' published in #ahej1 stated that the constitution of the body to which the meteors of #ahcc belonged bore 8a strong analogy to comets40 ,reichenbach1 in #aheh1 wrote a paper in which it was sought to prove that a comet is a swarm of meteorites4 ,prof4 ,kirkwood1 in #ahfa1 also concluded that 8meteors and meteoric rings are the debris of ancient but now disintegrated comets1 whose matter has become distributed around their orbits40 ,but it remained for ,schiaparelli1 of ,milan1 in #ahff1 to demonstrate the identity of meteoric and cometary systems4 ,others had reasoned up to it1 and observers had amassed many useful observations bearing on the subject2 but absolute proof was wanting until ,schiaparelli supplied it4 ,he computed elements for a well-known shower of meteors occurring on ,august #ajth1 and found the orbit presented a very close resemblance to that of ,comet ,,iii4 #ahfb2 and he detected a similar analogy between the ,november meteors and ,comet ,i4 #ahff4 ,the orbit of the ,april meteors was afterwards shown by ,galle and ,weiss to agree with the path of ,comet ,i4 #ahfa2 and a meteor-shower occurring at the end of ,november was found to coincide with ,biela's ,comet4 ,facts like these could not be disproved4 ,comets were thenceforth known to be the parents--the derivative source--of meteors4 ,thus two important classes of objects became as one1 the differences observed being merely those of aspect due to the variable conditions under which they were presented4 ,the great meteor-shower of ,november was found to be the dispersed materials of ,tempel's ,comet of #ahff seen in detail and from a near standpoint4 ,every meteoric display was known to be the visible effects of the collision of the ,earth with a comet or with the great stream of planetary fragments describing a cometary orbit4 ,illustration3 ,fig4 #ec4 #a4 ,double meteor1 ,dec4 #bi1 #ahhf4 #b4 ,curved meteor1 ,dec4 #be1 #ahhf4 #c4 ,fireball1 ,sept4 #g1 #ahhh4 ,illustration3 ,fig4 #ed4 ,meteorite found in ,chili in #ahff4 ,illustration3 ,fig4 #ee4 ,meteorite which fell at ,orgueil in #ahfd4 ,aerolites4--,meteors enter our atmosphere with such great velocity that the friction induced by their impact is sufficient to destroy them by combustion4 ,they rarely approach the ,earth's surface within #ae miles4 ,occasionally1 however1 a slow-moving meteor of large size1 and formed of a very compact substance1 will penetrate entirely through the air-strata and fall upon the ,earth's surface4 ,many instances of the kind have been recorded1 and a few of these are quoted below3-- #adgh ,b4,c4 ,the ,parian chronicle records that an aerolite or thunder-stone fell in the island of ,crete4 ,this appears to be the earliest stone-fall described in history4 #fed ,b4,c4 ,a shower of stones descended near ,rome4 #dfe ,b4,c4 ,a stone1 surrounded with fire1 fell in ,thrace4 ,this stone is referred to by several ancient writers4 ,it was termed the 8,mother of the ,gods0 and is said to have fallen at the feet of the poet ,pindar4 #eb ,b4,c4 ,a shower of iron descended at ,lucania1 in the time of ,crassus4 #adib ,a4,d4 ,a stone weighing #bfb lb4 fell at ,ensisheim1 in ,alsace4 #afdb4 ,a stone of #d lb4 fell near ,woodbridge1 in ,suffolk4 #agie1 ,dec4 #ac4 ,a stone of #ef lb4 fell at ,wold ,cottage1 ,thwing1 ,yorkshire4 #ahfj1 ,july #ad4 ,a shower of aerolites fell at ,dhurmsala1 in ,india4 ,a tremendous detonation attended their descent1 and the natives became greatly alarmed4 ,they supposed the stones to have been thrown by some of their deities from the summit of the ,himalayas1 and many of them were preserved as objects of religious veneration4 #ahfd1 ,may #ad4 ,a very large meteor was observed in ,france4 ,at ,montauban and the neighbourhood deafening explosions occurred1 and showers of stones fell near the villages of ,orgueil and ,nohic4 #ahgf1 ,april #bj4 ,a piece of iron weighing #g-c_/d lb4 fell at ,rowton1 ,shropshire4 #ahha1 ,march #ad4 ,a stone weighing #c lb4 #h-a_/d oz4 fell at ,middlesborough1 ,yorkshire1 on a part of the ,north-,eastern ,railway ,company's branch line4 ,the descent of the aerolite was witnessed by an inspector and three platelayers1 who were working about fifty yards distant4 ,at first they became aware of a whizzing or rushing noise in the air1 immediately followed by the sudden blow of a body striking the ground near4 ,the hole1 #aa inches deep1 which the stone made was found directly after1 and the stone was extracted4 ,many other examples might be given1 but the above will be sufficient for our purpose4 ,records of this nature were discredited in former times2 but more modern researches have long since placed their reality beyond all question4 ,the fall of stones from the sky is no longer regarded as a mere legendary tale1 but as one of the well-assured operations of nature4 ,meteoric stones and irons have been classified according to the ingredients of their composition4 ,those in which iron is found in considerable amount are termed siderites1 those containing an admixture of iron and stone1 siderolites1 and those consisting almost entirely of stone are known as aerolites4 ,the siderite which fell in ,shropshire on ,april #bj1 #ahgf1 forms only the seventh recorded instance where a mass of meteoric iron has been actually seen to fall4 ,fireballs4--,the table on p4 #bfh gives the dates1 heights1 c4 of fifteen fireballs observed during the last quarter of a century4 ,fireballs are sometimes detonating1 though more often silent4 ,the fireball of ,nov4 #bc1 #ahgg1 gave a sound like salvoes of artillery1 and doors and windows were shaken violently4 ,at ,chester the noise of its explosion was compared to loud but distant thunder4 ,lieut4-,col4 ,tupman says that 8thunder1 to be loud1 must be within five miles2 hence it appears that the violence of the explosion must have been at least a hundred times greater than a peal of thunder1 the intensity of sound-waves diminishing as the square of the distance40 8,the explosion of a #ac-;inch bomb-shell1 consisting of some #bjj lb4 of iron1 would not have produced a sound of one hundredth part of the intensity of the meteor-explosion40 ,this fireball must therefore have been an object of considerable mass before its dissolution2 and it is fortunate that such bodies are usually destroyed by the effects of combustion before they reach the ,earth's surface4 ,these phenomena exhibit many varieties of appearance4 ---------------------------------------- ---------------------------------------- ---------------------------- ,height4 ,real ,date of ------------------------------------- ,length ,velo- ,apparition4 ,g4,m4,t4 ,at ,ap- ,at ,disap-of ,path4city4 pearance4 pearance4 ---------------------------------------- ---------------------------------------- ---------------------------- h m miles4 miles4 miles4 miles4 #ahfe1 ,april #bi #ab #db #eb #cg #ge #bj #ahfh1 ,sept4 #e #h #e #bej #he #abjj #bh #ahfi1 ,nov4 #f #f #ej #ij #bg #agj #ce #ahgb1 ,july #bb #h #ee #gg #cg #hh #ahgd1 ,aug4 #aj #aa #ec #gg #cc #aje #ag #ahge1 ,sept4 #c #i #ee #ge #dj #ce #bg #ahge1 ,sept4 #ad #h #bh #eb #ac #ajd #ac #ahgf1 ,sept4 #bd #f #cj #eh #af #de #ae #ahgg1 ,nov4 #bc #h #be #ie #ad #ace #ag #ahgh1 ,june #g #i #ec #fe #cg #afj #ai #ahgi1 ,feb4 #bc #ad #ec #fj #g #ajb #ad #ahhf1 ,nov4 #ag #g #ah #if #ba #abc #ag #ahhg1 ,may #h #h #bb #gj #ad #aaj #ah #ahhh1 ,aug4 #ac #aa #cc #gh #dg #df #ahhi1 ,may #bi #aj #dd #eh #bc #gf #h ---------------------------------------- ---------------------------------------- ---------------------------- ---------------------------------------- ------------------------------------- ,radiant- ,date of ,point4 ,apparition4 ,authority4 ,r4,a4 ,dec4 ---------------------------------------- ------------------------------------- #ahfe1 ,april #bi #gc #dg ,a4 ,s4 ,herschel4 #ahfh1 ,sept4 #e #ad -#b ,g4 von ,niessl4 #ahfi1 ,nov4 #f #fb #cg ,a4 ,s4 ,herschel4 #ahgb1 ,july #bbbdf -#aa ,t4 ,h4 ,waller4 #ahgd1 ,aug4 #ajcbe -#ag ,w4 ,h4 ,wood4 #ahge1 ,sept4 #ccaa #eb ,g4 ,l4 ,tupman4 #ahge1 ,sept4 #adcdh -#j ,g4 ,l4 ,tupman4 #ahgf1 ,sept4 #bdbhe #ce ,a4 ,s4 ,herschel4 #ahgg1 ,nov4 #bc #fb #ba ,g4 ,l4 ,tupman4 #ahgh1 ,june #gbdg -#be ,a4 ,s4 ,herschel4 #ahgi1 ,feb4 #bccaj #ee ,j4 ,e4 ,clark4 #ahhf1 ,nov4 #ag #cd #ai ,w4 ,f4 ,denning4 #ahhg1 ,may #haia -#e ,w4 ,f4 ,denning4 #ahhh1 ,aug4 #ac #dc #ef ,w4 ,f4 ,denning4 #ahhi1 ,may #bibaf #g ,d4 ,booth4 ---------------------------------------- ------------------------------------- ,illustration3 ,fig4 #ef4 ,fireball of ,nov4 #bc1 #ahgg1 #h;h #bdm1 emerging from behind a cloud4 7,drawn by ,j4 ,plant1 ,salford47 ,sometimes there is no visible explosion2 the bright nucleus slowly dies out until reduced to a faint spark before final disappearance4 ,several outbursts of light are often noted2 and a curious halting motion has been observed in regard to large slow-moving meteors4 ,i have occasionally remarked a succession of four brilliant flashes given by individual fireballs4 ,these flashes1 though sometimes of startling intensity1 are somewhat different to the transient vividness of lightning2 they come more softly1 and remind one forcibly of moonlight breaking suddenly from the clear intervals in passing clouds4 ,fireballs differ vastly from shooting-stars in point of size2 but their origin is identical4 ,the ,august meteor-shower yields the smallest shooting-stars and the largest type of fireballs4 ,the great display of meteors on ,nov4 #bg1 #ahhe1 not only presented us with large and small members1 but it also furnished us with a siderite or piece of iron1 presumably from ,biela's ,comet4 ,this fell at ,mazapil1 ,mexico2 and as considerable interest is attached to the case1 ,i quote a part of the discoverer's statement3-- 8,it was at about #i o'clock on the night of ,november #bgth1 when ,i went out to the corral to feed certain horses3 suddenly ,i heard a loud sizzing noise1 exactly as though something red-hot was being plunged into cold water2 and almost instantly there followed a somewhat loud thud4 ,at once the corral was covered with a phosphorescent light2 while suspended in the air were small luminous sparks1 as though from a rocket4444 ,a number of people came running towards me2 and when we had recovered from our fright we saw the light disappear1 and bringing lanterns to look for the cause found a hole in the ground1 and in it a ball of light4 ,we retired to a distance1 fearing it would explode and harm us4 ,looking up to the sky1 we saw from time to time exhalations of stars1 which soon went out without noise4 ,we returned after a little1 and found in the hole a hot stone which we could barely handle2 this1 on the next day1 we saw looked like a piece of iron4 ,all night it rained stars2 but we saw none fall to the ground1 as they all seemed to be extinguished while yet very high up40 ,this is the first observed instance in which a meteorite has actually reached the ,earth's surface during the progress of a star-shower4 ,if its identity with the meteors of ,biela's ,comet is admitted1 then all classes of meteoric phenomena would appear to have a community of origin4 ,differences of ,motion4--,great differences are observed in the velocity of meteors4 ,an observer may notice all varieties on the same night of observation4 ,some will move very slowly1 others shoot quickly across the sky4 ,these differences are occasioned by the astronomical conditions affecting the position of the meteor-orbit relatively to the motion of the ,earth4 ,thus the meteors of ,nov4 #ac move with great velocity 7#dd miles per second71 because they come directly from that part of the heavens towards which the ,earth is moving2 hence the orbital speed of the ,earth 7#ah miles per second7 and meteors 7#bf miles per second7 is combined in the observed effects4 ,but in the case of the meteor-shower of ,nov4 #bg the motions are extremely slow 7about #aj miles per second71 as the ,earth and the meteors are travelling nearly parallel in the same direction1 and the latter have to overtake the ,earth4 ,nomenclature of ,meteor-,systems4--,it is customary to name the showers after the constellation from which the meteors appear to diverge4 ,thus the meteors of ,april #bj are called ,lyrids1 the radiant being in ,lyra2 the meteors of ,august #aj are termed ,perseids1 the point of emanation being in ,perseus4 ,the two great streams of ,november are known as the ,leonids 7#acth7 and ,andromedes 7#bgth74 ,several showers are often visible in the same constellation2 and when it is desired to name these according to the above system1 it is necessary to add the approximate star to distinguish them4 ,thus1 in ,august there are showers of ,perseids1 ,perseids1 and ,perseids1 in addition to the well-known ,perseids of ,august #aj4 ,meteor-,storms4--,on ,nov4 #ab1 #agii1 ,humboldt1 at ,cumana1 in ,south ,america1 saw 8thousands of bolides and falling stars succeed each other during four hours40 ,on ,nov4 #ab1 #ahcc1 this shower recurred1 and was witnessed with magnificent effect in ,america4 ,one observer stated that between #d and #f ,a4,m4 7,nov4 #ac7 about #ajjj meteors per minute might have been counted6 ,another display occurred on ,nov4 #ac1 #ahff1 and on this occasion #hdhe meteors were enumerated by several observers at ,greenwich4 ,a different system gave us a brilliant exhibition on ,nov4 #bg1 #ahgb1 when #cc1jjj meteors were counted by ,denza and his assistants at ,moncalieri1 in ,italy1 between the hours of #e;h #ejm and #aj;h #cjm ,p4,m4 ,a repetition of this phenomenon occurred on ,nov4 #bg1 #ahhe1 when the same observers counted nearly #dj1jjj meteors between #f;h and #aj;h ,p4,m4 ,illustration3 ,fig4 #eg4 ,,vertical4 ,flight of ,telescopic ,meteors seen by ,w4 ,r4 ,brooks1 ,nov4 #bh1 #ahhc4 ,telescopic ,meteors4--,observers who are engaged in seeking for comets or studying variable stars employ low powers and large fields1 and during the progress of their work notice a considerable number of small meteors4 ,at some periods these bodies are more plentiful than at others1 and appear in such rapid succession that the observer's attention is distracted from the special work he is pursuing to watch them more narrowly and record their numbers4 ,schmidt saw #adf telescopic meteors during ten years4 ,they ranged between the #gth and #aath mags4 ,winnecke in the year #ahed noticed #aje of these objects on thirty-two evenings of observation with a #c-;inch finder1 power #ae1 and field of #c4 ,i have also remarked many of these objects when using the comet-eyepieces of my #aj-;inch reflector#de1 and find they are apparently more numerous than the ordinary naked-eye meteors in the proportion of #bb to #a4 ,it would be supposed from the great rapidity with which the latter shoot across the firmament that the smaller telescopic meteors are scarcely distinguishable by their motion1 as they must dart through the field instantaneously and only be perceptible as lines of light4 ,but this impression is altogether inconsistent with the appearances observed4 ,they possess no such velocity1 but usually move with extreme slowness1 and not unfrequently the whole of the path is comprised within the same field of view4 ,the eye is enabled to follow them as they leisurely traverse their courses1 and to note peculiarities of aspect4 ,of course1 there are considerable differences of speed observed1 but as a rule the rate is decidedly slow and far less than that shown by naked-eye meteors4 ,i believe that telescopic meteors are situated at great heights in the atmosphere1 and that their diminutive size and slowness of movement are due to their remoteness4 ,this conclusion will hardly be avoided by anyone who attentively studies the several classes of meteors in their various aspects4 ,unfortunately no attempt appears to have been hitherto made to determine the actual heights of telescopic meteors1 owing to the difficulty of obtaining two reliable observations of the same object4 ,the only way of securing such data would be for several observers to watch certain selected regions by prearrangement either with a low-power telescope or field-glass1 and record the exact times and paths of the meteors seen4 ,on a comparison of the results a good double observation of the same object might be found1 in which case the real path could be readily computed4 ,future observers should note the different forms of telescopic meteors4 ,safarik has divided them into four classes1 viz43--7#a7 ,well-defined star-like objects of very small size2 7#b7 ,large luminous bodies of some minutes of arc in diameter2 7#c7 ,well-defined disks of a very perceptible diameter brighter at the border than at the centre1 which gives them the aspect of hollow transparent shells2 and 7#d7 faint diffused masses of irregular shape1 considerable size1 and different colours4 ,he has seen hundreds of meteors of every magnitude from the #bnd down to the #abth pass through the field of his #f-;inch reflector 7ordinary power #cb1 field #ed74 ,on ,aug4 #cj1 #ahhj1 #i;h to #ae;h he observed between #ej and #ajj telescopic meteors1 and many others were seen on the following night4 ,whenever a shower of these bodies1 such as that witnessed by ,brooks on ,nov4 #bh1 #ahhc1 occurs1 observers should notice whether the objects participate in a common direction of motion2 because1 if so1 the radiant-point will admit of determination4 ,the horary rate of their apparition ought also to be ascertained4 ,those who habitually search for comets should invariably make a note of telescopic meteors1 as such records would aid inquiries into the relative frequency of these phenomena4 ,meteor ,showers4--,the following short list includes the principal displays of the year3-- ---------------------------------------- ---------------------------------------- ---------------------------------------- ----- ,name of ,duration4 ,date of ,radiant- ,sun's ,shower4 ,max4 ,point4 ,longitude4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ----- ,quadrantids ,dec4 #bh-;,jan4 #d ,jan4 #b #bbih #ebe #bhaf ,lyrids ,april #af-bb ,april #bj #bfig #cbe #cac ,aquarids ,april #cj-,may #f ,may #f #ccgf - #ba #dfc ,aquarids ,july #bc-;,aug4 #be;,july #bh #ccid -#aaf #abef ,perseids ,july #h-;,aug4 #bb ,aug4 #aj #dei #efi #ache ,orionids ,oct4 #i-bi ,oct4 #ah #iba #aee #bjei ,leonids ,nov4 #i-ag ,nov4 #ac #aejj #bbi #bcae ,andromedes ,nov4 #be-cj ,nov4 #bg #bec #dch #bdeh ,geminids ,dec4 #a-ad ,dec4 #aj #ajha #cbf #beie ---------------------------------------- ---------------------------------------- ---------------------------------------- ----- ,notes4 ,quadrantids4 ,heis was the first to determine this radiant accurately4 ,it was subsequently observed by ,masters and ,prof4 ,herschel 7#ahfc-d74 ,the radiant is circumpolar in this latitude1 but low down during the greater part of the night1 hence the display is usually seen to the best advantage on the morning of ,jan4 #b4 ,lyrids4 ,attention was first drawn to the ,april meteors by ,herrick in the ,united ,states4 ,active displays occurred in #ahfc and #ahhd4 ,aquarids4 ,further observations are urgently required of this stream4 ,the radiant is only visible for a short time before sunrise4 ,there is a considerable difference between my results and those secured by ,lieut4-,col4 ,tupman1 the discoverer of this system in #ahgj1 whose observations place the radiant at #cbf--b ,april #bi-,may #c4 ,these ,may ,aquarids are interesting from the fact that they present an orbital resemblance to ,halley's ,comet1 which makes a near approach to the ,earth on ,may #d1 twelve days before reaching the descending node4 ,aquarids4 ,the meteoric epoch1 ,july #bf-cj1 was first pointed out by ,quetelet many years ago4 ,biot also found1 from the oldest ,chinese observations1 a general maximum between ,july #ah and #bg 7,humboldt74 ,showers of ,aquarids were remarked by ,schmidt1 ,tupman 7#ahgj71 and others2 but it was not known until my observations in #ahgh that the ,aquarids formed the special display of the epoch1 and that there were many early ,perseids visible at the same time4 ,perseids4 ,muschenbroeck1 in his work on #8,natural ,philosophy1' printed in #agfb1 mentions that he observed shooting-stars to be more numerous in ,august than in the other months of the year4 ,quetelet1 in #ahce1 was1 however1 the first to attribute a definite maximum to the #ith-#ajth4 ,this stream is remarkable for its extended duration1 and for the obvious displacement which occurs from night to night in the place of its radiant4 ,it furnishes an annual display of considerable strength1 and is1 perhaps1 the best known system of all4 ,orionids4 ,profs4 ,schmidt and ,herschel were the first to discover the ,orionids as the most brilliant display of the ,october period1 and accurately determined its radiant in #ahfc-d-e4 ,herrick recorded a shower at #ii #bf1 ,oct4 #bj-bf1 #ahci1 and ,zezioli in #ahfh recorded many meteors which were ascribed to a radiant at #aaa #bi2 but there is no doubt that the ,orionids were observed in both these cases1 though the radiant was badly assigned4 ,the radiant of the ,orionids shows no displacement like that of the ,perseids4 ,leonids4 ,observed from the earliest times4 ,humboldt and ,bonpland saw it well on the night of ,november #aa-ab1 #agii1 and the phenomenon at its magnificent return on ,november #ab1 #ahcc1 was ably discussed by ,olmsted4 ,it furnished a splendid shower in #ahff1 ,november #ac1 and many meteors were seen at the few subsequent returns4 ,i observed fairly conspicuous showers of ,leonids in #ahgi and #ahhh4 ,there is no doubt the meteors form a complete ellipse1 for the earth encounters a few of them at every passage through the node4 ,grand displays may be expected at the end of this century4 ,andromedes4 ,observed by ,brandes1 at ,hamburg1 ,dec4 #g1 #agih4 ,it also recurred in #ahch2 the very brilliant showers of ,november #bg1 #ahgb and #ahhe1 are still fresh in the memory4 ,it is uncertain whether this group forms an unbroken stream2 if so1 the regions far removed from the parent comet must be extremely attenuated4 ,some of the meteors were seen in #ahgg and #ahgi4 ,the radiant is diffuse to the extent of #g or #aj4 ,returns of the shower should be looked for in #ahib and #ahih4 ,geminids4 ,mr4 ,greg first called attention to the importance of this shower4 ,it was well observed by ,prof4 ,herschel in #ahfa-c-d1 and some later years4 ,there are an enormous number of minor systems1 but these are generally feeble1 and interesting only to the regular observer of meteors4 ,many showers are so slightly manifested that they yield but one visible meteor in #f or #g hours1 and on the same night of observation there are often as many as #ej or #fj different systems in operation4 ,i gave a list of #iah radiant-points of showers observed at ,bristol in the #8,monthly ,notices1' ,may #ahij1 and other catalogues will be found in the #8,british ,association ,reports' for #ahgd and #ahgh4 ,varieties of ,meteors4--,the amateur who systematically watches for meteors will occasionally remark instances of anomalous character4 ,i have sometimes observed meteors which are apparently very near1 and move with enormous velocity4 ,they are mere gleams of pale light1 which have little analogy to ordinary shooting-stars1 and suggest an electric origin1 though ,i do not know whether the marvellous quickness with which they flash upon the eye is not to be held responsible for the impression of nearness4 ,they are somewhat rare1 and one may watch through several entire nights without a single example1 but as far as my memory serves ,i must have witnessed some scores of these meteoric flashes4 ,one of the most interesting class of meteors includes those which move so slowly that the eye is enabled to note the details of their appearance4 ,some of these objects are small when first seen1 but enlarge considerably under the increasing