,,the ,,trouvelot ,,astronomical ,,drawings ,,manual ,,by ,e4 ,l4 ,,trouvelot1 ,,formerly ,,connected ,,with ,,the ,,observatory ,,of ,,harvard ,,college2 ,,fellow ,,of ,,the ,,american ,,academy ,,of ,,arts ,,and ,,sciences1 ,,and ,,member ,,of ,,the ,,seleno-,,graphical ,,society ,,of ,,great ,,britain2 ,,in ,,charge ,,of ,a ,,government ,,expedition ,,to ,,observe ,,the ,,total ,,solar ,,eclipse ,,of #ahgh4 ,,new ,,york ,,charles ,,scribner',s ,,sons #ahhb ,,introduction ,during a study of the heavens1 which has now been continued for more than fifteen years1 ,i have made a large number of observations pertaining to physical astronomy1 together with many original drawings representing the most interesting celestial objects and phenomena4 ,with a view to making these observations more generally useful1 ,i was led1 some years ago1 to prepare1 from this collection of drawings1 a series of astronomical pictures1 which were intended to represent the celestial phenomena as they appear to a trained eye and to an experienced draughtsman through the great modern telescopes1 provided with the most delicate instrumental appliances4 ,over two years were spent in the preparation of this series1 which consisted of a number of large drawings executed in pastel4 ,in #ahgf1 these drawings were displayed at the ,united ,states ,centennial ,exhibition at ,philadelphia1 forming a part of the ,massachusetts exhibit1 in the ,department of ,education and ,science4 ,the drawings forming the present series comprise only a part of those exhibited at ,philadelphia2 but1 although fewer in number1 they are quite sufficient to illustrate the principal classes of celestial objects and phenomena4 ,while my aim in this work has been to combine scrupulous fidelity and accuracy in the details1 ,i have also endeavored to preserve the natural elegance and the delicate outlines peculiar to the objects depicted2 but in this1 only a little more than a suggestion is possible1 since no human skill can reproduce upon paper the majestic beauty and radiance of the celestial objects4 ,the plates were prepared under my supervision1 from the original pastel drawings1 and great care has been taken to make the reproduction exact4 ,the instruments employed in the observations1 and in the delineation of the heavenly bodies represented in the series1 have varied in aperture from #f to #bf inches1 according to circumstances1 and to the nature of the object to be studied4 ,the great ,washington refractor1 kindly placed at my disposal by the late ,admiral ,c4 ,h4 ,davis1 has contributed to this work1 as has also the #bf inch telescope of the ,university of ,virginia1 while in the hands of its celebrated constructors1 ,alvan ,clark ,sons4 ,the spectroscope used was made by ,alvan ,clark ,sons4 ,attached to it is an excellent diffraction grating1 by ,mr4 ,l4 ,m4 ,rutherfurd1 to whose kindness ,i am indebted for it4 ,those unacquainted with the use of optical instruments generally suppose that all astronomical drawings are obtained by the photographic process1 and are1 therefore1 comparatively easy to procure2 but this is not true4 ,although photography renders valuable assistance to the astronomer in the case of the ,sun and ,moon1 as proved by the fine photographs of these objects taken by ,m4 ,janssen and ,mr4 ,rutherfurd2 yet1 for other subjects1 its products are in general so blurred and indistinct that no details of any great value can be secured4 ,a well-trained eye alone is capable of seizing the delicate details of structure and of configuration of the heavenly bodies1 which are liable to be affected1 and even rendered invisible1 by the slightest changes in our atmosphere4 ,the method employed to secure correctness in the proportions of the original drawings is simple1 but well adapted to the purpose in view4 ,it consists in placing a fine reticule1 cut on glass1 at the common focus of the objective and the eye-piece1 so that in viewing an object1 its telescopic image1 appearing projected on the reticule1 can be drawn very accurately on a sheet of paper ruled with corresponding squares4 ,for a series of such reticules ,i am indebted to the kindness of ,professor ,william ,a4 ,rogers1 of the ,harvard ,college ,observatory4 ,the drawings representing telescopic views are inverted1 as they appear in a refracting telescope--the ,south being upward1 the ,north downward1 the ,east on the right1 and the ,west on the left4 ,the ,comet1 the ,milky-,way1 the ,eclipse of the ,moon1 the ,aurora ,borealis1 the ,zodiacal ,light and the ,meteors are represented as seen directly in the sky with the naked eye4 ,the ,comet was1 however1 drawn with the aid of the telescope1 without which the delicate structure shown in the drawing would not have been visible4 ,the plate representing the ,november ,meteors1 or so-called ,leonids1 may be called an ideal view1 since the shooting stars delineated1 were not observed at the same moment of time1 but during the same night4 ,over three thousand ,meteors were observed between midnight and five o'clock in the morning of the day on which this shower occurred2 a dozen being sometimes in sight at the same instant4 ,the paths of the ,meteors1 whether curved1 wavy1 or crooked1 and also their delicate colors1 are in all cases depicted as they were actually observed4 ,in the ,manual1 ,i have endeavored to present a general outline of what is known1 or supposed1 on the different subjects and phenomena illustrated in the series4 ,the statements made are derived either from the best authorities on physical astronomy1 or from my original observations1 which are1 for the most part1 yet unpublished4 ,the figures in the ,manual relating to distance1 size1 volume1 mass1 etc41 are not intended to be strictly exact1 being only round numbers1 which can1 therefore1 be more easily remembered4 ,it gives me pleasure to acknowledge that the experience acquired in making the astronomical drawings published in ,volume ,,viii4 of the ,annals of the ,harvard ,college ,observatory1 while ,i was connected with that institution1 has been of considerable assistance to me in preparing this work2 although no drawings made while ,i was so connected have been used for this series4 ,e4 ,l4 ,,trouvelot4 ,cambridge1 ,march1 #ahhb4 ,,contents ,,introduction ,,list ,,of ,,plates ,,the ,,sun ,,general ,,remarks ,,on ,,the ,,sun ,,sun-,,spots ,,and ,,veiled ,,spots ,,solar ,,protuberances ,,total ,,eclipse ,,of ,,the ,,sun ,,the ,,auroral ,,and ,,zodiacal ,,lights ,,the ,,aurora ,,borealis ,,the ,,zodiacal ,,light ,,the ,,moon ,,the ,,moon ,,eclipses ,,of ,,the ,,moon ,,the ,,planets ,,the ,,planets ,,the ,,planet ,,mars ,,the ,,planet ,,jupiter ,,the ,,planet ,,saturn ,,comets ,,and ,,meteors ,,comets ,,shooting-,,stars ,,and ,,meteors ,,the ,,stellar ,,systems ,,the ,,milky-,,way ,,or ,,galaxy ,,the ,,star-,,clusters ,,the ,,nebul ,,appendix ,,list ,,of ,,plates#a ,,plate ,i4 ,,group ,,of ,,sun-,,spots ,,and ,,veiled ,,spots4 ,observed ,june #ag1 #ahge1 at #g h4 #cjm4 ,a4 ,m4 ,,ii4 ,,solar ,,protuberances4 ,observed ,may #e1 #ahgc1 at #i;h4 #djm4 ,a4 ,m4 ,,iii4 ,,total ,,eclipse ,,of ,,the ,,sun4 ,observed ,july #bi1 #ahgh1 at ,creston1 ,wyoming ,territory4 ,,iv4 ,,aurora ,,borealis4 ,as observed ,march #a1 #ahgb1 at #i;h4 #bem4 ,p4 ,m4 ,v4 ,,the ,,zodiacal ,,light4 ,observed ,february #bj1 #ahgf4 ,,vi4 ,,mare ,,humorum4 ,from a study made in #ahge4 ,,vii4 ,,partial ,,eclipse ,,of ,,the ,,moon4 ,observed ,october #bd1 #ahgd4 ,,viii4 ,,the ,,planet ,,mars4 ,observed ,september #c1 #ahgg1 at #aa;h4 #eem4 ,p4 ,m4 ,,ix4 ,,the ,,planet ,,jupiter4 ,observed ,november #a1 #ahhj1 at #i;h4 #cjm4 ,p4 ,m4 ,x4 ,,the ,,planet ,,saturn4 ,observed ,november #cj1 #ahgd1 at #eth4 #ejm4 ,p4 ,m4 ,,xi4 ,,the ,,great ,,comet ,,of #ahha4 ,observed on the night of ,june #be-bf1 at #a;h4 #cjm4 ,a4 ,m4 ,,xii4 ,,the ,,november ,,meteors4 ,as observed between midnight and #c o'clock ,a4 ,m41 on the night of ,november #ac-ad1 #ahfh4 ,,xiii4 ,,part ,,of ,,the ,,milky-,,way4 ,from a study made during the years #ahgd1 #ahge and #ahgf4 ,,xiv4 ,,star-,,cluster ,,in ,,hercules4 ,from a study made in ,june1 #ahgg4 ,,xv4 ,,the ,,great ,,nebula ,,in ,,orion4 ,from a study made in the years #ahgc-gf4 ,footnote #a3 ,for ,key to the ,plates1 see ,appendix4 ,reproduced from the ,original ,drawings1 by ,armstrong ,company1 ,riverside ,press1 ,cambridge1 ,mass4 ,,general ,,remarks ,,on ,,the ,,sun ,the ,sun1 the centre of the system which bears its name1 is a self-luminous sphere1 constantly radiating heat and light4 ,its apparent diameter1 as seen at its mean from the ,earth1 subtends an angle of #cb'1 or a little over half a degree4 ,a dime1 placed about six feet from the eye1 would appear of the same proportions1 and cover the ,sun's disk1 if projected upon it4 ,that the diameter of the ,sun does not appear larger1 is due to the great distance which separates us from that body4 ,its distance from the ,earth is no less than #ib1jjj1jjj miles4 ,to bridge this immense gap1 would require #aa1fbc globes like the ,earth1 placed side by side1 like beads on a string4 ,the ,sun is an enormous sphere whose diameter is over #ajh times the diameter of our globe1 or very nearly #hfj1jjj miles4 ,its radius is nearly double the distance from the ,earth to the ,moon4 ,if we suppose1 for a moment1 the ,sun to be hollow1 and our globe to be placed at the centre of this immense spherical shell1 not only could our satellite revolve around us at its mean distance of #bch1hjj miles1 as now1 but another satellite1 placed #aij1jjj miles farther than the ,moon1 could freely revolve likewise1 without ever coming in contact with the solar envelope4 ,the circumference of this immense sphere measures #b1hjj1jjj miles4 ,while a steamer1 going at the rate of #cjj miles a day1 would circumnavigate the ,earth in #hc days1 it would take1 at the same rate1 nearly #be years to travel around the ,sun4 ,the surface of the ,sun is nearly #ab1jjj times the surface of the ,earth1 and its volume is equal to #a1cjj1jjj globes like our own4 ,if all the known planets and satellites were united in a single mass1 #fjj such compound masses would be needed to equal the volume of our luminary4 ,although the density of the ,sun is only one-quarter that of the ,earth1 yet the bulk of this body is so enormous that1 to counterpoise it1 no less than #cad1gfj globes like our ,earth would be required4 ,the ,sun uniformly revolves around its axis in about #be days4 ,its equator is inclined #g #ae' to the plane of the ecliptic1 the axis of rotation forming1 therefore1 an angle of #hb #de' with the same plane4 ,as the ,earth revolves about the ,sun in the same direction as that of the ,sun's rotation1 the apparent time of this rotation1 as seen by a terrestrial spectator1 is prolonged from #be days to about #bg days and #g hours4 ,the rotation of the ,sun on its axis1 like that of the ,earth and the other planets1 is direct1 or accomplished from ,west to ,east4 ,to an observer on the ,earth1 looking directly at the ,sun1 the rotation of this body is from left to right1 or from ,east to ,west4 ,the general appearance of the ,sun is that of an intensely luminous disk1 whose limb1 or border1 is sharply defined on the heavens4 ,when its telescopic image is projected on a screen1 or fixed on paper by photography1 it is noticed that its disk is not uniformly bright throughout1 but is notably more luminous in its central parts4 ,this phenomenon is not accidental1 but permanent1 and is due in reality to a very rare but extensive atmosphere which surrounds the ,sun1 and absorbs the light which that body radiates1 proportionally to its thickness1 which1 of course1 increases towards the limb1 to an observer on the ,earth4 ,,the ,,enveloping ,,layers ,,of ,,the ,,sun ,the luminous surface of the ,sun1 or that part visible at all times1 and which forms its disk1 is called the ,photosphere1 from the property it is supposed to possess of generating light4 ,the photosphere does not extend to a great depth below the luminous surface1 but forms a comparatively thin shell1 #c1jjj or #d1jjj miles thick1 which is distinct from the interior parts1 above which it seems to be kept in suspense by internal forces4 ,from the observations of some astronomers it would appear that the diameter of the photosphere is subject to slight variations1 and1 therefore1 that the solar diameter is not a constant quantity4 ,from the nature of this envelope1 such a result does not seem at all impossible1 but rather probable4 ,immediately above the photosphere lies a comparatively thin stratum1 less than a thousand miles in thickness1 called the ,reversing ,layer4 ,this stratum is composed of metallic vapors1 which1 by absorbing the light of particular refrangibilities emanating from the photosphere below1 produces the dark ,fraunhofer lines of the solar spectrum4 ,above the reversing layer1 and resting immediately upon it1 is a shallow1 semi-transparent gaseous layer1 which has been called the ,chromosphere1 from the fine tints which it exhibits during total eclipses of the ,sun1 in contrast with the colorless white light radiated by the photosphere below4 ,although visible to a certain extent on the disk1 the chromosphere is totally invisible on the limb1 except with the spectroscope1 and during eclipses1 on account of the nature of its light1 which is mainly monochromatic1 and too feeble1 compared with that emitted by the photosphere1 to be seen4 ,the chromospheric layer1 which has a thickness of from #c1jjj to #d1jjj miles1 is uneven1 and is usually upheaved in certain regions1 its matter being transported to considerable elevations above its general surface1 apparently by some internal forces4 ,the portions of the chromosphere thus lifted up1 form curious and complicated figures1 which are known under the names of ,solar ,protuberances1 or ,solar ,flames4 ,above the chromosphere1 and rising to an immense but unknown height1 is the solar atmosphere proper1 which is only visible during total eclipses of the ,sun1 and which then surrounds the dark body of the ,moon with the beautiful rays and glorious nimbus1 called the ,corona4 ,these four envelopes3 the photosphere1 the reversing layer1 the chromosphere1 and the corona1 constitute the outer portions of our luminary4 ,below the photosphere little can be seen1 although it is known1 as will appear below1 that at certain depths cloud-like forms exist1 and freely float in an interior atmosphere of invisible gases4 ,beyond this all is mystery1 and belongs to the domain of hypothesis4 ,,structure ,,of ,,the ,,photosphere ,,and ,,chromosphere ,the apparent uniformity of the solar surface disappears when it is examined with a telescope of sufficient aperture and magnifying powers4 ,seen under good atmospheric conditions1 the greater part of the solar surface appears mottled with an infinite number of small1 bright granules1 irregularly distributed1 and separated from each other by a gray-tinted background4 ,these objects are known under different names4 ,the terms granules and granulations answer very well for the purpose1 as they do not imply anything positive as to their form and true nature4 ,they have also been called ,lucul1 ,rice ,grains1 ,willow ,leaves1 etc41 by different observers4 ,although having different shapes1 the granulations partake more or less of the circular or slightly elongated form4 ,their diameter1 which varies considerably1 has been estimated at from #j4e to #c1 or from #bbd to #a1cdd miles4 ,the granulations which attain the largest size appear1 under good atmospheric conditions1 to be composed of several granules1 closely united and forming an irregular mass1 from which short appendages protrude in various directions4 ,the number of granulations on the surface of the ,sun varies considerably under the action of unknown causes4 ,sometimes they are small and very numerous1 while at other times they are larger1 less numerous1 and more widely separated4 ,other things being equal1 the granulations are better seen in the central regions of the ,sun than they are near the limb4 ,usually the granulations are very unstable2 their relative position1 form1 and size undergoing continual changes4 ,sometimes they are seen to congregate or to disperse in an instant1 as if acting under the influence of attractive and repulsive forces2 assembling in groups or files1 and oftentimes forming capricious figures which are very remarkable1 but usually of short duration4 ,in an area of great solar disturbances1 the granulations are often stretched to great distances1 and form into parallel lines1 either straight1 wavy1 or curved1 and they have then some resemblance to the flowing of viscous liquids4 ,the granulations are usually terminated either by rounded or sharply pointed summits1 but they do not all rise to the same height1 as can be ascertained with the spectroscope when they are seen sidewise on the limb4 ,in the regions where they are most abundant1 they usually attain greater elevations1 and when observed on the limb with the spectroscope1 they appear as slender acute flames4 ,the granulations terminated by sharply-pointed crests1 although observed in all latitudes1 seem to be characteristic of certain regions4 ,a daily study of the chromosphere1 extending over a period of ten years1 has shown me that the polar regions are rarely ever free from these objects1 which are less frequent in other parts of the ,sun4 ,in the polar regions they are sometimes so abundant that they completely form the solar limb4 ,these forms of granulation are comparatively rare in the equatorial zones1 and when seen there1 they never have the permanency which they exhibit in the polar regions4 ,when observed in the equatorial regions1 they usually appear in small groups1 in the vicinity of sun spots1 or they are at least enclosed in areas of disturbances where such spots are in process of formation4 ,in these regions they often attain greater elevations than those seen in high latitudes4 ,as we are certain that in the equatorial zones these slender flames 7i4 e41 granulations7 are a sure sign of local disturbance1 it may be reasonably supposed that the same kind of energy producing them nearly always prevails in the polar regions1 although it is there much weaker1 and never reaches beyond certain narrow limits4 ,studied with the spectroscope1 the granulations are found to be composed in the main of incandescent hydrogen gas1 and of an unknown substance provisionally called helium4 ,among the most brilliant of them are found traces of incandescent metallic vapors1 belonging to various substances found on our globe4 ,the chromosphere is not fixed1 but varies considerably in thickness in its different parts1 from day to day4 ,its thickness is usually greater in the polar regions1 where it sometimes exceeds #f1gjj miles4 ,in the equatorial regions the chromosphere very rarely attains this height1 and when it does1 the rising is local and occupies only a small area4 ,in these regions it is sometimes so shallow that its depth is only a few seconds1 and is then quite difficult to measure4 ,these numbers give1 of course1 the extreme limits of the variations of the chromosphere2 but1 nearly always1 it is more shallow in the equatorial regions2 and1 as far as my observations go1 the difference in thickness between the polar and equatorial zones is greater in years of calm than it is in years of great solar activity4 ,but ten years of observation are not sufficient to warrant any definite conclusions on this subject4 ,there is undoubtedly some relation between the greater thickness of the chromosphere in the polar regions1 and the abundance and permanence of the sharply-pointed granulations observed in the same regions4 ,this becomes more evident when we know that the appearance of similarly-pointed flames in the equatorial zones is always accompanied with a local thickening of the chromosphere4 ,the thickening in the polar regions may be only apparent1 and not due to a greater accumulation of chromospheric gases there2 but may be caused by some kind of repulsive action or polarity1 which lifts up and extends the summit of the granulations in a manner similar to the well-known mode of electric repulsion and polarity4 ,as it seems very probable that the heat and light emanating from the ,sun are mainly generated at the base of the granulations1 in the filamentary elements composing the chromosphere and photosphere1 it would follow that1 as the size and number of these objects constantly vary1 the amount of heat and light emitted by the ,sun should also vary in the same proportion4 ,the granulations of the solar surface are represented on ,plate ,i41 and form the general background to the group of ,sun-spots forming the picture4 ,,the ,,facul ,although the solar surface is mainly covered with the luminous granulations and the grayish background above described1 it is very rare that its appearance is so simple and uniform as already represented4 ,for the most part1 on the contrary1 it is diversified by larger1 brighter1 and more complicated forms1 which are especially visible towards the border of the ,sun4 ,owing to their extraordinary brilliancy1 these objects have been called ,facul 7torches74 ,although the facul are very seldom seen well beyond #ej heliocentric degrees from the limb1 yet they exist1 and are as numerous in the central parts of the disk as they are towards the border2 since they form a part of the solar surface1 and participate in its movement of rotation4 ,their appearance near the limb has been attributed to the effect of absorption produced by the solar atmosphere on the light from the photosphere2 but this explanation seems inadequate1 and does not solve the problem4 ,the well-known fact that the solar protuberances--which are in a great measure identical with the facul--are much brighter at the base than they are at the summit1 perhaps gives a clue to the explanation of the phenomenon2 especially since we know that1 in general1 the summit of the protuberances is considerably broader than their base4 ,when these objects are observed in the vicinity of the limb1 they present their brightest parts to the observer1 since1 in this position1 they are seen more or less sidewise2 and1 therefore1 they appear bright and distinct4 ,but as the facul recede from the limb1 their sides1 being seen under a constantly decreasing angle1 appear more and more foreshortened2 and1 therefore1 these objects grow less bright and less distinct1 until they finally become invisible1 when their bases are covered over by the broad1 dusky summit generally terminating the protuberances4 ,the facul appear as bright and luminous masses or streaks on the granular surface of the ,sun1 but they differ considerably in form and size4 ,two types at least are distinguishable4 ,in their simplest form they appear either as isolated white spots1 or as groups of such spots covering large surfaces1 and somewhat resembling large flakes of snow4 ,in their most characteristic types they appear as intensely luminous1 heavy masses1 from which1 in most cases1 issue intricate ramifications1 sometimes extending to great distances4 ,generally1 the ramifications issuing from the masses of facul have their largest branches directed in the main towards the eastern limb of the ,sun4 ,some of these branches have gigantic proportions4 ,occasionally they extend over #fj and even #hj of the solar surface1 and1 therefore1 attain a length of from #dej1jjj to #fjj1jjj miles4 ,although the facul may be said to be seen everywhere on the surface of the ,sun1 there is a vast difference in different regions1 with regard to their size1 number1 and brilliancy4 ,they are largest1 most abundant1 and brightest on two intermediate zones parallel to the solar equator1 and extending #ce or #dj to the north and to the south of this line4 ,the breadth of these zones varies considerably with the activity of the solar forces4 ,when they are most active1 the facul spread on either side1 but especially towards the equator1 where they sometimes nearly meet those of the other zone4 ,in years of little solar activity the belts formed by the facul are very narrow--the elements composing them being very few and small1 although they never entirely disappear4 ,the facul are very unstable1 and are constantly changing3 those of the small types sometimes form and vanish in a few minutes4 ,when an area of disturbance of the solar surface is observed for some time1 all seems in confusion2 the movements of the granulations become unusually violent2 they congregate in all sorts of ways1 and thus frequently form temporary facul4 ,action of this kind is1 for the most part1 peculiar to the polar regions of the ,sun4 ,the larger facul have undoubtedly another origin1 as they seem to be mainly formed by the ejection of incandescent gases and metallic vapors from the interior of the photosphere4 ,in their process of development some of the heavy masses of facul are swollen up to great heights1 being torn in all sorts of ways1 showing large rents and fissures through which the sight can penetrate4 ,very few facul are represented in ,plate ,i42 several streaks are shown at the upper left-hand corner1 some appearing as whitish ramifications among the granulations representing the general solar surface4 ,,sun-,,spots ,,and ,,veiled ,,spots ,,plate ,i ,besides the brilliant facul already described1 much more conspicuous markings1 though of a totally different character1 are very frequently observed on the ,sun4 ,on account of their darkish appearance1 which is in strong contrast with the white envelope of our luminary1 these markings were called ,macul1 or ,sun-spots1 by their earlier observers4 ,the ,sun-spots are not equally distributed on the solar surface2 but like the facul1 to which they are closely related1 they occupy two zones--one on each side of the equator4 ,these zones are comprised between #aj and #ce of north latitude1 and #aj and #ce of south latitude4 ,between these two zones is a belt #bj in width1 where the ,sun-spots are rarely seen4 ,above the latitudes #ce north and south1 the ,sun-spots are rare1 and it is only occasionally1 and during years of great solar activity1 that they appear in these regions2 in only a few cases have spots of considerable size been seen there4 ,a few observers1 however1 have seen spots as far as #dj and #ej from the equator2 and ,la ,hire even observed one in #gj of north latitude2 but these cases are exceedingly rare4 ,it is not uncommon1 however1 to see very small spots1 or groups of such spots1 within #h or #aj from the poles4 ,the activity of the ,sun is subject to considerable fluctuation1 and accordingly the ,sun-spots vary in size and number in different years4 ,during some years they are large1 complicated1 and very numerous2 while in others they are small and scarce1 and are sometimes totally absent for weeks and months together4 ,the fluctuations in the frequency of ,sun-spots are supposed to be periodical in their character1 although their periods do not always appear to recur at exactly regular intervals4 ,sometimes the period is found to be only nine years1 while at other times it extends to twelve years4 ,the period generally adopted now is #aa years1 nearly2 but further investigations are needed to understand the true nature of the phenomenon4 ,the number of ,sun-spots does not symmetrically augment and diminish1 but the increase is more rapid than the diminution4 ,the period of increase is only about four years1 while that of decrease is over seven years2 each period of ,sun-spot maximum being nearer the preceding period of ,sun-spot minimum than it is to that next following4 ,the cause of these fluctuations in the solar energy is at present wholly unknown4 ,some astronomers1 however1 have attributed it to the influence of the planets ,venus and ,jupiter1 the period of revolution of the latter planet being not much longer than the ,sun-spot period2 but this supposition lacks confirmation from direct observations1 which1 so far1 do not seem to be in favor of the hypothesis4 ,at the present time the solar activity is on the increase1 and the ,sun-spots will probably reach their maximum in #ahhc4 ,the last minimum occurred in #ahgi1 when only sixteen small groups of spots were observed during the whole year4 ,sun-spots vary in size and appearance2 but1 unless they are very small1 in which case they appear as simple black dots1 they generally consist of two distinct and well-characterized parts1 nearly always present4 ,there is first1 a central part1 much darker than the other1 and sharply divided from it1 called the ,umbra2 second1 a broad1 irregular radiated fringe of lighter shade1 completely surrounding the first1 and called the ,penumbra4 ,reduced to its simplest expression1 a ,sun-spot is a funnel-shaped opening through the chromosphere and the photosphere4 ,the inner end of the funnel1 or opening1 gives the form to the umbra1 while its sloping sides form the penumbra4 ,the umbra of ,sun-spots1 whose outlines approximately follow the irregularities of the penumbral fringe1 has a diameter which generally exceeds the width of the penumbral ring4 ,sometimes it appears uniformly black throughout2 but it is only so by contrast1 as is proved when either ,mercury or ,venus passes near a spot during a transit over the ,sun's disk4 ,the umbra then appears grayish1 when compared with the jet-black disk of the planet4 ,the umbra of spots is rarely so simple as just described2 but it is frequently occupied1 either partly or wholly1 by grayish and rosy forms1 somewhat resembling loosely-entangled muscular fibres4 ,these forms have been called the ,gray and ,rosy ,veils4 ,frequently these veils appear as if perforated by roundish black holes1 improperly called ,nuclei1 which permit the sight to penetrate deeper into the interior4 ,to all appearance the gray and rosy veils are of the same nature as the chromosphere and the facul1 and are therefore mainly composed of hydrogen gas4 ,whatever can be known about the interior of the ,sun1 must be learned from the observations of these openings1 which are comparatively small4 ,but whatever this interior may be1 we certainly know that it is not homogeneous4 ,apparently1 the ,sun is a gigantic bubble1 limited by a very thin shell4 ,below this shell exists a large open space filled with invisible gases1 in which1 through the openings constituting the ,sun-spots1 the gray and rosy veils described above are occasionally seen floating4 ,the fringe forming the penumbra of spots is much more complicated than the umbra4 ,in its simpler form1 it is composed of a multitude of bright1 independent filaments of different forms and sizes1 partly projecting one above the other1 on the sloping wall of the penumbra1 from which they seem to proceed4 ,seen from the ,earth1 these filaments have somewhat the appearance of thatched straw1 converging towards the centre of the umbra4 ,it is very rare1 however1 that the convergence of the penumbral filaments is regular1 and great confusion sometimes arises from the entanglement of these filaments4 ,some of these elements appear straight1 others are curved or loop-shaped2 while still others1 much larger and brighter than the rest1 give a final touch to this chaos of filaments1 from which results the general thatched and radiating appearance of the penumbra4 ,the extremities of the penumbral filaments1 especially of those forming the border of the umbra1 are usually club-shaped and appear very brilliant1 as if these elements had been superheated by some forces escaping through the opening of the spots4 ,besides these characteristics1 the ,sun-spots have others1 which1 although not always present1 properly belong to them4 ,comparatively few spots are so simple as the form just described4 ,very frequently a spot is accompanied by brilliant facul1 covering part of its umbra and penumbra1 and appearing to form a part of the spot itself4 ,when seen projected over ,sun-spots1 the facul appear intensely bright1 and from these peculiarities they have been called ,luminous ,bridges4 ,they are1 in fact1 bridges1 but in most cases they are at considerable heights above the spots1 kept there by invisible forces4 ,when such spots with luminous bridges approach the ,sun's limb1 it is easy to see1 by the rapid apparent displacement which they undergo1 that they are above the general level4 ,when the spots are closing up1 the inverse effect is sometimes observed4 ,on several occasions1 ,i have seen huge masses of facul advance slowly over the penumbra of a spot and fall into the depths of the umbra1 resembling gigantic cataracts4 ,i have seen narrow branches of facul1 which1 after having fallen to great depths in the umbra1 floated across it and disappeared under the photosphere on the opposite side4 ,i have also seen luminous bridges1 resembling cables1 tightly stretched across the spots1 slackening slowly1 as if loosened at one end1 and gently curving into the umbra1 where they formed immense loops1 large enough to receive our globe4 ,it is to be remarked that1 in descending under the photospheric shell1 the bright facul and the luminous bridges gradually lose their brilliancy4 ,at first they appear grayish1 but in descending farther they assume more and more the pink color peculiar to the rosy veils4 ,the pinkish color acquired by the facul when they reach a certain depth under the photosphere1 is precisely the color of the chromosphere and of the solar protuberances1 as seen during total eclipses of the ,sun--a fact which furnishes another proof that the facul are of the same nature as the protuberances4 ,i record here an observation which1 at first sight1 may appear paradoxical2 but which seems1 however1 to be of considerable importance1 as it shows unmistakably that the solar light is mainly1 if not entirely1 generated on its surface1 or at least very near to it4 ,on ,may #bf1 #ahgh1 ,i observed a large group of ,sun-spots at a little distance from the east limb of the ,sun4 ,the spot nearest to the limb was partly covered over on its eastern and western sides by bright and massive facul which concealed about two-thirds of the whole spot1 only a narrow opening1 running from north to south1 being left across the middle of the spot4 ,owing to the rotundity of the ,sun1 the penumbra of this spot1 although partly covered by the facul1 could1 however1 be seen on its eastern side1 since the sight of the observer could there penetrate sidewise under the facul4 ,upon that part of the penumbra appeared a strong shadow1 representing perfectly the outline of the facular mass situated above it4 ,the phenomenon was so apparent that no error of observation was possible1 and a good drawing of it was secured4 ,if this facul had been as bright beneath as it was above1 it is evident that no shadow could have been produced2 hence the light of these facul must have been mainly generated on or very near their exterior surfaces4 ,this1 with the well-proved fact that the bright facul lose their light in falling into the interior of the ,sun1 seems to suggest the idea that the bright light emitted by the facul1 and very probably all the solar light1 can be generated only on its surface2 the presence of the coronal atmosphere being perhaps necessary to produce it4 ,several times before this observation1 ,i had suspected that some facul were casting a shadow1 but as this seemed so improbable1 my attention was not awakened until the phenomenon became so prominent that it could not escape notice4 ,with due attention1 some glimpses of the phenomenon can frequently be observed through the openings of some of the facul projecting over the penumbra of ,sun-spots4 ,it is very seldom that the structure of the penumbra is seen through such openings1 which usually appear as dark as the umbra of the large spots1 although they do not penetrate through the photosphere like the latter4 ,it is only when the rents in the facul are numerous and quite large1 that the penumbral structure is recognized through them4 ,since these superficial rents in the facul do not extend through the photosphere1 and appear black1 it seems evident that the penumbra seen through them cannot be as bright as it is when no facul are projected upon it1 and therefore that the facul intercept light from the exterior surface1 which would otherwise reach the penumbra4 ,while the matter forming the facul sometimes falls into the interior of the ,sun1 the same kind of matter is frequently ejected in enormous quantities1 and with great force1 from the interior1 through the visible and invisible openings of the photosphere1 and form the protuberances described in the following section of this manual 7,solar protuberances7 ,it is not only the incandescent hydrogen gas or the metallic vapors which are thus ejected1 but also cooler hydrogen gas1 which sometimes appears as dark clouds on the solar surface4 ,on ,december #ab1 #ahge1 ,i observed such a cloud of hydrogen issuing from the corner of a small ,sun-spot4 ,it traveled several thousand miles on the solar surface1 in a north-easterly direction1 before it became invisible4 ,solar spots are formed in various ways2 but1 for the most part1 the apparition of a spot is announced beforehand1 by a great commotion of the solar surface at the place of its appearance1 and by the formation of large and bright masses of facul1 which are usually swollen into enormous bubbles by the pressure of the internal gases4 ,these bubbles become visible in the spectroscope while they are traversing the solar limb1 as they are then presented to us sidewise4 ,under the action of the increasing pressure1 the base of the facul is considerably stretched1 and1 its weakest side finally giving way1 the facular mass is torn in many places from the solar surface1 and is perforated by holes of different sizes and forms4 ,the holes thus made along the border of the facul appear as small black spots1 separated more or less by the remaining portion of the lacerated facul1 and they enlarge more and more at the expense of the intervening portions1 which thus become very narrow4 ,this perforated side of the facul1 offering less resistance1 is gradually lifted up1 as would be the cover of a box1 for example1 while its opposite side remains attached to the surface4 ,the facular matter separating the small black holes is greatly stretched during this action1 and forms long columns and filaments4 ,these appear as luminous bridges upon the large and perfectly-formed spot1 which is then seen under the lifted facular masses4 ,the spots thus made visible are soon freed from the facular masses1 which are gradually shifted towards the opposite side4 ,in such cases the spots are undoubtedly formed under the facul before they can be seen4 ,this becomes evident when such spots1 not yet cleared from the facul covering them1 are observed near the east limb2 since in this position the observer can see through the side-openings of the facul1 and sometimes recognize the spots under their cover4 ,it frequently occurs that the spots thus formed under the facul continue to be partly covered by the facular clouds1 the forces at work in them being apparently too feeble to shift them aside4 ,in such cases these spots are visible when they are in the vicinity of the limb1 where they are seen sidewise2 but when observed in the east1 in being carried forward by the solar rotation towards the centre of the disk1 they gradually diminish in size1 and finally become invisible4 ,the disappearance of these spots1 however1 is only apparent1 being due to the fact that1 as they advance towards the centre of the disk1 our lateral view of them is gradually lost1 and they are finally hidden from sight by the overhanging facul which then serve as a screen between the observer and the spot4 ,this class of spots may be called ,lateral ,spots1 from the fact that they can only be seen laterally1 and near the ,sun's limb4 ,solar spots are also formed in various other ways4 ,some1 like those