temperature1 and after a great slackening of speed 7due to atmospheric resistance7 their nuclei are finally spent in thick streams of luminous dust4 ,on ,dec4 #bh1 #ahhh1 ,i recorded a meteor which on its first apparition was tolerably bright1 small1 and compact4 ,it moved slowly1 and ,i had an excellent view of its passage4 ,the nucleus quickly expanded1 though with no increase of brilliancy4 ,towards the end it assumed a sensible disk1 and at the last phase the mass spread or deployed itself into a wide stream of fine ashes and disappeared4 ,the whole phenomenon was so curious1 and observed with such distinctness1 that ,i made the above sketch of it directly afterwards4 ,illustration3 ,fig4 #eh4 ,meteor of ,dec4 #bh1 #ahhh1 #f;h #agm4 ,heights of ,meteors4--,usually the height of meteors at their first appearance is less than #ij miles1 and at disappearance more than #dj miles4 ,from a comparison of a large number of computations ,i derived the following average values3-- ,beginning height #gfd miles 7#fhc meteors7 ,end height #ejh 0 7#gef 0 7 ,but if fireballs and the smaller shooting-stars are separated ,i find the usual heights at disappearance are3--fireballs1 #cj miles2 shooting-stars1 #ed miles4 ,fireballs therefore approach much nearer to the ,earth's surface before disruption than the ordinary falling stars4 ,illustration3 ,fig4 #ei4 ,large ,meteor1 and successive appearances of its streak1 seen at ,cape ,jask1 in the ,persian ,gulf1 on ,june #h1 #ahhc1 #g;h #eam to #h;h #ccm4 ,a very slight acquaintance with trigonometry will enable anyone to compute the real path of a meteor if two or more observations1 made at distant stations1 are available for the purpose4 ,the observed courses of the meteor should be marked upon a celestial globe1 and extended backwards to the point where they mutually intersect2 this will be the radiant-point4 ,the globe having been set for the time and latitude1 the apparent tracks should also be prolonged in a forward direction until they meet the horizon1 this will indicate the ,earth-points1 or azimuths of the place where the meteor would have been precipitated on the ,earth had it been enabled to continue its flight so far4 ,the azimuths and altitudes of the beginning and end of the path1 and the azimuths of the ,earth-point should then be read off1 and by means of a reliable map and a protractor their points of intersection over the ,earth's surface may be readily found by lines drawn from the two places of observation4 ,from the spot where the ,earth-points intersect a straight line should also be drawn in the direction of the radiant1 and it is along this line the meteor's motion was directed4 ,the coordinates of the observed points of appearance and disappearance of the meteor1 at the two stations1 would intersect this line at identical points were the observations perfectly accurate1 but this is rarely the case4 ,the distance between the observer's station and the places over which the meteor began and ended is easily derived from the map1 and the height of the object may be found by adding the logarithm of the distance to the log4 of the tangent of the altitude4 ,thus1 if the end of a meteor is witnessed from ,london in azimuth #acj ,w4 of ,s4 7alt4 #be71 and from ,bristol in azimuth #baf ,w4 of ,s4 7alt4 #cj7 the place of intersection on the map will be at ,warwick1 so that the meteor must have disappeared when vertically over this city4 ,london is distant from ,warwick about #hf miles1 and from ,bristol #gj miles1 and the resulting height of the meteor is3-- ,london4 ,bristol4 #hf log4 #aicdej #gj log4 #ahdeaj #be tan #iffhfg #cj tan #igfadd ------- ------- #afjcag #dja #afjfed #djd so that the observations accord very closely in fixing the height at a little exceeding #dj miles at disappearance1 but a slight correction is necessary to allow for the ,earth's curvature4 ,there are other methods of computing the heights1 one of which is explained by ,prof4 ,a4 ,s4 ,herschel in a paper entitled 8,height of a ,meteor0 7#8,monthly ,notices1' vol4 xxv4 p4 #bea74 ,meteoric ,observations4--,a large number of meteor-showers still await discovery1 and there are features even in connection with the best known streams which remain to be elucidated4 ,such doubts as now exist are only to be cleared away by assiduous observation made with the utmost accuracy possible both of the directions and durations of meteors4 ,this attractive field of investigation has certainly been neglected in recent years1 and the reason of this may perhaps be found in the complications inseparable from it1 in the need of great patience and scrupulous care in observation1 and the necessity of gaining experience before the observer can feel a reliance on his work1 and draw safe conclusions4 ,meteors are so fugitive1 so diverse and erratic in their apparitions1 as to be quite beyond the scope of instrumental refinements4 ,they must necessarily be observed under many disadvantages4 ,positions have to be fixed from very hurried and often imperfect impressions4 ,but these drawbacks1 formidable as they at first appear1 may be severally overcome by practice1 by careful regard for the conditions under which meteors are displayed1 and the marked differences of aspect induced by these conditions4 ,when the observer has acquired a practical knowledge he will proceed with confidence in his work1 and avoid many of the difficulties surrounding it4 ,in recording meteor-tracks for the purpose of discovering the radiant-points1 the chief feature in which precision is essential is the direction of flight4 ,a perfectly straight wand1 held in the hand for the purpose1 should be projected upon the path of every meteor directly it is seen1 and then when the eye has quickly noted the position and slope relatively to the fixed stars near1 it should be reproduced on the chart or celestial globe4 ,the time1 mag41 estimated duration1 and details of appearance should be registered in a tabular form1 with the ,r4,a4 and ,dec4 of the beginning-point and probable radiant4 ,the end-point and length of path may be left until next day1 in order to save valuable time4 ,the wand is a great assistance to the eye in retaining the approximate directions and noting the places4 ,if a meteor belongs to the slow1 trained class1 or if it belongs to the swift1 streak-leaving order1 the path may be very accurately noted1 for the wand can be adjusted to its direction before the meteor or its visible offcome has died away4 ,in the case of short1 quick meteors1 devoid of either streaks or trains1 and generally shooting from radiants at high altitudes1 they are more difficult to secure1 as they vanish before one may turn1 and the observer must rely upon the mere impression he received4 ,but even these succumb to experience1 and will be found to resolve themselves into a number of sharply defined radiants scarcely less certain than the positions derived from the streaked or trained meteors4 ,these positions are only to be fixed by the exercise of much cautious discrimination on the part of the observer1 for the direction of the flight is not sufficient1 alone1 to indicate it4 ,the visible aspect of the meteor has to be equally considered1 for the place of its radiant imparts certain peculiarities to it which are rarely to be mistaken4 ,first1 the astronomical position of the radiant4 ,if the radiant is at1 or within #ej of1 the ,earth's apex 7a point #ij preceding the ,sun along the ecliptic1 and towards which the ,earth's motion is directed7 the meteors generally leave streaks1 especially the brighter ones1 and move with great speed4 ,they are usually white1 exhibiting a high degree of incandescence4 ,if the radiant is near the anti-apex or anywhere in the anti-apex half-sphere the meteors are streakless1 they travel slowly or very slowly1 and often leave trails of yellowish sparks4 ,bearing these facts in mind the region may be assigned in which any radiant is situated1 if not the exact position of the radiant itself4 ,if1 say1 on ,aug4 #aj1 at midnight a swift1 streaked meteor is seen shooting from the ,pleiades towards ,aldebaran1 just risen1 the radiant is either in ,musca1 ,triangulum1 or ,andromeda4 ,but if the meteor is slow1 with a train1 then we must go further back in the direction of its flight1 and seek the radiant in the ,s4 or ,s4,w4 sky4 ,if the motion is very slow1 the radiant may be as far away as ,aquila4 ,second1 the sensible position of the radiant4 ,a low radiant yields long-pathed meteors1 characterized by slowness of speed and a flaky appearance either of the streaks or trains4 ,a radiant near the zenith gives short1 darting meteors1 with rather dense streaks or trains4 ,these nearly vertical meteors have a less extensive range of atmosphere to penetrate than the horizontal meteors1 which are sometimes abnormally long4 ,in the case of brilliant meteors1 however1 the paths occasionally extend over considerable arcs though the radiant may be high4 ,third1 the position of the radiant relatively to the path of a meteor4 ,if a meteor is close to its radiant its track is usually slow1 and appears greatly foreshortened by the effects of perspective4 ,it is travelling 7approaching7 nearly in the line of sight1 and the streak or offcome of sparks is especially dense because it is seen through its entire depth2 and the nucleus in such a case has a brushy diffused appearance4 ,such meteors often traverse sinuous1 or curved paths of #b1 #c1 or #d1 and they are readily distinguishable from other meteors far from the radiants to which they belong4 ,a good method of tabulating meteor-tracks is that adopted by ,lieut4-,col4 ,tupman in his catalogue published by the ,british ,association in #ahgd4 ,i have adopted the same form1 and herewith append a copy of my register of a few isolated bright meteors observed in the autumn of #ahij3-- ---------------------------------------- ---------------------------------------- ---------------------- ,observed ,path ,date ,g4,m4,t4 ,mag4 --------------------------------------,l ength,dura- #ahij4 ,from ,to of tion4 ,r4,a4 ,dec4 ,r4,a4 ,dec ,path4 ---------------------------------------- ---------------------------------------- ---------------------- h m o o o o o sec4 ,oct4 #ag #aj #cg #a #baifa #beefe #af #ce #ai #aj #ce #a #fabf #ddbg #ae #jg #ai #ab #j #cbf-h #cai-aj #g #je #be #ag #ah #afhcd #ahjbd #ad #jh #bf #g #cc #cbifi #bdcea #db #dj ,nov4 #a #g #a #a #bghdi #bddaa #df #fj #a #i #ag #a #cdeaa #cjga #ci #dj #e #aj #dj #bh-be #be-bi #e #jg #af #aa #ae #bgdgg #bfefg #aj #ae ---------------------------------------- ---------------------------------------- ---------------------- ---------------------------------------- ---------------------------------- ,date ,appearance4 ,probable #ahij4 ,radiant4 ---------------------------------------- ---------------------------------- o o ,oct4 #ag ,v4 slow1 ,b4 train4 #bjdef4 #ai ,swift1 streak4 ,orion4 #ai ,swift1 streak4 ,orion4 #be ,swift1 streak4 ,lynx4 #bf ,slow4 #cbah4 ,nov4 #a ,very slow4 #ejae4 #a ,slow4 #ejae4 #e ,swift1 strk4 #ae sec4 ,taurus4 #af ,not very swift4 ,auriga4 ---------------------------------------- ---------------------------------- ,the duration of flight is a most important element to estimate correctly1 as it affords data wherewith the real velocity may be computed1 and enables the nature of the orbit in which the meteor is moving to be definitely assigned4 ,this feature is1 however1 one of the most difficult of all to derive with satisfactory precision4 ,in the case of very slow meteors lasting several seconds1 it is easy by means of a stop-watch1 or by other methods1 to get the times of flight within narrow limits of error1 but the swifter class of meteors complete their visible trajectories in the fraction of a second1 and are gone before any effort can be made to gauge their durations1 so that a value has to be attributed which is little better than a mere guess4 ,every adopted radiant-point should be based on at least five paths1 unless the conditions are special1 and these must show a very definite centre1 and present family resemblances4 ,it is often possible to detect a good centre from very few paths1 when the radiant is low on the horizon1 or when it occupies an isolated position4 ,in recording meteors the details of their appearances should also be appended to the paths4 ,foreshortened and crooked courses1 fluctuations of brightness1 halting motion1 spark-trains1 phosphorescent streaks1 broken streaks1 and other features must be invariably noted when observed1 as likely to assist in fully comprehending these bodies4 ,a streak will sometimes brighten up perceptibly after the head has died out4 ,one of the principal aims of future observers should be to ascertain the visible duration of meteor-showers1 and the displacement or fixed position of the radiants during the period of their continuance4 ,the ,perseids seem to endure for forty-six nights 7,july #h-;,august #bb7 while the radiant moves from #c #di to #gf #eg4 ,the ,lyrids also exhibit a shifting radiant1 and it is highly probable some other showers are to be included in the same category4 ,in investigating these1 the observations of single nights should be kept separate1 and the radiant determined from each set of paths4 ,the positions when compared will then exhibit the rate and direction of the displacement4 ,as to radiants which are apparently stationary#df during long intervals1 these should be closely observed4 ,are the centres of radiation1 as successively determined1 identical1 allowing for the slight errors of observation8 ,are they continuously in operation1 or intermittent8 ,meteors with motions in declination and near their radiants will be specially valuable in settling these questions1 and if observed at more than one station will possess great significance4 ,if it can be proved that a radiant is fixed and continuous during a few weeks1 there can be no reason why it may not be stationary for a much more lengthy interval1 unless the circumstances are exceptional4 ,though ,i have pointed out the urgency of noting the directions and durations of meteors1 there are other features in such observations that must not be disregarded4 ,if the paths are being recorded for the particular purpose of getting duplicate observations and calculating the heights1 then it is desirable to note the beginning-and end-points of the flights as exactly as possible1 for unless this is done the combined paths will show great discordances4 ,those who have acquired a familiar knowledge of the constellations will1 however1 experience little trouble in insuring accuracy in these records4 ,observers1 particularly those residing in towns1 must be constantly on their guard against mistakes in identifying meteors from terrestrial objects such as fire-balloons and the various forms of pyrotechnic display4 ,that such caution is necessary will be admitted when we read the two following letters1 which were published in the #8,times' some years ago3-- 8,,sir1-- 8,a large meteor was seen to-night at #h4bg1 moving very slowly along the northern horizon1 from west to east1 at an altitude of about #h deg4 ,it was at least three times as brilliant as ,venus1 remaining visible for nearly five minutes1 moving slower than any hitherto observed4 ,i should be glad to receive observations made at more favourable stations4444 8,i remain1 ,sir1 your obedient ,servant1 8,,thomas ,,crumplen4 8,mr4 ,slater's ,observatory1 ,euston ,road1 ,august #ajth40 8,,sir1-- 8,the #8large meteor' seen by ,mr4 ,crumplen on ,monday evening at #h4bg1 three times as brilliant as ,venus1 and moving from west to east1 was a fire-balloon sent up shortly after #h o'clock from the ,eton and ,middlesex ,cricket ,ground1 ,primrose ,hill1 as a finale to some athletic sports which had taken place during the afternoon4 8,i am1 ,sir1 your obedient ,servant1 8,b4 ,c4 ,c4 8,st4 ,john's ,wood1 ,august #abth40 ,in concluding this chapter ,i may briefly mention that an old idea concerning meteors was that they originated gales of wind1 and that1 in fact1 they were the usual precursors of stormy weather4 ,this belief is thus expressed in ,dryden's #8,virgil'3-- 8,oft shalt thou see1 ere brooding storms arise1 ,star after star glide headlong down the skies1 ,and1 where they shot1 long trails of lingering light1 ,sweep far behind1 and gild the shades of night40 ,,footnotes3 #de ,during the seven months from ,may to ,november #ahij ,i noted ninety-five telescopic meteors while engaged in comet-seeking4 #df ,a list of these was published in the #8,monthly ,notices1' vol4 #a4 p4 #dff4 ,see also #8,monthly ,notices1' vol4 xlv4 pp4 #ic et seq4 ,,chapter ,,xvi4 ,,the ,,stars4 ,sidereal ,work4--,greek alphabet4--,learning the ,names of the ,stars4--,the ,constellation figures4--,means of ,measurement4--,dividing power4--,number of ,stars4--,magnitudes4--,the ,milky ,way4--,scintillation of the ,stars4--,star-,disks4--,distance of the ,stars4--,proper ,motion of ,stars4--,double ,stars and ,binary ,systems4--,variable ,stars4--,new or ,temporary ,stars4--,star ,colours4--,groups of ,stars4--,further ,observations4 8,ten thousand suns appear ,of elder beam2 which ask no leave to shine ,of our terrestrial star1 nor borrow light ,from the proud regent of our scanty day40 ,,barbauld4 ,the planetary observer has to accept such opportunities as are given him2 he must use his telescope at the particular seasons when his objects are well presented4 ,these are limited in number1 and months may pass without one of them coming under favourable review4 ,in stellar work no such irregularities can affect the progress of observations4 ,the student of sidereal astronomy has a vast field to explore1 and a diversity of objects of infinite extent4 ,they are so various in their lustre1 in their grouping1 and in their colours1 that the observer's interest is actively retained in his work1 and we often find him pursuing it with unflagging diligence through many years4 ,no doubt there would be many others employing their energies in this rich field of labour but for the uninteresting character of star-disks1 which are mere points of light1 and therefore incapable of displaying any detail4 ,those who study the ,sun1 ,moon1 or planets have a large amount of surface-configuration to examine and delineate1 and this is ever undergoing real or apparent changes4 ,but this is wholly wanting in the telescopic images of stars1 which exhibit a sameness and lack of detail that is not satisfying to the tastes of every observer4 ,true there are some beautiful contrasts of colour and many striking differences of magnitude in double stars2 there are also the varying position and distance of binary systems1 the curious and mysterious fluctuations in variable stars1 and some other peculiarities of stellar phenomena which must1 and ever will1 attract all the attention that such important and pleasing features deserve4 ,and these1 it must be conceded1 form adequate compensation for any other shortcomings4 ,the observer who is led to study the stars by comparisons of colour and magnitude or measures of position1 will not only find ample materials for a life-long research1 but will meet with many objects affording him special entertainment4 ,and his work1 if rightly directed and accurately performed1 will certainly add something to our knowledge of a branch in which he will certainly find much delectation4 ,greek ,alphabet4--,the amateur must1 at the outset of his career1 thoroughly master the ,greek alphabet4 ,this will prevent many time-wasting references afterwards1 and avoid the doubt and confusion that must otherwise result4 ,the naked-eye stars in each constellation have ,greek letters affixed to them on our celestial globes and star-maps4 ,alpha ,beta ,gamma ,delta ,epslon ,zta ,eta ,theta ,iota ,kappa ,lambda ,mu ,nu ,xi ,omcron ,pi ,rho ,sigma ,tau ,upslon ,phi ,chi ,psi ,omga4 ,the letters are applied progressively to the stars 7generally according to brightness7 in each constellation4 ,the #ast-mag4 stars frequently have a duplicate name4 ,thus ,leonis is also known as ,regulus1 and ,canis ,majoris as ,sirius1 the ,dog-star4 ,learning the ,names of the ,stars4--,a knowledge of the stars as they are presented in the nocturnal sky may be regarded as the entrance to the more advanced and difficult branches of the science1 and forms the young observer's introductory lesson4 ,when he has learnt a few of the principal constellations1 and can point them out to his friends1 he already begins to feel more at home with the subject1 and regards it with a different eye to what he did before when the names and configurations of the stars were alike unknown to him4 ,he no longer views the heavens as a mysterious assemblage of confusing objects1 for here and there he espies certain well-known groups always preserving the same relative positions to each other4 ,the unconscious gaze he formerly directed to the sky has given way to the intelligent look of recognition with which he now surveys the firmament4 ,an acquaintance with the leading constellations1 and with the names or the letters of the brighter stars in each1 becomes very important in some departments of observation1 and various methods have been suggested as likely to impress the positions and names on the memory4 ,the beginner must first be content to get familiar with a few of the brighter stars1 and make these the base for extending his knowledge4 ,the objects are so numerous that it is impossible his primary attempts can be anything like complete4 ,he must advance step by step in his survey1 and feel his way cautiously1 setting out from certain conspicuous stars with which he has already become conversant4 ,a lantern and a series of star-maps are the only aids required1 and with these he ought to make satisfactory progress4 ,the stars as they are seen in the sky may be compared with those figured in the maps1 and their names and the constellations in which they lie may then be identified4 ,it is an excellent plan as conducing to fix the positions indelibly in the memory to construct maps from personal observation1 and to compare these afterwards with the published maps for identification of the constituent stars4 ,this plan1 if repeated several times1 has the effect of impressing the positions of the leading stars forcibly upon the observer's mind4 ,it is not intended to give1 in this place1 any details as to the places or distribution of the stars4 ,without diagrams1 such a description could not be made readily intelligible4 ,to those1 however1 who are commencing their studies1 ,i would recommend the northern sky as the most suitable region to aid their initiatory efforts4 ,for 8,he who would scan the figured sky ,its brightest gems to tell1 ,must first direct his mind's eye north ,and learn the ,bear's stars well40 ,the seven bright stars of ,ursa ,major are familiar to nearly everyone4 ,two of them1 called the ,pointers1 serve to direct the eye to the ,polar star1 which1 though not a brilliant one1 stands out prominently in a region comparatively bare of large stars4 ,it is important to know the ,polar star1 as it is situated near the centre of the apparent motion of the firmament4 ,when the student has assured himself as to the northern stars he will turn his attention southwards1 and recognize the beautiful ,orion and the curious groups in ,taurus4 ,he will also observe1 much further east1 the well-known sickle of ,leo1 and in time become acquainted with the many other constellations that make the winter sky so attractive4 ,illustration3 ,fig4 #fj4 ,the constellation ,orion4 ,the ,constellation ,figures4--,the observer will soon realize that the creatures after which the constellations have been named bear no resemblance to the configuration of the stars they represent4 ,if we look for a ,bear amongst the stars of ,ursa1 for