represented in ,plate ,i41 appearing without being announced by any apparent disturbance of the surface1 or by the formation of any facul1 form and develop in a very short time4 ,others1 appearing at first as very small spots having an umbra and a penumbra1 slowly and gradually develop into very large spots4 ,this mode of formation1 which would seem to be the most natural1 is1 however1 quite rare4 ,spots of this class have a duration and permanence not observed in those of any other type4 ,these spots of slow and regular development are never accompanied by facul or luminous bridges1 nor have they any gray or rosy veils in their interior2 a fact which may1 perhaps1 account for their permanent character4 ,another class of spots1 which is also rare1 appear as long and narrow crevasses showing the penumbral structure of the ordinary spots2 but these rarely have any umbra4 ,these long1 and sometimes exceedingly narrow fissures of the solar envelopes1 with their radiated penumbral structure1 strongly suggest the idea that the photosphere is composed of a multitude of filamentary elements having the granulations for summits4 ,such a crevasse is represented on ,plate ,i41 and unites the two spots which form the group4 ,the duration of ,sun-spots varies greatly4 ,some last only for a few hours2 while others continue for weeks and even months at a time1 but not without undergoing changes4 ,the modes of disappearance of ,sun-spots are as various as those of their apparition4 ,the spots rarely close up by a gradual diminution or contraction of their umbra and penumbra4 ,this mode of disappearance belongs exclusively to the spots deprived of facul and veils4 ,one of the most common modes of the disappearance of a spot is its invasion by large facular masses1 which slowly advance upon its penumbra and umbra and finally cover it entirely4 ,it is a process precisely the reverse of that in which spots are formed by the shifting aside of the facul1 as above described4 ,in other types1 the spots close up by the gradual enlargement of the luminous bridges traversing them1 which are slowly transformed into branches of the photosphere1 all of the characteristics of which they have acquired4 ,in many cases1 the spots covered over by the facul continue to exist for some time1 hidden under these masses1 as is often proved1 either by the appearance of small spots on the facular mass left at the place they occupied1 or even by the reappearance of the same spot4 ,apart from the general movement of rotation of the solar surface1 some of the spots seem to be endowed with a proper motion of their own1 which becomes greater the nearer the spots are to the solar equator4 ,according to the observations of ,mr4 ,carrington1 the period of rotation of the ,sun1 as deduced from the observations of the solar spots during a period of seven years1 is #be days at the equator2 while at #ej of heliocentric latitude it is #bg days4 ,but the period of rotation1 as derived from the observations of spots occupying the same latitude1 is far from being constant1 as it varies at different times1 with the frequency of the spots and with the solar activity1 so that at present the law of these variations is not well known4 ,from the character of the solar envelope1 it seems very natural that the rotation should differ in the different zones and at different times1 since this envelope is not rigid1 but very movable1 and governed by forces which are themselves very variable4 ,although it is a general law that the spots near the equator have a more rapid motion than those situated in higher latitudes1 yet1 in many cases1 the proper motion of the spots is more apparent than real4 ,for the most part1 the changes of form and the rapid displacements observed in some spots are only apparent1 and due to the fact that the large masses of facul which are kept in suspense above them are very unstable1 and change position with the slightest change in the forces holding them in suspension4 ,since in these cases we view the spots through the openings of the facul situated above them1 the slightest motion of these objects produces an apparent motion in the spots1 although they have remained motionless4 ,accordingly1 it has been remarked that of all the spots1 those which have the greater proper motion are precisely those which have the most facul and luminous bridges2 while the other spots in the same regions1 but not attended by similar phenomena1 are comparatively steady in their movement4 ,these last spots are undoubtedly better adapted than any others to exhibit the rotation of the ,sun2 but it is probable that this period of rotation will never be known with accuracy1 simply because the solar surface is unstable1 and does not rotate uniformly4 ,the ,sun-spots have a remarkable tendency to form into groups of various sizes1 but whatever may be the number of spots thus assembled1 the group is nearly always composed of two principal spots1 to which the others are only accessories4 ,the tendency of the ,sun-spots to assemble in pairs is general1 and is observed in all latitudes1 even among the minute temporary groups formed in the polar regions4 ,whenever several are situated quite close together1 those belonging to the same group can be easily recognized by this character4 ,whatever may be the position of the axis of the two principal spots of a group when it is first formed1 this axis has a decided tendency to place itself parallel to the solar equator1 no matter to what latitude the group belongs2 and if it is disturbed from this position1 it soon returns to it when the disturbance has ceased4 ,it is also remarkable that the spots observed at the same time remain in nearly the same parallel of latitude for a greater or less period of time2 but they keep changing their position from year to year1 their latitude decreasing with the activity of the solar forces4 ,among the ,sun-spots1 those associated with facul form the groups which attain the largest proportions4 ,when such groups acquire an apparent diameter of #a' or more1 they are plainly visible to the naked eye1 since for a spot to be visible to the naked eye on the ,sun1 it need only subtend an angle of #ej4 ,i have sometimes seen such groups through a smoky atmosphere1 when the solar light was so much reduced that the disk could be observed directly and without injury to the sight4 ,the largest spot which ever came under my observation was seen during the period from the #acth to the #aith of ,november1 #ahgj4 ,this spot1 which was on the northern hemisphere of the ,sun1 was conspicuous among the smaller spots constituting the group to which it belonged1 and followed them on the east4 ,on ,november #afth1 when it attained its largest size1 the diameter of its penumbra occupied fully one-fifth of the diameter of the ,sun2 its real diameter being1 therefore1 not less than #agb1jjj miles1 or nearly #bb times the diameter of the ,earth4 ,as the umbra of this spot occupied a little more than one-third of its whole diameter1 seven globes like our own1 placed side by side on a straight line1 could easily have passed through this immense gap4 ,to fill the area of this opening1 about #de such globes would have been needed4 ,this spot was1 of course1 very easily seen with the naked eye1 its diameter being almost eight times that required for a spot to be visible without a telescope4 ,ancient historians often speak of obscurations of the ,sun1 and it has been supposed by some astronomers that this phenomenon might have been due in some cases to the apparition of large spots4 ,a few spots on the surface of the ,sun1 like that just described1 would sensibly reduce its light4 ,besides the ordinary ,sun-spots already described1 others are at times observed on the surface of the ,sun1 which show some of the same characteristics1 but never attain so large proportions4 ,they always appear as if seen through a fog1 or veil1 between the granulations of the solar surface4 ,on account of their vagueness and ill-defined contours1 ,i have proposed for these objects the term1 ,veiled ,spots4 ,veiled spots have a shorter duration than the ordinary spots1 the smaller types sometimes forming and vanishing in a few minutes4 ,some of the larger veiled spots1 however1 remain visible for several days in succession1 and show the characteristics of other spots in regard to the arrangement of their parts4 ,the veiled spots have no umbra or penumbra1 although they are usually accompanied by facul resembling those seen near the ordinary spots4 ,they are frequently seen in the polar regions1 but are there always of small size and of short duration4 ,the veiled spots are larger1 and more apt to arrange themselves into groups1 in the regions occupied by the ordinary spots1 and it is not rare to observe such spots transform themselves into ordinary spots1 and vice versa4 ,the veiled spots1 therefore1 seem to be ordinary spots filled up1 or covered over by the granulations and semi-transparent gases composing the chromospheric layer4 ,that it is so1 becomes more evident1 from the fact that large ,sun-spots in process of diminution are sometimes gradually covered with faint and scattered granules which descend in long1 narrow filaments1 and become less and less distinguishable as they attain greater depth4 ,this phenomenon1 associated with the fact that the luminous bridges seen over the ,sun-spots which are closing up are sometimes transformed into branches which show the characteristic structure of the photosphere1 goes far to prove that the solar envelopes are mainly composed of an innumerable quantity of radial filaments of varying height4 ,,plate ,i4--,,group ,,of ,,sun-,,spots ,,and ,,veiled ,,spots4 ,observed on ,june #agth #ahge at #g h4 #cj m4 ,a4,m4 ,the group of ,sun-spots represented in ,plate ,i41 was observed and drawn on ,june #agth1 #ahge1 at #g;h4 #cjm4 ,a4 ,m4 ,the first traces of this group were seen on ,june #aeth1 at noon1 and consisted of three small black dots disseminated among the granulations4 ,at that time1 no disturbance of the surface was noticeable1 and no facul were seen in the vicinity of these spots4 ,on ,june #afth1 at #h o'clock ,a4 ,m41 the three small spots had become considerably enlarged1 and1 as usual1 the group consisted of two principal spots4 ,between these two spots all was in motion3 the granulations1 stretched into long1 wavy1 parallel lines1 had somewhat the appearance of a liquid in rapid motion4 ,at #a o'clock1 ,p4 ,m41 on the same day1 the group had considerably enlarged2 the facul1 the granulations1 and the penumbral filaments being interwoven in an indescribable manner4 ,on the morning of the #agth1 these spots had assumed the complicated form and development represented in the drawing2 while at the same time two conspicuous veiled spots were seen on the left hand1 at some distance above the group4 ,some luminous bridges are visible upon the left hand spot1 traversing the penumbra and umbra of this spot in various directions4 ,the umbra of one of the spots is occupied1 and partly filled with gray and rosy veils1 similar to those above described1 and the granulations of the solar surface form a background to the group of spots4 ,this group of spots was not so remarkable for its size as for its complicated structure4 ,the diameter of the group from east to west was only #b minutes of arc1 or about #fg1jjj miles4 ,the upper part of the umbra of the spot situated on the right hand side of the group was nearly #g1jjj miles in diameter1 or less by #a1jjj miles than the diameter of the ,earth4 ,some of the long filaments composing that part of the penumbra1 situated on the left hand side of the same spot1 were #ag1jjj miles in length4 ,one of these fiery elements would be sufficient to encircle two-thirds of the circumference of the ,earth4 ,,solar ,,protuberances ,,plate ,,ii ,the chromosphere forming the outlying envelope of the ,sun1 is subject1 as has been shown above1 to great disturbances in certain regions1 causing considerable upheavals of its surface and violent outbursts of its gases4 ,from these upheavals and outbursts of the chromosphere result certain curious and very interesting forms1 which are known under the name of ,solar ,protuberances1 ,prominences1 or ,flames4 ,these singular forms1 which could1 until recently1 be observed only during the short duration of the total eclipses of the ,sun1 can now be seen on every clear day with the spectroscope1 thanks to ,messrs4 ,janssen and ,lockyer1 to whose researches solar physics is so much indebted4 ,,plate ,,ii4--,,solar ,,protuberances4 ,observed on ,may #e1 #ahgc at #i;h1 #djm4 ,a4,m4 ,the solar protuberances1 the ,sun-spots1 and the facul to which they are closely related1 are confined within the same general regions of the ,sun1 although the protuberances attain higher heliocentric latitudes4 ,there is certainly a very close relation between the facul and the solar protuberances1 since when a group of the facul traverses the ,sun's limb1 protuberances are always seen at the same place4 ,it seems very probable that the facul and the protuberances are in the main identical4 ,the facul may be the brighter portion of the protuberances1 consisting of gases which are still undergoing a high temperature and pressure2 while the gases which have been relieved from this pressure and have lost a considerable amount of their heat1 may form that part of the protuberances which is only visible on the ,sun's limb4 ,a daily study of the solar protuberances1 continued for ten years1 has shown me that these objects are distributed on two zones which are equidistant from the solar equator1 and parallel with it4 ,the zone arrangement of the protuberances is more easily recognized during the years of minimum solar activity1 as in these years the zones are very narrow and widely separated4 ,during these years the belt of protuberances is situated between #dj and #de of latitude1 north and south4 ,in years of great solar activity the zones spread considerably on either side of these limits1 especially towards the equator1 which they nearly reach1 only a narrow belt1 usually free from protuberances1 remaining between them4 ,towards the poles the zones do not spread so much1 and there the space free from protuberances is considerably greater than it is at the equator4 ,during years of maximum solar activity1 the protuberances1 like the ,sun-spots and the facul1 are very numerous1 very large1 and very complicated--sometimes occupying a great part of the whole solar limb4 ,as many as twenty distinct flames are sometimes observed at one time4 ,in years of minimum solar activity1 on the contrary1 the prominences are very few in number1 and they are of small size2 but1 as far as my observations go1 they are never totally absent4 ,in general1 the solar flames undergo rapid changes1 especially those which are situated in the vicinity of ,sun-spots1 although they occasionally remain unchanged in appearance and form for several hours at a time4 ,the protuberances situated in higher latitudes are less liable to great and sudden changes1 often retaining the same form for several days4 ,the changes observed in the protuberances of the equatorial regions are due in part to the comparatively great changes in their position with respect to the spectator1 which are occasioned by the rotation of the ,sun4 ,this rotation1 of course1 has a greater angular velocity on the equator than in higher latitudes4 ,in most cases1 however1 the changes of the equatorial protuberances are too great and too sudden to be thus explained4 ,they are1 in fact1 due to the greater solar activity developed in the equatorial zones1 and wherever spots are most numerous4 ,the solar protuberances appear under various shapes1 and are often so complicated in appearance that they defy description4 ,some resemble huge clumsy masses having a few perforations on their sides2 while others form a succession of arches supported by pillars of different styles4 ,others form vertical or inclined columns1 often surmounted by cloud-like masses1 or by various appendages1 which sometimes droop gracefully1 resembling gigantic palm leaves4 ,some resemble flames driven by the wind2 others1 which are composed of a multitude of long and narrow filaments1 appear as immense fiery bundles1 from which sometimes issue long and delicate columns surmounted by torch-like objects of the most fantastic pattern4 ,some others resemble trees1 or animal forms1 in a very striking manner2 while still others1 apparently detached from the solar limb1 float above it1 forming graceful streamers or clouds of various shapes4 ,some of the protuberances are very massive1 while others are so thin and transparent as to form a mere veil1 through which more distant flames can easily be seen4 ,notwithstanding this variety of form1 two principal classes of solar protuberances may be recognized3 the cloud-like or quiescent1 and the eruptive or metallic protuberances4 ,the first class1 which is the most common1 comprises all the cloud-like protuberances resting upon the chromosphere or floating about it4 ,the protuberances of this type often obtain enormous horizontal proportions1 and it is not rare to see some among them occupying #bj and #cj of the solar limb4 ,the height attained by protuberances of this class does not correspond in general to their longitudinal extent2 although some of their branches attain considerable elevations4 ,these prominences very seldom have the brilliancy displayed by the other type1 and are sometimes so faint as to be seen with difficulty4 ,although it is generally stated by observers that some of the protuberances belonging to this class are detached from the solar surface1 and kept in suspension above the surface1 like the clouds in our atmosphere1 yet it seems to me very doubtful whether protuberances are ever disconnected from the chromosphere1 since1 in an experience of ten years1 ,i have never been able to satisfy myself that such a thing has occurred4 ,many of them have appeared to me at first sight to be detached from the surface1 but with a little patience and attention ,i was always able to detect faint traces of filamentary elements connecting them with the chromosphere4 ,quite often ,i have seen bright protuberances gradually lose their light and become invisible1 while soon after they had regained it1 and were as clearly visible as before4 ,observations of this kind seem to show that while the prominences are for the most part luminous1 there are also a few which are non-luminous and invisible to the eye4 ,these dark and invisible forms are most generally found in the vicinity of ,sun-spots in great activity4 ,when observing such regions with the spectroscope1 it is not rare to encounter them in the form of large dark spots projecting on the solar spectrum near the hydrogen lines4 ,on ,july #bhth1 #ahgb1 ,i observed with the spectroscope a dark spot of this kind issuing from the vicinity of a large ,sun-spot1 and extending over one-fifth of the diameter of the ,sun4 ,this object had been independently observed in ,france a little earlier by ,m4 ,chacornac with the telescope1 in which it appeared as a bluish streak4 ,the second class of solar protuberances1 comprising the eruptive type1 is the most interesting1 inasmuch as it conveys to us a conception of the magnitude and violence of the solar forces4 ,the protuberances of this class1 which are always intensely bright1 appear for the most part in the immediate vicinity of ,sun-spots or facul4 ,these protuberances1 which seem to be due to the outburst of the chromosphere1 and to the violent ejection of incandescent gases and metallic vapors from the interior of the ,sun1 sometimes attain gigantic proportions and enormous heights4 ,while the spectrum of the protuberances of the cloudy type is simple1 and usually composed of four hydrogen lines and the yellow line ,d#c1 that of the eruptive class is very complicated1 and1 besides the hydrogen lines and ,d#c1 it often exhibits the bright lines of sodium1 magnesium1 barium1 titanium1 and iron1 and occasionally1 also1 a number of other bright lines4 ,the phenomena of a solar outburst are grand and imposing4 ,suddenly immense and acute tongues and jets of flames of a dazzling brilliancy rise up from the solar limb and extend in various directions4 ,some of these fiery jets appear perfectly rigid1 and remain apparently motionless in the midst of the greatest disorder4 ,immense straps and columns form and rise in an instant1 bending and waving in all sorts of ways and assuming innumerable shapes4 ,sometimes powerful jets resembling molten metal spring up from the ,sun1 describing graceful parabolas1 while in their descent they form numerous fiery drops which acquire a dazzling brilliancy when they approach the surface4 ,the upward motion of the protuberances in process of formation is sometimes very rapid4 ,some protuberances have been observed to ascend in the solar atmosphere at the rate of from #abj to #dig miles a second4 ,great as this velocity may appear1 it is nevertheless insignificant when compared with that sometimes attained by protuberances moving in the line of sight instead of directly upwards4 ,movements of this kind are indicated by the displacement of the bright or dark lines in the spectrum4 ,a remarkable instance of this kind occurred on the #bfth of ,june1 #ahgd4 ,on that day ,i observed a displacement of the hydrogen ,c line corresponding to a velocity of motion of #a1fjj miles per second4 ,the mass of hydrogen gas in motion producing such a displacement was1 according to theory1 moving towards the ,earth at this incredible rate1 when it instantly vanished from sight as if it had been annihilated1 and was seen no more4 ,until recently the protuberances had not been observed to rise more than #bjj1jjj miles above the solar surface2 but1 on ,october #gth1 #ahhj1 a flame1 which had an elevation of #hj1jjj miles when ,i observed it at #h;h4 #eem4 ,a4 ,m41 had attained the enormous altitude of #cej1jjj miles when it was observed at noon by ,professor ,c4 ,a4 ,young4 ,if we had such a protuberance on the ,earth1 its summit would be at a height sufficient not merely to reach1 but to extend #ajj1jjj miles beyond the ,moon4 ,although the solar protuberances represented in ,plate ,,ii4 have not the enormous proportions attained by some of these objects1 yet they are as characteristic as any of the largest ones1 and afford a good illustration of the purely eruptive type of protuberances4 ,the height of the largest column in the group equals #d' #dc1 or a little over #abf1jjj miles4 ,a large group of ,sun-spots was in the vicinity of these protuberances when they were observed and delineated4 ,,total ,,eclipse ,,of ,,the ,,sun ,,plate ,,iii ,a solar eclipse is due to the passage of the ,moon directly between the observer and the ,sun4 ,such an eclipse can only occur at ,new ,moon1 since it is only at that time that our satellite passes between us and the ,sun4 ,the ,moon's orbit does not lie precisely in the same plane as the orbit of the ,earth1 but is inclined about five degrees to it1 otherwise an eclipse of the ,sun would occur at every ,new ,moon1 and an eclipse of the ,moon at every ,full ,moon4 ,since the ,moon's orbit is inclined to that of the ,earth1 it must necessarily intersect this orbit at two opposite points4 ,these points are called the nodes of the ,moon's orbit4 ,when our satellite passes through either of the nodes when the ,moon is new1 it appears interposed to some extent between the ,sun and the ,earth1 and so produces a solar eclipse2 while if it passes a node when the ,moon is full1 it is more or less obscured by the ,earth's shadow1 which then produces an eclipse of the ,moon4 ,but1 on the other hand1 when the ,new ,moon and the ,full ,moon do not coincide with the passage of our satellite through the nodes of its orbit1 no eclipse can occur1 since the ,moon is not then on a line with the ,sun and the ,earth1 but above or below that line4 ,owing to the ellipticity of the ,moon's orbit1 the distance of our satellite from the ,earth varies considerably during each of its revolutions around us1 and its apparent diameter is necessarily subject to corresponding changes4 ,sometimes it is greater1 sometimes it is less1 than the apparent diameter of the ,sun4 ,if it is greater at the time of a solar eclipse1 the eclipse will be total to a terrestrial observer stationed nearly on the line of the centres of the ,sun and ,moon1 while it will be only partial to another observer stationed further from this line4 ,but the ,moon's distance from the ,earth may be so great and its apparent diameter consequently so small that even those observers nearest the central line of the eclipse see the border of the ,sun all round the black disk of the ,moon2 the eclipse is then annular4 ,even during the progress of one and the same eclipse the distance of the ,moon from the parts of the ,earth towards which its shadow is directed may vary so much that1 while the eclipse is total to some observers1 others equally near the central line1 but stationed at a different place1 will see it as annular4 ,the shadow cast by the ,moon on the ,earth during total eclipses1 travels along upon the surface of the ,earth1 in consequence of the daily movement of rotation of our globe combined with the movements of the ,earth and ,moon in their orbits4 ,the track of the ,moon's shadow over the ,earth's surface has a general eastward course1 so that the more westerly observers see it earlier than those east of them4 ,an eclipse may continue total at one place for nearly eight minutes1 but in ordinary cases the total phase is much shorter4 ,the nodes of the ,moon's orbit do not invariably occupy the same position1 but move nearly uniformly1 their position with regard to the ,sun1 ,earth1 and ,moon being at any time approximately what it formerly was at a series of times separated by equal intervals from each other4 ,each interval comprises #bbc lunations1 or #ah years1 #aa days1 and #g or #h hours4 ,the eclipses which occur within this interval are almost exactly repeated during the next similar interval4 ,this period1 called the ,saros1 was well known to the ancients1 who were enabled by its means to predict eclipses with some certainty4 ,,plate ,,iii4--,,total ,,eclipse ,,of ,,the ,,sun4 ,observed ,july #bi1 #ahgh1 at ,creston1 ,wyoming ,territory ,a total eclipse of the ,sun is a most beautiful and imposing phenomenon4 ,at the predicted time the perfectly round disk of the ,sun becomes slightly indented at its western limb by the yet invisible ,moon4 ,this phenomenon is known as the first contact4 ,the slight indentation observed gradually increases with the advance of the ,moon from west to east1 the irregularities of the surface of our satellite being plainly visible on the border of the dark segment advancing on the ,sun's disk4 ,with the advance of the ,moon on the ,sun1 the light gradually diminishes on the ,earth4 ,every object puts on a dull and gloomy appearance1 as when night is approaching2 while the bright sky1 losing its light1 changes its pure azure for a livid grayish color4 ,two or three minutes before totality begins1 the solar crescent1 reduced to minute proportions1 gives comparatively so little light that faint traces of the ,sun's atmosphere appear on the western side behind the dark body of the ,moon1 whose limb then becomes visible outside of the ,sun4 ,i observed this phenomenon at ,creston during the eclipse of #ahgh4 ,from #ae to #bj seconds before totality1 the narrow arc of the ,sun's disk not yet obscured by the ,moon seems to break and separate towards the extremities of its cusps1 which1 thus divided1 form independent points of light1 which are called ,baily's beads4 ,a moment after1 the whole solar crescent breaks into numerous beads of light1 separated by dark intervals1 and1 suddenly1 they all vanish with the last ray of ,sunlight1 and totality has begun with the second contact4 ,this phenomenon of ,baily's beads is undoubtedly caused by the irregularities of the ,moon's border1 which1 on reaching the solar limb1 divide the thin solar crescent into as many beads of light and dark intervals as there are peaks and ravines seen sidewise on that part of the ,moon's limb4 ,with the disappearance of the last ray of light1 the planets and the stars of the first and second magnitude seem to light up and become visible in the sky4 ,the darkness1 which had been gradually creeping in with the progress of the eclipse1 is then at its maximum4 ,although subject to great variations in different eclipses1 the darkness is never so great as might be expected from the complete obscuration of our luminary1 as the part of our atmosphere which is still exposed to the direct rays of the ,sun1 reflects to us some of that light1 which thus diminishes the darkness resulting from the disappearance of the ,sun4 ,usually the darkness is sufficient to prevent the reading of common print1 and to deceive animals1 causing them to act as if night was really approaching4 ,during totality the temperature decreases1 while the humidity of the atmosphere augments4 ,simultaneously with the disappearance of ,baily's beads1 a pale1 soft1 silvery light bursts forth from behind the ,moon1 as if the ,sun1 in disappearing1 had been vaporized and expanded in all directions into soft phosphorescent rays and streamers4 ,this pale light is emitted by gases constituting the solar atmosphere surrounding the bright nucleus now obscured by the dark body of our satellite4 ,this solar atmosphere is called ,corona1 from its distant resemblance to the aureola1 or glory1 represented by ancient painters around the heads of saints4 ,with the bursting forth of the corona1 a very thin arc of bright white light is seen along the ,moon's limb1 where the solar crescent has just disappeared4 ,this thin arc of light is the reversing layer1 which1 when observed with the spectroscope at that moment1 exhibits bright lines answering to the dark lines of the ordinary solar spectrum4 ,immediately above this reversing layer1 and concentric with it1 appears the pink-colored chromospheric layer1 with its curiously shaped flames and protuberances4 ,during totality1 the chromosphere and protuberances are seen without the aid of the spectroscope1 and appear of their natural color1 which1 although somewhat varying in their different parts1 is1 on the whole1 pinkish1 and similar to that of peach-blossoms2 yet it is mixed here and there with delicate prismatic hues1 among which the pink and straw colors predominate4 ,the color of the corona seems to vary in every eclipse1 but as its tints are very delicate1 it may depend1 in a great measure1 upon the vision of the observer2 although there seems to be no doubt that there are real variations4 ,at ,creston1 in #ahgh1 it appeared to both ,professor ,w4 ,harkness and myself of a decided pale greenish hue4 ,the corona appears under different forms1 and has never been observed twice alike4 ,its dimensions are also subject to considerable variations4 ,sometimes it appears regular and very little extended1 its distribution around the ,sun being almost uniform2 although in general it spreads a little more in the direction of the ecliptic1 or of the solar equator4 ,at other times it appears much larger and more complicated1 and forms various wings and appendages1 which in some cases1 as in #ahgh1 extend to immense distances2 while delicate rays radiate in straight or curved lines from the spaces left in the polar regions between the wings4 ,the corona has sometimes appeared as if divided by immense dark gaps1 apparently free from luminous matter1 and strongly resembling the dark rifts seen in the tails of comets4 ,this was observed in ,spain and ,sicily during the total eclipse of the ,sun in #ahgj4 ,different structures1 forming wisps and streamers of great length1 and interlaced in various ways1 are sometimes present in the corona1 while faint but more complicated forms1 distantly resembling enormous solar protuberances with bright nuclei1 have also been observed4 ,as the ,moon continues its eastward progress1 it gradually covers the chromosphere and the solar protuberances on the eastern side of the ,sun2 while1 at the same time1 the protuberances and the chromosphere on the opposite limb gradually appear from under the retreating ,moon4 ,then1 the thin arc of the reversing layer is visible for an instant1 and is instantly followed by the appearance of a point of dazzling white light1 succeeded immediately by the apparition of ,daily's beads on each side1 and totality is over1 with this third contact4 ,the corona continues to be visible on the eastern side of the ,sun for several minutes longer1 and then rapidly vanishes4 ,the thin solar crescent increases in breadth as the ,moon advances2 while1 at the same time1 the darkness and gloom spread over nature gradually disappear1 and terrestrial objects begin to resume their natural appearance4 ,finally the limb of the ,moon separates from that of the ,sun at the instant of fourth contact1 and the eclipse is over4 ,the phenomena exhibited by the corona in different eclipses are very complex1 and1 so far1 they have not been sufficiently studied to enable us to understand the true nature of the solar atmosphere4 ,from the spectral analysis of the corona1 and the phenomena of polarization1 it has been learned1 at least1 that while the matter composing the upper part of the solar atmosphere is chiefly composed of an unknown substance1 producing the green line #adgd1 its lower part is mainly composed of hydrogen gas at different temperatures1 a part of which is self-luminous1 while the other part only reflects the solar light4 ,but the proportion of the gaseous particles emitting light1 to those simply reflecting it1 is subject to considerable variations in different eclipses4 ,at present it would seem that in years of great solar disturbances1 the particles emitting light are found in greater quantity in the corona than those reflecting it2 but further observations will be required to confirm these views4 ,it is very difficult to understand how the corona1 which in certain eclipses extends only one diameter of the ,sun1 should1 in other cases1 as in #ahgh1 extend to the enormous distance of twelve times the same diameter4 ,changes of such magnitude in the solar atmosphere1 if due to the operation of forces with which we are acquainted1 cannot yet be accounted for by what is known of such forces4 ,their causes are still as mysterious as those concerned in the production of the monstrous tails displayed by some comets on their approach to the ,sun4 ,plate #c1 representing the total eclipse of the ,sun of ,july #bith1 #ahgh1 was drawn from my observations made at ,creston1 ,wyoming ,territory1 for the ,naval ,observatory4 ,the eclipse is represented as seen in a refracting telescope1 having an aperture of #f inches1 and as it appeared a few seconds before totality was over1 and when the chromosphere was visible on the western limb of the ,sun4 ,the two long wings seen on the east and west side of the ,sun1 appeared considerably larger in the sky than they are represented in the picture4 ,,the ,,aurora ,,borealis ,,plate ,,iv ,the name of ,polar ,auroras is given to certain very remarkable luminous meteoric phenomena which appear at intervals above the northern or the southern horizons of both hemispheres of the ,earth4 ,when the phenomenon is produced in our northern sky1 it is called ,aurora ,borealis1 or ,northern ,lights2 and when it appears in the southern sky1 it is called ,aurora ,australis1 or southern aurora4 ,marked differences appear in the various auroras observed from our northern latitudes4 ,while some simply consist in a pale1 faint luminosity1 hardly distinguishable from twilight1 others present the most gorgeous and remarkable effects of brightness and colors4 ,a great aurora is usually indicated in the evening soon after twilight1 by a peculiar grayish appearance of the northern sky just above the horizon4 ,the grayish vapors giving that appearance1 continuing to form there1 soon assume a dark and gloomy aspect1 while they gradually take the form of a segment of a circle resting on the horizon4 ,at the same time that this dark segment is forming1 a soft pearly light1 which seems to issue from its border1 spreads up in the sky1 where it gradually vanishes1 being the brightest at its base4 ,this arc of light1 gradually increasing in extent as well as in brightness1 reaches sometimes as far as the polar star4 ,on some rare occasions1 one or two1 and even three1 concentric arches of bright light form one above the other over the dark segment1 where they appear as brilliant concentric rainbows4 ,while the aurora continues to develop and spread out its immense arc1 the border of the dark segment loses its regularity and appears indented at several places by patches of light1 which soon develop into long1 narrow1 diverging rays and streamers of great beauty4 ,for the most part the auroral light is either whitish or of a pale1 greenish tint2 but in some cases it exhibits the most beautiful colors1 among which the red and green predominate4 ,in these cases the rays and streamers1 which are usually of different colors1 produce the most magnificent effects by their continual changes and transformations4 ,the brightness and extent of the auroral rays are likewise subject to continual changes4 ,an instant suffices for their development and disappearance1 which may be succeeded by the sudden appearance of others elsewhere1 as though the original streamers had been swiftly transported to a new place while invisible4 ,it frequently happens that all the streamers seem to move sidewise1 from west to east1 along the arch1 continuing meanwhile to exhibit their various changes of form and color4 ,for a time1 these appearances of motion continue to increase1 a succession of streamers alternately shooting forth and again fading1 when a sudden lull occurs1 during which all motion seems to have ceased4 ,the stillness then prevailing is soon succeeded by slight pulsations of light1 which seem to originate on the border-of the dark segment1 and are propagated upwards along the streamers1 which have now become more numerous and active4 ,slow at first1 these pulsations quicken by degrees1 and after a few minutes the whole northern sky seems to be in rapid vibration4 ,the lively upward and downward movement of these streamers entitles them to the name of merry dancers given them in northern countries where they are frequent4 ,long waves of light1 quickly succeeded by others1 are propagated in an instant from the horizon to the zenith2 these1 in their rapid passage1 cause bends and curves in the streamers1 which then1 losing their original straightness1 wave and undulate in graceful folds1 resembling those of a pennant in a gentle breeze4 ,although the coruscations add to the grandeur of the spectacle1 they tend to destroy the diverging streamers1 which1 being disconnected from the dark segment1 or torn in various ways1 are1 as it were1 bodily carried up towards the zenith4 ,in this new phase the aurora is transformed into a glorious crown of light1 called the ,corona4 ,from this corona diverge in all directions long streamers of different colors and forms1 gracefully undulating in numerous folds1 like so many banners of light4 ,some of the largest of these streamers appear like fringes composed of short transverse rays of different intensity and colors1 producing the most fantastic effects1 when traversed by the pulsations and coruscations which generally run across these rays during the great auroral displays4 ,the aurora has now attained its full development and beauty4 ,it may continue in this form for half an hour1 but usually the celestial fires begin to fade at the end of fifteen or twenty minutes1 reviving from time to time1 but gradually dying out4 ,the northern sky usually appears covered by gray and luminous streaks and patches