a ,bull amid the stars of ,taurus1 or for a flying ,swan in the stars of ,cygnus we shall utterly fail to find it4 ,the names appear to have been originally given1 not because of individual likenesses between them and the star-groups to which they are applied1 but simply on account of the necessity of dividing the sky into parts1 and giving each a distinguishing appellation1 so that it might be conveniently referred to4 ,there were pressing needs for a system of stellar nomenclature1 and the plan of grouping the stars into imaginary figures was the one adopted to avoid the confusion of looking upon the sky as a whole4 ,there are some who object to the method of the ,chaldean shepherds because the series of grotesque figures on our star-maps and globes bear no natural analogies4 ,but it would be unwise to attempt an innovation in what has been handed down to us from the myths of a remote antiquity1 for 8,time doth consecrate1 ,and what is grey with age1 becomes religion40 ,illustration3 ,fig4 #fa4 ,diagram illustrating the ,measurement of ,angles of ,position4 7,in measuring angles of position the larger star is always understood as central in the field4 ,the north point is zero1 and the angles are reckoned from this point towards the east4 ,if a star has a faint component lying exactly east or following it1 then the angle is #ij2 if the smaller star is south1 the angle is #ahj2 and so on47 ,means of ,measurement4--,a micrometer becomes an indispensable instrument to those who make sidereal observations of an exact character4 ,without such means it will be impossible to determine either positions or distances except by mere estimation1 and this is not sufficiently precise for double-star work4 ,with a reliable micrometer#dg excellent results may be obtained1 especially with regard to the varying angles of binary systems4 ,frequent remeasurement of these is desirable for comparison with the predicted places in cases where the orbits have been computed4 ,in this department of astronomy the names of ,herschel1 ,south1 ,struve1 ,dawes1 ,dembowski1 ,burnham1 and others are honourably associated1 and it is notable that refracting-telescopes have accomplished nearly the whole of the work4 ,but reflectors are little less capable1 though their powers seem to have been but rarely employed in this field4 ,mr4 ,tarrant has lately secured a large number of accurate measures with a #aj-;inch reflector by ,calver1 and if care is taken to secure correct adjustment of the mirrors1 there is no reason why this form of instrument should not be nearly as effective as its rival4 ,mr4 ,tarrant advises those who use reflectors in observing double stars 8to test the centering of the flat at intervals during the observations1 as the slightest shift of the large mirror in its cell will frequently occasion a spurious image which1 if it by chance happens to fall where the companion is expected to be seen1 will often lead to the conclusion that it has been observed4 ,in addition to this1 any wings or the slightest flare around a bright star will generally completely obliterate every trace of the companion1 especially if close and of small magnitude1 and such defects will in nine cases out of ten be found to be due to defective adjustment4 ,undoubtedly for very close unequal pairs the refractor possesses great advantages over a reflector of equal aperture2 in the case of close double stars the components of which are nearly equal there appears to be little1 if any1 difference between the two classes of instruments2 while for any detail connected with the colour of stars the reflector certainly comes to the fore from its being perfectly achromatic40 ,these remarks from a practical man will go far to negative the disparaging statements sometimes made with regard to reflectors and stellar work1 and ought to encourage other amateurs possessing these instruments to take up this branch in a systematic way4 ,dividing ,power4--,this mainly depends upon the aperture1 and it was made the subject of careful investigation and experiment by ,dawes1 who found that the diameters of the star-disks varied inversely as the aperture of the telescope4 ,adopting an inch as the standard1 he ascertained that this aperture divided stars of the sixth magnitude #def apart1 and on this base he constructed the following table3-- ,aperture ,least in inches4 separable distance4 #aj #def #af #bhe #bj #bbh #bbe #bjc #be #ahb #bge #aff #cj #aeb #ce #acj #ch #abj #dj #aad #de #aja #ej #jia #ee #jhc #fj #jgf #fe #jgj #gj #jfe #ge #jfa #hj #jeg #he #jecf #ij #j4ejg #ie #j4dhj #ajj #jdef #ab4j #jchj #aej #jcjd #bjj #jbbh #bej #jahb #cjj #jaeb ,dallmeyer1 the optician1 confirmed these values by remarking3--8,in all the calculations ,i have made1 ,i find that #dcc divided by the aperture gives the separating power4 ,thus1 #dcc inches separates #a 40 ,but a good deal depends upon the character of the seeing and upon other conditions4 ,a large aperture will sometimes fail to reveal a difficult and close comes to a bright star when a smaller aperture will succeed4 ,this is due to the position of the bright diffraction-ring1 which in a large instrument may overlap the faint companion and obscure it1 while in a small one the ring falls outside and the small star is visible#dh4 ,dawes concluded that 8tests of separation of double stars are not tests of excellence of figure10 and he gave much valuable information with regard to micrometers and double-star observations generally in the #8,monthly ,notices1' vol4 xxvii4 pp4 #bag-bch4 ,this paper will well repay attentive reading4 ,number of ,stars4--,in the northern hemisphere there are about #ejjjdi stars perceptible to the naked eye4 ,this is less than an observer would suppose from a casual glance at the firmament1 but hasty ideas are often inaccurate4 ,the scintillation of the stars and the fact that many small stars are momentarily glimpsed but cannot be held steadily have a tendency to occasion an exaggerated estimate of their numbers4 ,authorities differ as to the total of naked-eye stars4 ,sir ,r4 ,s4 ,ball says 8the number of stars which can be seen with the unaided eye in ,england may be estimated at about #cjjj40 ,gore gives #djjj4 ,backhouse mentions #efjj as visible in the northern hemisphere4 ,argelander1 who has charted #cbd1ahh stars between #b ,s4 of the equator and the ,n4 pole1 gives the following numbers of stars up to the #ith magnitude3-- #ast4 #bnd4 #crd4 #dth4 #eth4 #bj #fe #aij #dbe #aajj #fth4 #gth4 #hth4 #ith4 #cbjj #ac1jjj #dj1jjj #adb1jjj ,with every decrease in magnitude there is a great increase in numbers1 and if this is extended to still smaller magnitudes down to the #aeth or #afth we can readily understand that there exist vast multitudes of fainter stars4 ,paul ,henry1 of the ,paris ,observatory1 says there are about #a1ejj1jjj stars of the #aath mag41 and ,dr4 ,schnfield1 of ,bonn1 gives #c1bej1jjj as of the #aa mag4 ,it is probable that by means of photography and the largest telescopes considerably more than #ej millions of stars may be charted1 but this is a mere approximation4 ,roberts has photographed #af1bjf stars within an area of four square degrees in a very rich region of the ,galaxy near ,cygni1 and ,gore computes that were the distribution equal to this over the whole firmament the number of stars would reach #afg millions4 ,he also remarks that in the ,paris photographs of the ,pleiades1 #bcbf stars are shown in a space covering about three square degrees1 and this gives for the entire sky a total of #cc millions4 ,it is1 however1 manifest that unusually plentiful spots in the heavens cannot be accepted as affording a criterion of the whole4 ,magnitudes4--,according to ,argelander's figures1 above quoted1 each magnitude exhibits a rise of about #cjj per cent4 ,but authorities rarely agree as to scale1 as the following comparison between ,sir ,j4 ,herschel and ,struve will show3-- ,h4 ,s4 #dj #cf #de #da #ej #df #ee #eje #fj #ee #fe #eie #gj #fd #ge #fhe #hj #gc #he #gg #ij #ha #ie #he #ajj #hh #aje #ia #aaj #ic #aae #if #abj #ih #abe #ajj #acj #ajah #ace #ajcf #adj #ajed #ade #ajga #aej #ajhg #afj #aaac #agj #aach #ahj #aafa #aij #aahb #bjj #abjj ,argelander's magnitudes come between those of ,herschel and ,struve4 ,such disagreements are perplexing to observers1 and it is fortunate that in regard to the naked-eye stars we are now furnished with a more consistent and accurate series of magnitudes4 ,photometric determinations of the light of #dbfj stars not fainter than the #fth mag41 and between the ,n4 pole and #cj ,s4 declination1 were made at ,harvard ,college ,observatory1 and similar measures of #bghd stars between the ,n4 pole and #aj ,s4 declination were effected at the ,oxford ,university ,observatory1 and the results published in #ahhe4 ,the two catalogues are in very satisfactory agreement1 the accordances within one tenth of a mag4 being #ca per cent41 within one quarter of a mag4 #ga per cent41 and within one third of a magnitude #ie per cent4 ,the photometers used in the two independent researches were constructed on very different principles1 and the substantial agreement in the results indicates that 8a great step has been accomplished towards an accurate knowledge of the relative lustre of the stars0 7#8,monthly ,notices1' vol4 xlvi4 p4 #bgg74 ,the ,milky ,way4--,on dark nights when the ,moon is absent and the air clear1 a broad zone of glimmering1 filmy material is seen to stretch irregularly across the heavens4 ,it may be likened to a milky river running very unevenly amongst the constellations1 and showing many curves and branches along its course4 ,on very favourable occasions the unaided eye glimpses many hundreds of glittering points on this light background4 ,a field-glass reveals some thousands1 and shows that it is entirely composed of stars the blended and confused lustre of which occasions that track of whiteness which is so evident to the eye4 ,in a good telescope stars and star-dust exist in countless profusion1 and great diversity is apparent in their numbers and manner of grouping4 ,in certain regions the stars are concentrated into swarms1 and the sky is aglow with them2 while in others there are very few1 and dark cavernous openings offer a striking contrast to the silvery sheen of surrounding stars4 ,there are many of these void spaces in ,scorpio1 and a circular one in ,sagittarius ,r4,a4 #ag;h #efm1 ,dec4-#bg #ea has been particularly remarked4 ,these inequalities of grouping may be easily recognized with the naked eye1 especially in ,cygnus1 where bright star-lit regions frequently alternate with dark void spaces4 ,in the southern sky there is a noteworthy instance4 ,near the brilliant stars of ,crux and ,centaurus and closely surrounded by the ,milky ,way there is a large black vacancy very obvious at a glance1 and so striking to ordinary observers that it is known as the 8,coal-sack10 a name applied to it by the early navigators of the southern seas4 ,the course of the ,milky ,way may be described generally as flowing through ,auriga1 the club of ,orion1 feet of ,gemini1 western part of ,monoceros1 ,argo ,navis1 ,crux1 feet of ,centaurus1 ,circinus1 ,ara1 where it separates into two branches1 the western of which traverses the northern part of the tail of ,scorpio1 eastern side of ,serpens1 ,taurus ,poniatowski1 ,anser1 and ,cygnus4 ,the eastern branch crosses the tail of ,scorpio1 the bow of ,sagittarius1 ,antinous1 ,aquila1 ,vulpecula1 and then enters ,cygnus1 where it reunites with the other branch4 ,it thence passes through ,cepheus1 ,cassiopeia1 ,perseus1 and enters ,auriga4 ,in breadth it varies greatly1 being in some places only #d or #e1 whereas in others it reaches #bj4 ,it is1 of course1 best visible when twilight is absent1 but it is sometimes very plain1 even at midsummer1 for at this season some of its more conspicuous sections are favourably placed for observation4 ,it is supposed that fully nine tenths of the total number of stars in the firmament are included within the borders1 of the ,milky ,way4 ,some of the ancient philosophers1 including ,democritus1 formed just conceptions as to the real nature of this appearance4 ,though they lacked instruments wherewith to observe the stars forming it1 they yet saw them with the eye of reason4 ,but very vague and incorrect notions prevailed in early times1 when superstition was rife1 as to many celestial phenomena4 ,some of the ancient poets and learned men refer to the ,galaxy as the path by which heroes ascended to heaven4 ,thus we read in ,ovid3-- 8,a way there is in heaven's extended plain1 ,which when the skies are clear is seen below1 ,and mortals1 by the name of ,milky1 know2 ,the ground-work is of stars1 through which the road ,lies open to great ,jupiter's abode40 ,scintillation of the ,stars4--,the rapid variations of light known as the 8twinkling0 of the stars received notice from many ancient observers1 including ,aristotle1 ,ptolemy1 and others1 and they severally endeavoured to account for it1 but not in a manner altogether satisfactory4 ,at low altitudes bright stars exhibit this twinkling or scintillation in a striking degree1 but it is much less perceptible in stars placed at considerable elevations4 ,sirius1 the brightest star in the sky1 is a noted twinkler4 ,his excessive lustre and invariably low position are conditions eminently favourable to induce this effect4 ,but the planets seldom exhibit scintillation in a very marked degree4 ,the light of ,jupiter and ,saturn is steady1 even when these planets are close to the horizon4 ,mercury1 however1 twinkles most obviously1 and ,venus and ,mars1 when low down1 are often similarly affected1 especially in stormy weather when the air is much disturbed4 ,hooke1 in #affg1 concluded that the scintillation was due 8to irregular refractions of the light of the stars by differently heated layers of atmosphere40 ,m4 ,arago said it arose 8from the peculiar properties possessed by the constituent rays of light1 of moving with different velocities through the strata of the atmosphere1 and of producing what are called interferences40 ,more recently1 ,m4 ,montigney has conducted some interesting researches into this subject1 and he believes 8that not only is twinkling caused1 to a great extent1 by the deviations of portions of a star's light altogether away from us by variable layers of atmosphere1 but it is also affected1 both in frequency and in the colours displayed1 by the nature of the light emitted by the individual star40 ,the planets are little subject to scintillation1 as they present disks of sensible size1 and thus are enabled to neutralize the effect of atmospheric interferences4 ,it is curious1 however1 that the steadiness of telescopic images does not appear to be much improved at high altitudes1 and that the phenomenon of scintillation still operates powerfully as observed from mountainous stations4 ,in ,february #ahhh1 ,dr4 ,pernter1 of the ,vienna ,academy of ,sciences1 found 8that the scintillation of ,sirius was actually greater at the top of ,sonnblick1 #aj1jjj feet high1 than it was at the base of the mountain1 and he formed the opinion that scintillation has its origin in the upper strata of the atmosphere and not in the lower as usually assumed40 ,it would appear from this that lofty situations do not possess all the advantages claimed for them in regard to the employment of large telescopes4 ,star-,disks4--,the stars as observed in telescopes are shorn of the false rays apparent to the naked eye1 and they are seen with small spurious disks4 ,that the disks are spurious is evident from the fact that the larger the telescope employed1 the smaller the star-disks become4 ,and moreover1 when a star is occulted by the ,moon1 it disappears instantaneously4 ,there is no gradual diminution of lustre2 the star vanishes with great suddenness4 ,bright stars1 like ,aldebaran or ,regulus1 have been watched up to the ,moon's limb1 and observers have been sometimes startled at the abruptness with which they were blotted out4 ,an appreciable disk could not be withdrawn in this instantaneous manner2 it would exhibit a perceptible decadence as the ,moon increasingly overlapped it1 but no such appearance is observed4 ,on the occasion of the occultation of ,jupiter on ,aug4 #g1 #ahhi1 the planet's diameter was #dad1 and the disappearance occupied #he seconds4 ,now had ,aldebaran or ,regulus a real disk of only #a it would prevent their sudden extinctions1 and their disappearances would be spread over perceptible though short intervals of time#ej4 ,but there is every reason to conclude that the actual disks are to be represented by a small fraction of #a1 so that the largest instrument and the highest powers fail to reveal it4 ,in this connection1 ,mr4 ,gore1 in his #8,scenery of the ,heavens1' p4 #aeb1 says3--8,let us take the case of ,centauri1 which is1 as far as is known at present1 the nearest fixed star to the ,earth4 ,the distance of this star is about #be billions of miles4 ,from comparisons made between its light and the ,moon1 it has been found that its intrinsic brilliancy must be about four times that of the ,sun4 ,supposing its greater lustre is due to its greater size--a not improbable supposition--it would subtend1 if placed at the ,sun's distance1 an angle twice as great1 or about #a1 and hence we find that the angle subtended at its distance of #be billions of miles would be about #a_/gfth of a second of arc1 which the most powerful telescope yet constructed would be incapable of showing as a visible disk40 ,distance of the ,stars4--,the distances of the outer planets ,uranus and ,neptune1 mentioned in an earlier chapter of this work1 are sufficiently large to amaze us2 but the distances of the stars may be said to be relatively infinite4 ,for many years the problem of stellar distances defied all attempts to resolve it4 ,at length1 in #ahch-ci1 ,bessell1 ,henderson1 and ,struve obtained results for three stars--viz4 #fa ,cygni1 ,centauri1 and ,lyr1--which practically settled the question4 ,more recent measures of stellar parallax1 while correcting the earlier values1 have virtually corroborated them2 though the figures adopted can only be regarded as approximations1 owing to the difficult and delicate nature of the work4 ,the binary star ,centauri appears to be the nearest of all2 it has a parallax of #jge1 and its distance from us is equal to #bge1jjj times the distance of the ,sun4 ,light traversing space at the rate of #ahg1jjj miles per second would occupy #d-a_/c years in crossing this interval4 ,in the ,northern hemisphere #fa ,cygni is the nearest star1 with a parallax of #jdd and a distance of about #dgj1jjj times the ,sun's distance4 ,light would take more than seven years in reaching us from this star1 ,lyr has a parallax of #jae1 equal to nearly #bb light-years4 ,crucis shows a very small parallax 7#jjc71 and its distance is excessively remote--equal to about #ajh light-years6 ,proper ,motion of ,stars4--,a very slight motion affects the places of many of the so-called fixed stars4 ,this must1 after the lapse of long intervals of time1 materially alter the configuration of the constellations4 ,but the change is a very gradual one1 and must operate through many centuries before its effects will become appreciable in a general way4 ,the greatest proper motion yet observed is that in regard to two small stars 7one in ,ursa ,major and the other in ,piscis ,australis71 which amounts to about #g annually4 ,another motion has been recognized1 viz4 in the line of sight4 ,dr4 ,huggins made the initiatory efforts in this research by measuring the displacement of the ,f line in the spectrum of ,sirius4 ,the work has been actively pursued at the observatories of ,greenwich and ,rugby1 and with interesting results4 ,while certain stars exhibit a motion of approach1 others display a motion of recession4 ,thus ,vega1 ,arcturus1 and ,pollux are approaching us at the rate of about #dj miles per second2 while ,rigel is receding at the rate of #ag miles per second1 ,castor at the rate of #ai1 ,regulus #ad1 ,betelgeuse #be1 and ,aldebaran #ca4 ,sirius1 in the years from #ahge to #ahgh1 was receding from us at the rate of #bb miles per second2 but this decreased in subsequent years1 and in #ahhd-he the star was approaching with a motion of about #bb miles per second4 ,in #ahhf and #ahhg this rate was increased to about #cj miles per second1 as observed both at ,greenwich and ,rugby4 ,this confirms the idea that ,sirius is moving in an elliptical orbit4 ,similar observations1 in regard to the variable star ,algol1 have revealed that changes of velocity are connected with its changes of lustre4 ,before minimum the star recedes at the rate of #bd miles per second1 while after minimum the star approaches with a speed of #bh miles per second 7#8,monthly ,notices1' vol4 #a4 p4 #bda74 ,double ,stars and ,binary ,systems4--,telescopic power will often reveal two stars where but one is seen by the naked eye4 ,sometimes the juxtaposition of such stars is merely accidental2 though they are placed nearly in the same line of sight the conjunction is an optical one only1 and no connection apparently subsists between them4 ,in other cases1 however1 pairs are found which have a physical relation1 for one is revolving round the other2 and these are termed binary stars4 ,sir ,w4 ,herschel was the first to announce them1 from definite observations1 in #ahjb4 ,of double stars more than #aj1jjj are now known2 many of these are telescopic1 but the list includes some fine examples of naked-eye stars4 ,illustration3 ,fig4 #fb4 ,double ,stars4 ,orionis4 ,leonis4 ,urs ,minoris4 ,virginis4 ,cygni4 ,arietis4 ,andromed4 ,serpentis4 ,double stars are excellent telescopic tests4 ,a very close pair affords a good criterion as to the defining capacity of an instrument2 while a pair more widely separated and of greatly unequal magnitude1 like that of ,lyr1 offers a test of the light-grasping power4 ,but in these delicate observations1 as1 indeed1 in all others1 the character of the seeing exercises an important and variable influence4 ,a double star that is well shown on one night becomes utterly obliterated on another1 owing to the unsteadiness and flaring of the image4 ,on such occasions as the latter one is reminded of the 8twitching1 twirling1 wrinkling1 and horrible moulding0 of which ,sir ,john ,herschel complained1 and which unfortunately forms a too common experience of the astronomical observer4 ,a close double1 of nearly equal magnitudes1 requires a steady night1 such as is suitable for planetary details2 but a wide double consisting of a bright and a minute star rather needs a very clear sky than the perfection of definition4 ,certain doubles1 such as ,aurig1 ,cygni1 and ,herculis1 are often more easily seen in twilight than on a dark sky2 and some experienced observers1 conscious of this advantage1 have secured excellent measures in daylight4 ,mr4 ,gledhill says3--8,such stars as ,leonis and ,virginis are best measured before or very soon after sunset0 7#8,observatory1' vol4 iii4 p4 #ed74 ,list of ,double ,stars4 ,abbreviations in col4 #i3--41 ,burnham2 ,t41 ,tarrant2 ,s41 ,schiaparelli2 ,l41 ,leavenworth2 ,e41 ,engelmann2 ,p41 ,perrotin2 ,h41 ,h4 ,struve2 ,m41 ,maw4 ---------------------------------------- ---------------------------------------- ---------------------------------------- - ,position1 #ahij4 ,posit- ,no4 ,name of ,star4 -------------------------- ,mags4 ion- ,dis- ,epoch4,obser- ,r4,a4 ,dec4 ,angle tance4 ver4 ---------------------------------------- ---------------------------------------- ---------------------------------------- - h m o #a4 ,equulei #ba #ia #i #cd #d #e #ahii #jbe #ahhgg 4 ,most rapid binary known4 ,period #aa years 7,wrublewsky74 ,disc4 #aheb by ,o4 ,struve4 #b4,piazzi #aji #a #eaj #a #bj #g #g #bjfc #jbh #ahhha ,s4 ,an excessively close and difficult object4 ,binary4 #c4 ,delphini #bj #cbdad #ac #c #e #caja #jbi #ahhhf 4 ,a rapid binary4 ,period #bf years 7,doubjago74 ,disc4 #ahgc by ,burnham4 #d4b ,andromed #a #egada #dh #e #f #bggf #jce #ahhdh ,l4 ,distance in ,oct4 #ahhi less than #ja1 and very difficult with #cf-;inch 7,burnham74 #e4 ,coron ,bor4 #ae #chabf #ci #d #g #abff #jch #ahhge ,s4 ,a close binary4 ,period #ie years 7,doberck74 ,colours greenish-white and purple4 #f4ee ,tauri #d #acfaf #af #f #h #gfd #jdc #ahhgf ,s4 ,a binary4 ,difficult object with a #aj-;inch4 #g4 ,cassiopei #j #begec #ee #f #f #adfi #jde #ahhgc ,t4 ,another close binary4 ,distance of components shows little change4 #h4 ,botis #ad #ceiad #ab #d #d #bicd #jea #ahhge ,s4 ,a binary pair1 of equal mags4 ,period #abg years 7,doberck74 #i4db ,com ,bor4 #ac #dgah #g #e #f #ahif #jee #ahhia ,l4 ,a close binary1 of short period2 about #be years4 ,disc1 in #ahbg by ,o4 ,struve4 #aj4 ,cygni #bj #dcacf #h #e #g #gjf #jfc #ahhhh ,h4 ,a binary4 ,the distance between the components is increasing4 #aa4 ,coron ,bor4 #ae #ahgcj #da #e #f #aghe #jfc #ahhfe ,t4 ,a well-known binary1 of short period2 #da years 7,doberck74 #ab4 ,leonis #i #bbf #i #cb #e #g #ifh #jgj #ahhia ,l4 ,a close pair1 but not difficult4 ,binary4 ,period #aad years 7,doberck74 #ac4ae ,lyncis #f #dgheh #cd #e #f #ei #jgg #ahijc ,m4 ,a probable binary1 the position and distance exhibiting a gradual increase4 #ad4 ,orionis #e #ai #h #ba #e #g #aici #jii #ahhij ,l4 ,triple4 ,a low power shows many stars here4 #ae4 ,cancri1 ,a4,b4 #h #eiah #j #e #f #djc #aje #ahhib ,l4 ,a triple star4 ,a4,c4 ,pos4 #acdd2 ,dist4 #ecf2 ,mag4 #g2 #ahghc 7,hall74 #af4 ,scorpii1 ,a4,b4#af #ef-ai #aj #d #g #ic #ajh #ahhfe ,t4 ,a quadruple star1 forming one of the finest systems in the sky4 #ag4 ,cephei #bc #ddgd #dg #e #g #cbe #aaf #ahhhg ,h4 ,binary4 ,becoming more difficult with decrease of distance4 ,yellow and purple4 #ah4 ,arietis #b #ebibj #ed #e #f #bjbb #abh #ahhig ,l4 ,distance increasing4 ,good dividing-test for a #d-;inch aperture 7,t474 #ai4 ,ophiuchi #af #bed #b #ac #d #e #dbf #aee #ahhhd ,l4 ,binary1 but period not yet ascertained with accuracy4 ,yellow and bluish4 #bj4 ,herculis #af #cgaca #dh #c #f #feh #afh #ahijg ,m4 ,a fine1 rather close binary4 ,period #cd years 7,doberck74 ,single in #ahfe4 ,yellow and red4 #ba4 ,urs ,maj4 #aa #abccb #i #d #e #bbbg #afc #ahhic ,s4 ,one of the first-computed binaries4 ,period #fc years 7,breen74 ,excellent object4 #bb4 ,cygni #ai #daedd #eb #c #h #cagg #aff #ahhee ,t4 ,a well-known binary4 ,period #cgfg years 7,gore74 ,test for #d-;inch4 ,pale yellow and sea-green4 #bc4cc ,orionis #e #bee #c #ab #e #f #cbh #aha #ahhga ,t4 ,just visible in a #c-;inch4 ,white and pale blue4 #bd4 ,aurig1 ,a4,b4 #e #ebbcg #ab #c #h #be #aih #ahhea ,t4 ,a similar pair to ,cygni1 though the distance is wider4 #be4gj ,ophiuchi #ah #jj #b #cb #d #f #cdhg #baf #ahhic 4 ,binary4 ,period nearly #hh years 7,gore74 ,good object for a #c-;inch4 ,yellow and purple4 #bf4 ,leonis #aa #ahbaa #h #d #g #fbj #bef #ahhib ,l4 ,binary2 but distance shows little variation since #ahci4 ,yellowish and blue4 #bg4 ,botis #ad #djbbg #cb #c #e #cbha #bhh #ahhed ,t4 ,a very interesting object1 and visible in a small instrument4 #bh4 ,scorpii #af #bbg-bf #aa #a #h #bgag #bib #ahhjj 4 ,this pair forms an atmospheric rather than an optical test4 #bi4 ,ceti #b #cgf #b #df #c #g #bhig #bid #ahhci ,p4 ,a binary system4 ,test for a #b-;inch4 ,yellow and blue4 #cj4 ,piscium #a #efc #b #ad #e #f #cbai #cjc #ahhfi ,t4 ,a probable binary1 but since #ahca not much change in position or distance4 #ca4 ,aquarii #bb #bca- #j #ce #d #d #cbeh #cjh #ahhii ,l4 ,a fine binary1 with very long period4 #afbe years 7,doberck74 #cb4a ,lyr #ah #djgci #cd #d #f #aec #cbd #ahggd;,dob- erck4 #cc4b ,lyr #ah #djgci #cj #e #e #acgf #bde #ahggd ,hall ,these stars form a wide double 7distance #c #bg71 just separable by the naked eye4 ,a #b-;inch shows a fine double-double4 ,a #d-;inch reveals three faint stare between4 #cd4 ,hydr #h #daj #f #di #d #g #bbfe #caf #ahhia 4 ,a new comes1 ,pos4 #aedd2 ,dist4 #jbf2 ,mag4 #f1 #ahhi2 #cf-;inch1 power #ccjj6 4 #ce4 ,leonis1 ,a4,b4 #aj #acibj #bd #b #d #aadf #cea #ahhic 4 ,a fine binary4 ,period #djg years 7,doberck74 ,readily seen in a #c-;inch4 #cf4 ,serpentis #ae #bifaj #ee #c #e #ahii #ceb #ahhff;,ball4 ,probably binary4 ,fine object in small instruments4 #cg4 ,canis ,maj4 #f #djc-af #cd #a #aj #ceig #dai #ahijc 4 ,brilliant binary4 ,period #ehe years 7,gore74 ,colours white and yellow4 #ch4 ,herculis #ag #ifad #ca #c #d #aade #deh #ahhee ,t4 ,a splendid object4 ,orange and bluish green4 #ci4 ,cassiopei #j #dbdeg #ad #d #h #ahdg #dgf #ahhhc ,m4 ,binary4 ,period #aie years 7,gruber74 ,difficult object for #b-a_/d-;inch 7,johnson74 #dj4 ,virginis #ab #cfa- #j #ea #c #c #aeci #ede #ahhic ,l4 ,well-known binary4 ,period #ahb years 7,j4 ,herschel74 ,single in #ahcf4 #da4 ,geminorum #g #bgfcb #h #b #c #bbid #efh #ahhib ,l4 ,very fine object4 ,binary2 ,period doubtful 7,mdler #bcb years1 ,doberck #ajja years74 #db4 ,botis #ad #cefaf #ed #d #f #ajdc #fjd #ahhed ,t4 ,this pair has exhibited little change in pos4 or dist4 since #agha4 #dc4b ,capricorni1#bj #aai-ab #ec #c #ae #adig #fcj #ahgig 4 ,a4,b4 ,good light-test for #f-;inches4 ,companion double2 pos4 #bdj1 dist4 #ae4 #dd4 ,geminorum #g #acebb #aa #c #i #bjgb #fih #ahhfa ,t4 ,rather wide pair of unequal mags4 ,difficult with small apertures4 #de4 ,arietis #a #dgeah #de #d #e #aghc #hgh #ahhfi ,t4 ,a fine1 easy object4 ,discovered in #affd by ,hooke4 #df4 ,urs ,maj4 #h #eagdh #bh #c #ab #cefg #ief #ahhcd ,e4 ,well seen in a #d-;inch1 powers #hj and #acj4 ,good light-test4 #dg4 ,orionis #e #ic- #h #bj #a #i #bjbj #ifa #ahhgb ,t4 ,a fine object for small instruments4 ,visible in a #b-;inch refractor4 #dh4a ,andromed #a #egada #dh #c #f #fbf #ajej #ahgfj;,hall4 ,a splendid pair1 stationary in relative positions 7see no4 #d74 #di4 ,delphini #bj #dafae #dd #d #f #bgab #aaceahgig;,hall4 ,estimates of the colour of this pair differ1 and change is inferred4 #ej4 ,orionis1 ,a4,d4 #e #ccb- #b #dj #d #aj #bcfh #aafbahgeb ,multiple4 ,fine group here4 ,schrter saw #ab stars1 ,struve #ah4 #ea4 ,scorpii #ae #eij-ai #cj #b #e #bfg #abgbahgig 4 ,the brighter star is a close double2 ,pos4 #hg1 ,dist4 #jgc 7,burnham74 #eb4 ,urs ,maj4 #ac #aie #ee #cj #b #d #aeje #adchahhfb ,t4 ,fine object for small instruments4 ,other stars in the field4 #ec4 ,centauri #ad #cba -#fj #bc #a #b #bjbi #agabahhhf ,s4 ,a fine southern binary with ,period of #hjc years 7,elkin74 #ed4 ,urs ,min4 #a #ahe #hh #dc #b #i #baja #ahfj ,good test for a #b-;inch4 ,dawes saw it with #a-c_/aj-;inch1 ,ward with #a-a_/d inch4 #ee4fa ,cygni #ba #bj #ch #ab #e #f #abaj #bjehahhgg ,s4 ,probably a binary of long period 7#ghb years1 ,peters2 #aaei years1 ,mann74 #ef4cc ,arietis #b #cdc #bf #ce #e #h #jc #bigfahgig 4 ,a distant and easy pair in small instruments4 #eg4 ,cygni #ai #bfc #bg #dd #c #g #eea #cdcbahgig 4 ,a beautiful pair1 colours golden yellow and smalt blue4 #eh4 ,geminorum #g #chf #bh #ah #b #ad #bgdi #dcjjahggi 4 ,disc4 by ,burnham1 who also finds the companion double2 dist4 #ad 7#ahgib74 #ei4 ,capricorni #bj #aai -#ab #ec #baig #ddeeahgig 4 #a and #b ,capricorni 7,no4 #dc7 form a naked-eye double2 ,pos4 #bia1 ,dist4 #cgcd4 #fj4 ,canis ,min4 #g #ccf #e #cj #a #ad #cagc #ddfbahggi 4 ,difficult object2 just seen steadily by ,dawes with #h-a_/d-;inch refractor4 #fa4 ,lyr1 ,a4,b4 #ah #dfj #cc #ad #c #g #adhi #debjahhfi ,t4 ,there are three other faint and distant components4 #fb4 ,lyr #ah #ccb #ch #da #a #aa #aefa #dhjjahgig 4 ,good light-test for a #c-;inch4 ,there are other more distant companions4 #fc4 ,cassiopei #j #cdc #ee #ef #b #ac #bhjb #faccahgig 4 ,the #cf-;inch refractor shows a very faint comes2 ,dist4 #age 7,burnham74 #fd4 ,canis ,maj41 #f #djc -#af #cd #a #ac #aadi #gaciahgge;,hall4 ,a4,c4 ,this faint and distant companion to ,sirius was disc4 by ,marth4 #fe4 ,andromed #j #bg #bh #bi #b #aa #bgaf #gafjahghf ,g4 ,a wide double1 visible in a #c-;inch1 but comes very faint4 #ff4 ,tauri #d #bif #af #ag #a #ab #cda #aadifahgig 4 ,good light-test for a #c-;inch4 ,very faint comes ,pos4 #aji2 ,dis4 #cjd 7,burnham74 ---------------------------------------- ---------------------------------------- ---------------------------------------- ,the determination of the angles of position and distance of double stars forms a very important and extensive branch of work in connection with sidereal astronomy4 ,in cases where double stars preserve stationary places relatively to each other1 there is clearly no need for frequent re-observation4 ,but in those numerous instances where the two components form a binary system it is desirable to obtain as many measures as possible1 so as either to verify the calculated orbit or to furnish the materials for an orbit if one has not been computed before4 ,dr4 ,doberck1 whose name is well known in these researches1 mentioned1 in #ahhb1 that ample data for purposes of computation had not been secured for more than thirty or forty binaries out of between five and six hundred such systems that were probably known to exist4 ,sir ,w4 ,herschel1 in #ahjc1 estimated the period of revolution of ,geminorum as #cdb yrs4 #b mths4 and of ,virginis as #abjj yrs4 ,orbits#ea do not appear1 however1 to have been computed until #ahbg1 when ,savery of ,paris showed that the companion of ,urs ,majoris was revolving in an ellipse with a period of #eh-a_/d years4 ,the accomplished ,encke also turned his attention to this work1 and adopted a more elaborate method2 and many others have pursued the subject with very interesting and valuable results4 ,on pp4 #cjb-cje is a selected list of some of the most noteworthy double and binary stars1 arranged according to the distance between the components4 ,in compiling the above list1 ,i have used some of the latest measures available1 as most of these doubles are binary systems1 and therefore in motion1 so that a few years effect a perceptible difference in the angles of position and distance of the components4 ,some of the pairs are closing up1 others are opening1 and thus it happens that a binary star1 divided with great difficulty to-day1 may become an easy object some years hence1 and vice vers4 ,in fact1 as telescopic tests they are constantly varying4 ,before leaving this part of the subject it may be interesting to refer individually to a few brilliant examples of double stars4 ,canis ,majoris 7,sirius74 ,a red star according to ancient records1 but it is now intensely white4 ,in #ahdd ,bessel inferred from certain little irregularities in the proper motion of this star that it consisted of a binary system with a period of about half a century#eb4 ,peters confirmed this idea in #ahea1 and it was observationally verified eleven years afterwards4 ,on ,jan4 #ca1 #ahfb1 ,alvan ,clark1 jun41 while testing a new #ah-;inch refractor1 discovered a very faint companion #aj distant4 ,measures in the few subsequent years proved that the position-angle was decreasing1 while the distance showed a slight extension4 ,in #ahgb it was about #aaej1 but since then the two stars have been approaching each other1 and ,mr4 ,burnham's measures in ,april #ahij gave the distance as only #dai4 ,it is now1 therefore1 a very difficult object1 and only visible in large instruments4 ,in ,england it is never easy1 owing to its southern position1 and it has been little observed1 but it is satisfactory to note that the large refractors at ,washington1 ,princeton1 and ,chicago1 ,u4,s4,a41 have been often employed on this object in recent years4 ,mann gives a period of #eabb years for this interesting binary1 and places the time of periastron-passage as #ahijee4 ,this differs from ,gore's orbit1 quoted in the table4 ,orionis 7,rigel74 ,a favourite test-object for small instruments4 ,the companion has been seen with only #a-;inch aperture by experienced observers familiar with the object1 and accustomed to its appearance in larger telescopes4 ,the beginner may1 however1 esteem himself fortunate if he distinguishes the smaller star with #c inches of aperture4 ,when he has done this he may afterwards succeed with #b inches only1 and quite possibly with #b inches4 ,he can ascertain his ability in this direction by inserting cardboard diaphragms of the diameters referred to in the dew-cap of his telescope4 ,this object is not a binary2 the component stars are fixed relatively to each other1 and merely form an optical double4 ,the colours are pale yellow and sapphire blue4 ,burnham thought the smaller star was elongated1 as though a very close double1 but the #cf-;inch at ,mount ,hamilton has disproved the idea4 ,lyr 7,vega74 ,another well-known object1 and one upon which amateurs are constantly testing their means4 ,the companion star is extremely faint1 and small instruments would have no chance with it but for its comparatively wide distance from ,vega4 ,were it much nearer it would be obliterated in the glare4 ,this is a more difficult pair than that of ,rigel1 though certain lynx-eyed observers have glimpsed the minute star with ridiculously small apertures4 ,it is no mean feat1 however1 to discern the star with a #c-;inch telescope4 ,webb saw it more easily with a power of #hj than with #add on a #c-g_/aj-;inch4 ,there are many other stars in the same field1 though more distant than the companion alluded to4 ,with power #fj on my #aj-;inch reflector1 ,i counted eighteen stars in the field with ,vega on ,oct4 #i1 #ahhi1 though the full ,moon was shining at the time4 ,several faint stars have been alleged to exist much closer to ,vega than the well-known comes2 but these have resisted the great ,american refractors1 and it may be safely assumed that they were ghosts produced by a faulty image4 ,urs ,minoris 7,polaris74 ,this double1 from its constant visibility in northern latitudes1 from its unvarying brightness1 and from the relatively stationary positions of the stars composing it1 forms an excellent test for small instruments4 ,but it is a comparatively easy object1 and ought to be seen in a #b-;inch telescope4 ,with this aperture the primitive efforts of a young observer will probably be disappointing4 ,if possible he should first look at the pair through a #c-or #d-;inch1 and then he will know exactly what he may expect to see with inferior means4 ,a difficult object is often readily glimpsed in a small telescope after the eye has become acquainted with it in a larger one4 ,experience of this kind is very requisite1 and it is by thus educating the eye that observers are gradually enabled to reach objects which appeared hopelessly beyond them at their first attempts4 ,the companion to ,polaris1 like that of ,rigel and ,vega1 though situated in nearly the same line of sight is not physically related to the larger star1 the contiguity of the objects being accidental4 ,some dubious observations have been made of comites nearer to ,polaris than the one to which we have been adverting2 but ,burnham does not see these1 and we are forced to conclude that they have no objective existence4 ,scorpii 7,antares74 ,a fiery-red star1 with a rather close1 faint companion4 ,this object being in #bf of ,s4 declination is rarely seen with advantage in places with latitudes far north4 ,atmospheric disturbance usually affects the image in such degree that the smaller star is merged in the contortions of the larger4 ,this pair is1 however1 interesting from the circumstance that it is frequently liable to occultation by the ,moon4 ,a night on which this double star can be distinctly seen may be regarded as an exceptional one in point of definition4 ,it appears to have been discovered nearly half a century ago by ,grant and ,mitchel4 ,variable ,stars4--,a proportion of the stars exhibit fluctuations in their visible brightness4 ,in most cases1 however1 the variation is but slight1 though there are instances in which the differences are considerable4 ,the fluctuations are periodical in nature and capable of being exactly determined4 ,but the character of the variation and the period are very dissimilar in different stars4 ,some are of short period1 and their variations occupy a few days only2 others1 however1 are more gradual1 and twelve months or more may represent the complete cycle of their changes4 ,these alterations of brightness generally escape the notice of casual observers of the heavens4 ,to them the stars appear as constant in their relative magnitudes as they are in their relative positions4 ,but a close observer of the firmament1 who habitually watches and records the comparative lustre of the stars1 must soon discover numerous evidences of change4 ,he will remark certain stars which alternately grow bright and faint1 and1 in fact1 display a regular oscillation of brilliancy4 ,in the case of a pair of stars he may possibly notice that the superior lustre is emitted first by one and then by the other4 ,the observation of these variables dates from a period anterior to the invention of the telescope4 ,nearly three centuries ago ,fabricius remarked that ,ceti 7,mira7 suffered a great diminution of light2 for while it was of the #crd mag4 in ,aug4 #aeif1 it became invisible in the following autumn4 ,it was re-observed by ,holwarda in #afci1 and as he appears to have been the first to estimate its period1 some authors1 including ,argelander1 have credited him with the discovery4 ,the star has a period of about #ccac days4 ,its variations are somewhat erratic1 for at max4 it is sometimes only #dth mag41 while at others it is as bright as #bnd mag41 and its min4 are equally inconsistent4 ,persei 7,algol7 is another and perhaps the best known of all the variable stars4 ,its changes are very rapid1 for it passes through its various gradations of brilliancy in less than three days4 ,it was first noticed by ,montanari in #affi1 though it was left for ,goodricke in #aghb to ascertain its period4 ,the normal mag4 of the star is #bb1 and it only shows distinct variation during the five hours which precede and follow a minimum1 when it declines to #cg mag4 ,its period is shortening1 for in #aghb it was #b;d #bj;h #dhm #eis#d1 in #ahdb1 #b;d #dj;h #dhm #ees#b1 and at present ,chandler finds it #b;d #bj;h #dhm #eas4 ,as to the causes which contribute to these variations1 they are invested in mystery4 ,it has been conjectured that dark spots on the surfaces of the stars may1 by the effects of rotation1 introduce the observed alternations4 ,another surmise is that the temporary diminutions of lustre are to be ascribed to the interposition of dark satellites1 and this theory seems tenable in regard to stars of the ,algol type4 ,it is satisfactory to note that a large amount of systematic work is being done in this important and delicate branch of research4 ,such stars as are subject to variation have been classed as follows3--#a4 ,temporary or new stars2 #b4 ,stars having long and pretty regular variation2 #c4 ,stars irregularly variable2 #d4 ,stars varying in short periods2 #e4 ,stars of the type of ,algol1 which are liable to temporary diminutions of lustre4 ,on the preceding page is a list of the most noteworthy variable stars4 ,list of ,variable ,stars4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ---------- ,name of ,star4 ,position1 #ahij4 ,mags4 ,period4 ---------------------------------- ,r4,a4 ,dec4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ---------- h m ,cephei #j #eb4e #ha #ag #g4b #i4d #b;d #aa;h #ejm ,ceti #b #ac4h - #c #bi #b #j #cca-a_/c days ,persei #c #a4j #dj #cb #b4b #c4g #b;d #bj;h #dim ,tauri #c #edf #ab #aa #c4d #d4b #c;d #bb;h #ebm ,u ,orionis #e #dic #bj #i #f #ab ,geminorum #f #h4b #bb #cb #c4b #db #ace-aea days ,geminorum #f #eg4f #bj #dd #c4g #de #aj;d #c;h #dcm ,l#b ,puppis #g #ajb -#dd #bh #c4e #f4c #acf days ,r ,canis ,maj4 #g #ad4e -#af #aa #f4b #f4h #a;d #c;h #afm ,u ,geminorum #g #dh4f #bb #ah #i #ad #ga-abf days ,s ,cancri #h #cg4g #ai #bf #h4b #aag #i;d #aa;h #chm ,args #aj #dj4h -#ei #f #a #f #df or #fg yrs48 ,r ,hydr #ac #bc4g -#bb #dc #d #aj #dcf days ,libr #ad #ee4a -#h #e #d4i #fa #b;d #g;h #eam ,u ,coron #ae #ac4g #cb #c #g4f #hh #c;d #aj;h #eam ,herculis #ag #i4f #ad #ca #c4a #c4i #hh;d #ab;h 7irreg47 ,u ,ophiuchi #ag #aa4j #a #bj #f #f4g #j;d #bj;h #hm ,lyr #ah #df4j #cc #ad #c4e #d4e #ab;d #ba;h #dgm ,cygni #ai #dfc #cb #ch #d-f4e #ac #djf days ,aquil #ai #df4i #j #dd #c4f #d4g #g;d #d;h #adm ,y ,cygni #bj #dg4g #cd #ae #g4a #g4i #a;d #aa;h #egm ,cephei #ba #dj4a #eh #af #c4f #dh #dcb days8 ,cephei #bb #be4a #eg #ea #c4g #d4h #e;d #h;h #dhm ---------------------------------------- ---------------------------------------- ---------------------------------------- ---------- ---------------------------------------- ------------------------- ,name of ,star4 ,observer4 ---------------------------------------- ------------------------- ,cephei ,ceraski1 #ahhj4 ,ceti ,fabricius1 #aeif4 ,persei ,montanari1 #affi4 ,tauri ,baxendell1 #ahdh4 ,u ,orionis ,gore1 #ahhe4 ,geminorum ,schmidt1 #ahfe4 ,geminorum ,schmidt1 #ahdg4 ,l#b ,puppis ,gould1 #ahgb4 ,r ,canis ,maj4 ,sawyer1 #ahhg4 ,u ,geminorum ,hind1 #ahee4 ,s ,cancri ,hind1 #ahdh4 ,args ,burchell1 #ahbg4 ,r ,hydr ,maraldi1 #agjd4 ,libr ,schmidt1 #ahei4 ,u ,coron ,winnecke1 #ahfi4 ,herculis ,w4 ,herschel1 #agie4 ,u ,ophiuchi ,sawyer1 #ahha4 ,lyr ,goodricke1 #aghd4 ,cygni ,kirch1 #afhf4 ,aquil ,pigott1 #aghd4 ,y ,cygni ,chandler1 #ahhf4 ,cephei ,hind1 #ahdh4 ,cephei ,goodricke1 #aghd4 ---------------------------------------- ------------------------- ,new or ,temporary ,stars4--,these stars 7sometimes classed with variable stars7 furnish us with rare instances of vast physical changes occurring among sidereal objects1 usually so steadfast and endurable4 ,the alternating lustre of certain variable stars represents phenomena of regular recurrence1 and is probably to be explained by simple causes2 but the sudden outbursts and rapid decline of temporary stars are facts of a more startling character1 and need a more exceptional explanation4 ,the first of these objects recorded in history appears to have been seen in ,scorpio #acd years before the ,christian era1 and it suggested to ,hipparchus of ,rhodes the idea of forming a catalogue of stars1 so that in future ages observers might have the means of recognizing new stars or any other changes in the configuration of the heavens4 ,hipparchus completed his catalogue in #abh ,b4,c42 it contained #ajbe stars1 and forms one of the most valuable memorials we possess of the labours of the ancient astronomers4 ,another temporary star is said to have appeared in #acj ,a4,d41 but this and several other objects of presumably similar character noticed in later years may just possibly have been comets1 and considerable doubt hangs over the descriptions4 ,it will therefore be safest to confine our remarks to more modern and better attested instances of these phenomena#ec3-- #aegb1 ,november #aa4--,the famous star of ,tycho ,brahe4 ,he thus described his first view of it3--8,one evening when ,i was considering1 as usual1 the celestial vault1 the aspect of which is so familiar to me1 ,i perceived with indescribable astonishment a bright star of extraordinary magnitude near the zenith in the constellation of ,cassiopeia40 ,he adds3--8,the new star was destitute of a tail1 or of any appearance of nebulosity2 it resembled the other stars in all respects1 only that it twinkled even more than stars of the first magnitude4 ,in brightness it surpassed ,sirius1 ,lyr1 or ,jupiter4 ,it could be compared in this respect only to ,venus when she is nearest the earth 7when a fourth part of her illuminated surface is turned towards us74 ,persons who were gifted with good sight could distinguish the star in the daytime1 even at noon1 when the sky was clear40 ,this brilliant ,,nova began to fade early in ,dec4 #aegb1 and in ,april and ,may #aegc it resembled a star of the #bnd mag41 in ,july and ,aug4 one of the #crd mag41 and in ,oct4 and ,nov4 one of the #dth mag4 ,in ,march #aegd the star completely disappeared 7to the naked eye71 after a visibility of about #ag months4 ,it exhibited some curious variations of colour4 ,it was white when most brilliant2 it then became yellow1 and afterwards red1 so that its hue in the early part of #aegc was similar to that of ,mars4 ,but in ,may it again became white1 and continued so until it ceased to be visible4 ,the position of this star 7for #ahij7 is ,r4,a4 #j;h #ahm #das1 ,dec4 #fc #cbb4 ,it was supposed to be a reapparition of the brilliant stars which shone between ,cepheus and ,cassiopeia in #ide and #abfd1 and to have possibly been associated with the 8,star of ,bethlehem20 but there is no reliable evidence on which this view can be supported1 as the alleged 8stars0 of #ide and #abfd were undoubtedly comets1 misdescribed in old records4 ,cornelius ,gemma is reputed to have seen the celebrated star of #aegb a few days before ,tycho ,brahe1 viz41 on ,november #h1 #aegb4 #afjd1 ,october #aj4--;,discovered by ,brunowski1 who announced it to ,kepler4 ,it was brighter than a star of the #ast mag41 also than ,mars1 ,jupiter1 or ,saturn1 which were not far distant at the time4 ,it did not begin to fade immediately2 for a month after its discovery it was still brighter than ,jupiter1 and of a white lustre4 ,at the middle of ,november it surpassed ,antares1 but was inferior to ,arcturus4 ,in ,april #afje it had fallen to the #crd mag41 and went on decreasing until in ,october it could scarcely be seen with the naked eye owing to the twilight resulting from its proximity to the ,sun4 ,in ,march #afjf it was invisible4 ,the position of this object was about midway between and #eh ,ophiuchi1 or at ,r4,a4 #ag;h #bdm1 ,dec4-#ba #bjg 7#ahij74 #afgj1 ,june #bj4--;,discovered by the ,carthusian ,monk ,anthelme in ,r4,a4 #ai;h #dcm #cs1 ,dec4 #bg #c 7#ahij71 a few degrees east of ,cygni4 ,it was of the #crd mag41 and continued in view1 with constantly fluctuating brightness1 for nearly two years4 ,at the end of ,march #afgb it was #fth mag41 and has never reappeared4 ,hind found a small1 hazy1 and ill-defined star in the same place1 but this is probably not the same as ,anthelme's star of #afgj4 #ahdh1 ,april #bh4--;,during the long interval of #agh years separating #afgj from #ahdh not a single new star appears to have revealed itself4 ,observers had multiplied1 astronomical instruments had been much improved1 star-catalogues were plentiful1 and yet the sidereal heavens gave no intimation of a stellar outburst4 ,no better proof than this could be afforded as to the great rarity of temporary stars4 ,at length1 in the spring of #ahdh1 the spell was broken1 and ,mr4 ,hind announced that a new star of a reddish-yellow colour had appeared in ,ophiuchus1 ,r4,a4 #af;h #ecm #bjs1 ,dec4-#ab #dc 7#ahij74 ,he expressed himself as certain that no star brighter than the #ith mag4 had been there previous to ,april #e4 ,after rising to the #dth mag4 it soon faded1 and in #ahea could only be observed in large instruments4 ,in #ahge it was still visible as a very minute star4 #ahfj1 ,may #ba4--,m4 ,auwers1 of ,konigsberg1 noticed a star of the #gth mag4 near the centre of the bright resolvable nebula 7,m4 #hj71 lying between and ,scorpii1 ,r4,a4 #af;h #ajm #bis1 ,dec4-#bb #db 7#ahij74 ,on ,may #ah the star was not there1 and it disappeared altogether in three weeks4 ,it was independently seen by ,pogson on ,may #bh1 and to him it seemed that 8the nebula had been replaced by a star1 so entirely were its dim rays overpowered by the concentrated blaze in their midst40 #ahff1 ,may #ab4--;,discovered by ,birmingham at ,tuam4 ,it was of the #bnd mag41 and situated in ,corona1 ,r4,a4 #ae;h #edm #eds1 ,dec4 #bf #ad 7#ahij74 ,the outburst must have been very sudden1 as ,schmidt1 at ,athens1 was observing this region three hours before the new star was detected1 and is certain it was then fainter than the #dth mag4 ,the star was found to be identical with one on ,argelander's charts estimated as #i mag4 ,it faded from the #bnd to the #fth mag4 by ,may #bj1 and was thereafter invisible to the naked eye4 #ahgf1 ,nov4 #bd4--;,a yellow star of the #crd mag4 was seen by the ever vigilant ,schmidt at ,athens near ,cygni1 and where no such star existed on ,nov4 #bj4 ,the position of the object was ,r4,a4 #ba;h #cgm #bcs1 ,dec4 #db #bj 7#ahij74 ,it soon grew fainter1 so that on ,dec4 #ac it was of the #fth mag4 and devoid of colour4 ,in the spectroscope it presented much the same lines as ,birmingham's star of ,may #ahff4 ,in addition to the continuous spectrum it showed bright lines of hydrogen4 #ahhe1 ,august #ca4--;,dr4 ,hartwig announced the appearance of a star-like nucleus in the great nebula 7,m4 #ca7 of ,andromeda1 ,r4,a4 #j;h #cfm #dcs1 ,dec4 #dj #dj 7#ahij74 ,other observers soon corroborated the discovery4 ,the star appears to have been first seen on ,aug4 #ai2 it was not visible on the preceding night4 ,on ,sept4 #a its mag4 was #fe1 on ,sept4 #b1 #gc1 on ,sept4 #c1 #gb1 ,sept4 #d1 #hj1 ,sept4 #ah1 #ib1 c4 ,on ,feb4 #g1 #ahhf1 it had dwindled down to the #afth mag41 according to an estimate made by ,prof4 ,hall with the great ,washington refractor4 ,the spectrum was continuous1 and ,proctor and ,gore considered 8that the evidence of the spectroscope showed that the new star was situated in the nebula40 ,the phenomena presented by the temporary stars alluded to are so different to those of ordinary variables that it is very questionable whether they ought to be classed together4 ,our knowledge of the former would no doubt progress more rapidly were they specially looked for and more instances discovered4 ,those who have acquired a familiar acquaintance with the naked-eye stars should examine them as often as possible with this end in view4 ,some of these objects lose light so quickly that unless they are caught near the maximum they are likely to escape altogether1 and this shows the necessity of being constantly on the alert for their appearance4 ,i have frequently1 while watching for meteors1 reviewed the different constellations in the hope of picking up a new object1 but have never succeeded in doing so4 ,star ,colours form another interesting department of sidereal astronomy4 ,it is obviously desirable to record the hues presented1 not only by double stars and binary systems1 but by isolated stars also1 as changes of tint have been strongly suspected4 ,cicero1 ,seneca1 ,ptolemy1 and others speak of ,sirius as a red star1 whereas it is now an intense white2 and if we rely on ancient descriptions similar changes appear to have affected some other prominent stars4 ,but the old records cannot be implicitly trusted1 owing to the errors of transcribers and translators2 and ,mr4 ,lynn 7#8,observatory'1 vol4 ix4 p4 #ajd7 quotes facts tending to disprove the idea that ,sirius was formerly a red star4 ,in the majority of cases double stars are of the same colour1 but there are many pairs in which the complementary colours are very decided4 ,chambers remarks that the brighter star is usually of a ruddy or orange hue1 and the smaller one blue or green4 8,single stars of a fiery red or deep orange are not uncommon1 but isolated blue or green stars are very rare4 ,amongst conspicuous stars ,libr 7green7 appears to be the only instance40 ,as an example of fiery-red stars ,antares may be mentioned2 ,aldebaran is deep reddish orange1 and ,betelgeuse reddish orange4 ,amongst the more prominent stars ,capella1 ,rigel1 and ,procyon may be mentioned as showing a bluish tinge1 ,altair and ,vega are greenish1 ,arcturus is yellow1 while ,sirius1 ,deneb1 ,polaris1 ,fomalhaut1 and ,regulus are white4 ,mr4 ,birmingham published a catalogue of 8,the ,red ,stars0 in the #8,transactions of the ,royal ,irish ,academy'1 for ,august #ahgg1 and ,mr4 ,chambers has a working-catalogue of #gai such objects in the #8,monthly ,notices1' vol4 xlvii4 pp4 #cdh-chg4 ,the region of ,cygnus appears to be especially prolific in red stars1 and many of these objects are variable4 ,in a paper read at a recent meeting of the ,astronomical ,society of the ,pacific ,mr4 ,pierson stated that in binary systems where the stars are of equal magnitude the colours are invariably the same1 while those differing in magnitude differ also in colour and the larger star is always nearer the red end of the spectrum than its secondary4 ,in the estimation of star-colours reflecting-telescopes are very reliable owing to their perfect achromatism4 ,groups of ,stars4--,great dissimilarity is apparent in the clustering of stars4 ,the heavens furnish us with all gradations--from the loose1 open groups like that in ,coma ,berenices1 in the ,pleiades1 or in ,prsepe1 to the compact globular clusters1 in which some thousands of stars are so densely congregated that considerable optical power is required to disintegrate them4 ,some1 it is true1 yield more easily than others4 ,the great cluster 7,messier #ac7 in ,hercules readily displays the swarms of stars of which it is composed2 but others are so difficult that it is only in the largest instruments they are resolved into star-dust4 ,further references to these wonderful objects will be made in the next chapter1 and some of the principal examples described2 our purpose here is to allude to a few of the more scattered groups1 and to some noteworthy instances of multiple stars4 ,coma ,berenices4 ,a naked-eye cluster1 consisting of many stars1 chiefly from the #eth to #fth mags4 ,a telescope adds a number of smaller stars4 ,nebul may be often swept up hereabouts1 as it is not far north of the rich nebulous region of ,virgo4 ,the ,pleiades4 ,six stars are usually distinguished by the naked eye1 and a seventh is occasionally remarked4 ,mstlin 7the instructor of ,kepler7 counted fourteen1 ,miss ,airy has drawn twelve1 and ,carrington1 like ,mstlin1 saw fourteen4 ,in #ahgg ,i distinctly made out fourteen stars in this group4 ,the telescope reveals a considerable number of small stars and ,tempel's large nebula near ,merope4 ,kepler saw thirty-two stars with a telescope1 and ,hooke seventy-eight2 but ,wolf1 at ,paris1 after three years of unremitting labour with a #d-;foot reflector1 catalogued #fga stars in the group4 ,a photograph1 however1 with a #ab-;inch refractor showed #adba stars2 and a more recent negative includes no less than #bcbf4 ,there is an interesting little triangle close to the brightest star1 ,alcyone2 and several of the leading stars are involved in nebulosity1 discovered by means of photography4 ,prsepe4 ,a fine group of small stars1 divisible by the unaided eye on a clear night4 ,chambers says the components are not visible without a telescope2 while ,webb notes that the group is just resolvable by the naked eye4 ,thirty-six stars were glimpsed with ,galilei's telescope2 but modern instruments show many more4 ,marth1 using ,lassell's #d-;foot reflector at ,malta1 discovered several faint nebul and nebulous stars in this cluster4 ,persei4 ,perceptible to the eye as a patch of hazy material lying between the constellations ,cassiopeia and ,persei4 ,in a telescope it forms a double cluster1 and is one of the richest and most beautiful objects that the sky affords4 ,the tyro who first beholds it is astonished at the marvellous profusion of stars4 ,it can be fairly well seen in a good field-glass1 but its chief beauties only come out in a telescope1 and the larger the aperture the more striking will they appear4 ,it is on groups of this character that the advantage of large instruments is fully realized4 ,the power should be very low1 so that the whole of the two clusters may be seen in the field4 ,an eyepiece of #dj1 field #fe1 on my #aj-;inch reflector1 presents this object in its most imposing form4 ,crucis4 ,sir ,j4 ,herschel's observations at the ,cape have made this object familiar to northern observers4 ,it is composed of more than #ajj stars1 from the #gth mag4 downwards2 and some of the brighter ones are highly coloured1 so that the general effect is greatly enhanced and fully justifies ,herschel's statement that the group may be likened to 8a superb piece of fancy jewelry40 ,urs ,majoris 7,mizar74 ,this group is interesting both as a naked-eye and as a telescopic object4 ,there is a #eth mag4 star1 named ,alcor1 about #aa distant from ,mizar1 and the former was considered a good test-object for unaided vision by the ,arabian astronomers4 ,but the star has probably brightened2 for it can now be easily seen1 and certainly offers no criterion of good vision4 ,mizar is a fine telescopic double1 the companion being #dth mag4 and distant #ad4 ,any small telescope will show it1 and there is another #hth mag4 star very near4 ,orionis4 ,this appears as a double-quadruple star1 with several others in the same field4 ,a #c-;inch will reveal most of them1 though some of the fainter stars in the group will be beyond its reach4 ,orionis4 ,in the midst of the great nebula of ,orion there is a tolerably conspicuous quadruple star1 the components of which form a trapezium4 ,this is visible in a #b-;inch refractor4 ,in #ahbf ,struve discovered a fifth star1 and in #ahcj ,sir ,j4 ,herschel found a sixth2 these were both situated a little outside the trapezium4 ,all these stars have been seen in a #c-;inch telescope4 ,the great #cf-;inch equatoreal at ,mount ,hamilton has added several others2 one was detected by ,alvan ,g4 ,clark 7the maker of the object-glass7 and another by ,barnard4 ,these were excessively minute1 and placed within the trapezium4 ,barnard#ed has also glimpsed an extremely minute double star exterior to the trapezium1 and forming a triangle with the stars ,a and ,c on the following diagram3-- ,illustration3 ,fig4 #fc4 ,the ,trapezium in ,orion1 as seen with the #cf-;inch refractor4 ,several observers1 including ,huggins1 ,salter1 and others1 had previously drawn faint stars in the interior of the trapezium2 but these could not be seen by ,hall and ,burnham in the large refractors at ,washington and ,chicago1 and were thus proved to have no real existence4 ,the new stars observed in the #cf-;inch telescope are only just within the limits of its capacity1 and therefore cannot be identical with stars alleged to have been previously seen in small instruments4 ,the fifth and sixth stars in the trapezium have been supposed to be variable1 and not without reason2 possibly the others are equally liable to change1 but this is only conjecture4 ,sir ,j4 ,herschel says that to perceive the fifth and sixth stars 8is one of the severest tests that can be applied to a telescope0 7#8,outlines1' #aath edit4 p4 #faj72 yet ,burnham saw them both readily in a #f-;inch a few minutes before sunrise on ,mount ,hamilton in ,september #ahgi4 and ,lyr also form multiple groups1 which will well repay observation either with large or small telescopes4 ,further ,observations4--,anyone who attempts to indicate with tolerable fulness the methods and requirements of observation in the stellar department of astronomy will find a heavy task lies before him2 and it is one to which he will be unable to do justice in a small space1 owing to the variety of matters to be referred to and the necessity of being particular in regard to each one4 ,in what follows ,i shall merely make very brief allusions1 as it is hoped the description already given of past work will be a sufficient guide for the future4 ,moreover1 those who take up a special branch of inquiry will hardly rest content with the meagre information usually conveyed in a general work on astronomy1 but will consult those authorities who deal more exclusively with that branch4 ,double and binary stars may be said to form one department1 variable and temporary stars another1 the colours of stars a third1 while many others may be signified--such as the determination of star-magnitudes1 positions1 grouping1 and distances2 also the proper motions and number of stars1 besides photographic and spectroscopic work1--each and all of which comprise a field of useful and extensive inquiry4 ,the amateur will of course choose his own sphere of labour1 consistently with his inclination and the character of his appliances4 ,in connection with double stars1 valuable work yet remains to be done1 though the ,herschels and the ,struves gathered in the bulk of the harvest and ,burnham has gleaned much that was left4 ,with regard to bright stars1 it may be assumed that very few1 if any1 close companions1 visible in moderately small glasses1 now await discovery1 unless1 indeed1 in cases where the star forms part of a binary system of long period1 and the epoch of periastron has fallen in recent years4 ,but with telescopic stars there must be many interesting doubles1 some of them binaries1 still unknown4 ,these should be swept up and submitted to measurement4 ,a great desideratum in this branch is a new general catalogue of double stars2 for such a work would greatly facilitate reference1 and save the trouble of searching through different lists in order to identify an object4 ,burnham has given some practical hints on double-star work in the #8,sidereal ,messenger1' and his remarks are reproduced in that excellent work #8,astronomy for ,amateurs4' ,as to variable stars1 some of these permit of naked-eye estimation1 others need a field-glass1 and there are some which require to be followed in a good telescope4 ,the observer who enters this department may either desire to find new objects or to obtain further data with regard to old ones4 ,if the former1 he cannot do better than watch some of the suspected variables in ,gore's ,catalogue of #gcf objects1 published by the ,royal ,irish ,academy4 ,whether suspected or known variables are put under surveillance1 the plan of comparison will be the same4 ,several stars near the variable in position1 and nearly equal in light1 should be compared with it1 and the differences in lustre1 in tenths of a magnitude1 recorded as frequently as possible4 ,the extent and period of the variation will become manifest by a discussion of the results4 ,the comparison-stars should of course be constant in light1 and1 if naked-eye stars1 they may be selected from the ,uranometria ,nova ,oxoniensis or #8,harvard ,photometry4' ,if telescopic stars are required1 then recourse must be had to comprehensive charts such as ,argelander's ,durchmusterung1 which includes stars up to #i mag4 ,variable stars of the ,algol type are especially likely to escape recognition1 as they retain a normal brilliancy except during the few hours near the time of a minimum4 ,as to star-colours1 it must be admitted that our knowledge is in an unsatisfactory condition4 ,the results of past observation show discordances which are difficult to account for4 ,when1 however1 all the circumstances are considered1 we need feel no surprise at this want of unanimity4 ,in certain cases it is probable that actual and periodical changes occur in the colours of stars1 though absolute proof is still required4 ,atmospheric variations unquestionably affect the tints of stars1 and some alterations depend upon altitude1 for a celestial object seen through the dense lower air-strata near the horizon will hardly preserve the same apparent hues when on the meridian4 ,telescopes are also liable to induce false impressions of colour1 and especially by the employment of different eyepieces not equally achromatic4 ,and the observer's judgment is sometimes at fault through physiological influences1 or he may have a systematic preference for certain hues which little impress another observer4 ,those engaged in this branch feel the want of a reliable and ready means of comparison1 and several have been tried2 but there are objections to their use1 and it seems that the best objects are furnished by the stars themselves4 ,let the observer study the colours of well-known stars1 and familiarize his eye with the distinctions in various cases 7also with the differences due to meteorological effects c472 he will then gradually acquire confidence1 and may use these objects as standards4 ,the difficulty will be that they cannot be directly compared1 in the same field1 with other stars2 but relative differences may be noted by turning the telescope from one object to the other4 ,this will be better than forming estimates on the basis of an artificial method1 which will sure to be troublesome to arrange1 and probably erroneous in practice4 ,in some stars the colour is so curious as to be attributed with difficulty1 and with regard to faint stars colour-estimates are often unreliable2 so that it is not desirable to go below the #ith mag4 unless a very large instrument is employed4 ,the necessity of being constantly on the look-out for temporary stars has been already mentioned4 ,there is also the need for further observations of such of these objects as still exist4 ,they are1 however1 very minute1 and the observer will have to be careful as to their identity4 ,though no great revival in brilliancy is to be expected1 these objects exhibited some singular fluctuations during their decline1 and it is important to keep them under view as long as possible4 ,many other departments of sidereal work are best left to the professional astronomer4 ,the derivation of accurate star-places1 proper motions1 distances1 c4 requires instruments of great refinement and trained hands to use them4 ,researches such as these do not come within the scope of ordinary amateurs4 ,but a vast field is open to them in respect to double and variable stars2 and the physical relations of many of the former greatly intensify the interest in this branch1 and make it necessary to secure frequent observations4 ,,footnotes3 #dg ,there are several forms of this instrument3 for particulars of construction and use the reader is referred to ,thornthwaite's #8,hints on ,telescopes1' and ,chambers's #8,astronomy1' #dth ed4 vol4 ii4 #dh ,mr4 ,george ,knott1 of ,cuckfield1 mentions that the radius of the first bright diffraction-ring of a stellar image1 for a #g-a_/c-;inch aperture1 is #aja1 and for one of #b inches #cgj 7#8,observatory1' vol4 vi4 p4 #ai2 see also vol4 i4 pp4 #ajg and #ade74 ,mr4 ,dawes is quoted as giving #abe for a #g-;inch1 #afa for a #e-;inch1 and #ceg for a #bd-;inch4 ,these figures exceed the theoretical values1 if the latter are adopted from ,sir ,g4 ,b4 ,airy's #8,undulatory ,theory of ,optics1' where1 for mean rays1 we have3-- ,radius of object-glass in inches radius of bright ring in seconds #cgj4 #di ,the number visible to different persons varies according to eyesight4 ,some observers see thirteen or fourteen stars in the ,pleiades1 while others cannot discern more than six or seven4 #ej ,about #b seconds4 ,sir ,w4 ,herschel found the diameter of ,lyr with a power of #fdej to be #jceec4 ,tycho ,brahe1 before the invention of telescopes1 estimated the diameter of ,sirius as #abj4 ,j4 ,d4 ,cassini1 with a telescope #ce feet long1 found the diameter of the same star #e4 #ea ,dr4 ,doberck gives some valuable information with reference to the computation of binary star-orbits in #8,the ,observatory1' vol4 ii4 pp4 #aaj and #adj4 #eb ,the star ,canis ,minoris 7,procyon7 was also inferred to be a binary and to have a similar period4 ,several close companions appear to have been discovered 7,ast4 ,nach4 no4 #bjhj74 ,but ,prof4 ,hall1 using the #beh-;inch refractor at ,washington1 says3--8,i have never been able to see any of these companions that would stand the test of sliding and changing the eyepiece1 turning the micrometer1 c41 and am therefore doubtful of their existence4 ,this is an interesting star for the powerful telescopes of the future40 ,it has been surmised that the companion is a non-luminous one1 