after a great aurora1 these being occasionally rekindled1 but more often they gradually disappear1 and the sky resumes its usual appearance4 ,the number of auroras which develop a corona near the zenith is comparatively small in our latitudes2 but many of them1 although not exhibited on so grand a scale1 are nevertheless very interesting4 ,on some very rare occasions the auroral display has been confined almost exclusively to the dark segment1 which appeared then as if pierced along its border by many square openings1 like windows1 through which appeared the bright auroral light4 ,,plate ,,iv4--,,aurora ,,borealis4 ,as observed ,march #a1 #ahgb1 at #i;h4 #bem4 ,p4,m4 ,among the many auroras which ,i have had occasion to observe1 none are more interesting1 excepting the type first described1 than those which form an immense arch of light spanning the heavens from ,east to ,west4 ,this form of aurora1 which is quite rare1 ,i last observed on ,september #abth1 #ahha4 ,all the northern sky was covered with light vapors1 when a small auroral patch appeared in the ,east at about #bj above the horizon4 ,this patch of light1 gradually increasing westward1 soon reached the zenith1 and continued its onward progress until it arrived at about #bj above the western horizon1 where it stopped4 ,the aurora then appeared as a narrow1 wavy band of light1 crossed by numerous parallel rays of different intensity and color4 ,these rays seemed to have a rapid motion from ,west to ,east along the delicately-fringed streamer1 which1 on the whole1 moved southward1 while its extremities remained undisturbed4 ,aside from the apparent displacement of the fringes1 a singular vibrating motion was observed in the auroral band1 which was traversed by pulsations and long waves of light4 ,the phenomena lasted for about twenty minutes1 after which the arch was broken in many places1 and it slowly vanished4 ,the aurora usually appears in the early part of the evening1 and attains its full development between ten and eleven o'clock4 ,although the auroral light may have apparently ceased1 yet the phenomenon is not at an end1 as very often a solitary ray is visible from time to time2 and even towards morning these rays sometimes become quite numerous4 ,on some occasions the phenomenon even continues through the following day1 and is manifested by the radial direction of the cirrus-clouds in the heights of our atmosphere4 ,in #ahgb ,i1 myself1 observed an aurora which apparently continued for two or three consecutive days and nights4 ,in ,august1 #ahei1 the northern lights remained visible in the ,united ,states for a whole week4 ,the height attained by these meteors is considerable1 and it is now admitted that they are produced in the rarefied air of the upper regions of our atmosphere4 ,from the researches of ,professor ,elias ,loomis on the great auroras observed in ,august and ,september1 #ahei1 it was ascertained that the inferior part of the auroral rays had an altitude of #df miles1 while that of their summits was #dbh miles4 ,these rays had1 therefore1 a length of #chb miles4 ,from the observation of thirty auroral displays1 it has been found that the mean height attained by the summit of these streamers above the ,earth's surface was #dej miles4 ,but if the auroral streamers are generally manifested at great heights in our atmosphere1 it would appear from the observations of persons living in the regions where the auroras are most frequent1 as also from those who have been stationed in high northern and southern latitudes1 that the phenomenon sometimes descends very low4 ,both ,sabine and ,parry saw the auroral rays projected on a distant mountain2 ,ross saw them almost at sea-level projected on the polar ice2 while ,wrangel1 ,franklin1 and others observed similar phenomena4 ,dr4 ,hjaltalin1 who has lived in latitude #fd #df' north1 and has made a particular study of the aurora1 on one occasion saw the aurora much below the summit of a hill #a1fjj feet high1 which was not very far off4 ,the same aurora is sometimes observed on the same night at places very far distant from one another4 ,the great aurora borealis of ,august #bhth1 #ahei1 for instance1 was seen over a space occupying #aej in longitude--from ,california to the ,ural ,mountains in ,russia4 ,it even appears now very probable that the phenomenon is universal on our globe1 and that the northern lights observed in our hemisphere are simultaneous with the aurora australis of the southern hemisphere4 ,the aurora of ,september #b;d1 #ahei1 was observed all through ,north and ,south ,america1 the ,sandwich ,islands1 ,australia1 and ,africa2 the streamers and pulsations of light of the north pole responding to the rays and coruscations of the south pole4 ,of thirty-four auroras observed at ,hobart ,town1 in ,tasmania1 twenty-nine corresponded with aurora borealis observed in our hemisphere4 ,the auroral phenomena1 although sometimes visible within the tropics1 are1 however1 quite rare in these regions4 ,for the most part they are confined within certain zones situated in high latitudes north and south4 ,the zone where they are most frequent in our hemisphere forms an ellipse1 which has the north pole at one of its foci2 while the other is situated somewhere in ,north ,america1 in the vicinity of the magnetic pole4 ,the central line of the zone upon which the auroras seem to be most frequent passes from the northern coast of ,alaska through ,hudson's ,bay and ,labrador to ,iceland1 and then follows the northern coast of ,europe and ,asia4 ,the number of auroras diminishes as the observer recedes from this zone1 and it is only in exceptional cases that they are seen near the equator4 ,near the pole the phenomenon is less frequent than it is in the region described4 ,in ,north ,america we occupy a favorable position for the observation of auroras1 as we are nearer the magnetic poles than are the ,europeans and ,asiatics1 and we consequently have a greater number of auroras in corresponding latitudes4 ,the position of the dark auroral segment varies with the place occupied by the observer1 and its centre always corresponds with the magnetic meridian4 ,in our ,eastern ,states the auroral segment appears a little to the west of the north point2 but as the observer proceeds westward it gradually approaches this point1 and is due north when seen from the vicinity of ,lake ,winnipeg4 ,at ,point ,barrow1 in the extreme north-west of the ,united ,states1 the aurora is observed in the east4 ,in ,melville ,islands1 ,parry saw it in the south2 while in ,greenland it is directly in the west4 ,it is stated that auroras are more numerous about the equinoxes than they are at any other seasons2 and also1 when the earth is in perigee1 than when it is in apogee4 ,an examination which ,i have made of a catalogue by ,professor ,loomis1 comprising #d1acg auroras observed in the temperate zone of our hemisphere from #aggf to #ahgc1 sustains this statement4 ,during this period1 one hundred more auroras were recorded during each of the months comprising the equinoxes1 than during any other months of the year2 while eighty more auroras were observed when the earth was in perigee1 than when it was in apogee4 ,but to establish the truth of this assertion on a solid basis1 more observations in both hemispheres will be required4 ,the aurora is not simply a terrestrial phenomenon1 but is associated in some mysterious way with the conditions of the ,sun's surface4 ,it is a well-known fact that terrestrial magnetism is influenced directly by the ,sun1 which creates the diurnal oscillations of the magnetic needle4 ,between sunrise and two o'clock1 the north pole of the needle moves towards the west in our northern hemisphere1 and in the afternoon and evening it moves the other way4 ,these daily oscillations of the needle are not uniform in extent2 they have a period of regular increase and decrease4 ,at a given place the daily oscillations of the magnetic needle increase and decrease with regularity during a period which is equal to #aj years4 ,as this period closely coincides with the ,sun-spot period1 the connection between the variation of the needle and these solar disturbances has been recognized4 ,auroral phenomena generally accompany the extraordinary perturbations in the oscillations of the magnetic needle1 which are commonly called magnetic storms1 and the greater the auroral displays1 the greater are the magnetic perturbations4 ,not only is the needle subject to unusual displacements during an aurora1 but its movements seem to be simultaneous with the pulsations and waving motions of the delicate auroral streamers in the sky4 ,when the aurora sends forth a coruscation1 or a streamer in the sky1 the magnetic needle responds to it by a vibration4 ,the inference that the auroral phenomena are connected with terrestrial magnetism is further supported by the fact that the centre of the corona is always situated exactly in the direction of that point in the heavens to which the dipping needle is directed4 ,it has been found that the aurora is a periodical phenomenon1 and that its period corresponds very closely with those of the magnetic needle and ,sun-spots4 ,the years which have the most ,sun-spots and magnetic disturbances have also the most auroras4 ,there is an almost perfect similarity between the courses of the three sets of phenomena1 from which it is concluded that the aurora is connected in some mysterious way with the action of the ,sun1 as well as with the magnetic condition of the earth4 ,a very curious observation1 which has been supposed to have some connection with this subject1 was made on ,sept4 #ast1 #ahei1 by ,mr4 ,carrington and ,mr4 ,hodgson1 in ,england4 ,while these observers1 who were situated many miles from one another1 were both engaged at the same time in observing the same ,sun-spot1 they suddenly saw two luminous spots of dazzling brilliancy bursting into sight from the edge of the ,sun-spot4 ,these objects moved eastward for about five minutes1 after which they disappeared1 having then traveled nearly #cd1jjj miles4 ,simultaneously with these appearances1 a magnetic disturbance was registered at ,kew by the self-registering magnetic instruments4 ,the very night that followed these observations1 great magnetic perturbations1 accompanied by brilliant auroral displays1 were observed in ,europe4 ,a connection between the terrestrial magnetism and the auroral phenomena is further proved by the fact that1 before the appearance of an aurora1 the magnetic intensity of our globe considerably increases1 but diminishes as soon as the first flashes show themselves4 ,the auroral phenomena are also connected in some way with electricity1 and generate serious disturbances in the electric currents traversing our telegraphic lines1 which are thus often rendered useless for the transmission of messages during great auroral displays4 ,it sometimes happens1 however1 during such displays1 that the telegraphic lines can be operated for a long distance1 without the assistance of a battery2 the aurora1 or at least its cause1 furnishing the necessary electric current for the working of the line4 ,during auroras1 the telephonic lines are also greatly affected1 and all kinds of noises and crepitations are heard in the instruments4 ,two observations of mine1 which may have a bearing on the subject1 present some interest1 as they seem to indicate the action of the aurora on some of the clouds of our atmosphere4 ,on ,january #fth1 #ahgb1 after ,i had been observing a brilliant aurora for over one hour1 an isolated black cumulus cloud appeared at a little distance from the western extremity of the dark auroral segment4 ,this cloud1 probably driven by the wind1 rapidly advanced eastward1 and was soon followed by a succession of similar clouds1 all starting from the same point4 ,all these black clouds apparently followed the same path1 which was not a straight line1 but parallel to and concentric with the border of the dark auroral segment4 ,when the first cloud arrived in the vicinity of the magnetic meridian passing through the middle of the auroral arc1 it very rapidly dissolved1 and on reaching this meridian became invisible4 ,the same phenomenon was observed with the succession of black clouds following1 each rapidly dissolving as it approached the magnetic meridian4 ,this phenomenon of black clouds vanishing like phantoms in crossing the magnetic meridian1 was observed for nearly an hour4 ,on ,june #agth1 #ahgi1 ,i observed a similar phenomenon during a fine auroral display4 ,about midway between the horizon and the polar star1 but a little to the west of the magnetic meridian1 there was a large black cumulo-stratus cloud which very slowly advanced eastward4 ,as it progressed in that direction1 its eastern extremity was dissolved in traversing the magnetic meridian2 while1 at the same time1 several short and quite bright auroral rays issued from its western extremity1 which in its turn dissolved rapidly1 as if burned or melted away in the production of the auroral flame4 ,it seems to be a well observed fact1 that during auroras1 a strong sulphurous odor prevails in high northern latitudes4 ,according to ,dr4 ,hjaltalin1 during these phenomena1 the ozone of the atmosphere increases considerably1 and men and animals exposed out of doors emit a sulphurous odor when entering a heated room4 ,the ,esquimaux and other inhabitants of the northern regions assert that great auroras are sometimes accompanied by crepitations and crackling noises of various sorts4 ,although these assertions have been denied by several travelers who have visited the regions of these phenomena1 they are confirmed by many competent observers4 ,dr4 ,hjaltalin1 who has heard these noises about six times in a hundred observations1 says that they are especially audible when the weather is clear and calm2 but that when the atmosphere is agitated they are not heard4 ,he compares them to the peculiar sound produced by a silk cloth when torn asunder1 or to the crepitations of the electric machine when its motion is accelerated4 ,when the auroral light is much agitated and the streamers show great movements1 it is then that these noises are heard at different places in the atmosphere4 ,the spectrum of the auroral light1 although it varies with almost every aurora1 always shows a bright green line on a faint continuous spectrum4 ,in addition to this green line ,i have frequently observed four broad diffused bands of greater refrangibility in the spectra of some auroras4 ,in two cases1 when the auroras appeared red towards the west1 the spectrum showed a bright red line1 in addition to the green line and the broad bands described4 ,these facts evidently show that the light of the aurora is due to the presence of luminous vapors in our atmosphere2 and it may reasonably be supposed that these vapors are rendered luminous by the passage of electric discharges through them4 ,,the ,,zodiacal ,,light ,,plate ,v ,in our northern latitudes may be seen1 on every clear winter and spring evening1 a column of faint1 whitish1 nebulous light1 rising obliquely above the western horizon4 ,a similar phenomenon may also be observed in the east1 before day-break1 on any clear summer or autumn night4 ,to this pale1 glimmering luminosity the name of ,zodiacal ,light has been given1 from the fact that it lies in the zodiac along the ecliptic4 ,in common with all the celestial bodies1 the zodiacal light participates in the diurnal motion of the sky1 and rises and sets with the constellations in which it appears4 ,aside from this apparent motion1 it is endowed with a motion of its own1 accomplished from west to east1 in a period of a year4 ,in its motion among the stars1 the zodiacal light always keeps pace with the ,sun1 and appears as if forming two faint luminous wings1 resting on opposite sides of this body4 ,in reality it extends on each side of the ,sun1 its axis lying very nearly in the plane of the ecliptic4 ,in our latitudes the phenomena can be observed most advantageously towards the equinoxes1 in ,march and ,september1 when twilight is of short duration4 ,as we proceed southward it becomes more prominent1 and gradually increases in size and brightness4 ,it is within the tropical regions that the zodiacal light acquires all its splendor3 there it is visible all the year round1 and always appears very nearly perpendicular to the horizon1 while at the same time its proportions and brilliancy are greatly increased4 ,,plate ,v4--,,the ,,zodiacal ,,light4 ,observed ,february #bj1 #ahgf ,the zodiacal light appears under the form of a spear-head1 or of a narrow cone of light whose base apparently rests on the horizon1 while its summit rises among the zodiacal constellations4 ,in general appearance it somewhat resembles the tail of a large comet whose head is below the horizon4 ,the most favorable time to observe this phenomenon in the evening1 is immediately after the last trace of twilight has disappeared2 and in the morning1 one or two hours before twilight appears4 ,when observed with attention1 it is seen that the light of the zodiacal cone is not uniform1 but gradually increases in brightness inwardly1 especially towards its base1 where it sometimes surpasses in brilliancy the brightest parts of the ,milky-,way4 ,in general1 its outlines are vague and very difficult to make out1 so gradually do they blend with the sky4 ,on some favorable occasions1 the luminous cone appears to be composed of several distinct concentric conical layers1 having different degrees of brightness1 the inner cone being the most brilliant of all4 ,there is a remarkable distinction between the evening and morning zodiacal light4 ,in our climate1 the morning light is pale1 and never so bright nor so extended as the evening light4 ,in general1 the zodiacal light is whitish and colorless1 but in some cases it acquires a warm yellowish or reddish tint4 ,these changes of color may be accidental and due to atmospheric conditions1 and not to actual change in the color of the object4 ,although the zodiacal light is quite bright1 and produces the impression of having considerable depth1 yet its transparency is great1 since all the stars1 except the faint ones1 can be seen through its substance4 ,the zodiacal light is subject to considerable variations in brightness1 and also varies in extent1 the apex of its cone varying in distance from the ,sun's place1 from #dj to #ij degrees4 ,these variations cannot be attributed to atmospheric causes alone1 some of them being due to real changes in the zodiacal light itself1 whose light and dimensions increase or decrease under the action of causes at present unknown4 ,from the discussion of a series of observations on the zodiacal light made at ,paris and ,geneva1 it appears certain that its light varies from year to year1 and sometimes even from day to day1 independently of atmospheric causes4 ,some of my own observations agree with these results1 and one of them1 at least1 seems to indicate changes even more rapid4 ,on ,december #ahth1 #ahge1 ,i observed the zodiacal light in a clear sky free from any vapors1 at six o'clock in the evening4 ,at that time1 the point of its cone was a little to the north of the ecliptic1 at a distance of about #ij degrees from the ,sun's place4 ,ten minutes later1 its summit had sunk down #ce degrees1 the cone then being reduced to nearly one-half of its original dimensions4 ,ten minutes later1 it had risen #be degrees1 and was then #hj degrees from the ,sun's place1 where it remained all the evening4 ,on ,march #bb;d1 #ahgh1 the sky was very clear and the zodiacal light was bright when ,i observed it1 at eight o'clock4 ,at that moment the apex of the cone of light was a little to the south of the ,pleiades1 but this cone presented an unusual appearance never noticed by me before1 its northern border appearing much brighter and sharper than usual1 while at the same time its axis of greatest brightness appeared to be much nearer to this northern border than it was to the southern4 ,after a few minutes of observation it became evident that the northern border was extending itself1 as stars which were at some distance from it became gradually involved in its light4 ,at the same time that this border spread northward1 it seemed to diffuse itself1 and after a time the cone presented its usual appearance1 having its southern border brighter and better defined than the other4 ,it would have been impossible to attribute this sudden change to an atmospheric cause1 since only one of the borders of the cone participated in it1 and since some very faint stars near this northern border were not affected in the least while the phenomenon occurred4 ,besides these observations1 ,cassini1 ,mairan1 ,humboldt1 and many other competent observers have seen pulsations1 coruscations and bickerings in the light of the cone1 which they thought could not be attributed to atmospheric causes4 ,it has also been observed that at certain periods the zodiacal light has shone with unusual intensity for months together4 ,when this phenomenon is observed from the tropical regions1 it is found that its axis of symmetry always corresponds with its axis of greatest brightness1 and that both lie in the plane of the ecliptic1 which divides its cone into two equal parts4 ,but when the zodiacal light is observed in our latitude1 the axis of symmetry does not correspond with the axis of greatest brightness1 and both axes are a little to the north of this plane1 the axis of symmetry being the farther removed4 ,furthermore1 as already stated1 the southern border of the cone always appears better defined and brighter than the corresponding northern margin4 ,it is very probable1 if not absolutely certain1 that these phenomena are exactly reversed when the zodiacal light is observed from corresponding latitudes in the southern hemisphere1 and that there1 its axes1 both of symmetry and of greatest brightness1 appear south of the ecliptic1 while the northern margin is the brightest4 ,this seems to be established by the valuable observations of ,rev4 ,george ,jones1 made on board the ,u4 ,s4 steam frigate ,mississippi1 in ,california1 ,japan1 and the ,southern ,ocean4 ,when ,i was north of the ecliptic1 says this observer1 the greatest part of the light of the cone appeared to the north of this line2 when ,i was to the south of the ecliptic1 it appeared to be south of it2 while when my position was on the ecliptic1 or in its vicinity1 the zodiacal cone was equally divided by this line4 ,besides the zodiacal light observed in the ,east and ,west1 some observers have recognized an exceedingly faint1 luminous1 gauzy band1 about #aj or #ab degrees wide1 stretching along the ecliptic from the summit of the western to that of the eastern zodiacal cone4 ,this faint narrow belt has been called the ,zodiacal ,band4 ,it has been recognized by ,mr4 ,h4 ,c4 ,lewis1 who has made a study of this phenomenon1 that the zodiacal band has its southern margin a little brighter and a little sharper than the northern border4 ,this observation is in accordance with similar phenomena observed in the zodiacal light1 and may have considerable importance4 ,in #ahed1 ,brorsen recognized a faint1 roundish1 luminous spot in a point of the heavens exactly opposite to the place occupied by the ,sun1 which he has called ,gegenschein1 or counter-glow4 ,this luminous spot has sometimes a small nucleus1 which is a little brighter than the rest4 ,night after night this very faint object shifts its position among the constellations1 keeping always at #ahj degrees from the ,sun4 ,the position of the counter-glow1 like that of the zodiacal light and zodiacal band1 is not precisely on the plane of the ecliptic1 but a little to the north of this line4 ,it is very probable that near the equator the phenomenon would appear different and there would correspond with this plane4 ,there seems to be some confusion among observers in regard to the spectrum of the zodiacal light4 ,some have seen a bright green line in its spectrum1 corresponding to that of the aurora borealis2 while others could only see a faint grayish continuous spectrum1 which differs1 however1 from that of a faint solar light1 by the fact that it presents a well-defined bright zone1 gradually blending on each side with the fainter light of the continuous spectrum4 ,i have1 myself1 frequently observed the faint continuous spectrum of the zodiacal light1 and on one occasion recognized the green line of the aurora2 but it might have been produced by the aurora itself1 as yet invisible to the eye1 and not by the zodiacal light1 since1 later in the same evening1 there was a brilliant auroral display4 ,if it were demonstrated that this green line exists in the spectrum of the zodiacal light1 the fact would have importance1 as tending to show that the aurora and the zodiacal light have a common origin4 ,rev4 ,geo4 ,jones describes a very curious phenomenon which he observed several times a little before the moon rose above the horizon4 ,the phenomenon consisted in a short1 oblique1 luminous cone rising from the ,moon's place in the direction of the ecliptic4 ,this phenomenon he has called the ,moon ,zodiacal ,light4 ,in #ahgd1 ,i had an opportunity to observe a similar phenomenon when the ,moon was quite high in the sky4 ,by taking the precaution to screen the ,moon's disk by the interposition of some buildings between it and my eye1 ,i saw two long and narrow cones of light parallel to the ecliptic issuing from opposite sides of our satellite4 ,the phenomenon could not possibly be attributed to vapors in our atmosphere1 since the sky was very clear at the moment of the observation4 ,later on1 these appendages disappeared with the formation of vapors near the ,moon1 but they reappeared an hour later1 when the sky had cleared off1 and continued visible for twenty minutes longer1 and then disappeared in a clear sky4 ,although the zodiacal light has been studied for over two centuries1 no wholly satisfactory explanation of the phenomenon has yet been given4 ,now1 as in ,cassini's time1 it is generally considered by astronomers to be due to a kind of lens-shaped ring surrounding the ,sun1 and extending a little beyond the ,earth's orbit4 ,this ring is supposed to lie in the plane of the ecliptic1 and to be composed of a multitude of independent meteoric particles circulating in closed parallel orbits around the ,sun4 ,but many difficulties lie in the way of this theory4 ,it seems as incompetent to explain the slow and rapid changes in the light of this object as it is to explain the contractions and extensions of its cone4 ,it fails1 moreover1 to explain the flickering motions1 the coruscations observed in its light1 or the displacement of its cone and of its axes of brightness and symmetry by a mere change in the position of the observer4 ,rev4 ,geo4 ,jones1 unable to explain by this theory the phenomena which came under his observation1 has proposed another1 which supposes the zodiacal light to be produced by a luminous ring surrounding the ,earth1 this ring not extending as far as the orbit of the ,moon4 ,but this theory also fails in many important points1 so that at present no satisfactory explanation of the phenomenon can be given4 ,as the phenomenon is connected in some way with the ,sun1 and as we have many reasons to believe this body to be always more or less electrified1 it might be supposed that the ,sun1 acting by induction on our globe1 develops feeble electric currents in the rarefied gases of the superior regions of our atmosphere1 and there forms a kind of luminous ridge moving with the ,sun in a direction contrary to the diurnal motion1 and so producing the zodiacal light4 ,on this hypothesis1 the counter-glow would be the result of a smaller cone of light generated by the solar induction on the opposite point of the ,earth4 ,plate #e1 which sufficiently explains itself1 represents the zodiacal light as it appeared in the ,west on the evening of ,february #bjth1 #ahgf4 ,all the stars are placed in their proper position1 and their relative brightness is approximately shown by corresponding variations in size--the usual and almost the only available means of representation4 ,of course1 it must be remembered that a star does not1 in fact1 show any disk even in the largest telescopes1 where it appears as a mere point of light1 having more or less brilliancy4 ,the cone of light rises obliquely along the ecliptic1 and the point forming its summit is found in the vicinity of the well-known group of stars1 called the ,pleiades1 in the constellation of ,taurus1 or the ,bull4 ,,the ,,moon ,,plate ,,vi ,in its endless journey through space1 our globe is not solitary1 like some of the planets1 but is attended by the ,moon1 our nearest celestial neighbor4 ,although the ,moon does not attain to the dignity of a planet1 and remains a secondary body in the solar system1 yet1 owing to its proximity to our globe1 and to the great influence it exerts upon it by its powerful attraction1 it is to us one of the most important celestial bodies4 ,while the ,moon accompanies the ,earth around the ,sun1 it also revolves around the ,earth at a mean distance of #bch1hjj miles4 ,for a celestial distance this is only a trifling one2 the ,earth in advancing on its orbit travels over such a distance in less than four hours4 ,a cannon ball would reach our satellite in nine days2 and a telegraphic dispatch would be transmitted there in #a seconds of time1 if a wire could be stretched between us and the ,moon4 ,owing to the ellipticity of the ,moon's orbit1 its distance from the ,earth varies considerably1 our satellite being sometimes #ch1jjj miles nearer to us than it is at other times4 ,these changes in the distance of the ,moon occasion corresponding changes from #bi' to #cc' in its apparent diameter4 ,the real diameter of the ,moon is #b1afj miles1 or a little over one-quarter the diameter of our globe2 our satellite being #di times smaller than the ,earth4 ,the mean density of the materials composing the ,moon is only that of the materials composing the ,earth1 and the force of gravitation at the surface of our satellite is six times less than it is at the surface of our globe4 ,if a person weighing #aej lbs4 on our ,earth could be transported to the ,moon1 his weight there would be only #be lbs4 ,the ,moon revolves around the ,earth in about #bg days1 with a mean velocity of one mile per second1 the revolution constituting its sidereal period4 ,if the ,earth were motionless1 the lunar month would be equal to the sidereal period2 but owing to its motion in space1 the ,sun appears to move with the ,moon1 though more slowly1 so that after having accomplished one complete revolution1 our satellite has yet to advance #b days before reaching the same apparent position in regard to the ,earth and the ,sun that it had at first4 ,the interval of time comprised between two successive ,new ,moons1 which is a little over #bi days1 constitutes the synodical period of the ,moon1 or the lunar month4 ,the ,moon is not a self-luminous body1 but1 like the ,earth and the planets1 it reflects the light which it receives from the ,sun1 and so appears luminous4 ,that such is the case is sufficiently demonstrated by the phases exhibited by our satellite in the course of the lunar month4 ,every one is familiar with these phases1 which are a consequence of the motion of the ,moon around the ,earth4 ,when our satellite is situated between us and the ,sun1 it is ,new ,moon2 since we cannot see its illuminated side1 which is then turned away from us towards the ,sun4 ,when1 on the contrary1 it reaches that point of its orbit which1 in regard to us1 is opposite to the ,sun's place1 it is ,full ,moon2 since from the ,earth we can only see the fully illuminated side of our satellite4 ,again1 when the ,moon arrives at either of the two opposite points of its orbit1 the direction of which from the ,earth is at right angles with that of the ,sun1 it is either the ,first or the ,last ,quarter2 since in these positions we can only see one-half of its illuminated disk4 ,the curve described by the ,moon around the ,earth lies approximately in a plane1 this plane being inclined about #e to the ecliptic4 ,since our satellite1 in its motion around us and the ,sun1 closely follows the ecliptic1 which is inclined #bc to the equator1 it results that when this plane is respectively high or low in the sky1 the moon is also high or low when crossing the meridian of the observer4 ,in winter that part of the ecliptic occupied by the ,sun is below the equator1 and1 consequently1 the ,new ,moons occurring in that season are low in the sky1 since at ,new ,moon our satellite must be on the same side of the ecliptic with the ,sun4 ,but the ,full ,moons in the same season are necessarily high in the sky1 since a ,full ,moon can only occur when our satellite is on the opposite side of the ecliptic from the ,sun1 in which position it is1 of course1 as many degrees above the equator as the ,sun is below4 ,the ,full ,moon which happens nearest to the autumnal equinox is commonly called the ,harvest ,moon1 from the fact that1 after full1 its delays in rising on successive evenings are very brief and therefore favorable for the harvest work in the evening4 ,the same phenomenon occurs in every other lunar month1 but not sufficiently near the time of ,full ,moon to be noticeable4 ,when1 in spring1 a day or two after ,new ,moon1 our satellite begins to show its thin crescent1 its position on the ecliptic is north as well as east of that occupied by the ,sun2 hence1 its horns are nearly upright in direction1 and give it a crude resemblance to a tipping bowl1 from which many people who are unaware of its cause1 and that this happens every year1 draw conclusions as to the amount of rain to be expected4 ,one of the most remarkable features of the ,moon's motions is that our satellite rotates on its axis in exactly the same period of time occupied by its revolution around the ,earth1 from which it results that the ,moon always presents to us the same face4 ,to explain this peculiarity1 astronomers have supposed that the figure of our satellite is not perfectly spherical1 but elongated1 so that the attraction of the ,earth1 acting more powerfully upon its nearest portions1 always keeps them turned toward us1 as if the ,moon were united to our globe by a string4 ,it is not exactly true1 however1 that the ,moon always presents its same side to us1 although its period of rotation exactly equals that of its revolution2 since in consequence of the inclination of its axis of rotation to its orbit1 combined with the irregularities of its orbital motion about us1 apparent oscillations in latitude and in longitude1 called librations1 are created1 from which it results that nearly of the ,moon's surface is visible from the ,earth at one time or another4 ,the ,moon is a familiar object1 and every one is aware that our satellite1 especially when it is fully illuminated1 presents a variety of bright and dark markings1 which1 from their distant resemblance to a human face1 are popularly known as the man in the moon4 ,a day or two after ,new ,moon1 when the thin crescent of our satellite is visible above the western horizon after sunset1 the dark portion of its disk is plainly visible1 and appears of a pale1 ashy gray color1 although not directly illuminated by the ,sun4 ,this phenomenon is due to the ,earth-shine1 or to that portion of solar light which the illuminated surface of our globe reflects to the dark side of the ,moon1 exactly in the same manner that the ,moon-shine1 on our ,earth1 is due to the solar light reflected to our globe by the illuminated ,moon4 ,seen with a telescope of moderate power1 or even with a good opera-glass1 the ,moon presents a peculiar mottled appearance1 and has a strong resemblance to a globe made of plaster of ,paris1 on the surface of which numerous roundish1 saucer-shaped cavities of various sizes are scattered at random4 ,this mottled structure is better seen along the boundary line called the terminator1 which divides the illuminated from the dark side of the ,moon4 ,the line of the terminator always appears jagged1 and it is very easy to recognize that this irregularity is due to the uneven and rugged structure of the surface of our satellite4 ,a glance at the ,moon through a larger telescope shows that the bright spots recognized with the naked eye belong to very uneven and mountainous regions of our satellite1 while the dark ones belong to comparatively smooth1 low surfaces1 comparable to those forming the great steppes and plains of the ,earth4 ,when examined with sufficient magnifying power1 the white1 rugged districts of the ,moon appear covered over by numerous elevated craggy plateaus1 mountain-chains1 and deep ravines2 by steep cliffs and ridges2 by peaks of great height and cavities of great depth4 ,this rugged formation1 which is undoubtedly of volcanic origin1 gives our satellite a desolate and barren appearance4 ,the rugged tract occupies more than one-half of the visible surface of the ,moon1 forming several distinct masses1 the principal of which occupy the south and south-western part of the disk4 ,that this formation is elevated above the general level is proved by the fact that the mountains1 peaks1 and other objects which compose it1 all cast a shadow opposite to the ,sun2 and further1 that the length of these shadows diminishes with the elevation of the ,sun above the lunar horizon4 ,since ,galileo's time the surface of the ,moon has been studied by a host of astronomers1 and accurate maps of its topographical configuration have been made1 and names given to all features of any prominence4 ,it may even be said that in its general features1 the visible surface of our satellite is now better known to us than is the surface of our own ,earth4 ,one of the most striking and common features of the mountainous districts of the ,moon1 is the circular1 ring-like disposition of their elevated parts1 which form numerous crater-like objects of different sizes and depths4 ,many thousands of crater-like objects are visible on the ,moon through a good telescope1 and1 considering how numerous the small ones are1 there is1 perhaps1 no great exaggeration in fixing their number at #ej1jjj1 as has been done by some astronomers4 ,these volcanic regions of the ,moon cannot be compared to anything we know1 and far surpass in extent those of our globe4 ,the number and size of the craters of our most important volcanic regions in ,europe1 in ,asia1 in ,north and ,south ,america1 in ,java1 in ,sumatra1 and ,borneo1 are insignificant when compared with those of the ,moon4 ,the largest known craters on the ,earth give only a faint idea of the magnitude of some of the lunar craters4 ,the great crater ,haleakala1 in the ,sandwich ,islands1 probably the largest of the terrestrial volcanoes1 has a circumference of thirty miles1 or a diameter of a little less than ten miles4 ,some of the great lunar craters1 called walled plains1 such as ,hipparchus1 ,ptolemus1 etc41 have a diameter more than ten times larger than that of ,haleakala1 that of the first being #aae miles and that of the last #ajj miles4 ,these are1 of course1 among the largest of the craters of the ,moon1 although there are on our satellite a great number of craters above ten miles in diameter4 ,the crater-forms of the ,moon have evidently appeared at different periods of time1 since small craters are frequently found on the walls of larger ones2 and1 indeed1 still smaller craters are not rarely seen on the walls of these last4 ,the walls of the lunar craters are usually quite elevated above the surrounding surface1 some of them attaining considerable elevations1 especially at some points1 which form peaks of great height4 ,newton1 the loftiest of all1 rises at one point to the height of #bc1jjj feet1 while many others range from ten to twenty thousand feet in height4 ,several craters