and therefore invisible4 #ec ,it is remarkable that nearly all the temporary stars have appeared in the region of the ,milky ,way4 #ed ,this expert comet-finder would appear to have more acute1 sensitive vision on faint stars than ,burnham 7see #8,monthly ,notices'1 vol4 xlix4 p4 #ced74 ,,chapter ,,xvii4 ,,nebul ,,and ,,clusters ,,of ,,stars4 ,distinction4--,large number of ,nebul and ,clusters visible4--,varieties of form and grouping4--,distribution4--,early ,observations4--,variable ,nebul4--,nebulous ,stars4--,the ,magellanic ,clouds4--,double ,nebul4--,real dimensions of ,nebul and ,clusters4--,round ,nebul and ,clusters4--,description of ,objects4--,further ,observations required4--,lists of selected ,objects4 ,distinction4--,these objects1 though classed together in catalogues1 offer some great distinctions which the observer will not be long in recognizing4 ,it was thought at one period that all nebul were resolvable into stars#ee1 and that their nebulous aspect was merely due to the confused light of remote star-clusters4 ,but modern telescopes1 backed up by the unequivocal testimony of the spectroscope1 have shown that purely nebulous matter really exists in space4 ,the largest instruments cannot resolve it into stars1 and it yields a gaseous spectrum4 ,the conjecture has been thrown out that it may be considered as the unformed material of which suns and planets are made4 ,large ,number visible4--,d',arrest once said that nebul are so numerous as to be infinite1 and his opinion is supported by the rapid increase in the number known4 ,let us make a comparison4 ,messier inserted in the ,connaissances des ,temps for #aghc and #aghd 7published in #agha7 a catalogue containing #ajc nebul and star-clusters4 ,of these #fh were new4 ,in #ahhh a new edition of ,sir ,j4 ,herschel's catalogue of #ahfd 7revised and extended by ,dreyer7 was printed by the ,royal ,astronomical ,society1 and this includes #ghdj objects6#ef ,the labours of the ,herschels1 of ,lord ,rosse1 ,d',arrest1 ,marth1 ,tempel1 ,stephan1 and ,swift have vastly augmented our knowledge in this branch since the time of ,messier4 ,varieties of ,form and ,grouping4--,a telescope reveals all grades of condensation in stellar groups4 ,some consist of rather bright1 scattered stars1 and are easily resolved4 ,others contain more stars1 but they are smaller1 and greater power is required to show them4 ,others again are condensed into globular clusters needing high powers and good instruments to disconnect the mass of stars composing them4 ,some are faint1 and the stars so minute that they are only to be distinguished from nebul in the finest telescopes4 ,as to the nebul properly so called1 they exist in all forms4 ,they may be either round1 elliptical1 or in the form of a streak4 ,some are highly condensed in their centres1 others present well-defined circular disks like planets1 and a small proportion are in the form of rings#eg4 ,many peculiarities of detail have been remarked1 and a curious and complicated spiral structure has been discovered in certain prominent nebul4 ,one of these has been termed the 8,whirlpool0 ,nebula from its singular convolution of form4 ,other objects have received distinctive appellations agreeably to their appearance4 ,thus1 there is the 8,dumb-bell0 ,nebula1 the 8,crab0 ,nebula1 the 8,horseshoe0 ,nebula1 c4 ,lord ,rosse's #f-;foot reflector is in a large degree responsible for the particular knowledge we possess of many of these objects4 ,the large mirror commands a grasp of light which renders it very effective on forms of this character4 ,an instrument of small diameter is quite inadequate to deal with them4 ,they can be seen1 it is true1 and the general shape recognized in the most conspicuous examples1 but their details of structure are reserved for the greater capacity of large apertures4 ,distribution4--,with regard to distribution these objects exhibit the utmost irregularity1 for in certain regions of the heavens they are found to be very plentiful1 while in others they are singularly rare4 ,thus1 in ,virgo1 ,coma ,berenices1 ,leo1 and ,ursa ,major large numbers of nebul abound1 while in ,hercules1 ,draco1 ,cepheus1 ,perseus1 ,taurus1 ,auriga1 c41 very few are encountered4 ,taking the #ghdj objects in the ,new ,general ,catalogue of #ahhh it will be found that their distribution in hours of ,right ,ascension is as follows3-- ,r4,a4 ,nebul4 #j ,h4 #chg ,i #dbh ,,ii #cih ,,iii #cjj ,,iv #bgf ,v #cge ,,vi #aga ,,vii #aif ,,viii #bcj ,,ix #cfb ,x #djd ,,xi #ehe ,,xii #heh ,,xiii #ejd ,,xiv #cge ,,xv #bab ,,xvi #bcj ,,xvii #bei ,,xviii #bjc ,,xix #aag ,,xx #aec ,,xxi #ahh ,,xxii #bge ,,xxiii #ced ,the maximum is therefore reached at ,,xii hours1 while the minimum is shown at ,,xix h4 ,there is a secondary max4 at ,i h41 and a secondary min4 at ,,vi h4 ,early ,observations4--,the nebula in ,andromeda appears to have been the one first discovered1 for the distinguished ,persian astronomer ,al-,sfi 7who died in #ihf ,a4,d47 was undoubtedly acquainted with it4 ,the nebula is figured upon a ,dutch map of the stars nearly #djj years old4 ,in #afab ,simon ,marius redetected this object1 and appropriately likened its appearance to that of a 8candle shining through a piece of horn40 ,in #afah the nebula in ,orion was certainly known1 for ,cysatus of ,lucerne compared it with the head of the fine comet visible in ,december of that year4 ,huygens alighted upon the same object in #afef1 and appears to have been unconscious of its prior discovery4 ,only six 8nebul or lucid spots0 were known in #agaf1 and enumerated by ,halley in the #8,phil4 ,trans4' vol4 xxix4 ,these included those of ,andromeda and ,orion4 ,a third was situated in the space between the bow and head of ,sagittarius4 ,this is ,m4 #bb1 and consists of a bright globular cluster of ,stars4 ,the fourth was the fine star-group involving ,centauri1 which ,halley himself found in #afgg4 ,the fifth was another fine group in the right foot of ,antinous4 ,this is ,m4 #aa1 and was discovered by ,kirch in #afha4 ,the sixth was the magnificent globular cluster 7,m4 #ac7 in ,hercules1 discovered by ,halley in #agad4 ,in #agce the ,rev4 ,w4 ,derham published a list of #af of these objects1 and in #agfa ,lacaille summarized #db nebul and star-clusters which he had observed in the southern sky4 ,this was followed by ,messier's tables of #de nebul c4 in #agga1 and of #ajc in #aghaeh4 ,but these contributions1 important though they severally were1 sunk into insignificance beside the splendid results obtained by ,sir ,w4 ,herschel1 who during his prolonged and systematic sweeps of the heavens picked up no less than #bejj new nebul and clusters which he formed into three catalogues printed in the #8,phil4 ,trans4' as follows3--#aghf1 #ajjj objects1 #aghi1 #ajjj ditto1 #ahjb1 #ejj ditto4 ,variable ,nebul4--,it is in the highest degree probable that changes occur in the physical appearances of certain nebul1 though the opinion is not perhaps supported by a sufficient number of instances4 ,until ,sir ,w4 ,herschel began his review of the heavens very few nebul were known1 and the information possessed about them was very incomplete4 ,the early records1 obtained with small and inferior telescopes1 scarcely admit of comparison with recent observations1 for in matters of detail little agreement will be found2 and this proceeds certainly not so much from real changes in the objects as from differences due to the variety of instruments employed1 to atmospheric vagaries1 and to 8personal equation40 ,bullialdus and ,kirch in #affg and #afgf and ,le ,gentil in #agei supposed that remarkable changes were operating in the great elliptical nebula of ,andromeda4 ,but ,g4 ,p4 ,bond fully investigated the evidence1 and concluded that the variability of the object was by no means proved4 ,some observers have represented the nucleus as stellar1 while others have drawn it as a gradual condensation1 and ,dr4 ,copeland has shown that different magnifying powers alter the aspect of the nucleus1 8the lower powers making it more star-like1 the higher ones more soft-looking and extensive40 ,mairan and others entertained the view that the large irregular nebula in ,orion was subject to change4 ,this object received much attention from ,sir ,w4 ,herschel1 and he concluded that it underwent great alteration between #aggd and #ahaa4 ,d',arrest1 from his own researches and a discussion of other results1 expressed himself in #ahgb that 8the observed changes in this vast mass of gas seem exclusively to turn out to be temporary fluctuations of brightness40 ,prof4 ,holden has arrived at a similar conclusion1 and says3--8,the figure of the nebula has remained the same from #ageh till now 7if we except a change in its apex about #aggj1 which seems quite possible72 but in the brightness of its parts undoubted variations have taken place1 and such changes are still going on0#ei 7#8,monograph of the ,nebula in ,orion1' p4 #bbe74 ,hind discovered a faint nebula1 with a diameter of about #a1 on ,oct4 #aa1 #aheb4 ,it was situated in ,taurus1 the position being ,r4,a4 #d;h #aem #ccs1 ,dec4 #ai #aef 7for #ahij71 or about #b ,w4 of the star ,tauri 7mag4 #cg74 ,d',arrest1 on ,oct4 #c1 #ahfa1 searched for this object1 but found it had quite disappeared6 ,a small round nebula was seen in #ahfh1 about #d preceding ,hind's1 but this resisted some later attempts at observation4 ,in ,oct4 #ahij1 ,burnham and ,barnard1 with the #cf-;inch refractor of the ,lick ,observatory1 saw two nebul here1 one a very small1 condensed nebula1 with a stellar nucleus1 and the other an exceedingly faint nebulosity about #de in diameter 7see #8,monthly ,notices1' vol4 li4 pp4 #id1 #ie74 ,the nebula surrounding the star ,args has been suspected of variation1 particularly by ,abbott1 of ,hobart ,town1 ,tasmania4 ,vols4 xxv41 xxx41 and xxxi4 of the #8,monthly ,notices' contain many references to1 and figures of1 this interesting object4 ,but the alleged changes have not been substantiated1 and there seems no reason to doubt that they were purely imaginary4 ,the trifid nebula in ,sagittarius 7,m4 #bj7 is supposed by ,prof4 ,holden to have altered its position with reference to a triple star now situated in the ,s4 following part of the nebula4 ,sir ,j4 ,herschel1 more than half a century ago1 had described this star as placed in the middle of the vacuity by which the nebula is divided4 ,dreyer1 however1 points out that the drawings of this object differ in many details1 and that1 though changes of brightness may have taken place1 it is difficult to understand that the nebula should move so as to envelop the star in about #ahce1 8after which no sensible change occurred again1 so far as published observations go40 ,the nebula 7,m4 #ag7 just ,n4 of the bow of ,sagittarius was also inferred by ,holden to have shifted its place relatively to the small stars figured by ,lassell in this object2 but ,dreyer adduces facts which controvert this assumption4 7,see #8,monthly ,notices1' vol4 xlvii4 pp4 #dab-dbj1 where much valuable information will be found as to supposed variable nebul47 ,on ,oct4 #ai1 #ahei1 ,tempel discovered a faint1 large nebulosity attached to the star ,merope1 one of the ,pleiades1 and at first mistook it for a diffused comet4 ,its position is ,r4,a4 #c;h #cim#f1 ,dec4 #bc #bf 7#ahij74 ,an impression soon gained ground that this object was variable2 for while ,schmidt1 ,chacornac1 ,peters1 and others saw it with small instruments1 it could not be discerned by ,d',arrest and ,schjellerup with the large refractor at ,copenhagen4 ,swift saw the nebula easily in #ahgd with a #d-;inch refractor1 and has observed it with the aperture contracted to #b inches4 ,backhouse re-observed it in #ahhb with a #d-a_/d-;inch refractor4 ,yet in ,march #ahha ,hough and ,burnham sent a paper to the ,royal ,astronomical ,society with an endeavour to prove that the nebula did not exist6 ,they had frequently searched for it during the preceding winter1 but not a vestige of the object could be seen in the #ah-;inch refractor at ,chicago1 and they regarded the supposed nebula as due to the glow proceeding from ,merope and neighbouring stars4 ,but photography has entirely refuted this negative evidence1 and has shown1 not only ,tempel's nebula1 but others involving the stars ,maia1 ,alcyone1 and ,electra belonging to this cluster4 ,as to the alleged variations in the ,merope nebula1 there is every reason to suppose these were not real4 ,proper motion has been suggested in regard to a very small1 faint nebula 7,n4,g4,c4 #cbcf7 a few degrees following ,leonis4 ,but ,dreyer has disproved this by showing that there was no proper motion between #ahfe and #ahhg1 whence 8it may be safely inferred that there has been none since #ahcj1 unless we are to believe1 in this and similar cases1 that nebul in the good old days moved about as they liked1 but have been on their good behaviour since #ahfa40 ,nebulous ,stars4--,this name was applied by ,hipparchus and other ancient observers to the clusters of stars which1 to the naked eye1 appear as patches of nebulous light4 ,sir ,w4 ,herschel1 in #agia1 showed this designation to be incorrect1 and used it in connection with stars actually involved in nebulosity4 ,in sweeping the heavens he met with several instances of this kind4 ,thus1 #c ,e4,s4,e4 of ,persei he found a star of the #ith mag4 surrounded by a nebula #c in diameter4 ,he picked up another close to the star #fc ,geminorum4 ,this is a remarkable object--a star of the #ith mag4 surrounded by two dark and two bright rings4 ,on ,feb4 #c1 #ahfd1 ,lord ,rosse's telescope showed an opening in the outer bright ring1 and the latter seemed connected with the inner bright ring2 so that the object presented the aspect of a spiral nebula with a star in the centre4 ,the diameter of the whole nebulosity is #de4 ,key observed this object with an #ah-;inch reflector in #ahfh1 and described it as symmetrical--a central star1 with intervening dark and bright rings4 ,he found a power of #eaj the best1 for1 8like the annular nebula in ,lyra1 it bears magnifying wonderfully well40 ,since ,herschel's time many nebulous stars have been discovered4 ,there is one of about #fth mag4 in ,r4,a4 #h;h #fm#a1 ,dec4-#ab #cf4 ,the nebulosity round the star fades away gradually1 and its extreme diameter is #aeg4 ,there is a #gth mag4 star at ,r4,a4 #ba;h #jm #ads1 ,dec4 #fg #dd involved in a very large1 faint nebulosity4 ,this is a striking object1 and ,i have frequently picked it up while comet-seeking4 ,the star has such a foggy1 veiled appearance that on first remarking it the observer thinks his lenses are dewed1 but on viewing neighbouring stars he sees them sharp and clear on the dark sky1 and the contrast is very pronounced4 ,the nebulous star is much isolated1 though in a part of the sky where small stars abound4 ,this is one of ,herschel's discoveries and ,no4 #gjbc of the ,n4 ,g4 ,c42 ,dreyer says he has seen the nebulosity particularly distinct north and south of the star4 ,in some cases a double star is involved in nebulosity1 and there are instances in which two double stars are placed within an elliptical nebula4 ,the ,magellanic ,clouds#fj4--,these are marked as ,nubecula ,major and ,nubecula ,minor on celestial globes and charts4 ,they form two extensive aggregations of nebul and star-clusters1 and are readily visible to the naked eye in or near ,hydrus1 and not far from the south pole of the heavens4 ,they may be likened to detached patches of the ,milky ,way4 ,sir ,j4 ,herschel says the ,nubecula ,major is situated between the meridians of #d;h #djm and #f;h and the parallels of #ff and #gb of ,s4 declination1 and extends over a space of some #db square degrees4 ,the ,nubecula ,minor lies between #j;h #bhm and #a;h #aem and #gb and #ge of ,s4 declination1 and spreads over about #aj square degrees4 ,the composition of these objects is very complex and diversified1 and affords very rich ground for exploration with a large telescope4 ,nebul exist in profusion and in every variety1 and are intermingled with star-clusters varying in condensation from the compact globular form to groups more loosely scattered1 and such as we often find in the ,milky ,way4 ,nearly three hundred nebul and clusters are included in the major 8cloud10 while more than fifty others closely outlie its borders4 ,in the minor about forty such objects have been discovered4 ,it is very strange to find them collected together in this manner2 for in other regions of the firmament they are usually found separated1 and certain classes appear to have their own special zones or localities of distribution4 ,sir ,j4 ,herschel pointed out that 8globular clusters 7except in one region of small extent7 and nebul of regular elliptic forms are comparatively rare in the ,milky ,way1 and are found congregated in the greatest abundance in a part of the heavens most remote possible from that circle1 whereas in the ,nubecul they are indiscriminately mixed with the general starry ground and with irregular though small nebul40 ,double ,nebul4--,instances are not wanting of conspicuous double nebul4 ,m4 #ea and #gf1 near ,urs and ,andromed1 may be classed in this category4 ,there is a very interesting1 though a smaller object just ,w4 of and ,geminorum1 or in ,r4,a4 #g;h #ahm#f1 ,dec4 #bi #dc4 ,two bright1 round nebul are separated by an interval of #bh4 ,these double nebul are usually round1 and are sometimes resolvable into stars4 ,whether they are physical or mere optical pairs has yet to be ascertained4 ,so many examples exist that it seems highly probable they have a real connection1 though no motion has yet been certainly detected to prove they are binary systems4 ,such motion may1 however1 be very slow1 and require observations extending over a much longer interval before it is revealed4 ,real ,dimensions of ,nebul and ,clusters4--,it may be readily imagined that these objects are of immense size2 for though placed at distances of the utmost remoteness1 they spread over perceptible and comparatively large areas4 ,gore remarks that1 on the assumption that the globular cluster in ,hercules 7,m4 #ac7 is #e in diameter1 and its parallax one tenth of a second1 its real diameter must be #cjjj times the ,sun's mean distance from the ,earth1 or nearly #bhj billions of miles6 ,he further points out that1 though this group contains as many as #ad1jjj stars1 according to ,sir ,w4 ,herschel1 yet each component may be separated many millions of miles from the others1 owing to the vast dimensions of the group4 ,details like these are of course only approximate1 as the distance of a nebula or star-cluster has not yet been definitely ascertained4 ,the great nebul of ,orion and ,andromeda must extend over prodigious regions in distance-space2 but to quote figures seems useless1 in consequence of our inability to form just conceptions of such immensity4 ,round ,nebul and ,clusters4--,resolvable nebul and clusters are frequently circular in outline4 ,the central condensation is an indication of their globular form1 though not always so1 for many of these objects become suddenly much brighter in the middle1 and show an apparently stellar nucleus4 ,the material or stars forming the object cannot therefore be equally distributed4 ,where it suddenly brightens there is a great condensation1 and in some cases several of these are evident in the form of bright rings1 intensifying as the nucleus is approached4 ,this irregular aggregation denotes the operation of 8a force of condensation directed from all parts towards the centre of such systems40 ,in regard to planetary nebul1 they cannot be globular or they would exhibit a brightness increasing from the margin to the centre4 ,their even luminosity throughout affords the evidence of a special structure4 ,sir ,j4 ,herschel thought the planetary nebula 7,m4 #ig7 near ,urs ,majoris must either be in the form of a hollow globe or a flat circular disk lying perpendicular to the line of vision4 ,description of ,nebul and ,clusters of ,stars4--,the latter objects are included in this chapter for several reasons4 ,in a small telescope nearly all such clusters exhibit the aspect of nebul1 and they have been catalogued with them1 though1 as already explained1 some great distinctions are to be drawn4 ,to the naked eye the cluster ,prsepe1 in ,cancer1 is usually visible as a patch of nebulosity1 though on a very clear1 dark night stars may be glimpsed sparkling about the spot1 and a very small glass will suffice to show it as a nest of stars4 ,this object1 and some others of a more difficult character 7their component stars being smaller and more compressed71 are tabulated 7,i47 at the end of this chapter4 ,a summary 7,,ii47 of globular clusters is also given1 together with a list 7,,iii47 of nebul1 a few of which are resolvable into stars#fa4 ,it must be understood that these selections1 though comprising many notable objects1 are by no means exhaustive1 the intention being merely to indicate some typical examples of fine nebul and clusters and of peculiarities of form or appearance1 such as planetary1 annular1 elliptical1 and centrally condensed nebul and loose1 compressed1 and globular clusters4 ,some of these objects deserve individual references1 as they present interesting details to the telescopic observer and come within the reach of moderate appliances4 ,great ,nebula in ,andromeda 7,m4 #ca74 ,this object has often been mistaken for a comet1 for it is readily perceptible to the eye on a moonless night4 ,it is very large--#d by #b1 according to ,bond1 with a #ae-;inch refractor4 ,he discovered a pair of dark streaks in the brightest region of the nebula1 and these may be well seen in a #aj-;inch reflector4 ,it is really triple2 for about #be ,s4 of the nucleus there is a very bright1 round1 resolvable nebula1 discovered by ,le ,gentil1 and a third1 observed by ,caroline ,herschel1 lies rather further to the ,n4,w4 ,photographs by ,roberts show dark rings dividing the bright interior parts of the nebula from the outer1 and imparting to it a decided spiral tendency4 ,this nebula has hitherto resisted attempts to resolve it into stars1 though many hundreds have been seen in the foreground4 ,but its spectrum is continuous1 so that its stellar character is to be inferred4 ,great ,nebula in ,orion 7,m4 #db74 ,visible to the naked eye just below a line connecting and ,orionis1 and involving ,orionis4 ,it exhibits an extremely complicated structure1 and many of its irregular branches and condensations may be discerned in small instruments4 ,sir ,w4 ,herschel failed to resolve this object into stars with his #d-;foot reflector2 but ,lord ,rosse1 in #ahdd1 thought he had effected it with his #f-;foot mirror1 though the conclusion was premature4 ,the spectroscopic researches of ,huggins have shown this nebula to be composed of incandescent gases1 so that the stars telescopically observed in it are probably in the foreground and entirely disconnected from the nebulous mass4 ,effective photographs have been taken of it by ,draper1 ,common1 and ,roberts4 ,it certainly forms one of the grandest objects in the heavens4 ,the ,planetary#fb ,nebula 7,m4 #ig74 ,discovered by ,mechain in #agha4 ,in small telescopes it looks like a rather faint1 round mass of nebulosity1 somewhat brighter in the middle than at the edges4 ,in ,lord ,rosse's telescope it shows many details1 including a spiral arrangement and two dark spots in the middle inclosing bright1 eye-like condensations4 ,the margin is fringed with protuberances1 and from its peculiar aspect this object has been called the 8,owl0 ,nebula4 ,diameter between #aee and #afj4 ,it may readily be picked up #b-a_/d ,s4,e4 of ,urs ,majoris4 ,it yields a gaseous spectrum4 ,in ,draco at ,r4,a4 #ag;h #ehm #cfs1 ,dec4 #ff #ch there is a pretty small1 but exceedingly bright planetary