have their floor above the general surface--,plato1 for instance4 ,wargentin has its floor nearly on a level with the summit of its walls1 showing that at some period of its history liquid lavas1 ejected from within1 have filled it to the brim and then solidified4 ,the floors of some of the craters are smooth and flat1 but in general they are occupied by peaks and abrupt mountainous masses1 which usually form the centre4 ,many of their outside walls are partly or wholly covered by numerous ravines and gullies1 winding down their steep declivities1 branching out and sometimes extending to great distances from their base4 ,it would seem that these great volcanic mouths have at some time poured out torrents of lavas1 which1 in their descent1 carved their passage by the deep gullies now visible4 ,sometimes1 also1 the crater slopes are strewn with debris1 giving them a peculiar volcanic appearance4 ,notwithstanding their many points of similarity with the volcanoes of the ,earth1 the lunar craters differ from them in many particulars1 showing that volcanic forces acting on different globes may produce widely different results4 ,for example1 the floors of terrestrial craters are usually situated at considerable elevations above the general surface1 while those of the lunar craters are generally much depressed1 the height of their walls being only about one-half the depth of their cavities4 ,again1 while on the ,earth the mass of the volcanic cones far exceeds the capacity of their openings1 on the ,moon it is not rare to see the capacity of the crater cavities exceeding the mass of the surrounding walls4 ,on the ,earth1 the volcanic cones and mouths are comparatively regular and smooth1 and are generally due to the accumulation of the ashes and the debris of all kinds which are ejected from the volcanic mouths4 ,on the ,moon1 very few craters show this character1 and for the most part their walls have a very different structure1 being irregular1 very rugged1 and composed of a succession of concentric ridges1 rising at many points to great elevations1 and forming peaks of stupendous height4 ,again1 many of the larger terrestrial craters have their interior occupied by a central cone1 or several such cones1 having a volcanic mouth on their summits2 on the ,moon such central cones are very rare4 ,although many of the large lunar craters have their interior occupied by central masses which have been often compared to the central cones of our great volcanoes1 yet these objects have a very different character and origin4 ,for the most part1 they are mountainous masses of different forms--having very rarely any craters on them--and seem to have resulted from the crowding and lifting up of the crater floor by the phenomena of subsidence1 of which these craters show abundant signs4 ,besides1 the terrestrial craters are characterized by large and important lava streams1 while on the ,moon the traces of such phenomena are quite rare1 and when they are shown1 they generally differ from those of the ,earth by their numerous and complicated ramifications1 and also by the fact that many of these lava streamlets take their origin at a considerable distance from the crater slopes1 and are grooved and depressed as if the burning liquids which are supposed to have produced them had subsequently disappeared1 by evaporation or otherwise1 leaving the furrow empty4 ,the dark spots of the ,moon1 when viewed through a telescope1 exhibit a totally different character1 and show that they belong to a different formation from that of the brighter portions4 ,these darker tracts do not seem to have had a direct volcanic origin like the latter1 but rather appear to have resulted from the solidification of semi-fluid materials1 which have overflowed vast areas at different times4 ,the surface of this system is comparatively smooth and uniform1 only some small craters and low ridges being seen upon it4 ,the level and dark appearance of these areas led the ancient astronomers to the belief that they were produced by a liquid strongly absorbing the rays of light1 and were seas like our seas4 ,accordingly1 these dark surfaces were called ,maria1 or ,seas1 a name which it is convenient to retain1 although it is well known to have originated in an error4 ,the so-called seas of the ,moon are evidently large flat surfaces similar to the deserts1 steppes1 pampas1 and prairies of the ,earth in general appearance4 ,the great plains of the ,moon are at a lower level than that of the other formation1 and that which first attracts the observer's attention is the fact that they are surrounded almost on all sides by an irregular line of abrupt cliffs and mountain chains1 showing phenomena of dislocation4 ,this character of dislocation1 which is general1 and is visible everywhere upon the contours of the plains1 seems to indicate that phenomena of subsidence1 either slow or rapid1 have occurred on the ,moon2 while1 at the same time1 the sunken surfaces were overflowed by a semi-fluid liquid1 which solidified afterwards4 ,the evidences of subsidence and overflowing become unmistakable when we observe that1 along the borders of the gray plains1 numerous craters are more or less embedded in the gray formation1 only parts of the summit of their walls remaining visible1 to attest that once large craters existed there4 ,the farther from the border of the plain the vestiges of these craters are observed1 the deeper they are embedded in the gray formation4 ,that phenomena of subsidence have occurred on a grand scale on the ,moon1 is further indicated by the fact that the singular systems of fractures called clefts and rifts generally follow closely the outside border of the gray plains1 often forming parallel lines of dislocation and fractures4 ,in the interior regions of the gray formation1 these fractures are comparatively rare4 ,the gray1 lava-like formation is obviously of later origin than the mountainous system to which belong the embedded craters above described4 ,its comparatively recent origin might also be inferred from the smallness of its craters and its low ridges4 ,the few large craters observed on this formation evidently belong to the earlier system4 ,the color of this system of gray plains is far from being uniform4 ,in general appearance it is of a bluish gray1 but when observed attentively1 large areas appear tinted with a dusky olive-green1 while others are slightly tinged with yellow4 ,some patches appear brownish1 and even purplish4 ,a remarkable example of the first case is seen on the surface1 which encloses within a large parallelogram the two conspicuous craters1 ,aristarchus and ,herodotus4 ,this surface evidently belongs to a different system from that of the ,oceanus ,procellarum surrounding it1 as1 besides its color1 which totally differs from that of the gray formation1 its surface shows the rugged structure of the volcanic formation4 ,when the ,moon is full1 some very curious white1 luminous streaks are seen radiating from different centres1 which1 for the most part1 are important craters1 occupied by interior mountains4 ,the great crater ,tycho is the centre of the most imposing of the systems of white streaks4 ,some of the diverging rays of this great centre extend to a distance equal to one-quarter of the ,moon's circumference1 or about #a1gjj miles4 ,the true nature of these luminous streaks is unknown1 but it seems certain that they have their origin in the crater from which they diverge4 ,they do not form any relief on the surface1 and are seen going up over the mountains and steep walls of the crater1 as well as down the ravines and on the floors of craters4 ,the ,moon seems to be deprived of an atmosphere2 or1 if it has any1 it must be so excessively rare that its density is less than of the density of the ,earth's atmosphere1 since delicate tests afforded by the occultation of stars have failed to reveal its presence4 ,although no atmosphere of any consequence exists on the ,moon1 yet phenomena which ,i have observed seem to indicate the occasional presence there of vapors of some sort4 ,on several occasions1 ,i have seen a purplish light over some parts of the ,moon1 which prevented well-known objects being as distinctly seen as they were at other times1 causing them to appear as if seen through a fog4 ,one of the most striking of these observations was made on ,january #dth1 #ahgc1 on the crater ,kant and its vicinity1 which then appeared as if seen through luminous purplish vapors4 ,on one occasion1 the great crater ,godin1 which was entirely involved in the shadow of its western wall1 appeared illuminated in its interior by a faint purplish light1 which enabled me to recognize the structure of this interior4 ,the phenomenon could not be attributed in this case to reflection1 since the ,sun1 then just rising on the western wall of the crater1 had not yet grazed the eastern wall1 which was invisible4 ,it is not impossible that a very rare atmosphere composed of such vapors exists in the lower parts of the ,moon4 ,if the ,moon has no air1 and no liquids of any sort1 it seems impossible that its surface can maintain any form of life1 either vegetable or animal1 analogous to those on the ,earth4 ,in fact1 nothing indicating life has been detected on the ,moon--our satellite looking like a barren1 lifeless desert4 ,if life is to be found there at all1 it must be of a very elementary nature4 ,aside from the want of air and water to sustain it1 the climatic conditions of our satellite are very unfavorable for the development of life4 ,the nights and days of the ,moon are each equal to nearly fifteen of our days and nights4 ,for fifteen consecutive terrestrial days the ,sun's light is absent from one hemisphere of the ,moon2 while for the same number of days the ,sun pours down on the other hemisphere its light and heat1 the effects of which are not in any way mitigated by an atmosphere4 ,during the long lunar nights the temperature must at least fall to that of our polar regions1 while during its long days it must be far above that of our tropical zone4 ,it has been calculated that during the lunar nights the temperature descends to #bc below zero1 while during the days it rises to #dfh1 or #bef above the boiling point4 ,it has been a question among astronomers whether changes are still taking place at the surface of the ,moon4 ,aside from the fact that change1 not constancy1 is the law of nature1 it does not seem doubtful that changes occur on the ,moon1 especially in view of the powerful influences of contraction and dilatation to which its materials are submitted by its severe alternations of temperature4 ,from the distance at which we view our satellite1 we cannot expect1 of course1 to be able to see changes1 unless they are produced on a large scale4 ,theoretically speaking1 the largest telescopes ever constructed ought to show us the ,moon as it would appear to the naked eye from a distance of #dj miles2 but in practice it is very different4 ,the difficulty is in the fact that1 while we magnify the surface of a telescopic image1 we are unable to increase its light2 so that1 practically1 in magnifying an object1 we weaken its light proportionally to the magnifying power employed4 ,the light of the ,moon1 especially near the terminator1 where we almost always make our observations1 is not sufficiently bright to bear a very high magnifying power1 and only moderate ones can be applied to its study4 ,what we gain by enlarging an object1 we more than lose by the weakening of its light4 ,besides1 a high magnifying power1 by increasing the disturbances generally present in our atmosphere1 renders the telescopic image unsteady and very indistinct4 ,on the whole1 the largest telescopes now in existence do not show us our satellite better than if we could see it with the naked eye from a distance of #cjj miles or more4 ,at such a distance only considerable changes would be visible4 ,notwithstanding these difficulties1 it is believed that changes have been detected in ,linn1 ,marius1 ,messier1 and several other craters4 ,an observation of mine seems to indicate that changes have recently taken place in the great crater ,eudoxus4 ,on ,february #bjth1 #ahgg1 between #i;h4 #cjm4 and #aj;h4 #cjm41 ,i observed a straight1 narrow wall crossing this crater from east to west1 a little to the south of its centre4 ,this wall had a considerable elevation1 as was proved by the shadow it cast on its northern side4 ,towards its western end this wall appeared as a brilliant thread of light on the black shadow cast by the western wall of the crater4 ,the first time ,i had occasion to observe this crater again1 after this observation1 was a year later1 on ,february #agth1 #ahgh2 no traces of the wall were then detected4 ,many times since ,i have tried to find this narrow wall again1 when the ,moon presented the same phase and the same illumination1 but always with negative results4 ,it seems probable that this structure has crumbled down1 yet it is very singular that so prominent a feature should not have been noticed before4 ,,plate ,,vi4--,,mare ,,humorum4 ,from a study made in #ahge ,the ,mare ,humorum1 or sea of moisture1 as it is called1 which is represented on ,plate ,,vi41 is one of the smaller gray lunar plains4 ,its diameter1 which is very nearly the same in all directions1 is about #bgj miles1 the total area of this plain being about #ej1jjj square miles4 ,it is one of the most distinct plains of the ,moon1 and is easily seen with the naked eye on the left-hand side of the disk4 ,the floor of the plain is1 like that of the other gray plains1 traversed by several systems of very extended but low hills and ridges1 while small craters are disseminated upon its surface4 ,the color of this formation is of a dusky greenish gray along the border1 while in the interior it is of a lighter shade1 and is of brownish olivaceous tint4 ,this plain1 which is surrounded by high clefts and rifts1 well illustrates the phenomena of dislocation and subsidence4 ,the double-ringed crater ,vitello1 whose walls rise from #d1jjj to #e1jjj feet in height1 is seen in the upper left-hand corner of the gray plain4 ,close to ,vitello1 at the east1 is the large broken ring-plain ,lee1 and farther east1 and a little below1 is a similarly broken crater called ,doppelmayer4 ,both of these open craters have mountainous masses and peaks on their floor1 which is on a level with that of the ,mare ,humorum4 ,a little below1 and to the left of these objects1 is seen a deeply embedded oval crater1 whose walls barely rise above the level of the plain4 ,on the right-hand side of the great plain1 is a long fault1 with a system of fracture running along its border4 ,on this right-hand side1 may be seen a part of the line of the terminator1 which separates the light from the darkness4 ,towards the lower right-hand corner1 is the great ring-plain ,gassendi1 #ee miles in diameter1 with its system of fractures and its central mountains1 which rise from #c1jjj to #d1jjj feet above its floor4 ,this crater slopes southward towards the plain1 showing the subsidence to which it has been submitted4 ,while the northern portion of the wall of this crater rises to #aj1jjj feet1 that on the plain is only #ejj feet high1 and is even wholly demolished at one place where the floor of the crater is in direct communication with the plain4 ,in the lower part of the mare1 and a little to the west of the middle line1 is found the crater ,agatharchides1 which shows below its north wall the marks of rills impressed by a flood of lava1 which once issued from the side of the crater4 ,on the left-hand side of the plain1 is seen the half-demolished crater ,hippalus1 resembling a large bay1 which has its interior strewn with peaks and mountains4 ,on this same side can be seen one of the most important systems of clefts and fractures visible on the ,moon1 these clefts varying in length from #aej to #bjj miles4 ,,eclipses ,,of ,,the ,,moon ,,plate ,,vii ,since the ,moon is not a self-luminous body1 but shines by the light which it borrows from the ,sun1 it follows that when the ,sun's light is prevented from reaching its surface1 our satellite becomes obscured4 ,the ,earth1 like all opaque bodies exposed to sunlight1 casts a shadow in space1 the direction of which is always opposite to the ,sun's place4 ,the form of the ,earth's shadow is that of a long1 sharply-pointed cone1 which has our globe for its base4 ,its length1 varying with the distance of the ,earth from the ,sun1 is1 on an average1 #hee1jjj miles1 or #ajh times the terrestrial diameter4 ,this conical shadow of the ,earth1 divided longitudinally by the plane of the ecliptic1 lies half above and half below that plane1 on which the summit of the shadow describes a whole circumference in the course of a year4 ,if the ,moon's orbit were not inclined to the ecliptic1 our satellite would pass at every ,full ,moon directly through the ,earth's shadow2 but1 owing to that inclination1 it usually passes above or below the shadow4 ,twice1 however1 during each of its revolutions1 it must cross the plane of the ecliptic1 the points of its orbit where this happens being called nodes4 ,accordingly1 if it is near a node at the time of ,full ,moon1 it will enter the shadow of the ,earth1 and become either partly or wholly obscured1 according to the distance of its centre from the plane of the ecliptic4 ,the partial or total obscuration of the ,moon's disk thus produced constitutes a partial or total eclipse of the ,moon4 ,the essential conditions for an eclipse of the ,moon are1 therefore1 that our satellite must not only be full1 but must also be at or very near one of its nodes4 ,although inferior in importance to the eclipses of the ,sun1 the eclipses of the ,moon are1 nevertheless1 very interesting and remarkable phenomena1 which never fail to produce a deep impression on the mind of the observer1 inasmuch as they give him a clear insight into the silent motions of the planetary bodies4 ,at the mean distance of the ,moon from the ,earth1 the diameter of the conical shadow cast in space by our globe is more than twice as large as that of our satellite4 ,but1 besides this pure dark shadow of the ,earth1 its cone is enveloped by a partial shadow called ,penumbra1 which is produced by the ,sun's light being partially1 but not wholly1 cut off by our globe4 ,while the ,moon is passing into the penumbra1 a slight reduction of the light of that part of the disk which has entered it1 is noticeable4 ,as the progress of the ,moon continues1 the reduction becomes more remarkable1 giving the impression that rare and invisible vapors are passing over our satellite4 ,some time after1 a small dark-indentation1 marking the instant of first contact1 appears on the eastern or left-hand border of the ,moon1 which is always the first to encounter the ,earth's shadow1 since our satellite is moving from west to east4 ,the dark indentation slowly and gradually enlarges with the onward progress of the ,moon into the ,earth's shadow1 while the luminous surface of its disk diminishes in the same proportion4 ,the form of the ,earth's shadow on the ,moon's disk clearly indicates the rotundity of our globe by its circular outline4 ,little by little the dark segment covers the ,moon's disk1 and its crescent1 at last reduced to a mere thread of light1 disappears at the moment of the second contact4 ,with this the phase of totality begins1 our satellite being then completely involved in the ,earth's shadow4 ,the ,moon remains so eclipsed for a period of time which varies with its distance from the ,earth1 and with the point of its orbit where it crosses the conical shadow4 ,when it passes through the middle of this shadow1 while its distance from our globe is the least1 the total phase of an eclipse of the ,moon may last nearly two hours4 ,the left-hand border of our satellite having gone first into the ,earth's shadow1 is also the first to emerge1 and1 at the moment of doing so1 it receives the ,sun's light1 and totality ends with the third contact4 ,the lunar crescent gradually increases in breadth after its exit from the shadow1 and finally the ,moon recovers its fully illuminated disk as before1 at the moment its western border leaves the ,earth's shadow4 ,soon after1 it passes out of the penumbra1 and the eclipse is over4 ,in total eclipses1 the interval of time from the first to last contact may last #e;h4 #cjm1 but it is usually shorter4 ,soon after the beginning of an eclipse1 the dark segment produced by the ,earth's shadow on the ,moon's disk generally appears of a dark grayish opaque color1 but with the progress of the phenomenon1 this dark tint is changed into a dull reddish color1 which1 gradually increasing1 attains its greatest intensity when the eclipse is total4 ,at that moment the color of the ,moon is of a dusky1 reddish1 coppery hue1 and the general features of the ,moon's surface are visible as darker and lighter tints of the same color4 ,it sometimes happens1 however1 that our satellite does not exhibit this peculiar coppery tint1 but appears either blackish or bluish1 in which case it is hardly distinguishable from the sky4 ,it is very rare for the ,moon to disappear completely during totality1 and even when involved in the deepest part of the ,earth's shadow1 our satellite usually remains visible to the naked eye1 or1 at least1 to the telescope4 ,this phenomenon is to be attributed to the fact that the portion of the solar rays which traverse the lower strata of our atmosphere are strongly refracted1 and bend inward in such a manner that they fall on the ,moon1 and sufficiently illuminate its surface to make it visible4 ,the reddish color observed is caused by the absorption of the blue rays of light by the vapors which ordinarily-saturate the lower regions of our atmosphere1 leaving only red rays to reach the ,moon's surface4 ,of course1 these phenomena are liable to vary with every eclipse1 and depend almost exclusively on the meteorological conditions of our atmosphere4 ,in some cases the phase of totality lasts longer than it should1 according to calculation4 ,this can be attributed to the fact that the ,earth is enveloped in a dense atmosphere1 in which opaque clouds of considerable extent are often forming at great elevations4 ,such strata of clouds1 in intercepting the ,sun's light1 would have1 of course1 the effect of increasing the diameter of the ,earth's shadow1 in a direction corresponding to the place they occupy1 and1 if the ,moon were moving in this direction1 would increase the phase of total obscuration4 ,the eclipses of the ,moon1 like those of the ,sun1 as shown above1 have a cycle of #ah years1 #aa days and #g hours1 and recur after this period of time in nearly the same order4 ,they can1 therefore1 be approximately predicted by adding #ahy4 #aa;d4 #g;h4 to the date of the eclipses which have occurred during the preceding period4 ,during this cycle #gj eclipses will occur--#da being eclipses of the ,sun and #bi eclipses of the ,moon4 ,at no time can there ever be more than seven eclipses in a year1 and there are never less than two4 ,when there are only two eclipses in a year1 they are both eclipses of the ,sun4 ,although the number of solar eclipses occurring at some point or other of the ,earth's surface is greater than that of the eclipses of the ,moon1 yet at any single terrestrial station the eclipses of the ,moon are the more frequent4 ,while an eclipse of the ,sun is only visible on a narrow belt1 which is but a very small fraction of the hemisphere then illuminated by the ,sun1 an eclipse of the ,moon is visible from all the points of the ,earth which have the ,moon above their horizon at the time4 ,furthermore1 an eclipse of the ,sun is not visible at one time over the whole length of its narrow tract1 but moves gradually from one end of it to the other2 while1 on the contrary1 an eclipse of the ,moon begins and ends at the very same instant for all places from which it can be seen1 but1 of course1 not at the same local time1 which varies with the longitude of the place4 ,,plate ,,vii4--,,partial ,,eclipse ,,of ,,the ,,moon4 ,observed ,october #bd1 #ahgd ,the partial eclipse of the ,moon1 represented on ,plate ,,vii41 shows quite plainly the configuration of our satellite as seen with the naked eye during the eclipse1 with its bright and dark spots1 and its radiating streaks4 ,this eclipse was observed on ,october #bdth1 #ahgd4 ,,the ,,planets ,around the ,sun circulate a number of celestial bodies1 which are called ,planets4 ,the planets are opaque bodies1 and appear luminous because their surfaces reflect the light they receive from the ,sun4 ,the planets are situated at various distances from the ,sun1 and revolve around this body in widely different periods of time1 which are1 however1 constant for each planet1 so far as ascertained1 and doubtless are so in the other cases4 ,the ideal line traced in space by a planet in going around the ,sun1 is called the orbit of the planet2 while the period of time employed by a planet to travel over its entire orbit and return to its starting point1 is called the sidereal revolution1 or year of the planet4 ,the dimensions of the orbits of the different planets necessarily vary with the distance of these bodies from the ,sun1 as does also the length of their sidereal revolution4 ,the distance of a planet from the ,sun does not remain constant1 but is subject to variations1 which in certain cases are quite large4 ,these variations result from the fact that the planetary orbits are not perfect circles having the ,sun for centre1 but curves called ,ellipses1 which have two centres1 or foci1 one of which is always occupied by the ,sun4 ,this is in accordance with ,kepler's first law4 ,the ideal point situated midway between the two foci is called the centre of the ellipse1 or orbit2 while the imaginary straight line which passes through both foci and the centre1 with its ends at opposite points of the ellipse1 is called the major axis of the orbit4 ,it is also known as the line of the apsides4 ,the ideal straight line which1 in passing through the centre of the orbit1 cuts the major axis at right angles1 and is prolonged on either side to opposite points on the ellipse1 is called the minor axis of the orbit4 ,when a planet reaches that extremity of the major axis of its orbit which is the nearest to the ,sun1 it is said to be in its perihelion2 while1 when it arrives at the other extremity1 which is farthest from this body1 it is said to be in its aphelion4 ,when a planet reaches either of the two opposite points of its orbit situated at the extremities of its minor axis1 it is said to be at its mean distance from the ,sun4 ,the rapidity with which the planets move on their orbits varies with their distance from the ,sun2 the farther they are from this body1 the more slowly they move4 ,the rapidity of their motion is greatest when they are in perihelion1 and least when they are in aphelion1 having its mean rate when these bodies are crossing either of the extremities of the minor axes of their orbits4 ,the imaginary line which joins the ,sun to a planet at any point of its orbit1 and moves with this planet around the ,sun1 is called the radius vector4 ,according to ,kepler's second law1 whatever may be the distance of a planet from the ,sun1 the radius vector sweeps over equal areas of the plane of the planet's orbit in equal times4 ,there is a remarkable relation between the distance of the planets from the ,sun and their period of revolution1 in consequence of which the squares of their periodic times are respectively equal to the cubes of their mean distances from the ,sun4 ,from this third law of ,kepler1 it results that the mere knowledge of the mean distance of a planet from the ,sun enables one to know its period of revolution1 and vice versa4 ,the orbit described by the ,earth around the ,sun in a year1 or the apparent path of the ,sun in the sky1 is called the ecliptic4 ,like that of all the planetary orbits1 the plane of the ecliptic passes through the ,sun's centre4 ,the ecliptic has a great importance in astronomy1 inasmuch as it is the fundamental plane to which the orbits and motions of all planets are referred4 ,the orbits of the larger planets are not quite parallel to the ecliptic1 but more or less inclined to this plane2 although the inclination is small1 and does not exceed eight degrees4 ,on account of this inclination of the orbits1 the planets1 in accomplishing their revolutions around the ,sun1 are sometimes above and sometimes below the plane of the ecliptic4 ,a belt extending #h on each side of the ecliptic1 and1 therefore1 #af in width1 comprises within its limits the orbits of all the principal planets4 ,this belt is called the ,zodiac4 ,since all the planets have the ,sun for a common centre1 and have their orbits inclined to the ecliptic1 it follows that each of these orbits must necessarily intersect the plane of the ecliptic at two opposite points situated at the extremities of a straight line passing through the ,sun's centre4 ,the two opposite points on a planetary orbit where its intersections with the ecliptic occur1 are called the ,nodes1 and the imaginary line joining them1 which passes through the ,sun's centre1 is called the line of the nodes4 ,the node situated at the point where a planet crosses the ecliptic from the south to the north1 is called the ascending node while that situated where the planet crosses from north to south1 is called the descending node4 ,the planets circulating around the ,sun are eight in number1 but1 beside these1 there is a multitude of very small planets1 commonly called asteroids1 which also revolve around our luminary4 ,the number of asteroids at present known surpasses two hundred1 and constantly increases by new discoveries4 ,in their order of distance from the ,sun the principal planets are3 ,mercury1 ,venus1 ,earth1 ,mars1 ,jupiter1 ,saturn1 ,uranus and ,neptune4 ,the orbits of the asteroids are comprised between the orbits of ,mars and ,jupiter4 ,when the principal planets are considered in regard to their differences in size1 they are separated into two distinct groups of four planets each1 viz43 the small planets and the large planets4 ,the orbits of the small planets are wholly within the region occupied by the orbits of the asteroids1 while those of the large planets are wholly without this region4 ,when the planets are considered in regard to their position with reference to the ,earth1 they are called inferior planets and superior planets4 ,the inferior planets comprise those whose orbits are within the orbit of our globe2 while the superior planets are those whose orbits lie beyond the orbit of the ,earth4 ,since the orbits of the inferior planets lie within the orbit of the ,earth1 the angular distances of these bodies from the ,sun1 as seen from the ,earth1 must always be included within fixed limits2 and these planets must seem to oscillate from the east to the west1 and from the west to the east of the ,sun during their sidereal revolution4 ,in this process of oscillation these planets sometimes pass between the ,earth and the ,sun1 and sometimes behind the ,sun4 ,when they pass between us and the ,sun they are said to be in inferior conjunction1 while1 when they pass behind the ,sun1 they are said to be in superior conjunction4 ,when such a planet reaches its greatest distance1 either east or west1 it is said to be at its greatest elongation east or west1 as the case may be1 or in quadrature4 ,the superior planets1 whose orbits lie beyond that of the ,earth and enclose it1 present a different appearance4 ,a superior planet never passes between the ,earth and the ,sun1 since its orbit lies beyond that of our globe1 and1 therefore1 no inferior conjunction of such a planet can ever occur4 ,when one of these planets passes beyond the ,sun1 just opposite to the place occupied by the ,earth1 the planet is said to be in conjunction2 while1 when it is on the same side of the ,sun with our globe1 it is said to be in opposition4 ,while occupying this last position1 the planet is most advantageously situated for observation1 since it is then nearer to the ,earth4 ,the period comprised between two successive conjunctions1 or two successive oppositions of a planet1 is called its synodical period4 ,this period differs for every planet4 ,it is supposed that all the planets rotate from west to east1 like our globe2 although no direct evidence of the rotation of ,mercury ,uranus1 and ,neptune has yet been obtained1 it is probable that these planets rotate like the others4 ,it results from the rotation of the planets that they have their days and nights1 like our ,earth1 but differing in duration for every planet4 ,the axes of rotation of the planets are more or less inclined to their respective orbits1 and this inclination varies but little in the course of time4 ,from the inclination of the axes of rotation of the planets to their orbits1 it results that these bodies have seasons like those of the ,earth2 but1 of course1 they differ from our seasons in duration and intensity1 according to the period of revolution and the inclination of the axis of each separate planet4 ,,the ,,planet ,,mars ,,plate ,,viii ,mars is the fourth of the planets in order of distance from the sun2 ,mercury1 ,venus and the ,earth being respectively the first1 second and third4 ,owing to the great eccentricity of its orbit1 the distance of ,mars from the ,sun is subject to considerable variations4 ,when this planet is in its aphelion1 its distance from the ,sun is #aeb1jjj1jjj miles1 but at perihelion it is only #abf1jjj1jjj miles distant1 the planet being therefore #bf1jjj1jjj miles nearer the ,sun at perihelion than at aphelion4 ,the mean distance of ,mars from the ,sun is #aci1jjj1jjj miles4 ,light1 which travels at the rate of #ahe1jjj miles a second1 occupies #ab minutes in passing from the ,sun to this planet4 ,while the distance of ,mars from the ,sun varies considerably1 its distance from the ,earth varies still more4 ,when ,mars comes into opposition1 its distance from our globe is comparatively small1 especially if the opposition occurs in ,august1 as the two planets are then as near together as it is possible for them to be1 their distance apart being only #cc1jjj1jjj miles4 ,but if the opposition occurs in ,february1 the distance may be nearly twice as great1 or #fb1jjj1jjj miles4 ,on the other hand1 when ,mars is in conjunction in ,august1 the distance between the two planets is the greatest possible1 or no less than #bde1jjj1jjj miles2 while1 when the conjunction occurs in ,february1 it is only #baf1jjj1jjj miles4 ,hence the distance between ,mars and the ,earth varies from 4#cc to #bde millions of miles2 that is1 this planet may be #bab million miles nearer to us at its nearest oppositions than at its most distant conjunctions4 ,from these varying distances of ,mars from the ,earth1 necessarily result great variations in the brightness and apparent size of the planet1 as seen from our globe4 ,when nearest to us it is a very conspicuous object1 appearing as a star of the first magnitude1 and approaching ,jupiter in brightness2 but when it is farthest it is much reduced1 and is hardly distinguishable from the stars of the second and even third magnitude4 ,in the first position1 the apparent diameter of ,mars is #bf1 in the last it is reduced to #c only4 ,the orbit of ,mars has the very small inclination of #a #ea' to the plane of the ecliptic4 ,the planet revolves around the ,sun in a period of #fhg days1 which constitutes its sidereal year1 the year of ,mars being only #dc days less than two of our years4 ,mars travels along its orbit with a mean velocity of #ae miles per second1 being about of the velocity of our globe in its orbit4 ,the synodical period of ,mars is #b years and #dh days1 during which the planet passes through all its degrees of brightness4 ,mars is a smaller planet than the ,earth1 its diameter being only #d1bjj miles1 and its circumference #ac1bjj miles4 ,it seems well established that it is a little flattened at its poles1 but the actual amount of this flattening is difficult to obtain4 ,according to ,prof4 ,young1 the polar compression is 4 ,the surface of this planet is a little over of the surface of our globe1 and its volume is #f times less than that of the ,earth4 ,its mass is only about while its density is about that of the ,earth4 ,the force of gravitation at its surface is nearly of what it is at the surface of our globe4 ,the planet ,mars rotates on an axis inclined #fa #ah' to the plane of its orbit1 so that its equator makes an angle of #bh #db' with the same plane4 ,the period of rotation of this planet1 which constitutes its sidereal day1 is #bd h4 #cg m4 #bc s4 ,the year of ,mars1 which is composed of #ffi of these ,martial days1 equals #fhg of our days1 this planet rotating #ffi times upon its axis during this period4 ,but owing to the movement of ,mars around the ,sun1 the number of solar days in the ,martial year is only #ffh1 while1 owing to the same cause1 the solar day of ,mars is a little longer than its sidereal day1 and equals #bd h4 #ci m4 #ce s4 ,the days and nights on ,mars are accordingly nearly of the same length as our days and nights1 the difference being a little less than three-quarters of an hour4 ,but while the days and nights of ,mars are essentially the same as ours1 its seasons are almost twice as long as those of the ,earth4 ,their duration for the northern hemisphere1 expressed in ,martial days1 is as follows3 ,spring1 #aia2 ,summer1 #aha2 ,autumn1 #adi2 ,winter1 #adg4 ,while the ,spring and ,summer of the northern hemisphere together last #cgb days1 the ,autumn and ,winter of the same hemisphere last only #bif days1 or #gf days less4 ,since the summer seasons of the northern hemisphere correspond to the winter seasons of the southern hemisphere1 and vice versa1 the northern hemisphere1 owing to its longer summer1 must accumulate a larger quantity of heat than the last4 ,but on ,mars1 as on the ,earth1 there is a certain law of compensation resulting from the eccentricity of the planet's orbit1 and from the fact that the middle of the summer of the southern hemisphere of this planet1 coincides with its perihelion4 ,from the greater proximity of ,mars to the ,sun at that time1 the southern hemisphere then receives more heat in a given time than does the northern hemisphere in its summer season4 ,when everything is taken into account1 however1 it is found that the southern hemisphere must have warmer summers and colder winters than the northern hemisphere4 ,seen with the naked eye1 ,mars appears as a fiery red star1 whose intensity of color is surpassed by no other star in the heavens4 ,seen through the telescope1 it retains the same red tint1 which1 however1 appears less intense1 and gradually fades away toward the limb1 where it is replaced by a white luminous ring4 ,,plate ,,viii4--,,the ,,planet ,,mars4 ,observed ,september #c1 #ahgg1 at #aa;h4 #eem4 ,p4,m4 ,mars is a very difficult object to observe1 the atmosphere surrounding it being sometimes so cloudy and foggy that the sight can hardly penetrate through its vapors4 ,when this planet is observed under favorable atmospheric conditions1 and with sufficient magnifying power1 its surface1 which is of a general reddish tint1 is found to be diversified by white1 gray and dark markings4 ,the dark markings1 which are the most conspicuous1 almost completely surround the planet4 ,they are of different forms and sizes1 and very irregular1 as can be seen on ,plate ,,viii41 which represents one of the hemispheres of this planet4 ,many of them1 especially those situated in the tropical regions of the planet1 form long narrow bands1 whose direction is in the main parallel to the ,martial equator4 ,the dusky spots differ very much1 both from one another and in their several parts1 as regards intensity of shade4 ,some appear almost black1 while others which appear grayish1 are so faint1 that they can seldom be seen4 ,in the southern hemisphere1 the darkest part of the spots is generally found along their northern border2 especially where there are deep indentations4 ,some observers have described these spots as being greenish or bluish1 but ,i have never been able to see the faintest trace of these colors in them1 except when they were observed close to the limb1 and involved in the greenish tinted ring which is always to be seen there4 ,it is probably an effect of contrast1 since green and red are complementary colors1 and since this greenish tinge around the limb covers all kinds of spots1 whether white or dark4 ,when such dark spots1 involved in the greenish tint1 are carried by the rotation towards the centre of the disk1 they no longer show this greenish color4 ,to me1 these spots have always appeared dark1 and of such tints as would result from a mixture of white and black in different proportions2 except that on their lighter portions they show some of the prevalent reddish tint of the ,martial surface4 ,it is to be remarked that in moments of superior definition of the telescopic image1 the intensity of darkness of all the spots is considerably increased--some of them appearing almost perfectly black4 ,the markings on the surface of ,mars are now tolerably well known--especially those of its southern hemisphere1 which1 owing to the greater proximity of the planet to our globe when this hemisphere is inclined towards the earth1 have been better studied4 ,those of the northern hemisphere are not so well known1 since when this hemisphere is inclined towards us1 the distance of ,mars from the ,earth is #bf1jjj1jjj miles greater1 so that the occasions for observing them are not so favorable4 ,several charts of ,mars are in existence1 but as the same nomenclature has not been employed in all of them1 some confusion has arisen in regard to the names given to the most remarkable features of the planet's surface4 ,in order to give clearness to the subject1 it will be necessary here to give a brief description of the principal markings represented on ,plate ,,viii4 ,in this the nomenclature will be employed which has been adopted by the ,english observers in the fine chart of ,mr4 ,nath4 ,green4 ,the large dark spot represented on the left-hand side of the plate is called ,de ,la ,rue ,ocean4 ,the dark oval spot1 isolated in the vicinity of the centre of the disk1 is called ,terby ,sea2 while the dark1 irregular form on the right1 near the border1 represents the western extremity of ,maraldi ,sea4 ,the dusky spots of ,mars seem to be permanent1 and to form a part of the general surface of the planet4 ,that several among them1 at least1 are permanent1 is proved by the fact that they have been observed in the same position1 and with the same general form1 for over two centuries4 ,yet1 if we are to depend upon the drawings made fifty years ago by ,beer and ,maedler1 it would seem that the permanency of some of them does not exist1 since a very large spot represented by these astronomers on their chart of ,mars is not visible now4 ,this object1 which1 on their map1 has its middle at #bgj1 should be precisely under the prominent dark oval spot called ,terby ,sea1 seen near the centre of the picture1 and would extend down almost as far as the northern limb4 ,this can hardly be attributed to an error of observation1 since these observers were both careful1 and had great experience in this class of work4 ,it is a very singular fact that1 at the very same place where ,maedler represented the spot in question1 ,i found a conspicuous dark mark on ,december #af1 #ahha1 which was certainly not visible in #ahgg1 during one of the most favorable oppositions which can ever occur4 ,the object1 which is still visible 7,feb41 #ahhb71 consists of an isolated spot situated a little to the north of ,terby ,sea4 ,during the memorable opposition of #ahgg1 ,i investigated thoroughly the markings of ,mars1 and made over #bjj drawings of its disk1 #cb of which represent the ,terby ,sea2 but this isolated spot was not to be seen1 unless it be identified with the faint mark1 represented on the plate1 which occupied its place4 ,there cannot be the slightest doubt that a change has occurred at that place4 ,changes in the markings have also been suspected on the other hemisphere of the planet4 ,the well-known fact that the continents1 and especially the mountainous and denuded districts of our globe1 reflect much more light than the surfaces covered by water1 has led astronomers to suppose that the dark spots on ,mars are produced by a liquid strongly absorbing the rays of light1 like the liquids on the surface of the ,earth4 ,according to this theory the dark spots observed are supposed to be lakes1 seas1 and oceans1 similar to our own seas and oceans1 while the reddish and whitish surfaces separating these dark spots1 are supposed to be islands1 peninsulas1 and continents4 ,this supposition seems certainly to have a great deal of probability in its favor1 although some of the lighter markings may have a different origin1 and perhaps be due to vegetation2 but no observer has yet seen in them any of the changes which ought to result from change of seasons4 ,some of the changes in the dark spots might also be attributed to the flooding or drying up of marshes and low land4 ,the change which ,i have observed lately might be attributed to such a cause1 especially as my observation was made shortly after the spring equinox of the northern hemisphere of ,mars1 which occurred on ,december #hth4 ,besides the dark spots just described1 there are markings of a different character and appearance4 ,among the most conspicuous are two very brilliant white oval spots1 which always occupy opposite sides of the planet4 ,these two bright spots1 which correspond very closely with the poles of rotation of ,mars1 have been called polar spots4 ,on account of the inclination of the axis of rotation of this planet to the ecliptic1 it is rare that both of these spots are visible on the disk at the same time2 and when this occurs1 they are seen considerably foreshortened1 as they are then both on the limb of the planet4 ,usually only one spot is visible1 and it appears to its best advantage when the region to which it belongs attains its maximum of inclination towards the ,earth4 ,the polar spots change considerably in size1 as they do also in form4 ,sometimes they occupy nearly one-third of the disk1 as is proved by many of my observations2 while at other times they are so much reduced as to be totally invisible4 ,it is to be remarked that the reduction of these spots generally corresponds with the summer seasons1 and their enlargement with the winter seasons of the hemispheres to which they respectively belong4 ,from these well-observed facts it would appear that a relation exists between the temperature of the two hemispheres of ,mars and the variations of the white spots observed at its poles4 ,a similar relation is known to exist on our globe between the progress of the seasons and the melting away and the accumulation of snow in the polar regions4 ,astronomers have been led1 accordingly1 to attribute the polar spots of ,mars1 with all their variations1 to the alternate accumulation and melting of snows4 ,on this account1 the polar spots of ,mars are sometimes also called snow-spots4 ,errors have certainly been made by astronomers in some of their observations of the so-called polar snow-spots1 other objects occupying their place having been mistaken for them4 ,a regular series of observations on this planet1 which ,i have now continued for seven years1 has revealed the fact that during the winter seasons of the southern hemisphere of ,mars1 the polar spots are most of the time invisible1 being covered over by white1 opaque1 cloud-like forms1 strongly reflecting light4 ,in #ahgg1 during more than a month1 ,i1 myself1 mistook for the polar spots such a canopy of clouds1 which covered at least one-fifth of the surface of the whole disk4 ,i only became aware of my error when the opaque cloud1 beginning to dissolve at the approach of the ,martial summer1 allowed the real polar spot to be seen through its vapors1 as through a mist at first1 and afterwards with great distinctness4 ,in this particular case1 the snow-spot was considerably smaller than the cloudy cap which covered it1 and it is to be remarked that it was not situated at the centre of this cloudy cap1 but was east of that centre2 a fact which may account for the so-called polar spots not being always observed on exactly opposite sides of the disk4 ,from my observations of #ahgg1 #ahgh and #ahhj1 it appears that at the approach of the autumnal equinox of the southern hemisphere of ,mars1 large1 opaque masses1 like cumulus clouds in form1 began to gather in the polar regions of that hemisphere1 and continued through autumn and winter1 dissolving only at the approach of spring4 ,these clouds1 which varied in form and extent1 were very unsteady at first1 but as the winter drew nearer they enlarged and became more permanent1 covering large surfaces for months at a time4 ,that the large white spots under consideration are real clouds in the atmosphere of ,mars1 and are not due to a fall of snow1 is proved by the fact that these spots covered both seas and continents with equal facility1 even in the equatorial regions of the planet4 ,snow1 of course1 could not cover the seas of ,mars1 unless these were all frozen over1 even in the equatorial zones2 therefore1 if the dark spots of ,mars are assumed to be due to water1 these large white spots cannot well be ascribed to snow4 ,the real polar spots of ,mars seem to be in relief on the surface of the planet1 since the southern spot often appeared slightly shaded on the side opposite to the ,sun during my observations in #ahgg4 ,in certain cases1 when they are on or very near the limb1 they have been observed1 both by others and by myself1 to project from the disk slightly4 ,the polar spots of ,mars are doubtless composed of a material which1 like our snow or ice1 melts under the rays of the ,sun2 although it seems difficult to admit that the ,martial snow is identical with our terrestrial snow1 and that it melts at a like temperature4 ,the south polar spot of ,mars entirely disappeared from sight in its summer season in #ahgg1 although the planet receives less than one-half as much heat as we receive from the ,sun2 yet on our globe the arctic or antarctic ices and snow are perpetual--never melting entirely4 ,an important fact disclosed by the melting away of the southern polar spot is1 that in melting it is always surrounded with a very dark surface1 which takes the place of the melted portion of the spot1 as observed by myself in #ahgg-gh4 ,when the polar spot had entirely disappeared1 its place was occupied by a very dark spot4 ,now1 if the polar spot is really ice1 and the dark spots are actual seas1 this polar spot must be situated in mid-ocean1 since1 on melting away1 it is replaced by a dark spot4 ,if the polar spots are composed of a white substance melting under the rays of the ,sun1 as seems altogether probable1 its melting point must be above that of terrestrial snow4 ,many of the dark spots of ,mars1 and especially those whose northern border forms an irregular belt upon the equatorial regions of this planet1 are bordered on that side by a white luminous belt1 following all their sinuosities4 ,these white borders are variable4 ,sometimes they are very prominent and intensely bright1 especially at some points1 which occasionally almost equal the polar spots in brilliancy2 while at other times they are so faint1 that they can hardly be distinguished1 or are even invisible2 although the atmosphere is clear and the dark spots appear perfectly well defined4 ,while these white borders were invisible1 ,i have sometimes watched for several hours at a time to see if ,i could detect any traces of them in places where they usually appear the most prominent1 but generally without success4 ,on a few occasions1 however1 ,i had the good fortune to see some of these spots forming gradually in the course of one or two hours1 at places where nothing of them could be seen before4 ,these whitish fringes forming and vanishing along the coasts of the ,martial seas have been very little studied by astronomers4 ,from my observations made during the last seven years1 it appears very probable that this belt and its white spots are mainly due to the condensation of vapors around1 and over high peaks1 and extensive mountain chains1 forming the ,martial sea-coasts1 as the ,andes and ,rocky ,mountains form the sea-coasts of the ,pacific ,ocean4 ,these high mountains on ,mars1 condensing the vapors into fogs or clouds above them1 or at their sides1 as often happens in our mountainous districts1 would certainly suffice to produce the phenomena observed4 ,some of the highest peaks among these mountain chains may even have their summits covered with perpetual snow1 or some substance partaking of the nature of snow4 ,the temporary visibility and invisibility of the white spots seen on ,mars1 as well as the rapid transformations they sometimes undergo1 may be explained as caused by clouds having a high reflective power and a liability to form and disappear quickly4 ,the assumption that these irregular whitish bands and spots are formed by the condensation of vapors on mountain chains1 and elevated table lands1 is supported by my observations made in #ahgg and #ahgi4 ,when such white spots were traversing the terminator at sunrise1 they very often projected far into the night side1 thus indicating that they were at a higher level than that of the general surface4 ,indentations in the terminator1 corresponding to large dark spots crossing its line1 also clearly indicated the depression of the dark spots below the general surface4 ,the highest mountainous districts thus observed on ,mars1 are situated between #fj and #gj of south latitude1 towards the western extremity of ,gill ,land4 ,the mountain chain1 which almost completely forms the surface of this land1 is so elevated at some points1 that they not only change the form of the terminator when they are seen upon it1 but also the limb of the planet1 as seen by myself4 ,they then appear so brilliant1 that the principal summit among them has been mistaken by several observers for the polar spot itself1 as proved by the wrong position assigned to it on their drawings4 ,it seems probable that this high peak1 which appears always white1 is constantly covered with snow1 or the similar material replacing it on ,mars4 ,this high region is situated between longitudes #ahj and #aij4 ,the highest mountainous parts belonging to the hemisphere represented on ,plate ,,viii41 which are nearly always more or less visible as whitish spots and bands1 form a coast line along the northern 7lower7 border of ,de ,la ,rue ,ocean4 ,this great spot1 which is not so simple as it has been represented by observers1 is in fact divided by two narrow isthmuses1 one in the north1 the other in the east1 both joining1 in the interior of the great ocean1 a peninsula heretofore known as ,hall ,island4 ,upon the south-eastern extremity of this peninsula1 a white spot1 called ,dawes ,ice ,island1 was observed in #ahfe1 but it soon disappeared1 and was after that seen only now and then4 ,it is very probable that this so-called ,ice ,island was due to clouds forming around the summit of some high peak of this peninsula4 ,on the opposite hemisphere to that represented on ,plate ,,viii41 the white fringes bordering the dark spots are much more conspicuous than they are on this side4 ,on the eastern side of a remarkable dark spot called ,kaiser ,sea1 they are very bright1 and almost always present1 although they vary considerably1 both in brightness and in extent4 ,to the south of ,kaiser ,sea1 they are very conspicuous on the eastern border of ,lockyer ,land1 forming an elevated and deeply indented coast-line along ,lambert ,sea4 ,there the white spots never disappear entirely1 being always visible on the north side1 where they turn westward along ,dawes' ,ocean--the mountain chain attaining there its greatest altitude4 ,very frequently ,lockyer ,land1 which seems to be a vast plateau1 appears throughout white and brilliant1 this occurring usually towards the sunrise or sunset of that region1 probably from the condensation of vapors and the formation of fogs1 but generally this whiteness gradually disappears with the progress of the sun above this plateau4 ,inside of the great continents of ,mars these temporary white spots are not so frequent1 but when visible they occupy always the same positions--a fact which probably indicates that they occupy the culminating points of these continents4 ,one of these temporary white spots inside of the continents is represented on ,plate ,,viii41 on the left-hand side1 below ,de ,la ,rue ,ocean1 on ,maedler ,continent4 ,although large1 opaque1 cumulus-shaped1 cloud-like forms are seen in the polar regions of ,mars1 such forms are very seldom seen in the tropical zones1 or1 at least1 it appears so1 from the fact that my observations1 continued during the last seven years1 have disclosed no real opaque cloudy forms there4 ,although the ,martial sky is frequently overcast by dense vapors or thick fogs in these regions1 yet no real opaque clouds were ever seen2 the most prominent among the dusky spots being faintly visible through the vapory veil1 when they approached the centre of the disk4 ,besides these phenomena1 which prove that ,mars is surrounded by an atmosphere having a great deal of similarity to our own1 a further proof is afforded by the fact that the dark spots1 which appear sharply defined and black when they are seen near the centre1 become less and less visible as they advance towards the limb1 and are totally invisible before they reach it4 ,moreover1 the spectroscope also indicates the existence of an atmosphere1 and even the presence of watery vapor in it4 ,a very curious state of the ,martial atmosphere is revealed by my observations of #ahgg-gh4 ,during eight consecutive weeks1 from ,december #abth to ,february #fth1 a whole hemisphere of the planet--precisely that represented on ,plate ,,viii4--was completely covered by dense vapors1 or a thick fog which barely allowed the dark spots to be seen through it1 even when they were in the centre of the disk4 ,the opposite hemisphere of ,mars appeared just as clear and calm as possible2 there all the spots and their minutest details could be seen1 and when the planet was observed at the proper time1 the line separating the foggy from the clear side was plainly visible4 ,the reddish tint observed on the continents of ,mars has been supposed by some astronomers to be the real color of the atmosphere of this planet4 ,but1 for many reasons1 this explanation is not acceptable4 ,besides the fact that the border of the planet appears white1 while it should be more red than the other part1 owing to the greater depth of atmosphere there presented to us1 the polar spots1 the white bands along the sea-coasts1 and the cloud-like forms appear perfectly white1 not the slightest tint of red being visible on them1 as would be the case if these objects were seen through an atmosphere tinted red4 ,other astronomers have supposed that the vegetation of this planet has a reddish color2 but this is not supported by observation4 ,it has been again supposed1 with much more probability1 that the surface of ,mars is composed of an ochreous material which gives the planet its predominant ruddy color4 ,until lately ,mars was supposed to be without a satellite1 but in ,august1 #ahgg1 ,professor ,hall1 of the ,washington ,observatory1 made one of the most remarkable discoveries of the time1 and found two satellites revolving around this planet4 ,these satellites are among the smallest known heavenly bodies1 their diameter having been estimated at from #f to #aj miles for the outer satellite1 and from #aj to #dj miles for the inner one4 ,the most extraordinary feature of these bodies is the proximity of the inner satellite to the planet1 and the consequent rapidity of its motion4 ,the distance of the inner satellite from the centre of ,mars is about #f1jjj miles1 and from surface to surface it is less than #d1jjj miles1 or a little more than the distance from ,new ,york to ,san ,francisco4 ,the shortest period of revolution of any satellite previously known1 is that of the inner satellite of ,saturn1 which is a little more than #bb hours2 but the inner satellite of ,mars accomplishes its revolution in #g;h4 #chm41 or in #ag hours less than the period of rotation of the planet upon its axis4 ,the period of revolution of the outer satellite is greater1 of course1 and equals #cj;h4 #gm4 ,from this rapidity of motion of the inner satellite of ,mars1 a very curious result follows1 which at first sight may appear in contradiction with the fact that this body has a direct motion1 like that of all the planets of the solar system1 and moves around ,mars from west to east4 ,while the outer satellite of this planet1 in company with all the stars and planets1 rises in the east and sets in the west1 the inner satellite1 on the contrary1 rises in the west and sets in the east4 ,since the period of rotation of ,mars is greater than is the period of revolution of this satellite1 it necessarily follows that this last body must constantly be gaining on the rotation1 and1 consequently1 that the satellite sets in the east and rises in the west1 compassing the whole heavens around ,mars three times a day1 passing through all its phases in #aa hours1 each quarter of this singular ,moon lasting less than #c hours4 ,it has been shown above that ,mars has many points of resemblance to the ,earth4 ,it has an atmosphere constituted very nearly like ours2 it has fogs1 clouds1 rains1 snows1 and winds4 ,it has water1 or at least some liquids resembling it2 it has rivers1 lakes1 seas and oceans4 ,it has also islands1 peninsulas1 continents1 mountains and valleys4 ,it has two ,moons1 which must create great and rapid tides in the waters of its seas and oceans4 ,it has its days and nights1 its warm and cold seasons1 and very likely its vegetation1 its prairies and forests1 like the ,earth4 ,on the other hand1 its year and seasons are double those of the ,earth1 and its distance from the ,sun is greater4 ,is this planet1 which is certainly constituted very nearly like our globe1 and seems so nearly fitted for the wants of the human race1 inhabited by animals and intelligent beings8 ,to answer this question1 either in the negative or in the affirmative1 would be to step out of the pure province of science1 and enter the boundless domain of speculation1 since no observer has ever seen anything indicating that animal life exists on ,mars1 or on any other planet or satellite4 ,so far as observation goes1 ,mars seems to be a planet well suited to sustain animal life1 and we may reason from analogy that if animal life can exist at all outside of the ,earth1 ,mars must have its flora and fauna2 it must have its fishes and birds1 its mammalia and men2 although all these living beings must inevitably be very different in appearance from their representatives on the ,earth1 as can easily be imagined from the differences existing between the two planets4 ,although all this is possible1 and even very probable1 yet it must be remembered that we have not the slightest evidence that it is so2 and until we have acquired this evidence1 we may only provisionally accept this idea as a pleasing hypothesis1 which1 after all1 may be wrong and totally unfounded4 ,,the ,,planet ,,jupiter ,,plate ,,ix ,jupiter1 the giant of the planetary world1 is the fifth in order of distance from the ,sun1 and is next to ,mars1 our ruddy neighbor4 ,to the naked eye1 ,jupiter appears as a very brilliant star1 whose magnitude1 changing with the distance of this planet from the ,earth1 sometimes approaches that of ,venus1 our bright morning and evening star4 ,the mean distance of ,jupiter from the ,sun is #dge1jjj1jjj miles1 but owing to the eccentricity of its orbit1 its distance varies from #deb to #dih millions of miles4 ,the distance of this planet from the ,earth varies still more4 ,when nearest to our globe1 or in opposition1 its distance is reduced to #chd1jjj1jjj miles1 and its apparent diameter increased to #ej2 while when it is farthest1 or in conjunction1 its distance is increased to #efg1jjj1jjj miles1 and its apparent diameter reduced to #cj2 ,jupiter being thus #ahc1jjj1jjj miles nearer our globe while in opposition than when it is in conjunction4 ,this planet revolves around the ,sun in #aa years1 #aj months and #ag days1 or in only #ej days less than #ab terrestrial years4 ,such is the year of this planet4 ,the plane of its orbit is inclined #a #ai' to the ecliptic4 ,no planet1 except ,uranus1 has an orbit exhibiting a smaller inclination4 ,the planet advances in its orbit at the mean rate of #h miles a second2 which is a little less than half the orbital velocity of the ,earth4 ,jupiter is of enormous proportions4 ,its equatorial diameter measures #hh1jjj miles1 and its circumference no less than #bgf1dfj miles1 these dimensions being #aa times greater than those of the ,earth4 ,this planet1 notwithstanding its huge size1 rotates on its axis in not far from #i;h4 #eem4 #cfs41 which period constitutes its day4 ,owing1 however1 to the changeable appearance of its surface1 this period cannot be ascertained with very great exactitude4 ,in consequence of its rapid rotation1 the planet is far from spherical1 its polar diameter being shorter than the equatorial by about 1 or #e1ejj miles4 ,its surface is #abd times the surface of the earth2 while its volume is #a1chg times as great4 ,if ,jupiter occupied the place of our satellite in the sky1 it would appear #dj times as large as the ,moon appears to us1 and would cover a surface of the heavens #a1fjj times that covered by the full ,moon1 and would subtend an angle of #ba4 ,jupiter's mass does not correspond with its great bulk1 and is only of the mass of the ,sun1 and #caj times the mass of the earth2 its density being only of that of our globe4 ,the force of gravitation at the surface of this planet is over #b times what it is on the ,earth1 so that a terrestrial object carried to the surface of ,jupiter would weigh over two and a half times as much as on our globe4 ,observed with a telescope1 even of moderate aperture1 ,jupiter1 with its four attending satellites and its dazzling brilliancy1 appears as one of the most magnificent objects in the sky4 ,the general appearance of the disk is white2 but unlike that of ,mars1 it is brightest towards its central parts1 and a little darker around the limb1 especially on the side opposite to the ,sun4 ,although an exterior planet1 and so far from us1 ,jupiter shows faint traces of phases when observed near its quadratures1 but this gibbosity of its disk is very slight1 and is indicated only by a kind of penumbral shadow on the limb4 ,when observed with adequate power1 the disk of ,jupiter is found to be highly diversified4 ,the principal features consist of a series of alternate light and dark streaks or bands1 disposed most of the time parallel with the ,jovian equator4 ,these bands differ from each other in intensity as well as in breadth2 those near the equator being usually much more prominent than those situated in higher latitudes north and south4 ,the equatorial zone of ,jupiter is occupied most of the time by a broad1 prominent belt #bj or #cj wide1 limited on each side by a very dark narrow streak4 ,between these two dark borders1 but seldom occupying the whole space between them1 appears an irregular white belt1 apparently composed of dense masses of clouds strongly reflecting the ,sun's light1 some of these cloudy masses being very brilliant4 ,the spaces left between the cloudy belt and the dark borders1 usually exhibit a delicate pink or rosy color1 which produces a very harmonious effect with the varying grayish and bluish shades of some of the belts and streaks seen on the disk4 ,quite often the cloudy belt is broken up1 and consists of independent cloudy masses1 separated by larger or smaller intervals1 these intervals disclosing the rosy background of this zone4 ,on each side of the equatorial belt there is usually a broad whitish belt1 succeeded by a narrow gray band2 the space left on each hemisphere between these last bands and the limb being usually occupied by two or three alternate white and gray bands4 ,a uniform gray segment usually forms a sort of polar cap to ,jupiter4 ,when observed under very favorable conditions1 all the lighter belts appear as if composed of masses of small cloudlets1 resembling the white opaque clouds seen in our atmosphere4 ,this1 as already stated1 is particularly noticeable on the equatorial belt4 ,it is not unusual1 when ,jupiter is in quadrature1 to see some of the most conspicuous white spots casting a shadow opposite to the ,sun2 a fact which sufficiently indicates that these spots are at different levels4 ,they probably form the summits of vast banks of clouds floating high up in the atmosphere of ,jupiter4 ,what we see of ,jupiter is chiefly a vaporous1 cloudy envelope4 ,if our sight penetrates anywhere deeper into the interior1 it can only be through the narrow fissures of this envelope1 which appear as gray or dark streaks or spots4 ,that most of the visible surface of ,jupiter is simply a cloudy covering1 is abundantly proved by the proper motion of its spots1 which sometimes becomes very great4 ,in periods of calm1 very few changes are noticeable in the markings of the planet1 except1 perhaps1 some slight modifications of form in the cloudy1 equatorial belt which1 in general1 is much more liable to changes than the other belts4 ,but the ,jovian surface is not always so tranquil1 great changes being observed during the terrific storms which sometimes occur on this mighty planet1 when all becomes disorder and confusion on its usually calm surface2 and nothing on the ,earth can give us a conception of the velocity with which some of its clouds and spots are animated4 ,new belts quickly form1 while old ones disappear4 ,the usual parallelism of the belts no more exists4 ,huge1 white1 cumulus-like masses advance and spread out1 the rosy equatorial belt enlarges sometimes to two or three times its usual size1 and occupies two-thirds1 or more1 of the disk1 the rosy tint spreading out in a very short time4 ,at times very dark bands extending across the disk are transformed into knots or dark spots1 which encircle the planet with a belt1 as it were1 of jet black beads4 ,sometimes1 also1 a secondary but narrower rosy belt forms either in the northern or the southern hemisphere1 and remains visible for a few days or for years at a time4 ,on ,may #be1 #ahgf1 ,i witnessed one of the grandest commotions which can be conceived as taking place in an atmosphere4 ,all the southern hemisphere of ,jupiter1 from equator to pole1 was in rapid motion1 the belts and spots being transported entirely across the disk1 from the eastern to the western limb1 in one hour's time1 during which the equatorial belt swelled to twice its original breadth1 towards the south4 ,now1 when one stops for a moment to think what is signified by that motion of the dark spots across the little telescopic disk of ,jupiter in an hour's time1 he may arrive at some conception of the magnitude of the ,jovian storms1 compared with those of our globe4 ,the circumference of ,jupiter's equator1 as stated above1 is #bgf1dfj miles2 half this number1 or #ach1bcj miles1 represents the length of the equatorial line seen from the ,earth4 ,now1 after taking into account the rotation of the planet1 which somewhat diminishes the apparent motion1 we arrive at the astonishing result that the spots and markings were carried along by this ,jovian storm1 at the enormous rate of #aaj1ehd miles an hour1 or over #cj4g miles a second4 ,on our globe1 a hurricane or tornado1 which blows at the rate of #ajj miles an hour1 sweeps everything before it4 ,what1 then1 must be expected from a velocity over #a1aje times as great8 ,enormous as this motion may appear1 its occurrence cannot be doubted1 since it is disclosed by direct observation4 ,the surface of ,jupiter1 it would seem1 has its periods of calm and activity like that of the ,sun1 although it is not yet known1 as it is for the latter1 that they recur with approximate regularity4 ,my observations of this planet1 which embrace a period of ten years1 seem to point in that direction1 for they show1 at least1 that ,jupiter has its years of calm and its years of disturbances4 ,the year #ahgf was a year of extraordinary disturbance on ,jupiter4 ,changes in the markings were going on all the time1 and no one form could be recognized the next day1 or even sometimes the next hour1 as shown above4 ,the cloudy envelope of the planet was in constant motion1 the equatorial belt1 especially1 showing the signs of greatest disturbance1 being1 for the most part1 two or three times as wide as in other years4 ,after #ahgf the calm was very great on the planet1 only a slight change now and then being noticeable1 the same forms being recognized day after day1 month after month1 and even year after year4 ,in one case the same marking has been observed for seventeen consecutive months1 and in another for twenty-eight months4 ,this state of quietude lasted until ,october1 #ahhj1 when considerable commotion occurred on the northern hemisphere1 where large round black spots1 somewhat resembling the ,sun-spots1 formed in the cloudy atmosphere1 and finally changed1 towards the end of ,december1 into a narrow pink belt1 which still exists4 ,,plate ,,ix4--,,the ,,planet ,,jupiter4 ,observed ,november #a1 #ahhj1 at #i;h4 #cjm4 ,p4,m4 ,the most curious marking ever seen on ,jupiter is undoubtedly the great ,red ,spot1 observed on the southern hemisphere of this planet for the last three years4 ,this interesting object1 seen first in ,july1 #ahgh1 disappeared for a time1 reappeared on ,september #be of the same year1 and has remained visible until now4 ,when seen by me in ,september1 it was much elongated1 and sharply pointed on one side1 like a spear-head1 but it subsequently acquired an irregular form1 with short appendages protruding from its northern border4 ,at first1 the changes were great and frequent1 but at length it acquired the regular oval form1 which1 with but slight modifications1 it has retained until now4 ,during the month of ,november1 #ahhj1 ,i noticed two small black specks upon this ,red ,spot1 and they were seen again in ,january of the succeeding year1 by ,mr4 ,alvan ,clark1 ,jr4 ,when the spot had attained its oval shape1 it appeared part of the time surrounded with a white luminous ring of cloudy forms which1 however1 was changing more or less all the time1 being sometimes invisible4 ,the color of this curious spot is a brilliant rosy red1 tinged with vermilion1 and altogether different in shade from the pinkish color of the equatorial belt4 ,the size of the spot varies1 but of late its changes have been slight4 ,its longer diameter may be estimated at #h1jjj miles1 and the shorter at #b1bjj miles4 ,the ,red ,spot is represented on ,plate ,,ix4 with its natural color1 and as it appears at the moments most favorable for observation4 ,in ordinary cases its color does not appear so brilliant1 but paler4 ,it is difficult to account for the color of the equatorial belt and that of the ,red ,spot2 but it is known1 at least1 that the material to which they are due cannot be situated at the level of the general surface visible to us1 and especially that of the cloudy forms of the equatorial zone4 ,undoubtedly the red layer lies deeper than the superficial envelope of the planet1 although it does not seem to be very deeply depressed4 ,jupiter is attended by four satellites1 which revolve around the planet at various distances1 and shine like stars of the #fth and #gth magnitude4 ,it is said that under very favorable circumstances1 and in a very clear sky1 the satellites can be seen with the naked eye1 but this requires exceptionally keen eyes1 since the glare of the planet is so strong as to overpower the comparatively faint light of the satellites4 ,however1 ,i myself have sometimes seen1 without the aid of the telescope1 two or three of the satellites as a single object1 when they were closely grouped on the same side of ,jupiter4 ,the four moons of ,jupiter are all larger than our ,moon1 except the first1 which has about the same diameter4 ,they range in size from #b1cjj to #c1djj miles in diameter1 the third being the largest2 the determination of their diameter is by no means accurate1 however1 as it is difficult to measure such small objects with precision4 ,their mean distance from the centre of ,jupiter varies from #bfg1jjj to #a1aib1jjj miles1 the first satellite1 the nearest to the planet1 being a little farther from ,jupiter then our satellite is from us4 ,the four satellites revolve around the planet in orbits whose planes have a slight inclination to the equator of ,jupiter1 and consequently to the ecliptic4 ,the diameter of the largest satellite is nearly half that of the ,earth1 or #c1dcf miles2 while its volume is five times that of our ,moon4 ,the period of revolution of these satellites varies from #a;d4 #ah;h4 for the first1 to #af;d4 #af;h4 for the last4 ,owing to the slight inclination of the plane of their orbits to that of the planet1 the three first satellites1 and generally the fourth1 pass in front of the disk and also through the shadow of the planet at every revolution1 and are accordingly eclipsed4 ,their passages behind ,jupiter's disk are called occultations2 those in front of it1 transits4 ,the eclipses1 the occultations and the transits of the moons of ,jupiter are interesting and important phenomena2 the eclipses being sometimes observed for the rough determination of longitudes at sea4 ,the satellites in transit present some curious phenomena4 ,when they enter the disk1 they appear intensely luminous upon its grayish border2 but as they advance1 they seem by degrees to lose their brightness1 until they finally become undistinguishable from the luminous surface of ,jupiter4 ,it sometimes happens1 however1 that the first1 the third and the fourth satellites1 after ceasing to appear as bright spots1 continue to be visible as dark spots upon the bright central portions of the planet's disk2 but in these cases their disks appear smaller than the shadows they cast4 ,undoubtedly these satellites have extensive atmospheres1 since they sometimes pass unperceived across the central parts of ,jupiter1 this being probably when their atmospheres are condensed into clouds1 strongly reflecting light2 while when these clouds are absent1 we can see their actual surface1 with traces of the dark spots upon them similar to those on ,mars4 ,from the variation in the brightness of these satellites1 which is said to be always observed in the same part of their orbit1 ,william ,herschel was led to suppose that these bodies1 like our ,moon1 rotate upon their axes in the same period in which they move round the planet1 so that they always present the same face to ,jupiter2 but these conclusions have been denied4 ,from my observations it is apparent1 however1 that the light reflected by them varies in intensity as well as in color4 ,but this is rather to be attributed to the presence of an atmosphere surrounding these bodies1 which when cloudy reflects more light than when clear1 with corresponding changes in the color of the light4 ,the satellites in transit are sometimes preceded or followed1 according to the position of the ,sun1 by a round black spot having about the same size as the satellite itself4 ,this black spot is the shadow of the satellite cast on the vapory envelope of ,jupiter1 similar to the shadow cast by the ,moon