nebula4 ,with a low power it looks like a star out of focus1 but a high power expands it into a well-defined planetary disk4 ,as observed in ,lord ,rosse's #c-;ft4 reflector on ,sept4 #ag1 #ahgc1 this nebula exhibited 8a round1 well-defined disk of a full blue colour1 light very equable1 diameter #bbd1 surrounded by an extremely faint nebulosity40 ,this is an excellent object of its class4 ,spiral ,nebula 7,m4 #ea74 ,discovered by ,messier on ,oct4 #ac1 #aggc4 ,it is situated in ,canes ,venatici1 and #d ,s4,w4 from ,urs ,majoris4 ,an ordinary instrument will reveal it as a double nebula1 and the two parts will be seen to differ greatly in size4 ,messier gave the distance separating them as #d #ce4 ,sir ,j4 ,herschel drew this object as a bright1 centrally condensed nebula1 surrounded by a dark space and then by a luminous ring divided through nearly one half of its circumference4 ,closely outlying this he placed a bright round nebula4 ,lord ,rosse's #f-;foot showed something very different4 ,in ,april #ahde its spiral character was discovered2 coils of nebulosity were observed tending in a spiral form towards the centre1 and the outlying nebula was seen to be connected with it4 ,some striking drawings have been published of this object4 ,those by ,sir ,j4 ,herschel and ,lord ,rosse differ essentially1 and would scarcely be supposed to represent the same nebula2 but when we reflect that the instruments used were respectively of #ah inches and #gb inches aperture1 the cause of the disparity becomes evident4 ,another fine example of a spiral nebula is ,m4 #ii1 in the northern wing of ,virgo1 and #h ,e4 of ,leonis4 ,this object was discovered by ,mechain2 its spiral form of structure was detected by ,lord ,rosse in #ahdh4 ,diameter #b ,like ,m4 #ea it gives a continuous spectrum and is resolvable into stars4 ,illustration3 ,fig4 #fd4 #a4 ,nebula with bright centre4 #b4 ,planetary ,nebula4 #c4 ,ring-nebula in ,lyra4 #d4 ,star-cluster in ,hercules4 ,the ,crab ,nebula in ,taurus 7,m4 #a74 ,discovered by ,bevis in #agca1 and situated #a ,n4,e4 of ,tauri4 ,its diameter is #e by #c4 ,an early drawing with ,lord ,rosse's telescope shows it with numerous radiations2 whence it was termed the ,crab ,nebula1 from the supposed resemblance3 but later observations have given it quite another form4 ,in #ahgg there was no trace of the nebulous arms3 it appeared as a well-defined1 oval nebula with some irregularities of structure4 ,this object is very plain in small telescopes1 and may be readily picked up from its proximity to ,tauri2 but in such instruments it is void of detail1 and merely presents a pale1 oval nebulosity4 ,it has not been clearly resolved1 though it has a mottled appearance1 indicating a stellar composition1 in large apertures4 ,the ,dumb-bell ,nebula 7,m4 #bg74 ,discovered by ,messier in #aggi1 and situated in ,vulpecula--a region very rich in small stars4 ,diameter about #g or #h4 ,its general form resembles a dumb-bell or hour-glass2 hence its name4 ,struve1 ,lord ,rosse1 and others have seen many stars in the nebulous mass1 but the latter is not resolvable4 ,i have seen seven stars in the nebula with a #aj-;inch reflector4 ,its peculiar shape is perceptible in a small instrument4 ,this object frequently serves to illustrate books on ,astronomy2 but the drawings by ,sir ,j4 ,herschel1 ,lord ,rosse1 and others are curiously discordant1 and show how greatly differences in telescopic power may affect the observed appearance of an object4 ,the ,ring-,nebula in ,lyra 7,m4 #eg74 ,discovered by ,messier between the stars and ,lyr4 ,diameter #hj by #fj4 ,this object is bright1 though rather small1 and it will stand high powers4 ,the dark centre may possibly be glimpsed in a #c-;inch refractor2 ,i have seen it readily in a #d-a_/d-;inch4 ,it was at one period thought to be resolvable1 but the spectroscope has negatived the idea1 and shown it probably consists of nitrogen gas4 ,a small star near the centre was frequently seen in ,lord ,rosse's telescope2 but the #cf-;inch refractor at ,mount ,hamilton reveals twelve stars projected on or within the ring1 and several others have been suspected4 ,there is a faint star exterior to the ring1 and following it2 this is visible in small telescopes4 ,the space within the ring is not quite dark1 and the structure of the nebula is somewhat complicated as seen in large instruments4 ,another fine instance of an annular nebula may be found #c preceding the #dth mag4 star #da ,cygni1 but it is not so large or conspicuous as that in ,lyra4 ,its diameter is #dg by #da4 ,several stars were seen sparkling in it by ,lord ,rosse1 who found the centre was filled with faint light and the ,n4 side of the ring broadest and brightest4 ,elliptical nebul are well represented by the pair 7,m4 #ha and #hb7 about #b ,e4 of 7#bb7 ,urs ,majoris4 ,they are separated by about #ch of declination1 so that they may be observed in the same field of a low-power eyepiece4 ,the preceding one is very bright and large 7#h by #b74 ,the following one is a ray or streak of nebulosity 7#g by #c_/d74 ,on ,may #ba1 #ahga1 the great ,rosse telescope showed the latter as a most extraordinary object1 at least #aj in length and crossed by several dark bands4 ,roberts photographed these nebul on ,march #ca1 #ahhi4 8,the negative shows that the nucleus of ,m4 #ha1 which has not a well-defined boundary1 is surrounded by rings of nebulous or meteoric matter1 and that the outermost rings are discontinuous in the ,n4p4 and ,s4f4 directions40 ,m4 #hb is 8probably a nebula seen edgeways1 with several nuclei of a nebulous character involved1 and the rifts and attenuated places in it are the divisions of the rings that would be visible as such if we could photograph the nebula from the direction perpendicular to its plane0 7#8,monthly ,notices1' vol4 xlix4 p4 #cfc74 ,this fine pair may be easily picked up in a small instrument4 ,another grand object of this class 7discovered by ,caroline ,herschel in #aghc7 lies in ,r4,a4 #j;h #dbm#b1 ,dec4-#be #ed1 between the stars ,ceti and ,sculptoris4 ,globular clusters furnish us with many examples of easily resolved and richly condensed balls of stars4 ,m4 #c 7discovered by ,messier71 ,m4 #e 7discovered by ,g4 ,kirch71 and ,m4 #ac 7discovered by ,halley7 may be selected as amongst the finest of these objects in the northern hemisphere4 ,they are severally visible to the naked eye1 and may be found in a telescope directed as follows3--,m4 #c1 between ,arcturus and ,cor4 ,caroli1 and nearer the former2 ,m4 #e1 #g ,s4,w4 of ,serpentis and close to the double star #e ,serpentis2 ,m4 #ac1 one third the distance from to ,herculis4 ,they are brilliant objects from #e to #g diameter4 ,with power #fj on my #aj-;inch reflector they are spangled with stars1 though not fully resolved4 ,smyth described ,m4 #c as consisting of about #ajjj small stars1 blazing splendidly towards the centre4 ,webb hardly resolved it with a #c-g_/aj-;inch refractor4 ,another fine object of this class 7,m4 #hj7 will be encountered midway between and ,scorpii4 ,sir ,w4 ,herschel described it as the richest and most compact group of stars in the sky1 and it is noteworthy from the fact that a new star burst forth near its centre in #ahfj4 ,there is a magnificent cluster1 involving ,centauri1 which ,sir ,j4 ,herschel considered as 8beyond all comparison the richest and largest object of the kind in the heavens40 ,it is visible to the naked eye as a #dth mag4 star1 but residents in northern latitudes are precluded from a view of it4 ,pegasus also supplies us with some fine clusters2 ,maraldi picked up two in #agdf 7,m4 #b and #ae71 and these will respectively be found #e ,n4 of and #d ,w4,n4,w4 of ,pegasi4 ,they are to be classed amongst the grandest objects of their kind4 ,in ,cygnus1 at ,r4,a4 #bj;h #dam #gs1 ,dec4 #cj #ai1 near and especially in the region immediately north-east1 there exist irregular and extensive streams of faint nebulosity which may be said to form a telescopic milky way1 ,nebul and stars are curiously grouped together1 forming a remarkable arrangement which will well repay study4 ,to see these objects satisfactorily1 a moonless night1 free from haze or fog1 should be chosen1 and the power should be moderately low1 or some of the more feeble nebulous films will be lost4 ,the observer may spend some agreeable hours in sweeping over this region1 which is one of the best in a wonderfully rich constellation4 ,further ,observations4--,the fact that ,swift has discovered many hundreds of nebul during the last few years affords indubitable proof that considerable numbers of these objects still await detection4 ,no doubt they are generally small and faint1 but it is necessary they should be observed and catalogued1 so that our knowledge in this department may be rendered as complete as possible4 ,new nebul are sometimes mistaken for expected comets1 and occasionally give rise to misconceptions which would be altogether avoided were our data more exhaustive4 ,those who sweep for nebul must have the means of determining positions1 and a small telescope will be inadequate to the work involved4 ,a reflector of at least #aj inches1 or refractor of #h inches1 will be required2 and a still larger instrument is desirable1 for to cope successfully with objects of this faint character needs considerable grasp of light4 ,the power employed should be moderate2 it must be high enough to reveal a very small nebula1 but not so high as to obliterate a large1 diffused1 and faint nebula4 ,in forming his first catalogue of #ajjj nebul1 ,sir ,w4 ,herschel used a ,newtonian reflector of #ahg inches aperture1 power #aeg1 field #ae #ad2 ,swift's recent discoveries were effected with a #af-;inch refractor and a periscopic positive eyepiece1 power #acb1 field #cc4 ,with a low power a very extensive field will be obtained1 and a large part of the sky may soon be examined1 but it will be done ineffectively4 ,it is better to use a moderately high power1 and thoroughly sweep a small region4 ,the work is somewhat different to comet-seeking2 it must proceed more slowly and requires greater caution1 for every field has to be attentively and steadily scanned4 ,if the telescope is kept in motion1 a faint nebula will pass unseen4 ,some of these objects are so feeble that they are only to be glimpsed by averted vision4 ,when the eye is directed1 say1 to the ,e4 side1 a faint momentary glow comes from the ,w4 side of the field2 but the observer discerns nothing on looking directly for the object4 ,on again diverting his gaze he receives another impression of faint nebulosity from the same point as before1 and becomes conscious of its reality4 ,frequently1 while comet-seeking1 ,i meet with a small indefinite object1 the character of which cannot be determined by direct scrutiny4 ,on withdrawing the eye to another part of the field1 however1 the mystery is solved4 ,if the object is a nebula1 it flashes very distinctly on the retina2 but if a small cluster1 the individual stars are seen sparkling in it4 ,these indirect views are usually so effective that the trouble of applying higher powers is dispensed with4 ,the glow from a faint nebula or comet often apparently fluctuates in a remarkable manner4 ,light-pulsations affect it1 causing the nebulosity to be intermittently visible4 ,it flashes out and enlarges1 then becomes excessively feeble and indeterminate4 ,the changes are not real1 but due to the faint and delicate nature of the object1 which is only fugitively glimpsed and presents itself differently with the slightest change in the manner of viewing it4 ,burnham has said there is no such thing as glimpsing an object2 but he is wrong4 ,it is the intermediate step between steady visibility and absolute invisibility4 ,the work of sweeping for nebul is much delayed by the comparisons necessary for the identification of objects4 ,the path may be smoothed by marking the known nebul on a good chart1 like ,argelander's4 ,the observer may then see1 by reference1 whether the objects he encounters have been picked up before4 ,the labour of projecting all the nebul contained in the ,new ,general ,catalogue would of course be considerable1 and the observer will probably find it expedient to select certain regions for examination1 and map such nebul as are included within their borders4 ,the discovery of new nebul offers an inviting field to amateurs4 ,vast numbers of these objects have escaped previous observation1 for though the sky has been swept again and again1 its stores have not been nearly exhausted4 ,mr4 ,barnard recently stated that with the powers of the great #cf-;inch refractor the number of known nebul 7more than #hjjj7 might readily be doubled6 ,as an example of their plentiful distribution in certain regions it may be mentioned that ,mr4 ,burnham very recently discovered eighteen new nebul in a small area of #af by #ee near the position in ,r4,a4 #ac;h #chm1 ,dec4 #ef #bj ,n4 ,near the pole of the northern heavens there exist many unrecorded nebul1 as this region does not appear to have been thoroughly examined with a large instrument4 ,it is often the case that several nebul are clustered near together4 ,whenever a new one is discovered the surrounding space should therefore be carefully surveyed in search of others4 ,the region immediately outlying known objects may also be regarded as prolific ground for new discoveries4 ,after several hours' employment in the work of searching for nebul or comets the eye is enabled to discern faint objects which were invisible at first1 as it is in a better condition to receive feeble impressions4 ,while comet-seeking in #ahhi and #ahij ,i discovered ten new nebul1 all near the ,n4 pole1 and their approximate positions are given below3-- ---------------------------------------- ---------------------------------------- ---------------------------------------- ,ref4,date of ,position #ahij4 ,no4 ,discovery4 -------------------------- ,description ,r4,a4 ,dec4 ---------------------------------------- ---------------------------------------- ---------------------------------------- h m s #a4 #ahhi1 ,aug4 #bfd #bi #eige #beb;,f41 ,s41 b4 ,m41 99#ab1 n4p4 #b4 #ahij1 ,nov4 #g #d #dj #aigh #gi ,f41 ,s41 ,r4 #c4 #ahij1 ,oct4 #aid #df #chfh #ih ,f41 ,s41 ,r41 b4 ,m4,n41 ,f4 double 99 s4f4 #d4 #ahij1 ,nov4 #afe #ej #g #hj #caj v4,f41 ,s4 #e4 #ahij1 ,nov4 #i #f #aa #dehc #ai ,f41 ,s41 ,r41 m4 b4 ,m4 #f4 #ahij1 ,oct4 #agf #ei #bfhe #dejv4 ,f41 v4v4,s41 #ab s4s4f4 ,n4,g4,c4 #bcjj #g4 #ahij1 ,nov4 #g #g #h #eb #hj #gd v4 ,f41 p4 ,s41 #bb s4 s4 f4 ,n4,g4,c4 #bccf4 #h4 #ahij1 ,sept4#adg #bc #bdhe #cjj;,f41 ,s41 ,e41 #df s4 f4 ,n4,g4,c4 #bcjj4 #i4 #ahij1 ,sept4 #hh #ba #cghf #gd p4 ,f41 ,s41 m4 b4 ,m41 99 n4 f4 #aj4ahij1 ,aug4 #bch #cd #cjhe #edd;,f41 ,s41 ,r41 g4 b4 ,m41 near preceding4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ,abbreviations3--,f41 faint2 ,s41 small2 ,r41 round2 ,m41 middle2 ,n41 nucleus1 ,e41 extended2 v41 very2 b41 brighter2 n41 north2 s41 south2 f41 following2 p41 pretty1 preceding2 m41 much2 g41 gradually2 991 star2 ,n4,g4,o41 ,new ,general ,catalogue4 ,no4 #h is placed centrally within a curious semicircle of stars1 thus3-- ,illustration3 ,fig4 #fe4 ,i4--,,clusters ,,of ,,stars4 ---------------------------------------- ---------------------------------------- ---------------------------------------- -------- ,position1 #ahij4 ,no4 ,no4 --------------------------------- ,n4,g4,c41 ,m41 ,description4 #ahhh4 #agha4 ,r4,a4 ,dec4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------ h m #bbe4 #j #cga #fa #c ,stars #ith-#ajth mags4 ,between and ,cassiopei4 #hfi4 #b #aac #ef #ch ,in ,perseus4 ,stars #gth-#adth mags4 #ajci4 #cd4 #b #cej #db #ah ,a fine group1 chiefly of #ith mag4 stars4 #aiab4 #ch4 #e #bac #ce #dd ,stars of various mags4 ,in ,auriga4 #aifj4 #cf4 #e #bij #cd #d ,stars of #ith-#aath mags4 ,near #aiab4 #bjii4 #cg4 #e #dea #cb #ca ,stars and star-dust4 #e ,s4 of ,aurig4 #bafh4 #ce4 #f #bj #bd #ba ,stars of #ith-#afth mags1 near ,geminorum4 #bbhg4 #ad4 #f #dbc -#bj #ch ,visible to naked eye4 #d ,s4 of ,sirius4 #bdcg4 #df4 #g #cfh -#ad #cd ,nebula involved with cluster of #hth-#acth mag4 stars4 #bdgg4 #g #dhd -#ch #af ,fine group of #abth mag4 stars near ,args4 #beaf4 #g #efe -#fj #cd ,visible to naked eye4 #bjj stars of #gth-#acth mags4 #bedg4 #h #gd -#dh #ef ,vis4 n4e4 ,stars #gth-#afth mags4 ,diameter #bj4 #bedh4 #h #hc -#e #bh ,stars of #ith-#acth mags4 ,in ,monoceros4 #bfcb4 #dd4 #h #cdj #bj #bb ,prsepe4 ,group of bright stars vis4 n4 e4 #bfhb4 #fg4 #h #deb #ab #ac ,large group of stars of #ajth-#aeth mags4 #dgee4 #ab #dga -#ei #de ,very large group about ,crucis4 #faba4 #d4 #af #afi -#bf #af ,close to ,antares4 ,group and line of stars through it4 #ffjc4 #bd4 #ah #abj -#ah #bh ,stars of #aeth mag4 #c ,n4 of ,sagittarii4 #ffaa4 #af4 #ah #abg -#ac #ej ,group of at least #ajj stars of various mags4 #fgje4 #aa4 #ah #dea -#f #bd ,stars of #aath mag4 and fainter4 ,fine object4 #fhch4 #ga4 #ai #dhh #ah #bi ,stars of #aath-#afth mags4 ,in ,sagitta4 #gbdc4 #bb #aji #di #bj ,a clustering of many bright stars4 #gfed4 #eb4 #bc #aid #fa #j ,irregular group of #ith-#acth mag4 stars4 #gghi4 #bc #eae #ef #f ,grand cluster of #aath-#ahth mag4 stars4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------ ,,ii4--,globular ,clusters of ,stars4 ---------------------------------------- ---------------------------------------- ---------------------------------------- -------- ,position1 #ahij4 ,no4 ,no4 --------------------------------- ,n4,g4,c41 ,m41 ,description4 #ahhh4 #agha4 ,r4,a4 ,dec4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------ h m #ajd4 #j #aia -#gb #db ,very large2 more than #ae diameter4 #bhh4 #j #dgh -#bg #aa ,slightly elliptical4 ,stars #abth-#afth mags4 #cfb4 #j #ehe -#ga #bf ,stars #acth-#adth mags4 ,diameter #d4 #abfa4 #c #ic -#ee #ch ,large4 ,stars and star-dust4 #ahea4 #e #aje -#dj #aj ,very bright and large4 ,fine object4 #dadg4 #ab #de #ai #i ,pretty large1 round4 ,minute stars4 #deij4 #fh4 #ab #ccg -#bf #i ,much compressed group of #abth mag4 stars4 #ejbd4 #ec4 #ac #ge #ah #de ,fine object4 ,chiefly #abth mag4 stars4 #eaci4 #ac #bjb -#df #dd ,very large2 diameter #bj4 ,at ,centauri4 #ebgb4 #c4 #ac #cga #bh #ef ,visible to naked eye4 ,diameter #g4 #efcd4 #ad #bch - #e #bi ,very bright1 considerably large4 ,round4 #eijd4 #e4 #ae #acj #b #bi ,visible naked eye4 ,stars #aath-#aeth mags4 ,diam4 #e4 #eihf4 #ae #chh -#cg #be ,stars of #acth-#aeth mags4 ,in ,lupus4 #fjic4 #hj4 #af #aje -#bb #db ,stars of #adth mag4 ,between and ,scorpii4 #fbje4 #ac4 #af #cgg #cf #dj ,visible naked eye4 ,a grand object1 in ,hercules4 #fbah4 #ab4 #af #dae - #a #de ,stars of #ajth mag4 and fainter4 ,diam4 #d4 #fbed4 #aj4 #af #ead - #c #ef ,stars of #ajth-#aeth mags4 ,diameter #d4 #fbff4 #fb4 #af #edb -#bi #eg ,stars of #adth-#afth mags4 ,in ,scorpio4 #fccc4 #i4 #ag #abh -#ah #bd ,much compressed group of #adth mag4 stars4 ,diam4 #d4 #fcda4 #ib4 #ag #ach #dc #ae ,a mass of stars and star-dust4 #g ,n1 ,herculis4 #fdjb4 #ad4 #ag #cah - #c #aa ,chiefly stars #aeth mag4 ,diameter #d4 #ffef4 #bb4 #ah #big -#bd #j ,stars of #aath-#aeth mags4 ,in ,sagittarius4 #fggi4 #ef4 #ai #abc #cj #j ,stars #aath-#adth mags4 ,between ,cygni and ,lyr4 #fhji4 #ee4 #ai #ccj -#ca #ad ,fine1 large1 round cluster of stars #aath-#acth mags4 #gjgh4 #ae4 #ba #bdg #aa #da ,group of stars and star-dus4 ,diameter #e4 #gjhi4 #b4 #ba #bgh - #a #ai ,exceedingly small stars4 ,diameter #e4 #gjii4 #cj4 #ba #cda -#bc #da ,stars #abth-#afth mags4 ,diameter #c4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------ ,,iii4--,,nebul4 ---------------------------------------- ---------------------------------------- ---------------------------------------- -------- ,position1 #ahij4 ,no4 ,no4 --------------------------------- ,n4,g4,c41 ,m41 ,description4 #ahhh4 #agha4 ,r4,a4 ,dec4 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------ h m #ahe4 #j #cbi #dg #dd ,very large2 pretty bright4 ,resolvable into stars4 #bbd4 #ca4 #j #cfg #dj #dj ,great nebula in ,andromeda4 #bec4 #j #dbb -#be #ed ,very1 very large and bright4 #bd by #c4 #eih4 #cc4 #a #bgf #bi #ega ,exceedingly bright and large4 ,nucleus4 #fej4 #gf4 #a #ced #ea #a ,very bright double nebula4 #acfe4 #c #bid -#cf #cj ,very bright and large4 ,elliptical4 #aeja4 #c #ege #fj #cg ,pretty bright planetary nebula4 ,diam4 #a4 #aead4 #d #bd #cj #bi ,star of #ith mag4 in nebula #c diameter4 #aieb4 #a4 #e #bgi #ba #ef ,great ,crab ,nebula1 near ,tauri4 ,stars4 #aigf4 #db4 #e #bii - #e #bh ,great nebula involving ,orionis4 #aiij4 #e #cjf - #a #af ,star 7 ,orionis7 involved in nebulosity4 #bjgj4 #e #cie -#fi #i ,visible to naked eye4 ,great 8looped0 nebula4 #bcib4 #g #bbg #ba #h ,nebulous star of #ith mag4 #bdjc4 #g #bfb #fe #ej ,very large and bright4 ,elliptical4 #bfee4 #h #dab #gh #ch ,very bright4 ,condensed in the middle4 #bfha4 #h #def #ea #dd ,very large and bright4 ,centre star #ajth mag4 #bfhc4 #h #dei #cc #ea ,very large and bright4 ,elliptical4 #bhda4 #i #add #ea #bf ,very large and bright4 ,centre star #ajth mag4 #bijc4 #i #bei #bb #j ,large1 elliptical1 double nebula4 #cjca4 #ha4 #i #dfe #fi #ce ,exceedingly bright and large4 ,elliptical4 #cjcd4 #hb4 #i #dfg #gj #ac ,a bright ray4 ,in field with preceding4 #cbdb4 #aj #aie -#ah #e ,bright planetary nebula4 ,diameter #de4 ,blue4 #ccgb4 #aj #djh -#ei #f ,great nebula surrounding ,args4 #ceef4 #aa #ed #ef #af ,large1 rather bright4 ,elliptical4 #cehg4 #ig4 #aa #hd #ee #cg ,fine planetary nebula4 ,diam4 #c4,near ,urs ,majoris4 #cfbc4 #fe4 #aa #acb #ac #db ,large1 bright1 elliptical4 ,near following one4 #cfbg4 #ff4 #aa #ade #ac #cf ,large elliptical nebula4 ,near ,leonis4 #dbed4 #ii4 #ab #acc #ae #b ,very fine #c-;branched spiral nebula4 #dcba4 #ajj4 #ab #agd #af #bf ,very large #b-;branched spiral nebula4 #dchb4 #he4 #ab #aii #ah #dh ,very bright2 pretty large4 ,round4 #ddgb4 #di4 #ab #bdb #h #cg ,bright2 round4 ,resolvable into stars4 #ddhf4 #hg4 #ab #bec #ac #j ,large2 round4 ,bright centre4 ,third of three4 #defe4 #ab #cji #bf #cf ,a ray of bright nebulosity ,e4 of ,coma4 #dgcf4 #id4 #ab #deg #da #dc ,large and bright4 ,nucleus4 ,resolvable4 #eabh4 #ac #aij -#db #bg ,very large and bright4 ,elliptical4 ,bifid4 #eaid4 #ea4 #ac #beb #dg #df ,great spiral nebula near ,urs ,maj4 #ebcf4 #hc4 #ac #cjh #bi #ah ,fine object4 #c-;branched spiral4 #ecfg4 #ac #eaa -#ci #bg ,very large and bright4 ,condensed in the middle4 #eijg4 #ae #acj #ef #dd ,large1 elliptical4 ,another very close to it4 #fcfi4 #ag #bbf -#bc #dj ,pretty bright1 small ring-nebula4 #fead4 #bj4 #ag #eeg -#bc #a ,bright2 large4 ,trifid4 ,double star involved4 #febc4 #h4 #ag #efi -#bd #bc ,bright1 with loose cluster of stars4 #ffah4 #ag4 #ah #add -#af #ac ,bright and extremely large4 #b-;hooked4 #fgbj4 #eg4 #ah #die #cb #ed ,ring-nebula between and ,lyr4 #fhbf4 #ai #dah #ej #af ,pretty large and bright planetary nebula4 #fhec4 #bg4 #ai #edi #bb #be ,the 8,dumb-bell0 ,nebula4 ,fine object4 #fifj4 #bj #daa #cj #ai ,large and bright1 ,cygni involved4 #gjji4 #bj #ehb -#aa #dh ,very bright1 small1 planetary nebula4 ,elliptical4 #gffb4 #bc #bjf #da #ef ,very bright1 pretty small1 planetary or ring-nebula4 ---------------------------------------- ---------------------------------------- ---------------------------------------- -------- ,,footnotes3 #ee ,sir ,w4 ,herschel at first entertained this view1 finding that with every increase of telescopic power more nebul were resolved4 ,but in #agia he said1 8perhaps it has been too hastily surmised that all milky nebulosity is owing to starlight only40 ,lacaille had remarked in #agee that 8it is not certain the whiteness of parts of the ,milky ,way is caused by clusters of stars more closely packed together than in other parts of the heavens40 #ef ,this is exclusive of #dg new nebul discovered by ,prof4 ,safford1 