on the ,earth1 during eclipses of the ,sun2 in fact1 all the ,jovian regions traversed by these shadows have the ,sun totally eclipsed4 ,sometimes it happens that the shadow appears elliptical4 ,this occurs either when it is observed very near the limb1 or when entering upon a round1 cloud-like spot4 ,this effect is attributable to the perspective under which the shadow is seen on the spherical globe or spot4 ,the proper motion of the satellites in the ,jovian sky is much more rapid than that of the ,moon in our sky4 ,during one ,jovian day of ten hours1 the first satellite advances #hd2 the second1 #db2 the third1 #bj and the fourth1 #i4 ,the first satellite passes from ,new ,moon to its first quarter in a little more than a ,jovian day1 while the fourth occupies ten such days in attaining the same phase4 ,in density1 as well as in physical constitution1 ,jupiter differs widely from the interior planets1 and especially from the ,earth2 and1 as has been shown1 it is surrounded by a dense1 opaque1 cloudy layer1 which is almost always impenetrable to the sight1 and hides from view the nucleus1 which we may conceive to exist under this vaporous envelope4 ,in #ahgf1 the year of the great ,jovian disturbances1 ,i observed frequently in the northern hemisphere of the planet a very curious phenomenon1 which seems to prove that its cloudy envelope is at times partially absent in some places1 its vapors being apparently either condensed1 or transported to other parts of its surface1 and that1 therefore1 a considerable part of the real globe of the planet was visible at these places4 ,the phenomenon consisted in the deformation of the northern limb1 which had a much shorter radius on all of this hemisphere situated northward of the white belt which adjoins the equatorial zone4 ,the deformation of the limb on both sides1 where it passed from a longer to a shorter radius1 was abrupt1 and at right angles to the limb1 forming there a steplike indentation which was very prominent4 ,the polar segment having a smaller radius1 appeared unusually dark1 and was not striped1 as usual1 but uniform in tint throughout4 ,on ,september #bgth1 the third satellite passed over this dark segment1 and emerged from the western border1 a little below the place where the limb was abruptly deformed1 as above described4 ,when the satellite had fully emerged from this limb1 it was apparent that if the portion of the limb having a longer radius had been prolonged a little below1 and as far as the satellite1 it would have enclosed it within its border1 and thus retarded the time of emersion4 ,the depth of deformation of the limb was accordingly greater than the diameter of the third satellite1 and certainly more than #d1jjj miles4 ,that the phenomenon was real1 is proved by the fact that the egress of this satellite occurred at least four minutes sooner than the time predicted for it in the ,american ,ephemeris4 ,other observations seem to point in the same direction1 since some of the satellites which were occulted have been seen through the limb of ,jupiter by different astronomers1 as if this limb was sometimes semi-transparent4 ,another observation of mine seems to confirm these conclusions4 ,on ,april #bdth1 #ahgg1 at #ae;h4 #bem4 the shadow of the first satellite was projected on the dark band forming the northern border of the equatorial belt1 the shadow being then not far from the east limb4 ,close to this shadow1 and on its western side1 it was preceded by a secondary shadow1 which was fainter1 but had the same apparent size4 ,this round dark spot was not the satellite itself1 as ,i had supposed at first1 since this object was yet outside of the planet1 on the east1 and entered upon it only at #af;h4 #dm4 ,i watched closely this strange phenomenon1 and at #af;h4 #dem41 when the shadow had already crossed about of the disk1 it was still preceded by the secondary1 or mock shadow1 as it may be called2 the same relative distance having been kept all the while between the two objects1 which had therefore traveled at the same rate4 ,it is obvious that this dark spot could not be one of the planet's markings1 since the shadow of the first satellite moves more quickly on the surface of ,jupiter than a spot on the same surface travels by the effect of rotation1 so that in this case the shadow would soon have passed over this marking1 and left it behind1 during the time occupied by the observation4 ,from these observations it seems very probable that ,jupiter has a nucleus1 either solid or liquid1 which lies several thousand mites below the surface of its cloudy envelope4 ,it is also probable that the uniformly shaded dark segment seen in #ahgf1 was a portion of the surface of this nucleus itself4 ,when the cloudy envelope is semi-transparent at the place situated on a line with an occulted satellite and the eye of an observer1 this satellite may accordingly remain visible for a time through the limb1 as shown by observation4 ,the phenomenon of the mock shadow may also be attributed to a similar cause1 where semi-transparent vapors receive the shadow of a satellite at their surface1 while at the same time part of this shadow1 passing through the semi-transparent vapors1 may be seen at the surface of the nucleus1 or of a layer of opaque clouds situated at some distance below the surface4 ,some astronomers are inclined to think that ,jupiter is at a high temperature1 and self-luminous to a certain extent4 ,if this planet is self-luminous to any degree1 we might expect that some light would be thrown upon the satellites when they are crossing the shadow cast into space by the planet2 but when they cross this shadow they are totally invisible in the best telescopes1 a proof that they do not receive much light from the non-illuminated side of ,jupiter4 ,it would1 indeed1 seem probable that some of the intensely white spots occasionally seen on the equatorial belt of the planet are self-luminous in a degree1 yet not enough to render the satellites visible while they are immersed in ,jupiter's shadow4 ,it does not seem impossible that the planet should have the high temperature attributed to it1 when we remember the terrific storms observed in its atmosphere1 which1 owing to the great distance of ,jupiter from the ,sun1 do not seem to be attributable to this body1 but rather to some local cause within the envelope of the planet4 ,astronomy1 which is a science of observation1 is naturally silent with regard to the inhabitants of ,jupiter4 ,if there are any such inhabitants1 they are confined to the domain of conjecture1 under the dense cloudy envelope of the planet4 ,the conditions of habitability on ,jupiter must differ very widely from those of our globe4 ,comparatively little direct light from the ,sun reaches the surface of the globe of ,jupiter1 except that which passes through the narrow openings forming the dark clouds4 ,all the rest of the planet's surface1 being covered perpetually by opaque clouds1 receives only diffused light4 ,on ,jupiter there are practically no seasons1 since its axis is nearly perpendicular to its orbit4 ,the force of gravity on the surface of ,jupiter being more than double what it is on the ,earth1 living bodies would there have more than double the weight of similar bodies on the ,earth4 ,furthermore1 ,jupiter only receives #j4jaa of the light and heat which we receive from the ,sun2 and its year is nearly equal to #ab of our years4 ,if there are living beings on ,jupiter1 they must1 then1 be entirely different from any known to us1 and they may have forms never dreamed of in our most fantastic conceptions4 ,the two round black spots represented towards the central parts of ,plate ,,ix4 are the shadows of the first and second satellite2 while the two round white spots seen on the left of the disk1 are the satellites themselves1 as they appeared at the moment of the observation4 ,the first satellite and its shadow are the nearest to the equator2 while the second satellite and its shadow are higher1 the last being projected on the ,great ,red ,spot4#b ,the row of dark circular spots represented on the northern1 or lower hemisphere1 when they first appeared1 had some resemblance to ,sun-spots without a penumbra1 with bright markings around them1 resembling facul4 ,these round spots subsequently enlarged considerably1 until they united along the entire line1 encircling the planet1 and finally forming a narrow pink belt1 which is still visible4 ,footnote #b3 ,by an accidental error in enlarging the original drawing1 the satellites and shadows appear in ,plate ,,ix4 of double their actual size4 ,the error is one easy of mental correction4 ,,the ,,planet ,,saturn ,,plate ,x ,saturn1 which is next to ,jupiter in order of distance from the ,sun1 while not the largest1 is certainly the most beautiful and interesting of all the planets1 with his grand and unique system of rings1 and his eight satellites1 which1 like faithful servants1 attend the planet's interminable journey through space4 ,seen with the naked eye1 ,saturn shines in the night like a star of the first magnitude1 whose dull1 soft whiteness is1 however1 far from attaining the brilliancy of ,venus or ,jupiter1 although it sometimes approaches ,mars in brightness4 ,saturn hardly ever exhibits the phenomenon of scintillation1 or twinkling1 a peculiarity which makes it easily distinguishable among the stars and planets of the heavens4 ,the synodical period of ,saturn occupies #a year and #ac days1 so that every #cgh days1 on an average1 this planet holds the same position in the sky relatively to the ,sun and the ,earth4 ,the mean distance of ,saturn from the ,sun is a little over #i times that of our globe1 or #hgb1jjj1jjj miles4 ,owing to the orbital eccentricity1 this distance may increase to #iba1jjj1jjj miles1 when the planet is in aphelion2 or decrease to #hbc1jjj1jjj miles1 when it is in perihelion2 ,saturn being therefore #ih1jjj1jjj miles nearer to the ,sun when in perihelion than in aphelion4 ,if gravitation were free to exert its influence alone1 ,saturn would fall into the ,sun in #e years and #b months4 ,the distance of ,saturn from the ,earth varies1 according to the position of the two planets in their respective orbits4 ,at the time of opposition1 when the ,earth lies between the ,sun and ,saturn1 this distance is smallest2 while1 on the contrary1 at the time of conjunction1 when the ,sun lies between the ,earth and ,saturn1 it is greatest4 ,owing1 however1 to the eccentricity of the orbits of ,saturn and our globe1 and the inclination of their planes to each other1 and owing also to the variable heliocentric longitude of the perihelion1 the distance of the two planets from each other at their successive conjunctions and oppositions is rendered extremely variable4 ,at present it is when the oppositions of ,saturn occur in ,december that this planet comes nearest to us2 while when the conjunctions take place in ,june1 the distance of ,saturn from the ,earth is the greatest possible4 ,in the former case the distance of the planet from our globe is only #gcj1jjj1jjj miles2 while in the last it is #a1jad1jjj1jjj miles1 the difference between the nearest and farthest points of ,saturn's approach to us being no less than #bhd1jjj1jjj miles1 or over three times the mean distance of the ,sun from the ,earth4 ,from the great variations in the distance of ,saturn from the ,earth1 necessarily result corresponding changes in the brightness and apparent diameter of this body4 ,when it is farthest from us1 its angular diameter measures but #ad2 while1 when it is nearest1 it measures #bj4 ,the orbit of ,saturn is inclined #bcj' to the ecliptic1 and its eccentricity1 which equals #j1jef1 is over three times that of the ,earth's orbit4 ,this planet revolves around the ,sun in a period of #bi years and #e months1 or #aj1gei terrestrial days1 which constitutes its sidereal year4 ,the extension of the immense curve forming the orbit of this planet1 is no less than #e1eje1jjj1jjj miles1 which is traversed by the planet with a mean velocity of a little less than #f miles per second1 or three times less than the motion of our globe in space4 ,the real dimensions of the globe of ,saturn are not yet known with accuracy1 and the equatorial diameter has been variously estimated by observers1 at from #ga1jjj to #gi1jjj miles4 ,if we adopt the mean of these numbers1 #ge1jjj miles1 the circumference of the ,saturnian equator would measure #bce1fbj miles1 or #i times the circumference of our globe2 the surface of ,saturn would be #hf times1 and its volume over #haj times that of the ,earth4 ,however great the volume of ,saturn1 its mass is proportionally small1 being only #ij times greater than that of our globe2 the mean density of the materials composing this planet being less than that of cork1 and only #j4fh the density of water4 ,the force of gravitation at the surface of ,saturn is greater1 by a little over 1 than it is at the surface of the ,earth2 a body falling in a vacuum at its surface1 would travel #ag4ei feet during the first second4 ,from observations of markings seen on the surface of ,saturn1 and from the study of their apparent displacements on the disk1 ,william ,herschel found that the planet rotated upon its axis in #aj;h4 #afm4 #j4bds4 ,since ,herschel's determination1 new researches have been made1 and lately1 ,professor ,hall1 noticing a bright spot1 followed it for nearly a month1 observing its transits across the central meridian of the disk4 ,from these observations he has obtained for the rotation period #aj;h4 #adm4 #bc4hs41 a result which agrees very closely with that obtained #hb years earlier by ,herschel1 considering the fact that the markings from which the period of rotation is ascertained are not fixed on the planet1 but are always more or less endowed with proper motion4 ,the velocity of rotation at the equator is #ba1ech miles per hour1 or nearly #f miles per second4 ,the axis of rotation of ,saturn is inclined #fd #ah' to the plane of the orbit1 so that its equator makes an angle of #be #db' with the same plane4 ,the seasons of this planet therefore present greater extremes of temperature than those of the ,earth1 but not quite so great variations as the seasons of ,mars4 ,the globe of ,saturn is not a perfect sphere1 but its figure is that of an oblong spheroid1 flattened at the poles4 ,the polar compression of ,saturn is greater than that of any other planet1 surpassing even that of ,jupiter4 ,though not yet determined with a great degree of accuracy1 the compression is known to be between and of the equatorial diameter2 that is1 a flattening of about #c1hid miles1 at each pole1 the polar diameter being #g1ghh miles shorter than the equatorial4 ,the internal condition of the planet ,saturn1 whether solid1 liquid or gaseous1 cannot be discovered from the examination of its surface1 as its globe is enwrapped in a dense opaque layer of vapors and cloud-like forms1 through which the sight fails to penetrate4 ,the appearance of this vapory envelope is like that of cumulus clouds1 and one of its characteristics is to arrange itself into alternate bright and dark parallel belts1 broader than those seen on ,jupiter1 and also more regular and dark4 ,these belts1 which are parallel to the equator of the planet1 vary in curvature with the inclination of its axis of rotation to the line of sight4 ,the belts of ,saturn1 like those of ,jupiter1 are not permanent1 but keep changing more or less rapidly4 ,sometimes they have been observed to be quite numerous2 while at other times they are few4 ,occasionally conspicuous white or dark spots are seen on the surface1 although the phenomenon is quite rare4 ,it is from the observation of such spots that ,saturn's period of rotation has been determined1 as stated above4 ,the equatorial zone of ,saturn always appears more white and brilliant than the other parts1 as it also appears more mottled and cloud-like4 ,in late years the globe has been characterized1 and much adorned1 by a pale pinkish tint on its equatorial belt1 resembling that of ,jupiter1 but somewhat fainter4 ,on either side of the equatorial belt there is a narrower band1 upon which the mottled appearance is visible4 ,below these1 one or two dark belts1 separated by narrow white bands1 are usually seen2 but1 of late1 the bands have been less numerous1 being replaced in high latitudes by a dark segment1 which forms a polar cap to ,saturn4 ,the globe of ,saturn does not anywhere appear perfectly white1 and when compared with its ring1 it looks of a smoky yellowish tint1 which becomes an ashy gray on its shaded parts4 ,it usually appears darker near the limb than in its central portions2 although on some occasions ,i have seen portions of the limb appear brighter1 as if some white spots were traversing it4 ,some observers have seen the limb deformed and flattened at different places1 and ,w4 ,herschel even thought such a deformation to be a permanent feature of this globe1 which he termed diamond-shaped1 or square shouldered4 ,but this was evidently an illusion1 since the planet's limb usually appears perfectly elliptical1 although it occasionally appears as if flattened at some points1 especially where it comes in apparent contact with the shadow cast by the globe on the ring1 as observed by myself many times4 ,but with some attention1 it is generally found that this deformation is apparent rather than real1 and is caused by the passage of some large dark spots over the limb1 which is thus rendered indistinguishable from the dark background upon which it is projected4 ,what distinguishes ,saturn from all known planets1 or heavenly bodies1 and makes it unique in our universe1 is the marvelous broad flat ring which encircles its equator at a considerable distance from it4 ,with a low magnifying power this flat ring appears single1 but when carefully examined with higher powers1 it is found to consist of several distinct concentric rings and zones1 all lying nearly in the same plane with the planet's equator4 ,,plate ,x4--,,the ,,planet ,,saturn4 ,observed on ,november #cj1 #ahgd1 at #e;h4 #cjm4 ,p4,m4 ,at first sight only two concentric rings are recognized1 the outer and the middle1 or intermediary1 which are separated by a wide and continuous black line1 called the principal division4 ,this line1 and indeed all the features of the surface of the rings are better seen1 and appear more prominent on that part of the ring on either side called the ansa1 or handle4 ,besides these two conspicuous rings1 a third1 of very dark bluish or purplish color1 lies between this middle ring1 to which it is contiguous1 and the planet4 ,this inner ring1 which is quite wide1 is called the gauze or dusky ring4 ,closer examination shows that the outer ring is itself divided by a narrow1 faint1 grayish line called the pencil line1 which1 from its extreme faintness1 is only visible on the ans4 ,moreover1 the middle ring is composed of three concentric zones1 or belts1 which1 although not apparently divided by any interval of space1 are distinguished by the different shadings of the materials composing them4 ,the outer zone of this compound middle ring is1 by far1 the brightest of all the system of rings and belts1 especially close to its external border1 where1 on favorable occasions1 ,i have seen it appear on the ans as if mottled over1 and covered throughout with strongly luminous cloud-like masses4 ,on the ans of the double outer ring1 similar cloudy forms have also been seen at different times4 ,the second zone of the middle ring is darker than the first1 the innermost being darker still4 ,all the characteristic points which have thus been described1 are shown in ,plate ,x4 ,although suspected in #ahch1 the dusky ring was not recognized before #ahej1 when ,g4 ,p4 ,bond discovered it with the #ae-;inch refractor of the ,cambridge ,observatory4 ,it was also independently discovered the same year in ,england by ,dawes and ,lassell4 ,the dusky ring differs widely in appearance and in constitution from the other rings1 inasmuch as these last are opaque1 and either white or grayish1 while the former is very dark1 and yet so transparent that the limb of the planet is plainly seen through its substance4 ,on particularly favorable occasions1 the appearance of this ring resembles that of the fine particles of dust floating in a ray of light traversing a dark chamber4 ,whatever may be the material of which this ring is composed1 it must be quite rarefied1 especially towards its inner border1 which appears as if composed of distinct and minute particles of matter feebly reflecting the solar light4 ,that the inner part of the dusky ring is composed of separate particles1 is proved by the fact that the part of the ring which is seen in front of the globe of ,saturn has its inner border abruptly deflected and curved inward on entering upon the disk1 causing it to appear considerably narrower than it must be in reality1 a peculiarity which is shown in the ,plate4 ,this phenomenon may be attributed to an effect of irradiation1 due to the strong light reflected by the central parts of the ball1 which so reduces the apparent diameter of the individual particles that they become invisible to us1 especially those near the inner border1 which are more scattered and less numerous than elsewhere4 ,the dusky ring1 which was described by ,bond1 ,lassell and other astronomers as being equally transparent throughout all its width1 has not been found so by me in later years4 ,the limb of the planet1 seen by these observers through the whole width of the dusky ring in #ahej1 could not be traced through its outer half by myself in #ahgb and #ahgd1 and this with the very same instrument used by ,bond in his observations of #ahdh and #ahej4 ,moreover1 ,i have plainly seen that its transparency was not everywhere equal1 but greatest on the inner border1 from which it gradually decreases1 until it becomes opaque1 as proved by the gradual loss of distinctness of the limb1 which vanishes at about the middle of the dusky ring4 ,these facts1 which have been well ascertained1 prove that the particles composing this ring are not permanently located1 and are undergoing changes of relative position4 ,it will be shown that the surface of the other rings is also subject to changes1 which are sometimes very rapid4 ,the globe of ,saturn is not self-luminous1 but opaque4 ,it shines by the solar light1 as is proved by the shadow it casts opposite the ,sun upon the ring4 ,although receiving its light from the ,sun1 ,saturn does not exhibit any traces of phases1 like the other planets nearer to the ,sun1 owing to its great distance from the ,earth4 ,when near its quadratures1 however1 the limb opposite to the ,sun appears much darker1 and shows traces of twilight4 ,as far as can be ascertained1 the rings1 with the exception of the inner one1 are opaque1 as proved by the strong shadow which they cast on the globe of ,saturn4 ,the shadows cast by the planet on the ring1 and by the ring on the planet1 are very interesting phenomena1 inasmuch as they enable the astronomer to recognize the form of the surface which receives them4 ,the shadow cast by the ring on the ball is not quite so interesting as the other1 although it has served to prove that the surface of this globe is not smooth1 as is likewise suggested by its mottled appearance4 ,i have sometimes found1 as have also other observers1 that the outline of this shadow upon the ball was irregular and indented1 an observation which proves either that the surface of the ball is irregular1 or that the border of the ring casting the shadow was jagged4 ,the shadow of the globe on the rings has much more interest1 as it enables us to get at some knowledge of the form of the surface of the rings1 which otherwise is very difficult to discover1 owing to the oblique position in which we always see them4 ,in general1 the shadow of the ball on the middle ring has its outline concave towards the planet2 while on the outer ring it is usually slanting1 and at a greater distance from the limb than on the middle1 and dusky rings4 ,this form of the shadow evidently proves that the middle ring stands at a higher level than the two others1 especially towards its outer margin4 ,the system seems to increase gradually in thickness from the inner border of the dusky ring to the vicinity of the outer margin of the middle ring1 after which it rapidly diminishes on this border1 while the surface of the outer ring is almost level4 ,but this surface is by no means fixed1 as its form sometimes changes1 as proved by my observations and those of others4 ,as may be noticed on ,plate ,x41 the outline of the shadow of the planet on the rings is strongly deviated towards the planet1 near the outer margin of the middle ring2 the notch indicating an abrupt change of level1 and a rise of the surface at that point4 ,some observers have endeavored to explain these deviations by the phenomena of irradiation1 from which it would follow that the maximum effect of deviation should be observed where the ring is the brightest1 which does not accord with observation2 as the deepest depression in the shadow is not to be found usually at the brightest part1 which is towards the outer border of the middle ring1 but occurs near its centre4 ,from these observations it is undoubtedly established that the surface of the rings is far from being flat throughout1 and is1 besides1 not permanent1 but changes1 as would1 for instance1 the surface of a large mass of clouds seen from the top of a high mountain4 ,in general1 the system is thickest not very far from the outer border of the intermediary ring4 ,some interesting phenomena which ,i had occasion to observe before and after the passage of the ,sun through the plane of the rings1 on ,february #fth1 #ahgh1 conclusively show that the surface of this system cannot be of a uniform level1 but must be thicker towards the outer border of the middle ring1 thence gradually sloping towards the planet4 ,many of my observations irresistibly lead to this conclusion4 ,as it would1 however1 be out of place to have them recorded here in detail1 ,i will simply give one of the most characteristic among them4 ,from ,december #ahth1 #ahgg1 when the ,sun was about #da' above the plane of the rings1 to ,february #fth1 #ahgh1 the day of its passage through their plane1 the illuminated surface of this system gradually decreased in breadth with the lowering of the ,sun1 until it was lost sight of1 ,february #eth1 on the eve of the passage of the ,sun through their plane4 ,the phenomenon in question consisted in the gradual invasion of their illuminated surface by what appeared to be a black shadow1 apparently cast by the front part of the outer portion of the middle ring the nearest to the ,sun4 ,on ,january #beth1 when the elevation of the ,sun above the plane of the rings was reduced to #ae'1 the shadow thus cast had extended so far on their surface that it reached the shadow cast by the globe on the opposite part of the ring in the east1 and accordingly the remaining portion of the illuminated surface of the eastern ansa then appeared entirely disconnected from the ball1 by a large dark gap1 corresponding in breadth to that of the globe's shadow on the rings4 ,on ,february #dth1 when the ,sun was only #e' above the plane of the rings1 their illuminated and only visible surface was reduced to a mere thread of light1 which on the #eth appeared broken into separate points4 ,it is evident that the phenomenon was not caused by the obliquity of the ring as seen from our globe1 since the elevation of the ,earth above the plane of the rings--which on ,december #ahth was #c #bj'--was still #a #bj' on the #dth of ,february4 ,in ordinary circumstances1 when the ,sun is a little more elevated1 and the rings seen at this last angle1 they appear quite broad and conspicuous1 and even the dark open space separating the dusky ring from the planet is perfectly visible on the ans1 where the ,earth's elevation above their plane is reduced to #dj'4 ,it is also evident that the phenomenon was not to be attributed to the reduction of the light which they received from the ,sun1 although the illumination in ,february might be expected to be comparatively feeble1 since the ,sun then shone upon the rings so obliquely2 yet 7on the supposition that their surface is flat7 they should have been illuminated throughout1 and if not very brightly1 sufficiently so1 at least1 to make them visible and as bright as was the narrow thread of light observed on the #dth of ,february4 ,the phenomenon actually observed may be explained most readily by assuming1 as other phenomena also indicate1 that the surface of the ring is not flat1 but more elevated towards1 or in the vicinity of its outer border1 from which place it slopes inwardly towards the planet4 ,on this assumption1 it is evident that the elevated part of the ring the nearest to the ,sun would cast a shadow1 which1 with the increasing obliquity of the ,sun1 would gradually cover the whole surface comprised within the elevated part1 and thus become invisible to us4 ,several observations made by ,bond and other observers undoubtedly show the same phenomenon1 and do not seem to be intelligible on any other supposition4 ,from my observations made in #ahha it would appear1 however1 that the opposite surfaces of the rings do not exactly correspond in form1 but this may not be a permanent feature1 as the surface of this system is subject to changes1 as already shown4 ,the dimensions of the rings are great1 the diameter of the outer one being no less than #agb1ihb miles1 the distance from the centre of the globe to the outer border of the system being1 therefore1 #hf1dia miles4 ,the breadth of the outer ring is #i1ida miles2 that of the principal division1 #b1aca miles2 that of the middle ring1 #ai1ijb miles1 and that of the dusky ring1 #h1ggb miles4 ,the breadth of all the rings taken together is1 therefore1 #dj1gdf miles4 ,the interval between the surface of ,saturn and the inner border of the dusky ring is #g1hdc miles4 ,the thickness of the system of rings has been variously estimated by astronomers1 on account of the great difficulties attending its determination4 ,while ,sir ,john ,herschel estimated it at more than #bej miles1 ,g4 ,p4 ,bond reduces it to #dj miles4 ,both of these numbers are evidently too small1 as so slight a thickness cannot explain the observed phenomenon of the shadow cast by a portion of the ring on its own surface1 when the ,sun is very low in its horizon1 as shown above4 ,the plane of the system of rings is inclined #bg to the planet's orbit1 and is parallel1 or at least very nearly so1 with the equator of the planet1 passing1 therefore1 through its centre1 and dividing its globe into northern and southern hemispheres4 ,seen from the ,earth1 a portion of the ring always appears projected in front of the planet1 thus concealing a small part of its globe1 while the opposite portion passes behind the globe1 which hides it from sight4 ,as the plane of the ring is not affected by the motion of the planet around the ,sun1 but always remains parallel to itself1 it follows that as ,saturn advances in its orbit the rings must successively present themselves to us under various angles of inclination1 appearing1 therefore1 more or less elliptical1 and presenting two maxima and two minima of inclination in the course of one of its revolutions4 ,as the revolution of ,saturn is accomplished in #bi years1 the maxima and the minima must recur every #ad years and #i months2 the maxima being separated from the minima by an interval of #g years and #d months4 ,when ,saturn arrives at the two opposite points of its orbit1 where the major axis of its ring is at right angles to the line joining its centre to that of the ,sun1 the ring1 which is then viewed at an inclination of #bg1 the greatest angle at which it can ever be seen1 has reached its maximum opening1 the smaller diameter of its ellipse being then about half that of the larger4 ,at this moment the outer ring projects north and south beyond the globe1 which is then completely enclosed in its ellipse4 ,the maximum opening of the northern surface of the ring takes place1 at present1 when ,saturn arrives in longitude #bfb1 in the constellation ,sagittarius1 and that of the southern surface when it arrives in longitude #hb in the constellation ,taurus4 ,when1 on the contrary1 ,saturn reaches the two opposite points of its orbit1 where the plane of its ring is parallel to the line joining its centre to that of the ,sun1 the opening vanishes1 as only the thin edge of the ring is then presented to the ,sun and receives its light1 the rest being in darkness4 ,at this moment the ring disappears1 except in the largest telescopes1 where it is seen as an exceedingly thin thread of light2 and the ,saturnian globe1 having apparently lost its ring1 appears solitary in the sky1 like the other planets4 ,the disappearance of the ring from this cause occurs now when ,saturn arrives at #ij from either of the positions of maximum inclination1 that is1 in longitude #ceb in the constellation ,pisces1 and in longitude #agb in the constellation ,leo4 ,when the planet is in any other position than one of these last two1 either the northern or the southern surface of the ring is illuminated by the ,sun1 while the opposite surface is in the night1 and does not receive any direct sunlight4 ,at the time of the passage of the plane of the ring through the ,sun's centre1 a change takes place in the illumination of the ring4 ,if it is the northern surface which has received the rays of the ,sun during the previous half of the ,saturnian year1 at the moment the plane has passed the centre of the ,sun1 the southern surface1 after having been buried in darkness for #ad years1 sees the dawn of its long day of the same length4 ,such a phenomenon will not occur until #ahib1 when the passage of the ,sun from the northern to the southern side of the ring will close in twilight the day commenced in #ahgh4 ,aside from the periodic disappearance of the ring1 resulting from the passage of the ,sun through its plane1 the ring may also disappear from other reasons4 ,just before or just after the time of the passage of the ,sun through the plane of the ring1 the ,earth and the ,sun may occupy such positions1 that while the one is north of the plane of the ring1 the other is south of it1 or vice versa1 in which event the ring becomes invisible1 because its dark and non-illuminated surface is presented to us4 ,the ring may also become invisible to us when the ,earth passes through its plane4 ,since the distance from ,saturn to the ,sun is to the distance of the ,earth from this last body as #i4ed is to #a2 and since the circumference of a circle increases in the same proportion as its radius1 it follows that the diameter of the ,earth's orbit projected on the orbit of ,saturn would occupy only part of the latter1 or about #ab #b'1 this being #f #a' on either side of the nodes of the rings4 ,to describe such an arc on its orbit1 it takes ,saturn almost #cfj days on an average1 or almost a complete year2 the ,earth describing therefore almost a whole revolution around the ,sun during the time it takes ,saturn to advance #ab #b' on its orbit4 ,then1 when ,saturn occupies a position comprised within an arc #f #a' from either side of the nodes of its ring1 the ,earth1 by its motion1 is liable to encounter the plane of the ring1 when therefore it will only present its thin edge to us1 and becomes invisible4 ,at least one such encounter is unavoidable within the time during which ,saturn occupies either of these positions on its orbit2 while three frequently happen1 and two are possible4 ,the natural impression received by looking at the rings1 while seeing the ponderous globe of ,saturn enclosed in its interior1 is that this gigantic1 but very delicate structure1 in order to avoid destruction1 must be endowed with a swift movement of rotation on an axis perpendicular to its plane1 and that the centrifugal force thence arising counterbalances the powerful attraction of the planet1 and thus keeps the system in equilibrium4 ,theoretically1 the rotation of the rings is admitted by every astronomer1 as being an essential condition to the existence of the system1 which otherwise1 it is thought1 would fall upon the planet4 ,although the rotation of the rings seems so probable that it is theoretically considered as certain1 yet its existence has not been satisfactorily demonstrated by direct observation1 which alone can establish it on a firm basis as a matter of scientific knowledge4 ,the determination of the period of rotation of the rings1 which is supposed to be #aj;h4 #cbm4 #aes41 rests only on the observations of ,w4 ,herschel1 made in #agij1 from the apparent displacement of irregularities on the ring2 but his results have been contradicted by other observations1 and even by those of ,herschel himself1 made in later years4 ,although the system of rings is very nearly concentric with the globe of ,saturn1 yet the coincidence is not considered as mathematically exact4 ,it seems to have been satisfactorily demonstrated by direct observations that the centre of gravity of the system oscillates around that of the planet1 thus describing a minute orbit4 ,this peculiarity is in accordance with theory1 which has shown it to be essential to the stability of the system4 ,besides its system of rings1 which makes ,saturn the most remarkable planet of the solar system1 this globe is attended by eight satellites1 moving in orbits whose planes very nearly coincide with the plane of the rings1 except that of the most distant one1 which has an inclination of about #ab #ad'4 ,in the order of their distance from the planets1 the satellites of ,saturn are as follows3 ,mimas1 ,enceladus1 ,tethys1 ,dione1 ,rhea1 ,titan1 ,hyperion and ,iapetus4 ,the three first satellites are nearer to ,saturn than the ,moon is to the ,earth2 while ,iapetus1 the farthest1 is #i times the distance of our satellite from us4 ,all the satellites1 with the exception of the farthest1 move more rapidly around ,saturn than the ,moon moves around the ,earth2 while ,iapetus1 on the contrary1 takes almost three times as long to make one revolution4 ,the period of revolution of the four inner satellites is accomplished in less than three days1 that of ,mimas being only a little more than #bb hours4 ,from such swiftness of motion1 it is easily understood how short must be the intervals between the different phases of these satellites4 ,mimas1 for instance1 passes from ,new ,moon to ,first ,quarter in less than #f hours4 ,the distance of the nearest satellite from the planet's surface is #hd1jjj miles1 and its distance from the outer ring only #cf1jjj miles4 ,it is difficult to determine the diameter of objects so faint and distant as are some of these satellites1 but the diameter of ,titan1 the largest of all1 is pretty well known1 and estimated to be the diameter of the planet1 or more than half the diameter of our globe4 ,iapetus is subject to considerable variations in brilliancy1 and as the maxima and minima always occur when this satellite occupies the same parts of its orbit1 it was conjectured by ,w4 ,herschel that1 like our ,moon1 it turns once upon its axis during each of its revolutions about the planet4 ,it has been shown by my observations1 that ,iapetus attains its maximum brightness a little before it reaches its greatest western elongation1 and its minimum on the opposite side4 ,as the planes of the orbits of the satellites are inclined to the planet's orbit1 it follows that their transits1 occultations and eclipses1 are only possible when ,saturn is near its equinoxes4 ,passages of the satellites and their shadows across the disk1 although rare1 have been observed1 and they somewhat resemble the phenomena exhibited by the satellites of ,jupiter in transit4 ,when the ,earth is very near the plane of the rings1 the satellites1 except the farthest1 appear to be in a straight line nearly coincident with the plane of the rings1 and are seen occasionally moving along the thin edge of the rings1 appearing as luminous beads moving on a thread of light4 ,owing to the considerable inclination of the axis of rotation of ,saturn to its orbit1 the seasons of this planet must have greater extremes of temperature than those of the ,earth4 ,as the year of ,saturn consists of #be1bag ,saturnian days1 each season1 on the average1 is composed of #f1cjd ,saturnian days4 ,to an observer on ,saturn1 the immense arches formed by its rings would appear as objects of great magnificence1 spanning the sky like soft colorless rainbows4 ,moreover1 the eight moons1 several of which are always visible1 would be of the highest interest1 with their swift motions and rapid phases4 ,mimas1 traveling in its orbit at the rate of #af of arc per minute of time1 moves over a space equal to the apparent diameter of our ,moon in two minutes1 or at the rate of #af an hour4 ,owing to the globular form of ,saturn1 the rings would be invisible in latitudes situated above #fe from its equator1 and their apparent form and breadth would naturally vary with the latitude4 ,at #fc only a very small portion of the outer ring would be visible above the equatorial horizon1 where it would appear as a small segment of a circle4 ,at #fb the principal division would just graze the horizon4 ,at #df the outer portion of the dusky ring would become visible1 while at #ce its inner edge would appear above the horizon4 ,from #fe of latitude down to the equator1 the arches of the rings would be seen more and more elevated above the equatorial horizon1 but at the same time that they are seen higher up1 their apparent breadth gradually diminishes1 owing to the effect of foreshortening1 and at the equator itself the system would only present its thin edge to view4 ,during the summer seasons of either hemisphere of ,saturn1 the surface of the rings turned towards such hemisphere1 being fully illuminated by the ,sun1 is visible from these regions4 ,in the day time its light must be feeble and similar to the light reflected by our ,moon during sunshine2 but at night the system would display all its beauty1 and the different rings1 with their divisions and their various reflective powers1 must present a magnificent sight4 ,during the nights of the long winter seasons on ,saturn1 on the contrary1 the surface of the rings turned towards the hemisphere undergoing winter1 receives no light from the ,sun1 and is invisible1 or very nearly so1 except towards morning and evening1 when it may be faintly illuminated by the secondary light which it receives from the illuminated globe of ,saturn4 ,although dark and invisible1 the rings may make their form apparent at night by the absence of stars from the region which they occupy in the sky4 ,again1 in other seasons1 the days present very curious phenomena4 ,in consequence of the diurnal rotation of the planet1 the ,sun seems to move in circular arcs1 which1 owing to the inclination of ,saturn's axis1 are more or less elevated above its horizon1 according to the position of the planet in its orbit4 ,as such arcs described by the ,sun in the sky of ,saturn are liable to encounter the rings1 the ,sun in passing behind them becomes eclipsed4 ,it must be a magnificent spectacle to witness the gradual disappearance of the fiery globe behind the outer ring1 and its early reappearance1 but for a moment only1 through the narrow gap of the principal division2 to see it vanish again behind the middle ring1 to reappear a little later through the semi-transparent dusky ring1 but very faint and red colored at first2 and then1 gradually brighten up1 and finally emerge in all its beauty from the inner edge of the dusky ring4 ,it is in latitude #bc that the rings produce the most prolonged eclipses of the ,sun4 ,during a period equivalent to ten of our terrestrial years1 such eclipses continually succeed each other with but very short periods of interruption2 and even during a long series of rotations of ,saturn1 the ,sun remains completely invisible in those regions where the apparent arcs which it describes coincide with the arcs of the rings4 ,in neighboring latitudes1 the eclipses of the ,sun1 although still frequent1 would have a shorter and shorter duration as the observer should travel north or south4 ,these eclipses of the ,sun must produce a partial darkness of the regions involved in the shadow of the rings1 which may be compared to the darkness produced on our globe by a total eclipse of the ,sun4 ,the frequent recurrence of these eclipses1 and their comparatively long duration in some regions1 must still further reduce the duration of the short ,saturnian days4 ,the globe of ,saturn1 as already shown1 casts a shadow on the rings1 which1 according to the position of the planet in its orbit1 either extends across their whole breadth1 or covers only a part of their surface4 ,the shadow on the rings rising in the east after sunset1 ascends to the culminating point of their arcs in the sky1 in #b;h4 #cdm41 and as rapidly descends on the western horizon1 to disappear with sunrise4 ,this shadow1 when projected on the rings in the sky1 must be hardly distinguishable from the dark background of the heavens1 except from the absence of stars in the regions which it occupies4 ,it must appear as a large dark gap1 separating the rings into two parts1 and constantly moving from east to west4 ,possibly the refraction of the solar rays1 in passing through ,saturn's atmosphere1 may cast some colored light on the rings1 similar to that observed on the ,moon during its eclipses4 ,an observer on the rings would behold phenomena still more curious1 a long day of #ad years being followed by a long night of #ad years4 ,the long days of ,saturn's rings are1 however1 diversified by numerous eclipses of the ,sun1 which regularly occur every #aj hours2 the phenomenon being due to the interposition of the globe of ,saturn between the rings and the ,sun4 ,these eclipses produce partial obscurations of their surface1 lasting from #a to #b hours at a time4 ,although the surface of the rings never receives direct sunlight during their long nights1 yet they are not plunged all the time in total darkness1 as they receive some reflected light from that part of the globe of ,saturn which is illuminated by the ,sun4 ,to the supposed observer on the rings1 during every #aj hours1 the immense globe would exhibit continually changing phases4 ,at first he would see a point of light rapidly ascending from the horizon1 and appearing under the form of a half crescent of considerable radius2 #e hours later1 the crescent having gradually increased1 would appear as a half circle1 covering of the visible heavens1 its surface being more than #bj1jjj times as large as the surface of the ,moon4 ,upon this brilliantly illuminated semi-circle would be projected the shadows of the rings1 appearing as black belts separated by a narrow luminous band4 ,it is very difficult for one to conceive how such a delicate structure1 as the system of rings appears to be1 can keep together in equilibrium and avoid destruction from the powerful attraction of the planet on one side and the disturbing influence of the satellites on the other4 ,to explain it1 several hypotheses have been advanced4 ,the rings were first supposed to be solid1 and upon this supposition ,laplace determined the necessary conditions for their equilibrium2 the most important of which require that the cross section of the rings should be an ellipse of irregular curvature1 and having its major axis directed towards the centre of the planet1 and also that the system should rotate upon an axis perpendicular to the plane of the rings4 ,this theory was superseded by another1 which supposed the rings to be fluid4 ,this one was soon rejected for a third1 assuming the system to be composed of vapors or gases2 and more recently1 all these theories were considered untenable1 and replaced by a fourth1 which supposes the system of rings to be made up of a congregation of innumerable small1 independent bodies1 revolving around ,saturn in concentric zones4 ,naturally1 such a divergence of opinion can only result from our comparative ignorance of the subject1 and sufficiently indicates our inability to explain the phenomena2 and it must be admitted that1 so far1 nothing is certainly known about this strange system4 ,we shall probably remain in the same uncertainty until the rotation of the rings is ascertained by direct observations4 ,it is pretty certain1 however1 that none of these theories account for the observed phenomena in their details1 although a partial explanation may be obtained by borrowing something from each hypothesis4 ,it has been conjectured1 and a theory has been advanced1 that the breadth of the whole ring system is gradually increasing inwards1 and that it will come in contact with the planet in about #b1aej years2 but the question seems to have been settled in the negative by the elaborate measurements of the ,english observers4 ,it is likely that the increase is only in the defining power of the instruments4 ,,comets ,,plate ,,xi ,among the celestial phenomena1 none are more interesting than those mysterious apparitions from the depths which unexpectedly display their strange forms in our familiar constellations1 through which they wander for a time1 until they disappear like phantoms4 ,a comet1 with its luminous diffused head1 whence proceeds a long vapory appendage gradually fading away in the sky1 presents an extraordinary aspect1 which may well astonish and deeply impress the observer4 ,although these visitors from infinite space do not now inspire dread1 as in by-gone times1 yet1 owing to the mystery in which the phenomenon is still involved1 the apparition of a large comet1 even in our days1 never fails to create a profound sensation1 and in some cases that unconscious fear which results from the unknown4 ,the effect of such a spectacle largely depends upon its rarity2 but since the telescope has been applied to the sounding of the heavens1 it has been found that the appearance of comets is by no means an unusual occurrence4 ,if so few comets1 comparatively1 are seen1 it is because most of them are telescopic objects1 and are therefore invisible to the naked eye4 ,most of the telescopic comets are not only too faint to be perceived by the unaided eye1 but are insignificant objects1 even when observed through the largest telescopes4 ,it was ,kepler's opinion that comets are as numerous in the sky as fishes are in the ocean4 ,undoubtedly the number of these bodies must be great1 considering that we can only see them when they come into the neighborhood of the ,earth1 and that many even here remain invisible1 or at least pass unperceived4 ,that many of them have passed unperceived heretofore1 is proved by the fact that the number of those observed becomes greater every year1 with the increase of the number of instruments used in their search4 ,the number of comets observed with the naked eye during historic times is nearly #fjj1 and that of telescopic comets1 which1 of course1 all belong to the last few centuries1 is more than #bjj1 so that we have a total number of about #hjj comets of which records have been kept4 ,from theoretical considerations1 ,lambert and ,arago estimated their entire number at several millions1 but such speculations have generally no real value1 since they cannot be established on a firm basis4 ,comets remain visible for more or less time1 according to their size and the nature and position of their orbits1 but in general1 the large ones can be followed with the telescope for several months after they have become invisible to the naked eye4 ,the comet of #ahfa1 for example1 remained telescopically visible for a year1 and that of #ahaa1 for #ag months after disappearing from ordinary sight4 ,while a comet remains visible1 it appears to revolve daily about us like the stars in general2 but it also moves among the constellations1 and from this movement its orbit may be computed like that of a planet4 ,from the apparent diurnal motion of a comet with the heavens1 result the changes of position which it seems to undergo in the course of a night4 ,the direction of the head and tail of a comet1 of course1 has only changed in regard to the horizon1 but not in regard to the sky1 in which they occupy very nearly the same position throughout a given night1 and even for many nights in succession4 ,the movements of the comets in their orbits are1 like those of the planets1 in accordance with ,kepler's laws1 the ,sun occupying one of the foci of the orbit they describe2 but the orbits of comets differ1 however1 in several points from those of the planets4 ,their eccentricity is always great1 being sometimes apparently infinite1 in which case the orbit is said to be parabolic1 or hyperbolic2 but the smallness of the portion of a cometary orbit which can ordinarily be observed1 makes it difficult to determine this with certainty4 ,again1 while the planetary orbits are usually near the plane of the ecliptic1 those of comets frequently have great inclinations to that plane1 and even when the inclination is less than #ij1 the comet may have a retrograde movement1 or1 in other words1 a movement contrary to the course in which all the planets revolve about the ,sun4 ,notwithstanding these differences between the elements of the orbits of the comets and those of the planets1 the fact that each has the ,sun in one focus indicates that the body moving in it is a member of the solar system1 either for the time1 or permanently1 according to the nature of its orbit4 ,a distinction may accordingly be made between the comets which are permanent members of our solar system and those which are only accidental or temporary visitors4 ,those moving in elliptical orbits around the ,sun1 like the planets1 and therefore having a determinate period of revolution1 from which the time of their successive returns may be predicted1 are permanent members of our system1 and are called periodic comets4 ,all comets moving in parabolical or hyperbolical curves1 are only temporary members of the solar system1 being apparently strangers who have been diverted from their courses by some disturbing influence4 ,no comet is classed as periodical which does not follow a perceptibly elliptical orbit4 ,any comet passing around the ,sun at the mean distance of the ,earth from this body1 with a velocity of #bf miles per second1 will fly off into infinite space1 to return to us no more4 ,the time of revolution of the different periodic comets thus far observed varies greatly1 as do also the distances to which they recede from the ,sun at aphelion4 ,whilst the period of revolution of ,encke's comet1 the shortest thus far known1 is only #c years1 that of the comet of #ahdd1 ,,ii41 is #ajb1jjj years2 and whilst the orbit of the first is comprised within the orbit of ,jupiter1 that of the last extends to a distance equal to #adg times the distance of ,neptune from the ,sun4 ,but so vast an orbit cannot be accurately determined from the imperfect data at our disposal4 ,the periodic comets are usually divided into two classes4 ,the comets whose orbits are within the orbit of ,neptune are called interior comets1 while those whose orbits extend beyond that of ,neptune are called exterior comets4 ,the known interior periodic comets are twelve in number1 while1 including all the cases in which there is some slight evidence of elliptic motion1 the number of exterior comets observed is six or seven times as great4 ,the periodic comets of short period are very interesting objects1 inasmuch as by their successive returns they afford an opportunity to calculate their motions and to observe the physical changes which they undergo in their intervals of absence4 ,from observation of the periodic comets1 it has been learned that the same comet never presents twice the same physical appearance at its different returns1 its size1 shape and brilliancy varying so greatly that a comet can never be identified by its physical characters alone4 ,it is only when its elements have been calculated1 and are found to agree with those of a cometary orbit previously known1 that the two comets can be identified one with the other4 ,there are reasons to believe that1 in general1 comets decrease in brightness and size at each of their successive returns1 and that they are also continually losing some of their matter as they traverse their orbits4 ,when very far away from us1 all comets appear nearly alike1 consisting of a faint nebulosity1 of varying dimensions4 ,when a comet first appears in the depths of space1 and travels towards the ,sun1 it generally resembles a faint1 uniformly luminous nebulosity1 either circular or slightly elongated in form4 ,as it approaches nearer to the ,sun1 a slight condensation of light appears towards its centre1 and as it draws still nearer1 it becomes brighter and brighter1 and in condensing forms a kind of diffused luminous nucleus4 ,at the same time that the comet acquires this concentration of light1 the nebulosity gradually becomes elongated in the direction of the ,sun4 ,these effects generally go on increasing so long as the comet is approaching the ,sun2 the condensation of light sometimes forms a bright nucleus1 comparable to a very brilliant star1 while the elongation becomes an immense appendage or tail4 ,when the comet has passed its perihelion and recedes from the ,sun1 the inverse phenomena are observed2 the comet1 decreasing in brightness1 gradually loses its nucleus and tail1 resumes its nebulous aspect1 and finally vanishes in space1 to appear again in due course1 if it chance to be a periodic comet4 ,while all comets become brighter in approaching the ,sun1 they do not all1 however1 develop a large tail1 some of them showing only a slight elongation4 ,when a comet is first discovered with the telescope at a great distance from the ,sun1 it is difficult to predict whether it will become visible to the naked eye1 or will remain a telescopic object1 as it is only in approaching the ,sun that these singular bodies acquire their full development4 ,thus1 ,donati's comet1 whose tail became so conspicuous an object at its full appearance in #aheh1 remained two months after its discovery by the telescope without any indication of a tail4 ,the comet of ,halley1 which before and after its return in #agei1 remained five years inside of the orbit of ,saturn1 showed not the least trace of its presence during the greater part of this time4 ,nothing but calculation could then indicate the position in the sky of this invisible object1 which was so prominent when it approached the ,sun4 ,another curious phenomenon exhibited by comets1 and first noticed by ,valz1 is that in approaching the ,sun the nebulosity composing these bodies contracts1 instead of dilating1 as would be naturally supposed from the greater amount of solar heat which they must then receive4 ,in receding from the ,sun1 on the contrary1 they expand gradually4 ,as comets approach the ,sun1 the tail and nucleus are developed1 while the nebulosity originally constituting these comets contracts1 as if its material had been partly consumed in this development4 ,in a certain sense it may be said that the comets are partly created by the ,sun2 in more exact terms1 the changes of form which they undergo are induced by the ,sun's action upon them at different distances and under varying conditions4 ,moreover1 they are rendered visible by its influence1 without which they would pass unperceived in our sky4 ,when a comet disappears from view1 it is not because its apparent diameter is so much reduced by the distance that it vanishes1 but rather on account of the diminution of its light1 both that which it receives from the ,sun1 and its own light2 these bodies being in some degree self-luminous1 as will be shown below4 ,the large comets1 such as can be seen with the naked eye1 always show the following characteristics1 on examination with the telescope4 ,a condensation of light resembling a diffused star forms the brightest part of the comet1 this condensation being situated towards the extremity the nearest to the ,sun4 ,it is this starlike object which is called the nucleus4 ,the nucleus seems to be entirely enclosed in a luminous vapory envelope of the same general texture1 called the coma4 ,this envelope1 which is quite variable in brightness and form1 is brightest next to the nucleus1 and gradually fades away as it recedes from it4 ,the nucleus and the coma1 considered as a whole1 constitute the head of a comet4 ,from the head of a comet proceeds a long trail of pale nebulous light1 which usually grows wider1 but fainter1 as it recedes from the nucleus1 and insensibly vanishes in the sky4 ,this delicate appendage1 or tail1 as it is commonly called1 varies very much in size and shape1 not only in different comets1 but in the very same comet1 at different times4 ,its direction is generally opposite to that of the ,sun from the head of the comet4 ,the nuclei vary very much in brightness1 in size and in shape2 and while in some telescopic comets they are either absent or barely distinguishable as a small condensation of light1 in bright comets they may become plainly visible to the naked eye1 and they sometimes even surpass in brightness the most brilliant stars of the heavens4 ,but whatever may be the size of cometary nuclei1 they are subject to sudden and rapid changes1 and vary from day to day4 ,sometimes they appear exceedingly brilliant and sharply outlined1 while at other times they are so dim and diffused that they are hardly distinguishable from the coma of which they seem then to form a part4 ,,plate ,,xi4--,,the ,,great ,,comet ,,of #ahha4 ,observed on the night of ,june #be-bf at #a;h4 #cjm4 ,a4,m4 ,from my observations upon the comets which have appeared since the year #ahgc1 it is apparent that the changes in the nucleus1 coma and tail1 are due to a solar action1 which contracts or expands these objects in such a manner that the nuclei become either bright and star-like1 or dim and diffused1 in a very short time4 ,i had excellent opportunity1 especially in the two large comets of #ahha1 to observe some of these curious changes1 a description of which will give an idea of their extent and rapidity4 ,on ,july #b;d1 #ahha1 at #i o'clock1 the nucleus of comet #ahha1 ,,iii41 which is represented on ,plate ,,xi41 appeared sharply defined1 bright and considerably flattened crosswise2 but half an hour later it had considerably enlarged and had become so diffused that it could hardly be distinguished from the coma1 with which it gradually blended4 ,it is perhaps worth mention that1 at the time this last observation was made1 an aurora borealis was visible4 ,this comet #ahha1 ,,iii41 underwent other very important changes of its nucleus1 coma and tail4 ,on ,june #beth1 the nucleus1 which was bright and clearly defined1 was ornamented with four bright diverging conical wings of light1 as shown on ,plate ,,xi4 ,on the #bfth these luminous wings had gone1 and the nucleus appeared one-third smaller4 ,on the #bhth it had enlarged1 but on the #bith its shape was considerably altered1 the nucleus extending in one direction to three or four times its diameter on previous nights1 and being curved1 so as to resemble a comma4 ,on the #fth of ,july the nucleus of this comet showed the greatest disturbances4 ,the nucleus1 which had appeared perfectly round on the evening of the #eth1 was found much elongated at #aj o'clock on the #fth1 forming then a straight1 acute1 and well-defined wedge of light1 inclined upwards to the left4 ,the length of the nucleus1 at this time1 was three or four times its ordinary diameter4 ,at the same time rapid changes occurred2 the strangely shaped nucleus soon became unsteady1 extending and contracting alternately1 and varying greatly in brightness4 ,at #aj;h4 #dem41 the elongated nucleus1 then gently curved1 took the shape of a succession of luminous knots1 which at times became so brilliant and distinct that they seemed to be about to divide and form separate nuclei2 but such a separation did not actually occur1 at least while ,i was observing4 ,while these important changes were going on in the comet1 a bright auroral arch appeared in the north1 which lasted only a short time4 ,on ,july #gth1 the sky being cloudy1 no observations were made1 but on the #hth ,i observed the comet again4 ,the nucleus had then resumed its circular form1 but it was yet very unsteady1 being sometimes small1 bright and sharp1 while a few seconds later it appeared twice as large1 but dim in outlines2 and sometimes an ill-defined secondary nucleus appeared at its centre4 ,on several occasions the nucleus appeared as if it were double1 one nucleus being apparently projected partly upon the other4 ,the nuclei of comets are sometimes very small1 and in other cases very large4 ,among those which have been measured1 the nucleus of the comet of #agih1 ,i41 was only #bh miles in diameter1 but that of ,donati's comet1 in #aheh1 was #e1fjj miles1 and that of the comet of #ahde was #h1jjj miles in diameter4 ,the coma of comets is found to be even more variable than the nucleus4 ,the changes observed in the coma are generally in close connection with those of the nucleus and tail1 the same perturbations affecting simultaneously the whole comet4 ,while the coma of the comet of #ahdg was only #ah1jjj miles in diameter1 that of ,halley's comet1 in #ahce1 was #ceg1jjj miles1 and that of the comet of #ahaa was #a1abe1jjj miles in diameter4 ,in general1 as already stated1 the coma of a comet decreases in size in approaching the ,sun4 ,that of ,encke's comet1 which1 on ,october #ith1 #ahch1 had a diameter of #bha1jjj miles1 gradually decreased at a daily mean rate of #d1jhh miles in going towards the ,sun2 so that1 on ,december #agth1 when the distance of the comet from the ,sun was more than four times less than it was on the first date1 its diameter was reduced to #c1jjj miles4 ,the form of the coma1 in that part which is free from the tail1 is in general a portion of a circle1 but is sometimes irregular1 with its border deformed4 ,thus1 the border of the coma of ,halley's comet was depressed at one point towards the ,sun4 ,i observed a similar phenomenon in ,coggia's comet1 with the great refractor of the ,harvard ,college ,observatory1 on ,july #acth1 #ahgd1 when its border appeared deeply depressed on the side nearest to the ,sun1 as if repelled by this body4 ,the coma of comet #ahha1 ,,iii41 showed also very singular outlines on the nights of the #beth and #bfth of ,june1 when its border was so deeply depressed that the coma appeared as if it were double4 ,luminous rays and jets often radiate from the nucleus across the coma1 and describe graceful lateral curves1 falling backwards and gradually fading away into the tail1 of which they then form a part4 ,the rays and jets emitted by the nucleus seem at first to obey the solar attraction and travel towards the ,sun2 but they are soon repelled1 and move backward towards the tail4 ,it is a mystery1 as yet unexplained1 how these cometary jets1 which at first seem to obey to the laws of attraction1 are compelled to retreat apparently by superior opposing forces4 ,among the forces of nature1 we know of no other than those of an electrical sort1 which would act in a similar manner2 but this explanation would require us to assume some direct electrical communication between the comet and the ,sun4 ,considering the distance between the two bodies1 and the probable absence or great tenuity of the gaseous material in interstellar space1 such an assumption is a difficult one4 ,under the action of the solar forces1 the coma also very frequently forms itself into concentric luminous arcs1 separated by comparatively dark intervals4 ,these luminous semi-circles vary in number1 but sometimes there are as many as four or five at a time4 ,all great comets show these concentric curves more or less1 but sometimes only a portion is visible1 the rest of the coma having a different structure4 ,when great comets approach near the ,sun1 their coma is generally composed of two distinct parts1 an inner and an outer coma1 the inner one being due to the luminous jets issuing from the nucleus1 which1 never extending very far1 form a distinct1 bright zone within the fainter exterior coma4 ,the tails of comets1 which are in fact a prolongation of the coma1 are likewise extremely variable in form4 ,they are sometimes straight like a rod2 again1 are curved like a sabre1 or even crooked like an ,s1 as was that of the comet of #agfi4 ,they are also fan-shaped1 pointed1 or of the same width throughout4 ,many of these appendages appear longitudinally divided through their middle by a narrow1 darkish rift1 extending from the nucleus to the extremity4 ,this peculiarity appears in the comet shown on ,plate ,,xi4 ,sometimes the dark rift does not commence near the nucleus1 but at some distance from it1 as ,i observed in the case of comet #ahha1 ,,iii41 on ,june #bfth4 ,this dark rift is not a permanent feature of a comet's tail1 but may be visible one day and not at all the next4 ,comet #ahha1 ,,iii41 which had shown a dark rift towards the end of ,june1 did not exhibit any such rift during ,july and ,august1 when1 on the contrary1 its tail appeared brighter in the middle4 ,coggia's comet1 which showed so prominent a dark rift in ,july1 #ahgd1 had none on ,june #ajth4 ,on the contrary1 the tail was on that date very bright along its middle1 as also along each of its edges4 ,the tail of a comet does not invariably point directly away from the ,sun1 as above mentioned1 and sometimes the deviation is considerable2 for instance1 the tail of the comet of #aegg deviated #ba from the point opposite to the ,sun4 ,in general1 the tail inclines its extremity towards the regions of space which it has just left1 always presenting its convex border to the regions towards which it is moving4 ,it is also a remarkable fact that this convex border1 moving first in space1 always appears brighter and sharper than the opposite one1 which is often diffused4 ,from these peculiarities it would seem that in moving about the ,sun the comets encounter some resistance to their motion1 from the medium through which they pass1 and that this resistance is sufficient to curve their tails away from the course in which they move1 and to crowd their particles together on the forward side4 ,it is especially when they approach their perihelion1 and move more rapidly on a curve of a shorter radius1 that the comets' tails show the greatest curvature1 unless their position in regard to the observer prevents their being advantageously seen4 ,the tail of ,donati's comet presented a fair illustration of this peculiarity1 its curvature having augmented with the velocity of the comet's motion about the ,sun4 ,but possibly this phenomenon has another cause1 and may be found rather in the solar repulsion which acts on comets and is not instantaneously propagated throughout their mass4 ,although1 in general1 comets have but one tail1 it is not very rare to see them with multiple tails4 ,the comets of #ahjg and #ahdc had each a double tail2 ,donati's comet1 in #aheh1 showed several narrow1 long rectilinear rays1 issuing from its abruptly curved tail4 ,the comet of #ahbe had five branches1 while that of #agdd exhibited no less than six distinct tails diverging from the coma at various angles4 ,in general character the multiple and single tails are similar4 ,when a comet has two tails1 it is not rare for the second to extend in the general direction of the ,sun1 as was the case with the great comet of #ahha1 ,,iii41 represented on ,plate ,,xi4 ,from ,july #adth to the #bast it exhibited quite an extended conical tail1 starting obliquely downwards from the right side of the coma1 and directed towards the ,sun4 ,from the #bdth of ,july to the #b;d of ,august this secondary tail was exactly opposite in its direction from that of the primary tail1 and gave to the head a very elongated appearance4 ,comet #ahha1 ,,iv41 also exhibited a secondary appendage1 not directed towards the ,sun1 but making an angle of about #de with the main tail4 ,these cometary appendages sometimes attain prodigious dimensions4 ,the comets of #afhj and #agfi had tails so extended that1 after their heads had set under the horizon1 the extremities of these immense appendages were still seen as far up as the zenith4 ,in a single day the tail of the comet of #ahdc extended #ajj1 and it was thrust from the comet as a dart of light to the enormous distance of #dh1ejj1jjj miles1 and yet of this immense appendage nothing was left on the following day4 ,the tail of ,donati's comet1 in #aheh1 attained a real length of #db1jjj1jjj miles1 while that of the great comet of #ahdc had the enormous length of #bjj1jjj1jjj miles4 ,if this last comet had occupied the position of the ,sun1 which it approached very nearly for a moment1 the extremity of its tail would have extended #fj1jjj1jjj miles beyond the orbit of ,mars4 ,in some cases the tails of comets have been seen undulating and vibrating in a manner similar to the undulations and coruscations of light characteristic of some auroras4 ,many observers report having seen such phenomena4 ,the comet of #agfi was traversed by luminous waves and pulsations1 comparable to those seen in the aurora borealis4 ,i myself observed these curious undulations in ,coggia's comet in #ahgd1 while the head of this object was below the horizon4 ,for an hour the undulations rapidly succeeded each other1 and ran along the whole length of the tail4 ,some of the brightest comets have shone with such splendor that they could be observed easily in full sunshine4 ,many comets1 such as those of #aegg and #agdd1 have equaled ,sirius and ,venus in brilliancy4 ,the great comet of #ahdc1 which suddenly appeared in our sky1 was so brilliant that it was seen by many observers at noon time1 within a few degrees from the ,sun4 ,i remember that ,i myself saw this remarkable object in the day time1 with a number of persons1 who were gazing at the wonderful apparition4 ,so brilliant was this comet1 that besides its nucleus and head1 a portion of its tail was also visible in the day time1 provided the observer screened his eyes from the full sunlight by standing in the shadow of some building4 ,of all the bodies revolving around the ,sun1 none have been known to approach so near its surface as did the comet of #ahdc4 ,when it arrived at perihelion1 the distance from the centre of its nucleus to the surface of the ,sun's photosphere was only #if1jjj miles1 while the distance from surface to surface was less than #fj1jjj miles4 ,this comet1 then1 went through the solar atmosphere1 and in traversing it with its tremendous velocity of #cff miles per second1 may very possibly have swept through some solar protuberances1 many of which attain much higher elevations than that at which the comet passed4 ,the comet of #afhj also approached quite near the surface of the ,sun1 and near enough to encounter some of the high solar protuberances1 its distance at perihelion being about two-thirds of the ,moon's distance from the ,earth4 ,the rapidity of motion of the comet of #ahdc was such1 when it approached the ,sun1 that it swept through all that part of its orbit which is situated north of the plane of the ecliptic in a little more than two hours1 moving in this short time from one node to the other1 or #ahjj4 ,but if some comets have a very short perihelion distance1 that of others is considerable4 ,such a comet was that of #agbi1 whose perihelion distance was #chc1jjj1jjj miles1 the perihelion point being situated between the orbits of ,mars and ,jupiter4 ,while some comets come near enough to the ,sun at perihelion to be volatilized by its intense heat1 others recede so far from it at aphelion that they may be said to be frozen4 ,the shortest cometary aphelion distance known is that of ,encke's comet1 whose greatest distance from the sun is #chh1jjj1jjj miles4 ,but that of the comet of #ahdd is #djf1jjj1jjj1jjj miles from the ,sun4 ,the comets of #ahfc and #ahfd are so remote in space when they reach their aphelion points that light1 with its velocity of #ahe1ejj miles a second1 would require #aga days in the first case1 and #bcj in the last1 to pass from them to the ,earth4 ,the period of revolution of different comets also varies immensely4 ,while that of ,encke's comet is only #c years1 that of comet #ahfd1 ,,ii41 is #bhj1jjj years4 ,among the periodic comets of short period1 some have exhibited highly interesting phenomena4 ,encke's comet1 discovered in #ahah1 is remarkable for the fact that its period of revolution diminishes at each of its successive returns1 and consequently this comet1 with each revolution1 approaches nearer and nearer to the ,sun4 ,the decrease of the period is about #b hours at each return4 ,although the decrease is small1 if it go on in future as it does at present1 the inevitable consequence will be that this comet will finally fall into the ,sun4 ,this curious phenomenon of retardation has been attributed by astronomers to the existence of a resisting medium filling space1 but so rare and ethereal that it does not produce any sensible effect on the movements of the planets4 ,but some other causes may retard this comet1 as similar retardations have not been observed in the case of other periodic comets of short period4 ,these1 however1 are not so near to the ,sun1 and perhaps our luminary may be surrounded by matter of extreme tenuity1 which does not exist at a greater distance from it4 ,another of the periodic comets which has exhibited a very remarkable phenomenon of transformation is ,biela's comet1 which divided into two distinct parts1 moving together in the same direction4 ,when this comet was first detected at its return in #ahde1 it presented nothing unusual1 but in the early part of #ahdf it was noticed by several astronomers to be divided into two parts of unequal brightness1 forming thus a twin comet4 ,at its next return in #aheb1 the two sister comets were still traveling in company1 but their distance apart1 which in #ahdf was #aeg1jjj miles1 had increased to #a1ejj1jjj miles4 ,at the two next returns in #ahei and #ahfe1 their position not being very favorably situated for observation1 the comets were not seen4 ,in #ahgb the position should have been favorable for observation1 and they were consequently searched for1 but in vain2 neither comet was found4 ,an astronomer in the southern hemisphere1 however1 found a comet on the track of ,biela's1 but calculation has shown that the two objects are probably not identical1 since this comet was two months behind the computed position for ,biela's4 ,it will be shown in the following chapter that our globe probably crossed the orbit of ,biela's comet on ,november #bgth1 #ahgb1 and the phenomena resulting from this passage will be there described4 ,it is seen from these observations that comets may be lost or dissipated in space by causes entirely unknown to us4 ,biela's comet is not the only one which has been thus disintegrated4 ,ancient historians speak of the separation of large comets into two or more parts4 ,in #affa ,hevelius observed the apparent division of the comet of that year and its reduction to fragments4 ,the return of this comet1 calculated for #agij1 was vainly waited for2 the comet was not seen4 ,other comets1 whose periods of revolution were well known1 have disappeared1 probably never to return4 ,such is ,lexell's comet1 whose period was #e years2 also ,de ,vico's comet1 both of which are now lost4 ,it is supposed that ,lexell's comet1 which passed twice very near the giant planet ,jupiter1 had its orbit changed from an ellipse to a parabola1 by the powerful disturbing influence of this planet1 and was thus lost from our system4 ,several