which form the appendix to the catalogue4 #eg ,chambers says only four examples are known1 but this is erroneous1 as ,lord ,rosse's telescope has added five ring-nebul to the four previously catalogued4 #eh ,some of the nebul in ,messier's list were discovered by ,mechain at ,paris1 who1 like ,messier1 earned celebrity by his cometary discoveries4 ,he was born at ,laon in #agdd1 and died at ,valencia in #ahje4 #ei ,o4 ,struve had expressed views identical with these in #aheg 7see #8,monthly ,notices1' vol4 xvii4 p4 #bcj74 #fj ,humboldt says this 8name is evidently derived from the voyage of ,magellan1 although he was not the first who observed them40 #fa ,i have selected the various objects in these lists from the ,new ,general ,catalogue4 #fb ,these forms are more numerous than the annular nebul4 ,they often exhibit a blue colour1 and the spectroscope shows them to consist of gas4 ,,notes ,,and ,,additions4 ,,large ,,and ,,small ,,telescopes4 ,p4 #ai4--,with reference to mountainous sites for large instruments1 a remark in ,sir ,isaac ,newton's #8,opticks' 7#agcj7 may be quoted3--8,telescopes 444 cannot be formed so as to take away that confusion of rays which arises from the tremors of the atmosphere4 ,the only remedy is a most serene and quiet air1 such as may perhaps be found on the tops of the highest mountains above the grosser clouds40 ,p4 #bg4--,lieut4 ,winterhalter1 of the ,united ,states ,navy1 recently visited a large number of ,european observatories1 and in describing that of ,nice says3--8,m4 ,perrotin declares that two hours' work with a large instrument is as fatiguing as eight with a small one1 the labour involved increasing in proportion to the cube of the aperture1 the chances of seeing decreasing in the same ratio1 while it can hardly be said that the advantages increase in like proportion40 ,the ,nice ,observatory1 and its splendid instruments 7including a #cj-;inch refractor71 are due to the munificence of ,m4 ,bischoffsheim1 who has expended about five million francs upon them4 ,p4 #cf4--,the large refractor to be erected on ,wilson's ,peak of the ,sierra ,madre range of mountains1 in ,southern ,california1 is to be #dj inches in diameter4 ,the rough unground disks of glass are already in the hands of the ,clarkes1 of ,cambridgeport1 ,mass4 ,it is estimated that the complete object-glass and cell will cost something like #fe1jjj1 and the focal length of the instrument will be about #eh feet4 ,,the ,,sun4 ,p4 #ajj4--,the last minimum of sun-spot frequency appears to have occurred at the middle of #ahhi4 ,conspicuous spots were very rare in the first half of #ahij1 but some fine groups were presented in the last half of the year4 ,on ,aug4 #ca ,i saw a group extending over #aac1jjj miles in length1 and on ,nov4 #bg there was another1 which measured #abc1gjj miles4 ,p4 #aaa4--,thompson's cardboard disks have been favourably spoken of as enabling observers to determine the positions of spots at any season of the year4 ,,mercury4 ,p4 #acg4--;,at the meeting of the ,british ,astronomical ,association on ,nov4 #bf1 #ahij1 ,mr4 ,g4 ,f4 ,chambers expressed his firm belief in the existence of an intra-,mercurial planet4 ,the ,president 7,capt4 ,w4 ,noble7 in his inaugural address pointed out the desirability of effecting further observations1 both of ,mercury and ,venus1 with a view to redetermine their rotation-periods4 ,he justly remarked that moderately small instruments might be fittingly employed in the work1 and that ,schiaparelli's deductions 7mentioned on pp4 #adb and #adi7 ought to be accepted with extreme reserve pending their verification4 ,,mars4 ,p4 #afj4--,prof4 ,w4 ,h4 ,pickering observed some of the canals on ,mars in #ahij with a #ab-;inch refractor1 but was not able to double any of them4 ,he says that1 in examining these objects1 the power employed should not 8exceed one or two hundred40 ,this is quite contrary to the advice of others1 who recommend high magnifiers2 and perhaps it accounts for ,prof4 ,pickering's failure in recognizing the duple canals4 ,with the great #cf-;inch refractor ,mr4 ,keeler saw1 on ,july #e and #f1 #ahij1 some curious white spots on the edges of the gibbous limb of ,mars1 something similar to those visible on the unilluminated part of the lunar disk4 ,the canals were observed as feeble diffused bands4 ,the two satellites were seen by a lady visitor1 though previously unaware of their existence4 ,p4 #afa4--,the method of deriving the rotation-period of ,mars is exemplified by ,mr4 ,proctor in the #8,monthly ,notices1' vol4 xxviii4 p4 #ch4 ,an interesting paper1 8,on the ,determination of the ,rotation-,period of ,jupiter in #ahce10 will be found in the #8,memoirs1' vol4 ix4 ,,planetoids4 ,p4 #afg4--,the #cjhth planetoid was discovered by ,charlois on ,march #e1 #ahia4 ,,jupiter4 ,p4 #agj4--;,dupret1 in ,algiers1 saw ,jupiter with the naked eye on ,sept4 #bf1 #ahij1 and following days1 twenty minutes before sunset4 ,p4 #aia4--,m4 ,guillaume1 during a recent transit of the shadow of ,jupiter's second satellite1 observed a duplicate shadow1 fainter than the ordinary one1 which partly covered its southern side4 ,,comets4 ,p4 #bej4--,on ,nov4 #af1 #ahij1 ,dr4 ,spitaler1 while looking for ,zona's ,comet with the #bg-;inch refractor of the ,vienna ,observatory1 discovered a new and very faint comet only #bc distant from the object of his search4 ,that two of these bodies should be found almost simultaneously and so near together must be regarded as a very singular coincidence4 ,,meteors4 ,p4 #bfa4--,mr4 ,proctor held the view that certain meteorites may have originally been ejected from the ,sun4 ,a recent writer thus summarizes our knowledge of them3--8,that they are independent bodies1 moving in orbits of their own in space2 that these dark bodies are abundant in the interplanetary spaces2 that those within the near range of solar or planetary attraction move with great velocity2 that many swarms of them follow well-known orbits2 and that1 in general1 their origin is undoubtedly the same as that of other celestial bodies0 7#8,sidereal ,messenger1' ,june #ahij1 p4 #bhd74 ,p4 #bfg4--,on ,may #b1 #ahij1 a brilliant fireball1 leaving a long train of fire and smoke1 and exploding with a noise like thunder1 was seen at many places in ,northern ,iowa1 ,minnesota1 ,u4,s4,a4 ,some fragments of the meteor fell on a farm a few miles from the south line of ,minnesota4 ,the largest piece was sold by auction for #ajj1 but it soon transpired that the person who sold it was only the lessee and not the owner of the ground on which the meteor fell4 ,the aerial visitor and its purchase-money were therefore peremptorily seized by legal authorities1 pending the decision of a ,court of ,justice as to the rightful ownership4 ,p4 #bfg4--,on ,december #ad1 #ahij1 at #i;h #dbm a large fireball of dazzling lustre1 and giving a report like thunder1 was widely observed in the southern parts of ,england4 ,at the end-point the fireball appears to have been only #h miles in height1 and over a point near ,brentwood1 in ,essex4 ,,the ,,stars4 ,p4 #cji4--,prof4 ,chandler1 of ,cambridge1 ,mass41 estimates that the total number of variable stars visible with a common field-glass is about #bjjj1 but with a large telescope there are probably hundreds of thousands within reach4 ,he further states that quite five sixths of the variable stars are reddish in colour1 and that the redness is usually a function of the length of the period of variation4 ,the redder the star the longer its period4 ,p4 #cab4--;,in a recent communication to the ,academy of ,sciences1 ,m4 ,lescarbault 7the alleged discoverer of ,vulcan in #ahei7 announced that on the night of ,january #aa1 #ahia1 he discovered a bright body in ,leo which he could not identify in any star-map1 and hence concluded it to be a new star1 or one suddenly increased in brilliancy4 ,the 8new star10 however1 subsequently turned out to be the planet ,saturn6 ,this ridiculous mistake 7so easily avoidable with a little care7 will naturally divest the supposed discovery of ,vulcan of the importance attached to it by some writers1 for ,m4 ,lescarbault obviously lacks the experience and caution necessary to command credit4 ,,nebul ,,and ,,clusters ,,of ,,stars4 ,p4 #cbg4--,mr4 ,roberts1 from a comparison of his photographs1 has found distinct evidence of variability in the nucleus of the great nebula in ,andromeda4 ,in some of the photographs the nucleus is shown to be stellar1 while in others there is no trace of this4 ,mr4 ,roberts remarks3--8,we may reasonably infer that the nucleus of the nebula is variable1 and that it will be practicable to study the character of the variability without the necessity of giving long exposures of the plates40 ,the period of the variation has now to be determined1 and it is advisable that telescopic observations of the nucleus should be made with the view of confirming the photographic results4 ,it would be premature to regard the changes as demonstrated before they have been submitted to thorough investigation4 ,p4 #cbg4--;,in the ,comptes ,rendus for ,march #b1 #ahia1 ,m4 ,bigourdan has a paper on the variability of the nebula ,n4,g4,c4 #aahf1 situated near ,algol4 ,this nebula was discovered by ,sir ,w4 ,herschel in #aghe1 and though ,sir ,j4 ,herschel re-observed it in #ahca1 ,lord ,rosse looked for it without success in #ahed and #ahfd4 ,on ,nov4 #h1 #ahfc1 ,d',arrest failed to detect the nebula1 though he searched for it with assiduity at a time when the sky was very favourable4 ,he was led to conclude that the object did not exist4 ,m4 ,bigourdan finds that the nebula is again visible in the position indicated by the two ,herschels1 viz4 ,r4,a4 #b;h #edm #bjs1 ,dec4 #db #aj1 he having observed it on ,jan4 #ca and ,feb4 #bf1 #ahia4 ,it is difficult to believe that this object could have escaped the scrutiny of ,lord ,rosse and ,d',arrest in #ahed1 #ahfc1 and #ahfd2 hence the variation is probably real4 ,the nebula may be easily found1 as it is very near the binary ,b4,d4 #db 7#aabc ,g4,c471 the position of which for #ahia is ,r4,a4 #b;h #ehm #fs1 ,dec4 #db #bi' 7#8,nature1' ,march #ab1 #ahia74 ,p4 #cbi4--,while examining the ,pleiades on the night of ,november #ad1 #ahij1 ,mr4 ,barnard discovered a new and considerably bright1 round1 cometary nebula #cf ,s4 and #i following ,merope4 ,the reason why this nebula has not been detected by photography is because it is so near ,merope that the over-exposed light from the star obliterates it4 ,but it is certainly very strange that the object alluded to has never been telescopically discovered before2 for the ,pleiades have been scrutinized repeatedly with all sorts of telescopes1 and particularly since ,tempel announced his discovery of a large faint nebula involving ,merope in #ahei4 ,mr4 ,barnard says the new nebula is #cj in diameter1 and that it is visible in a #ab-;inch refractor when ,merope is hidden with a wire4 ,,index4 ,action in ,sun-spots1 ,cyclonic1 #ajh4 ,active volcanoes on the ,moon1 #abj4 ,adams theoretically discovers ,neptune1 #bbb4 ,advantage of ,equatoreals1 #ed4 ,aerolites1 #bfd4 ,air and water on the ,moon1 ,absence of1 #aae4 ,algol1 #caj4 ,alleged satellite of ,venus1 #aeb4 ,almanacks1 #hc4 ,alphabet1 ,greek1 #bhg4 ,alpine ,valley1 #abg4 ,altitudes of markings on ,jupiter1 #ahe4 ,amateur's first view of ,mercury1 #aci4 ,ancient ideas concerning meteors1 #bfj4 ,andromeda1 ,great ,nebula in1 #ccd4 ,andromedes1 #bgf4 ,angles of ,position1 ,measurement of1 #bia1 #cjf4 ,announcement of a new comet1 #bdd4 ,annual rate of cometary discoveries1 #bee4 ,antares1 #cji4 ,anthelme1 ,discoverer of a new star in #afgj1 #cac4 ,apennines1 #acb4 ,aperture and ,power required for ,comet-seeking1 #beb4 ,apparitions1 ,meteoric1 #bfa4 ,appearance of ,comets1 #bbh4 ---- of ,mars1 #aee4 ,aquarids1 #bge4 ,archimedes1 #abg4 ,argelander's magnitudes of stars1 #bid4 ,aristarchus1 #abj4 ,ascertaining positions of ,comets1 #beg4 ,aspect of the rings of ,saturn1 #bjd4 ,atmosphere of ,jupiter1 #agg4 ---- of ,mars1 #afa4 ---- of ,mercury1 #aci4 ---- of ,venus1 #aea4 ,atmospheric undulations1 #bi4 ,attractions of ,telescopic work1 #he4 ,auwers1 ,discoverer of a new star in #ahfj1 #cad4 ,bacon1 ,roger1 ,early hints on refracted rays1 #c4 ,barnard1 ,his cometary discoveries1 #bee4 ---- observes ,brooks's multiple ,comet1 #bci4 ---- observes new stars in the ,trapezium1 #cai4 ---- observes a new nebula in the ,pleiades1 #cea4 ,beauty and brilliancy of ,venus1 #ade1 ,belts of ,sun-spots1 #ajd1 ---- on ,jupiter1 #agb4 ---- on ,saturn1 #aih4 ---- on ,uranus1 #bah4 ,berthon's dynamometer1 #ej4 ,biela's ,comet1 #bch4 ,bigourdan observes a variable ,nebula1 #cea4 ,binary ,stars1 #cjj4 ,birmingham discovers a new star in #ahff1 #cad4 ,bond1 ,g4 ,p41 discovers ,crape-ring of ,saturn1 #bjb4 ,brahe's1 ,tycho1 new star of #aegb1 #cab4 ,bright objects near the ,sun1 #ajg4 ,brightness and position of ,jupiter1 #agj4 ,brooks on ,comet-seeking1 #bec4 ---- on ,occultation of ,jupiter1 #ahg4 ---- on ,shower of telescopic ,meteors1 #bgb1 #bgd4 ,brooks's double ,comet of #ahhi1 #bci4 ,brorsen's ,comet1 #bci4 ,browning and reflecting-telescopes1 #fj4 ,brunowski discovers a new star1 #cac4 ,burnham1 ,discoverer of double ,stars1 #ca1 #cbj4 ---- discovers a group of #ah new nebul1 #cda4 ----1 ,measures of the companion to ,sirius1 #cjg4 ---- on the inutility of 8stops10 #eh4 ,calver compares light of reflectors and refractors1 #cg4 ----1 ,maker of glass specula1 #af1 #ag4 ,canal-shaped markings on ,mars1 #aei4 ,canis ,majoris 1 #cjg4 ,cassegrain's reflecting-telescope1 #aj4 ,cassini1 ,diameter of his object-glasses1 #i4 ---- discovers four satellites and the divided ring of ,saturn1 #i4 ----1 ,observations of ,jupiter1 #agb4 ----1 ---- of ,saturn1 #aih4 ----1 ---- of ,venus1 #adg4 ,celestial ,globe1 #fc4 ,centauri 1 ,diameter and distance1 #bii4 ,ceres1 #afh4 ,chambers on ,coloured ,stars1 #caf4 ---- on the intra-,mercurial ,planet1 #cdh4 ,chandler on ,variable ,stars1 #cej4 ,changes1 ,lunar1 #abj4 ---- on ,jupiter1 #ahb4 ---- on ,mars1 #afc4 ---- on ,saturn1 #bjf4 ,charts of ,mars1 #aeh4 ,cheapness of ,telescopes1 #eg4 ,choice of ,telescopes1 #ch4 ,clark1 ,alvan1 ,sons1 make large object-glasses1 #ah4 ----1 discovers the companion to ,sirius1 #cjg4 ,cleaning lenses1 #ei4 ,clusters of ,stars1 #cag4 ,coggia's ,comet of #ahgd1 #bcc4 ,colour of ,jupiter1 #aga4 ---- of ,mars1 #aee4 ---- of ,saturn1 #aie4 ---- of ,uranus1 #bag4 ,colouring of the eclipsed ,moon1 #aai4 ,colours of ,stars1 #cae4 ,coma ,berenices1 #cag4 ,,comets ,,and ,,comet-,,seeking1 #bbg4 ,ideas concerning ,comets1 #bbg4 ,appearance of ,comets1 #bbh4 ,large number visible1 #bbh4 ,nature of apparition1 #bbi4 ,tenuity1 #bbi4 ,differences of orbit1 #bcj4 ,discoveries of ,comets1 #bcj4 ,large ,comets1 #bca4 ,periodical ,comets1 #bcd4 ,halley's ,comet1 #bcf4 ,encke's ,comet1 #bcf4 ,biela's ,comet1 #bch4 ,brooks's double ,comet1 #bci4 ,brorsen's ,comet1 #bci4 ,faye's ,comet1 #bdj4 ,d',arrest's ,comet1 #bdj4 ,pons-,winnecke's ,comet1 #bdj4 ,tuttle's ,comet1 #bda4 ,grouping of ,periodical ,comets1 #bda4 ,further ,observations required1 #bdc4 ,nomenclature of ,comets1 #bdf4 ,curiosities of ,comets1 #bdh4 ,naked-eye ,comets1 #bdh4 ,comet-seeking1 #bdi4 ,english weather and ,comet-seeking1 #bea4 ,aperture and ,power required1 #beb4 ,annual rate of discovery1 #bee4 ,telescopic ,comets1 #bef4 ,ascertaining positions1 #beg4 ,dr4 ,doberck's hints1 #beh4 ,prizes for ,discoveries1 #beh4 ,common1 ,his large ,reflectors1 #ae2 ,their performance1 #bh4 ,computation of a ,meteor's real path1 #bgh4 ,conjunctions1 ,planetary1 #bbe4 ,constellation figures1 ,the1 #bij4 ,cooke ,sons mount a #bdh-;inch refractor1 #ah2 ,its barren record1 #be4 ,copernicus1 #abg4 ,course of the ,milky ,way1 #bif4 8,crab0 ,nebula in ,taurus 7,m4 #a71 #ccf4 ,crape-ring of ,saturn1 #bjb4 ,crucis 1 ,cluster at1 #cah4 ,curiosities of ,comets1 #bdh4 ,cyclonic action in ,sun-spots1 #ajh4 ,cygnus1 ,nebulous streams in1 #cci4 ,dallmeyer on ,dividing power1 #bic4 ,d',arrest's ,comet1 #bdj4 ,dawes's observations of ,jupiter1 #agc4 ---- observations of ,saturn's ,crape-ring1 #bjb4 ----1 ,on ,dividing power1 #bib4 ---- ,solar ,eyepiece1 #ib4 ,definition in towns1 #ha4 ,deimos1 ,outer ,satellite of ,mars1 #afe4 ,democritus explains the ,milky ,way1 #b4 ,dennett announces the ,red ,spot on ,jupiter1 #agc4 ,denning's ,comet1 #bdc4 ,denza on the ,meteors of ,nov4 #bg1 #bgb4 ,derham1 his list of ,nebul1 #cbg4 ,description of ,nebul and ,clusters of ,stars1 #ccc4 ,determination of the ,sun's rotation-period1 #ajd4 ,detonating ,fireballs1 #bfg4 ,dewing of ,mirrors1 #fb4 ,diffraction-rings1 #bic4 ,dimensions of ,nebul and ,scar-clusters1 #ccb4 ---- of ,sun-spots1 #id4 ,disappearance of ,saturn's ring1 #bje4 ,discordant observations of ,saturn1 #bjd4 ,discoveries of ,comets1 #bcj4 ---- of ,nebul1 #cda4 ,discovery of ,neptune1 #bba4 ---- of ,planetoids1 #afg4 ---- of ,uranus1 #bae4 ,distance of the stars1 #bii4 ,distinction between ,nebul and ,star-clusters1 #cbd4 ,distribution of ,nebul in ,r4,a41 #cbf4 ,disturbances1 ,recurrent solar1 #aaj4 ,dividing power1 #bib4 ,divisions in outer ring of ,saturn1 #bja4 ,doberck1 ,dr41 ,on the ,invention of the ,telescope1 #e4 ----1 ,on ,comet-seeking1 #beh4 ,dollond patents his ,achromatic ,telescope1 #ab4 ----1 ,his object-glasses1 #af4 ,donati's ,comet of #aheh1 #bcc4 ,drfel mountains1 #aca4 ,double ,comets3-- ,biela's1 #bch4 ,brooks's1 #bci4 ---- ,nebul1 #ccb4 ---- ,stars1 #cjj1 #cjb4 ,draco1 planetary nebula in1 #cce4 ,drawing1 #gc4 ,drawings of ,jupiter1 #ahe4 ,dumb-bell ,nebula 7,m4 #bg71 #ccg4 ,duration of meteor-flights1 #bhb4 ,duration of ,silver-on-glass films1 #fj4 ,dynamometer1 ,berthon's1 #ej4 ,early observations of ,jupiter1 #agb4 ---- ---- of nebul and star-clusters1 #cbf4 ---- ---- of ,neptune1 #bbb4 ---- ---- of ,saturn1 #aig4 ---- ---- of the ,sun1 #hh4 ---- ---- of ,uranus1 #baf4 ---- ---- of ,venus1 #adg4 ,earthshine on the ,moon1 #aaf4 ,eccentric position of ,saturn's rings1 #bjd4 ,eclipses of ,jupiter's satellites1 #ahi4 ---- of the ,moon1 #aah4 ---- of the ,sun1 #ig4 ,elger's lunar observations1 #abg1 #aca4 ---- ,drawings of lunar objects1 #abi1 #acj1 #acb4 ,ellipse1 #bcj4 ---- on ,jupiter1 ,gledhill's1 #agc4 ,elliptical nebul1 #cch4 ,elongations of ,mercury1 #ach4 ---- of ,venus1 #ade4 ,encke's ,comet1 #bcf4 ---- division in ,saturn's ring1 #bjb1 #bjh4 ,english weather and ,comet-seeking1 #bea4 ,equatoreal spots on ,jupiter1 ,bright1 #age1 #aha4 ---- ----1 ,dark1 #aha4 ,equatoreals1 ,advantage of1 #ed4 ,exceptional position of ,sun-spots1 #aaa4 ,eyepiece1 ,field of1 #ej4 ,eyepieces1 #df4 ----1 ,single-lens1 #dg4 ,fabricius observes ,sun-spots1 #hi4 ,facul1 ,sudden outburst of1 #ajh4 ,faint objects1 ,observation of1 #gb4 ,faintness of the markings on ,venus1 #aej4 ,falls of stone and iron1 #bff4 ,faye's ,comet1 #bdj4 ,field of eyepiece1 ,diameter of1 #ej4 ,figures1 ,the ,constellation1 #bij4 ,fireball of ,nov4 #bc1 #ahgg1 #bfg4 ,fireballs1 #bfg4 ----1 ,heights of1 #bfh4 ,first view of ,mercury1 ,amateur's1 #aci4 ,formations1 ,lunar1 #abc4 ,foucault parabolizes and silvers glass ,specul1 #ae4 ,fracastor1 ,his remarks on lenses in #aech1 #d4 ,friendly ,indulgences1 #gd4 ,future1 ,past and1 #hd4 ,future eclipses of the ,moon1 #aah4 ---- ---- of the ,sun1 #ih4 ,galaxy1 or ,milky ,way1 ,the1 #bie4 ,galilei and the invention of the ,telescope1 #b1 #d1 #e4 ----1 ,discovery of ,jupiter's satellites1 #ahg4 ----1 ,his first instrument and discoveries1 #f1 #g4 ,galle observes ,saturn's crape-ring1 #bjb4 ---- observes ,neptune1 #bbb4 ,geminids1 #bgf4 ,glass1 ,opera1 #fa4 ,gledhill's ellipse on ,jupiter1 #agc4 ,globe1 ,celestial1 #fc4 ,globular clusters4 #cch4 ---- ----1 ,list of1 #cdd4 ,gore1 ,diameter of ,centauri1 #bii4 ----1 ,dimensions of a ,star-cluster1 #ccb4 ----1 ,stellar distribution1 #bid4 ,greek alphabet1 #bhg4 ,gregory invents a reflecting-,telescope1 #aj4 ,grimaldi1 #abi4 ,grouping of periodical ,comets1 #bda4 ,groups of ,stars1 #caf4 ,grubb1 ,maker of a #d-;foot ,cassegrainian reflector1 #ad2 ,performance of1 #be4 ----1 ,maker of a #bg-;inch refractor1 #ah2 ,performance of1 #bg4 ,hall1 ,chester ,more1 invents achromatic ,object-glass1 #aa4 ,hall1 ,prof41 discovers a white spot on ,saturn1 #aii4 ----1 ,observations of ,saturn's satellites1 #bac4 ---- on the great ,washington refractor1 #bf4 ----1 ,remarks on large and small telescopes1 #ca4 ,halley's ,comet1 #bcf4 ---- list of ,nebul in #agaf1 #cbf4 ,harriot1 ,early observer of ,sun-spots1 #hi1 #ij4 ,hartwig1 ,discovers a new ,star in ,andromeda1 #cae4 ,heights of ,fireballs1 #bfh2 of ,meteors1 #bgg4 ,heis1 ,his labours in ,meteoric astronomy1 #bfb4 ,hencke1 ,discoverer of ,planetoids1 #afg4 ,henry1 ,bros41 make a #cj-;inch refractor1 #ah2 ,performance of1 #bg4 ---- observe the belts on ,uranus1 #bah4 ,herschel1 ,prof4 ,a4 ,s41 observes meteors1 #bfb4 ,herschel1 ,sir ,j41 ,comet of #ahfa1 #bcc4 ----1 ,description of k ,crucis1 #cah4 ----1 ,disappearance of ,saturn's ring1 #bje4 ----1 ,rediscovers ,uranus1 #bai4 ----1 ,satellites of ,uranus1 #bbj1 ----1 ,texture of ,comets1 #bbi4 ----1 ,thickness of ,saturn's ring1 #bje4 ----1 ,trapezium of ,orion1 #cah1 #cbj4 ,herschel1 ,sir ,w41 and ,cometary discovery1 #bca4 ----1 ,his discovery of ,nebul1 #cbg4 ----1 ,his discovery of nebulous ,stars1 #ccj4 ----1 ,his discovery of ,uranus1 #bae2 of ,satellites1 #bbj4 ----1 ,his method of observing ,sun-spots1 #ia4 ----1 ,his observations of ,jupiter1 #ahb4 ----1 ,his observations of ,mercury1 #adb4 ----1 ,his observations of ,saturn1 #aii4 ----1 ,his observations of ,venus1 #adi4 ----1 ,nucleus of ,comet of #ahaa1 #bcb4 ---- observes ,binary ,stars1 #cjj1 #cjf4 ----1 ,performance of #d-;ft4 reflector1 #ba4 ----1 ,remarks on eyepieces1 #dg4 ----1 ,rotation of ,jupiter's ,satellites1 #ahi4 ----1 ,singular figure of ,saturn1 #aif4 ,herschel's1 ,sir ,w41 ,telescopes1 #ab1 #ac1 #ci4 ,hevelius1 diameter of his object-glasses1 #i4 ,hind1 ,discoverer of a new ,star in #ahdh1 #cad4 ----1 ,discoverer of ,planetoids1 #afg4 ----1 ,discoverer of a variable ,nebula1 #cbh4 ,hipparchus forms a ,star-catalogue1 #cab4 ,hoek on the origin of ,comets1 #bdc4 ,hooke's observations of ,jupiter1 #agb4 ,hough's observations of ,jupiter1 #agd1 #ahb4 ,howlett's observations of ,sun-spots1 #aja1 #ajb4 ,huygens on the invention of the ,telescope1 #b4 ----1 ,discoveries on ,saturn1 #h1 #aih4 ----1 ,length of his instruments1 #h4 ,huygens's ,negative eyepiece1 #h1 #df4 ,hyginus1 ,the rill or cleft of1 #acj4 ,hyperbola1 #bcj4 ,identity of ,meteors and ,comets1 #bfb4 ,increasing number of ,telescopes1 #eg4 ,intra-,mercurial ,planet1 #acg4 ,jansen1 ,zachariah1 ,inventor of the ,telescope1 #d4 ,johnson's projections of ,solar ,eclipses1 #ii4 ,juno1 #afh4 ,,jupiter1 #agj4 ,an interesting object1 #agj4 ,brightness and position1 #agj4 ,period c41 #aga4 ,belts and spots1 #agb4 ,observations of ,hooke1 ,cassini1 and others1 #agb4 ,the 8,ellipse0 of #ahfi-gj1 #agc4 ,the red spot1 #agc4 ,rotation of red spot1 #age4 ,rotation of bright equatoreal spots1 #age4 ,rotation of dark spots in ,n4 hemisphere1 #age4 ,rotation-period1 #agf4 ,nature of the red spot1 #agg4 ,bright equatoreal spots1 #aha4 ,dark equatoreal spots1 #aha4 ,new belts1 #ahb4 ,changes on the planet1 #ahb4 ,further observations required1 #ahc4 ,occultations by the ,moon1 #ahe4 ,the four satellites1 #ahg4 ,their eclipses1 occultations1 and transits1 #ahi4 ,the planet without visible satellites1 #aib4 ,spots on the ,satellites1 #aic4 ,occultation of a ,star by ,jupiter1 #aic4 ,keeler1 ,white spots and canals on ,mars1 #cdh4 ,kitchiner1 ,the inutility of large ,telescopes1 #ce4 ----1 ,singular form of ,saturn1 #aif4 ,klein's supposed new crater near ,hyginus1 #abb4 ,large and small telescopes compared1 #bj4 ---- ,comets1 #bca4 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