other comets1 in traveling over their different orbits1 have approached near enough to ,saturn1 ,jupiter and the ,earth to have their orbits decidedly altered by the powerful attraction of these bodies4 ,but since comets are liable to pass near the planets1 and several have orbits which approach that of the ,earth1 it becomes important for us to know whether an encounter of such a body with our globe is possible1 and what would then be the result for us4 ,although that knowledge would not enable us to modify the possibilities of an encounter1 yet it is better to know the dangers of our navigation through space than to ignore them4 ,this question of a collision of the ,earth with a comet has been answered in different ways1 according to the ideas entertained in regard to the mass of these bodies4 ,while some have predicted calamities of all kinds1 such as deluges1 conflagrations1 or the reduction of the ,earth to incandescent gases1 others have asserted that it would produce no more effect than does a fly on encountering a railroad train4 ,in our days astronomers entertain very little fears from such an encounter1 because the probabilities of danger from an occurrence of this sort are very slight1 the mass of an ordinary comet being so small compared with that of our globe4 ,we know with certainty that the ,earth has never had an encounter with a comet by which it has been transformed into gases1 at least within the several millions of years during which animal and vegetable life have left their marks upon the stony pages of its history1 otherwise these marks would not now be seen4 ,if1 then1 such an accident has not happened during this long period1 the chances for its occurring must be very small1 so small indeed that they might almost be left out of the question4 ,it is true that our globe shows signs of great perturbations of its surface1 but we have not the slightest proofs that they resulted from an encounter with a celestial body4 ,it seems very probable that our globe passed through the tail of the comet of #ahfa1 before it was first seen on ,june #bith2 but nothing unusual was observed1 except perhaps some phosphorescent light in the atmosphere1 which was afterwards attributed to this cause4 ,the density and mass of comets must be comparatively very small4 ,their tails consist of matter of such extreme tenuity that it affects but very little the light of the small stars over which they pass4 ,the coma and nucleus1 however1 are not quite so transparent1 and may have greater masses4 ,on several occasions ,i have seen the light of stars reduced by the interposition of cometary matter1 comet #ahha1 ,,iii41 presenting remarkable cases of this sort4 ,on ,july #hth1 at #aj;h4 #ejm41 several small stars were involved in this comet1 one of which passed quite near the nucleus through the bright inner coma4 ,at that time the comet was greatly disturbed1 its nucleus was contracting and enlarging rapidly1 and becoming bright and again faint in an instant4 ,every time that the nucleus grew larger1 the star became invisible1 but reappeared the moment the nucleus was reduced in size4 ,this phenomenon could not be attributed to an atmospheric effect1 since1 while the nucleus was enlarging1 a very small inner nucleus was visible within the large diffused one1 the matter of which had apparently spread over the part of the coma in which the star was involved1 making it invisible4 ,that the mass of comets is small1 is proved by the fact that they have sometimes passed near the planets without disturbing them in any sensible manner4 ,lexell's comet1 which in #aggj remained four months very near ,jupiter1 did not affect in the least the orbits1 or the motions of its satellites4 ,the same comet also came within less than #a1ejj1jjj miles from the ,earth1 and on this occasion it was calculated that its mass could not have been the part of that of our globe1 since otherwise the perturbations which it would have caused in the elements of the ,earth's orbit would have been sensible4 ,there was1 however1 no change4 ,if this comet's mass had been equal to that of our globe1 the length of our year would have been increased by #b;h4 #dgm4 ,the comet of #ahcg remained four days within #c1ejj1jjj miles of the ,earth1 with no sensible effect4 ,it seems quite difficult to admit that the denser part of a comet forming the nucleus is solid1 as supposed by some physicists1 since it is so rapidly contracted and dilated by the solar forces1 while the comet is yet at a too great distance from the ,sun to allow these effects to be attributed to solar heat alone4 ,this part of a comet1 as indeed the other parts1 seems rather to be in the gaseous than in the solid state2 the changes observed in the intensity of its light and in its structure may be conceived as due to some solar action partaking of the nature of electricity4 ,it has been a question whether comets are self-luminous1 or whether they simply reflect the solar light4 ,when their light is analyzed by the spectroscope1 it is found that the nucleus of a comet generally gives a continuous spectrum1 while the coma and tail give a spectrum consisting of several bright diffused bands4 ,the spectrum given by the nucleus is rarely bright enough to allow the dark lines of the solar spectrum to be discerned upon it2 but such lines were reported in the spectrum of comet #ahha1 ,,iii41 a fact proving that this nucleus at least reflected some solar light4 ,the nucleus of a comet may be partly self-luminous1 and either solid1 liquid1 or composed of incandescent gases submitted to a great pressure4 ,as to the coma and tail1 they are evidently gaseous1 and partly1 if not entirely1 self-luminous1 as is proved by the band spectrum which they give4 ,the position of these bands1 moreover1 indicates that the luminous gases of which they are composed contain carbon4 ,the phenomena of polarization1 however1 seem to prove that these parts of comets also reflect some solar light4 ,no theory so far proposed1 to explain comets and the strange phenomena they exhibit1 seems to have been successful in its attempts1 and the mystery in which these bodies have been involved from the beginning of their apparition1 seems to be now nearly as great as ever4 ,it has been supposed that their tails have no real existence1 but are due to an optical illusion4 ,prof4 ,tyndall has endeavored to explain cometary phenomena by supposing these bodies to be composed of vapors subject to decomposition by the solar radiations1 and thus made visible1 the head and tail being an actinic cloud due to such decompositions4 ,according to this view1 the tails of comets would not consist of matter projected into spacer but simply of matter precipitated by the solar rays in traversing the cometary nebulosity4 ,the endeavor has also been made to explain the various phenomena presented by comets by an electrical action of the ,sun on the gases composing these objects4 ,theories taking this as a base seem to us to be more likely to lead to valuable results4 ,m4 ,faye1 who has devoted much time and learning to this subject1 assumes a real repulsive force of the ,sun1 acting inversely to the square of the distance and proportionally to the surface1 and not to the mass as attraction does4 ,he supposes1 however1 that this repulsive force is generated by the solar heat1 and not by electricity4 ,prof4 ,wm4 ,harkness says that many circumstances seem to indicate that the comets' tails are due1 in a great measure1 to electrical phenomena4 ,the fact that the tails of comets are better defined and brighter on the forward side1 associated with the other fact that they curve the most when their motion is most rapid1 sufficiently indicates that these appendages are material1 and that they either encounter some resistance from the medium in which they move1 or from a solar repulsion4 ,the phenomena of condensation and extension1 which ,i have observed in the comets of #ahgd and #ahha1 added to the curious behavior exhibited by the jets issuing from the nucleus1 seem to indicate the action of electrical forces rather than of heat4 ,the main difficulty encountered in the framing of a theory of comets consists in explaining how so delicate and extended objects as their tails seem to be1 can be transported and whirled around the ,sun at their perihelion with such an enormous velocity1 always keeping opposite to the ,sun1 and1 as expressed by ,sir ,john ,herschel1 in defiance of the law of gravitation1 nay1 even of the received laws of motion4 ,to consider the direction of the comets' tails as an indirect effect of attraction1 seems out of the question2 the phenomenon of repulsion so plainly exhibited by these objects seems to point to a positive solar repulsion1 as alone competent to produce these great changes4 ,the repulsive action of the ,sun on comets' tails might be conceived1 for instance1 as acting in a manner similar to that of a powerful current of wind starting from the ,sun1 and constantly changing in direction1 but always keeping on a line with the comet4 ,such a current1 acting on a comet's tail as if it were a pennant1 would drive it behind the nucleus just as observed4 ,if it could once be ascertained that the great disturbances on comets correspond with the magnetic disturbances on our globe and with the display of the auroral light1 the electric nature of the forces acting so strangely on the comets would be substantially demonstrated4 ,i have shown that some of the great disturbances observed in the comets of #ahgd and #ahha have coincided with auroral displays1 and it will be shown hereafter that similar displays have also coincided with the passage of meteoric showers through our atmosphere4 ,whether these simultaneous phenomena were simple coincidences having no connection1 or whether they are the result of a common cause1 can only be ascertained by long continued future observations4 ,,shooting-,,stars ,,and ,,meteors ,,plate ,,xii ,while contemplating the heavens on a clear moonless night1 we occasionally witness the sudden blazing forth of a star-like meteor1 which glides swiftly and silently across some of the constellations1 and as suddenly disappears1 leaving sometimes along its track a phosphorescent trail1 which remains visible for a while and gradually vanishes4 ,these strange apparitions of the night are called ,falling or ,shooting-stars4 ,there is certainly no clear night throughout the year during which some of these meteors do not make their appearance1 but their number is quite variable4 ,in ordinary nights only four or five will be observed by a single person in the course of an hour2 but on others they are so numerous that it becomes impossible to count them4 ,when the falling stars are only a few in number1 and appear scattered in the sky1 they are called ,sporadic ,meteors1 and when they appear in great numbers they constitute ,meteoric ,showers or ,swarms4 ,probably there is no celestial phenomenon more impressive than are these wonderful pyrotechnic displays1 during which the heavens seem to break open and give passage to fiery showers1 whose luminous drops describe fantastic hieroglyphics in the sky4 ,while observing them1 one can fully realize the terror with which they have sometimes filled beholders1 to whom it seemed that the stability of the universe had come to an end1 and that all the stars of the firmament were pouring down upon the ,earth in deluges of fire4 ,the ancients have left record of many great meteoric displays1 and the manner in which they describe them sufficiently indicates the fear caused by these mysterious objects4 ,among the many meteoric showers recorded by ancient historians may be mentioned one observed in ,constantinople1 in the month of ,november1 #dgb1 when all the sky appeared as if on fire with meteors4 ,in the year #eii1 meteors were seen on a certain night flying in all directions like fiery grasshoppers1 and giving much alarm to the people4 ,in ,march1 #gfc1 the stars fell suddenly1 and in such crowded number that people were much frightened1 and believed the end of the world had come4 ,on ,april #ajth1 #ajie1 the stars fell in such enormous quantity from midnight till morning that they were as crowded as are the hail stones during a severe storm4 ,in modern times the fall of the shooting-stars in great number has been frequently recorded4 ,one of the most remarkable meteoric showers of the eighteenth century occurred on the night of ,november #acth1 #agii1 and was observed throughout ,north and ,south ,america and ,europe4 ,on this memorable night thousands of falling stars were seen traversing the sky between midnight and morning4 ,humboldt and ,boupland1 then traveling in ,south ,america1 observed the phenomena at ,cumana1 between two and five o'clock in the morning4 ,they saw an innumerable number of shooting-stars going from north to south1 appearing like brilliant fire-works4 ,several of these meteors left long phosphorescent trails in the sky1 and had nuclei whose apparent diameter1 in some cases1 surpassed that of the ,moon4 ,the shower of ,november #acth1 #ahcc1 was still more remarkable for the great number of meteors which traversed the heavens1 and was visible over the whole of ,north and ,south ,america4 ,on that occasion the falling stars were far too numerous to be counted1 and they fell so thickly that ,prof4 ,olmsted1 of ,new ,haven1 who observed them carefully1 compared their number at the moment of their maximum fall to half that of the flakes of snow falling during a heavy storm4 ,this observer estimated at #bdj1jjj the number of meteors which must have traversed the heavens above the horizon during the seven hours while the display was visible4 ,,plate ,,xii4--,,the ,,november ,,meteors4 ,as observed between midnight and #e o'clock ,a4,m4 on the night of ,november #ac-ad #ahfh4 ,in the years #ahff1 #ahfg and #ahfh1 there were also extraordinary meteoric displays on the night of ,november #acth4 ,it was on the last mentioned date that ,i had the opportunity to observe the remarkable shower of shooting-stars of which ,i have attempted to represent all the characteristic points in ,plate ,,xii4 ,my observations were begun a little after midnight1 and continued without interruption till sunrise4 ,over three thousand meteors were observed during this interval of time in the part of the sky visible from a northern window of my house4 ,the maximum fall occurred between four and five o'clock1 when they appeared at a mean rate of #ae in a minute4 ,in general1 the falling stars were quite large1 many being superior to ,jupiter in brightness and apparent size1 while a few even surpassed ,venus1 and were so brilliant that opaque objects cast a strong shadow during their flight4 ,a great many left behind them a luminous train1 which remained visible for more or less time after the nucleus had vanished4 ,in general1 these meteors appeared to move either in straight or slightly curved orbits2 but quite a number among them exhibited very extraordinary motions1 and followed very complicated paths1 some of which were quite incomprehensible4 ,while some moved either in wavy or zig-zag lines1 strongly accentuated1 others1 after moving for a time in a straight line1 gradually changed their course1 curving upward or downward1 thus moving in a new direction4 ,several among them1 which were apparently moving in a straight line with great rapidity1 suddenly altered their course1 starting at an abrupt angle in another direction1 with no apparent slackening in their motion4 ,one of them1 which was a very conspicuous object1 was moving slowly in a straight course1 when of a sudden it made a sharp turn and continued to travel in a straight line1 at an acute angle with the first1 retreating1 and almost going back towards the regions from which it originally came4 ,as nearly all the meteors which exhibited these extraordinary motions left the trace of their passage in the sky by a luminous trail1 it was easily ascertained that these appearances were not deceptive4 ,on one occasion ,i noticed that the change of direction in the orbit corresponded with the brightening up of the meteor thus disturbed in its progress4 ,among these meteors1 some traveled very slowly1 and a few seemed to advance as if by jerks1 but in general they moved very rapidly4 ,one of the meteors thus appearing to move by jerks left a luminous trail1 upon which the various jerks seemed to be left impressed by a succession of bright and faint spaces along the train4 ,some of the largest meteors appeared to rotate upon an axis as they advanced1 and most of these revolving meteors1 as also a great number of the others1 seemed to explode just before they disappeared1 sending bright fiery sparks of different colors in all directions1 although no sound was at any time heard4 ,the largest and most brilliant meteor observed on that night appeared at #e;h4 #cjm41 a little before sunrise4 ,it was very bright1 and appeared considerably larger than ,venus1 having quite a distinct disk4 ,this meteor moved very slowly1 leaving behind a large phosphorescent trail1 which seemed to issue from the inside of the nucleus as it advanced4 ,for a moment the train increased in size and brightness close to the nucleus1 which then appeared as an empty transparent sphere1 sprinkled all over with minute fiery sparks2 the nucleus then suddenly burst out into luminous particles1 which immediately vanished1 only the luminous trail of considerable dimensions being left4 ,many of the trails thus left by the meteors retained their luminosity for several minutes1 and sometimes for over a quarter of an hour4 ,these trails slowly changed their form and position2 but it is perhaps remarkable that almost all those which ,i observed on that night assumed the same general form--that of an open1 irregular ring1 or horse-shoe1 somewhat resembling the letter ,c4 ,this ring form was subsequently transformed into an irregular1 roundish cumulus-like cloud4 ,the trail left by a very large meteor1 which ,i observed on the evening of ,september #eth1 #ahhj1 also exhibited the same general character of transformation4 ,while ,i was observing a long brilliant trail left by a meteor on the night of ,november #acth1 #ahfh1 it was suddenly crossed by another bright shooting-star4 ,the latter apparently went through the luminous substance forming the trail1 which was suddenly altered in form1 and considerably diminished in brightness simultaneously with this passage1 although electrical action at some distance might perhaps as well explain the sudden change observed4 ,in the majority of cases the meteors appeared white2 but many1 especially the largest1 exhibited a variety of brilliant colors1 among which the red1 blue1 green1 yellow and purple were the most common4 ,in general the trails exhibited about the same color as the nucleus1 but much fainter1 and they were usually pervaded by a greenish tint4 ,in some instances the trails were of quite a different color from the nucleus4 ,the luminous cloud observed at #e;h4 #cjm4 on the morning of ,november #adth1 #ahfh1 after having passed through the series of transformations above described1 remained visible for a long while after sunrise1 appearing then as a small cirrus cloud1 exactly similar in appearance to the hundreds of small cirrus clouds then visible in the sky1 which had probably the same meteoric origin4 ,for over three hours after sunrise1 these cirrus clouds remained visible in the sky1 moving all together with the wind in the high regions of the atmosphere4 ,although ,plate ,,xii4 is intended to represent all the characteristics exhibited by the meteors observed on that night1 every form represented having been obtained by direct observation1 yet the number is much greater than it was at any single moment during the particular shower of #ahfh4 ,as regards number1 the intention was to give an idea of a great meteoric shower1 such as that of #ahcc1 for instance4 ,although many of the falling stars seem to be close to the ,earth's surface1 yet this is only an effect of perspective due to their great distance1 very few of these meteors ever coming into the lower regions of our atmosphere at all4 ,the phenomena exhibited during other great meteoric showers have been similar to those presented by the shower just described1 the only differences consisting in variations of size and brightness in the meteors1 and also in the trails1 which sometimes are not so numerous as they were in #ahfh4 ,while some shooting-stars move so rapidly that they can hardly be followed in their orbits1 others move so slowly that the sight can easily follow them1 and even remark the peculiarities of their movements1 some remaining visible for half a minute4 ,some of the falling stars move at the rapid rate of #ajj miles a second1 but others only #aj miles a second1 and even less4 ,in general1 they move about half as fast again as the ,earth in its orbit4 ,the arcs described by the meteors in the sky are variable4 ,while some extend #hj and even #ajj1 others are hardly half a degree in length4 ,while some shooting-stars are so faint that they can hardly be seen through the largest telescopes1 others are so large and brilliant that they can be seen in the day-time4 ,in general1 a shooting-star of average brightness resembles a star of the third or fourth magnitude4 ,whatever may be the origin of the shooting-stars1 they are1 when we see them1 not in the celestial spaces1 like the planets1 the comets1 or the stars1 but in our atmosphere1 through which they travel as long as they remain visible4 ,the height at which they appear and disappear is variable1 but in general they are about #hj miles above the surface of our globe when they are first seen1 and at about #ee miles when they disappear4 ,in many cases1 however1 they have been observed at greater elevations1 as also at smaller4 ,a meteor simultaneously observed at two different stations first appeared at the height of #bhe miles1 and was last seen at #aib miles above the ,earth's surface2 but in rare cases the falling stars have been seen below a layer of clouds completely covering the sky4 ,i myself saw one such shooting-star a few years since4 ,the fact that the meteors are visible at so great elevations1 proves that our atmosphere extends much farther than was formerly supposed1 although at these great heights it must be extremely rarefied1 and very different from what it is in its lower regions4 ,there is a remarkable difference between the sporadic meteors seen in the sky on every night1 and the meteoric showers observed only at comparatively rare intervals4 ,while the first appear from different points in the sky and travel in all directions1 being perfectly independent1 the meteors of a shower all come from the same point of the heavens1 from which they apparently diverge in all directions4 ,this point of divergence of the meteors is called the radiant point of the shower4 ,although the meteors seem to diverge in all directions from the radiant point1 yet they all move in approximately parallel lines1 the divergence being an effect of perspective4 ,whatever may be the position of the radiant point in the constellations1 it remains as fixed in the sky as the stars themselves1 and participates with them in the apparent motion which they undergo by the effect of the diurnal motion1 and thus rises and sets with the constellation to which it belongs4 ,this fact is sufficient to prove that the orbits of these meteors are independent of the ,earth's motion1 and that consequently they do not originate in our atmosphere4 ,it has been shown by ,encke that the radiant point of the meteoric shower of ,november #acth is precisely the point towards which our globe moves in space on ,november #acth2 a tangent to the ,earth's orbit would pass through this radiant point4 ,the meteoric showers are particularly remarkable1 not merely because of the large number of meteors which are visible and the fact that they all follow a common orbit1 but chiefly because they have a periodic return1 either after an interval of a year1 or after a lapse of several years4 ,at the beginning of the present century only two meteoric showers were known1 those of ,august #ajth and of ,november #acth1 and their periodicity had not yet been recognized1 although it had begun to be suspected4 ,it was only in #ahcf that ,quetelet and ,olbers ventured to predict the reappearance of the ,november meteors in the year #ahfg4 ,having made further investigations1 ,prof4 ,newton1 of ,yale ,college1 announced their return in the year #ahff4 ,in both of these years1 as also in #ahfh1 the meteors were very numerous1 and were observed in ,europe and in ,america on the night of ,november #acth4 ,the predictions having thus been fulfilled1 the periodicity of the meteors was established4 ,since then1 other periodic showers have been recognized1 although they are much less important in regard to number than those of ,august and ,november1 except that of ,november #bgth1 which exhibited so brilliant a display in ,europe in #ahgb4 ,these successive appearances have established the main fact that meteoric showers are more or less visible every year when the ,earth occupies certain positions in its orbit4 ,the meteoric shower of the #ajth of ,august has its radiant point situated in the vicinity of the variable star ,algol1 in the constellation ,perseus1 from which its meteors have received the name of ,perseids4 ,although varying in splendor1 this meteoric swarm never fails to make its appearance every year4 ,the ,perseids move through our atmosphere at the rate of #cg miles per second4 ,the shower usually lasts about six hours4 ,the meteoric shower of ,november #acth has its radiant point situated in the vicinity of the star ,gamma1 in the constellation ,leo1 from which its meteors have been called ,leonids4 ,but while the ,august meteors recur regularly every year1 with slight variations1 the shower of ,november does not occur with the same regularity4 ,during several years it is hardly noticeable1 and is even totally absent1 while in other years it is very remarkable4 ,every #cc years an extraordinary meteoric shower occurs on the #acth of ,november1 and the phenomenon is repeated on the two succeeding years at the same date1 but with a diminution in its splendor at each successive return4 ,the ,leonids move in an opposite direction to that of the ,earth1 and travel in our atmosphere with an apparent velocity of #de miles per second1 this being about the maximum velocity observed in falling stars4 ,but when the motion of our globe is taken into account1 and a deduction is made of the #ah miles which it travels per second1 it is found that these meteors move at an actual mean rate of #bg miles a second4 ,in a meteoric shower the stars do not fall uniformly throughout the night1 there being a time when they appear in greater numbers4 ,usually it is towards morning1 between #d and #f o'clock1 that the maximum occurs4 ,the probable cause of this phenomenon will be explained in its place hereafter4 ,the orbits of the meteoric showers are not all approximately in the same plane1 like those of the planets1 but rather resemble those of comets1 and have all possible inclinations to the ecliptic4 ,like the comets1 too1 the different meteoric showers have either direct or retrograde motion4 ,the shooting-stars were formerly considered as atmospheric meteors1 caused by the combustion of inflammable gases generated at the surface of the ,earth1 and transported to the high regions of our atmosphere by their low specific gravity4 ,but the considerable height at which they usually appear1 the great velocity of their motion1 the common orbit followed by the meteors of the same shower1 and the periodicity of their recurrence1 do not permit us now to entertain these ideas1 or to doubt their cosmical origin4 ,but what is their nature8 ,it is now generally admitted that innumerable minute bodies1 moving in various directions around the ,sun1 are scattered in the interplanetary spaces through which our globe travels4 ,it has been supposed that congregations of such minute bodies form elliptical rings1 within which they are all moving in close parallel orbits around the ,sun4 ,on the supposition that such rings intersect the orbit of the ,earth at the proper places1 it was practicable to account for the shooting-stars by the passage through our atmosphere of the numerous minute cosmical bodies composing the rings1 and the ,leonid and ,perseid showers were so explained4 ,but when the elements of the orbits of these two last swarms came to be better known1 and were compared with those of other celestial bodies1 it was found necessary to alter this theory4 ,it had for a long while been suspected that some kind of relation existed between the shooting-stars and the comets4 ,this idea1 vaguely formulated by ,kepler more than two centuries ago1 more clearly expressed by ,chladni1 and still more by ,mr4 ,grey1 before the ,british ,association1 at ,liverpool1 in #ahee1 has recently received a brilliant confirmation by the researches of ,professor ,schiaparelli1 ,director of the ,observatory of ,milan4 ,a thorough investigation of the orbits of the ,august and ,november meteors led ,schiaparelli to the discovery of a remarkable relation between meteoric and cometary orbits4 ,by comparing the elements of these meteoric orbits with those of comets1 he found a very close resemblance between the orbit of the ,august meteors and that of the comet #ahfb1 ,,iii41 and again between the orbit of the ,november meteors and that of ,tempel's comet1 #ahff1 ,i4 ,these resemblances were too striking to be the result of mere chance1 and demonstrated the identity of these cometary orbits with those of the ,perseid and ,leonid showers4 ,in accordance with these new facts1 it is now admitted that the meteoric showers result from the passage of our globe through swarms of meteoric particles following the orbits of comets1 which intersect the orbit of the ,earth4 ,professor ,schiaparelli has attempted to show how these meteoric swarms were originally scattered along the orbits of comets1 by supposing these bodies to originate from nebulous masses1 which1 in entering the sphere of attraction of the ,sun1 are gradually scattered along their orbits1 and finally form comets followed by long trails of meteoric particles4 ,it has been shown that in approaching the ,sun the comets become considerably elongated1 their particles being disseminated over immense distances by the solar repulsion4 ,it seems probable that1 owing to its feeble attractive power1 the nucleus is incompetent to recall the scattered cometary particles and retain them in its grasp when they are relieved from the solar repulsion1 so that they remain free from the nucleus1 although they continue to move along its orbit4 ,it is supposable that these cometary particles will scatter more and more in course of time4 ,forming at first an elongated meteoric cloud1 they will finally spread along the whole orbit1 and thus form a ring of meteoric particles4 ,since our globe constantly moves in its orbit and daily occupies a different position1 it follows that at any point where such a cometary orbit happens to cross that of the ,earth1 our globe will necessarily encounter the cometary particles as a shower of meteors4 ,this encounter will take place at a certain time of the year1 either yearly1 if they form a continuous ring1 or after a succession of years1 if they simply form an elongated cloud4 ,such meteoric clouds or rings would not be visible in ordinary circumstances1 even through the largest telescopes1 except on penetrating the upper regions of our atmosphere1 when they would appear as showers of falling stars4 ,it is supposed that in penetrating our atmosphere1 even in its most rarefied regions1 these meteors are heated by the resistance offered by the air to their motion1 first becoming luminous and then being finally vaporized and burnt before they can reach the surface of the ,earth4 ,the orbit of the comet of #ahfb1 ,,iii41 which so closely corresponds with that of the ,perseid meteors1 is much more extended than that of ,tempel's comet corresponding with that of the ,leonids4 ,while the first extends far beyond the orbit of ,neptune1 the latter only goes a little beyond that of ,uranus4 ,the former orbit makes a considerable angle with the plane of the ,earth's orbit1 but the latter is much nearer to parallelism with it4 ,the period of revolution of the first is #ajh years1 and that of the last about #cc years4 ,from the fact that the ,perseid shower occurs yearly on the #ajth of ,august1 when the ,earth crosses the orbit of the comet of #ahfb1 ,,iii41 it is supposed that the cometary particles producing this shower are disseminated along the whole orbit1 and form a ring encircling the ,sun and ,earth4 ,to explain the yearly variations in the number of the shooting-stars observed1 these particles are supposed to be unequally distributed over the orbit1 being more crowded at one place than they are at another4 ,in order to explain the meteoric shower of ,leonids1 which appears in all its splendor every #cc years1 and then with diminished intensity for two successive years1 after which it is without importance1 it is supposed that the cometary particles of the comet of #ahff1 ,i41 have not as yet spread all along the orbit1 a sufficient time not having been allowed1 but form an elongated meteoric cloud1 more dense in its front than in its rear part4 ,from these considerations it has been supposed also that the comet of #ahff1 ,i41 is of a more recent date than that of #ahfb1 ,,iii4 ,while ,tempel's comet makes its revolution around the ,sun in about #cc years1 this meteoric cloud1 which has the same period and returns to the same point of its orbit every #cc years1 encounters our globe for three successive years4 ,the first year we are passing through its densest parts1 and the two following years in less and less crowded parts1 from which result the observed phenomena4 ,an idea of the extent of this meteoric cloud may be formed from the fact that1 with its cometary velocity of motion1 it takes this cloud three years at least to cross the ,earth's orbit4 ,from recent researches it would appear that the ,leonid cloud is not single1 but that at least two others of smaller importance exist1 and have periods of #cc years4 ,biela's comet1 which was divided into two parts in #ahdf1 is another of the few comets whose orbit approaches that of the ,earth4 ,possessing this knowledge1 and knowing then the close connection existing between meteors and comets1 astronomers supposed that there were sufficient reasons to expect a meteoric shower when this comet was passing near the ,earth4 ,they consequently expected a meteoric display in #ahgb1 when our globe was to cross its orbit4 ,their anticipation was plainly fulfilled1 and on the night of ,november #bgth1 #ahgb1 a splendid meteoric display1 having its radiant point in the constellation ,andromeda1 was observed in ,europe1 and also in ,america1 but the meteors seen here were not so numerous as in ,europe4 ,other meteoric showers of less importance1 such as that of ,april #bjth1 for instance1 have also been identified with cometary orbits1 so that now no doubt seems to remain as to the identity of cometary particles and shooting-stars4 ,the fact that the maximum number of meteors is always observed in the morning hours1 supports the hypothesis of the cosmic origin of the shooting-stars1 since the regions of the ,earth where it is morning are precisely those fronting the regions towards which our globe is moving in space1 and accordingly encounter more directly the meteors moving in their orbit4 ,the greater abundance of falling stars at that time may thus be accounted for4 ,the number of meteors penetrating our atmosphere must be very great2 there is not an hour and probably not a minute during which none fall4 ,from various considerations1 some astronomers have estimated at from #fe1jjj1jjj1jjj to #adf1jjj1jjj1jjj the total number of shooting-stars yearly penetrating in our atmosphere4 ,the actual number is undoubtedly great1 yet the fact that the meteors are rarely seen through the telescope while employed in observing various celestial objects1 does not indicate that they are so numerous as these figures imply4 ,it is only occasionally that one is seen traversing the field of the instrument4 ,even when the sky is observed with a low power eye-piece for several hours in succession1 many nights may pass without disclosing one1 although an observer1 sweeping the sky more freely with the naked eye1 may often perceive four or five during an ordinary night4 ,about the true nature of these bodies nothing is known with certainty4 ,from spectrum analysis it seems to be established that most of them contain sodium and magnesium1 while a few indicate the presence of strontium and iron1 and in some rare cases there are traces of coal-gas4 ,some of the nuclei give a continuous spectrum1 and others a spectrum of lines4 ,the trail always gives a spectrum of bright lines which indicates its gaseous state4 ,the traces of coal-gas rarely seen in meteors are1 however1 of great importance1 as it identifies them more closely with the comets1 which generally show a similar spectrum4 ,the continuous spectra exhibited by some nuclei would indicate that they are incandescent and either solid or liquid2 but it is difficult to conclude from their spectra what is their true nature1 since we do not know exactly what part the terrestrial atmosphere may play in producing the results4 ,the mass of the shooting-stars is not known with certainty1 but the fact that during great meteoric showers1 none are seen to reach the surface of the ,earth1 all being consumed in a few seconds1 sufficiently indicates that it must be very small4 ,it has been calculated that those equal to ,venus in apparent size and brilliancy may weigh several pounds1 while the faint ones would weigh only a few grains4 ,if the shooting-stars have even such a mass as that here attributed to some of them1 the extraordinary motions which ,i have described above seem to be unaccountable4 ,the change of direction of a heavy mass moving swiftly cannot be sudden4 ,the semi-circular1 the wavy and the angular orbits observed could not be described1 it would seem1 by such a mass animated with a great velocity4 ,although the meteors are said to be ignited by the transformation of part of their progressive motion into molecular motion1 yet it is not observed that the velocity of the falling stars diminishes when they are about to disappear4 ,the luminous trails they leave in the atmosphere do not appear to be endowed with any motion1 but remain for a time in their original positions4 ,these facts are apparently opposed to the hypothesis that such meteors have any appreciable mass4 ,the extraordinary motions exhibited by some meteors seem to indicate that some unsuspected force resides in these bodies1 and causes them to deviate from the laws of ordinary motion4 ,although it is very probable that the ordinary shooting-stars have no appreciable mass1 yet it is known that very heavy meteoric masses sometimes fall at the surface of the ,earth4 ,such falls are generally preceded by the sudden apparition in the sky of a large1 and usually very brilliant fire-ball1 which traverses the air at a great speed1 sometimes leaving behind it a luminous trail1 after which it explodes with a loud sound1 and heavy fiery meteoric fragments1 diverging in all directions1 fall at the surface of the ,earth4 ,the name of ,aerolites or ,meteorolites is given to these ponderous fragments4 ,as these meteors1 before they explode and fall to the ground1 have many points of resemblance with the shooting-stars1 they are generally supposed to be connected with them1 and to have a similar cometary origin4 ,the fact that the aerolites differ widely from each other in constitution1 and are all composed of substances found on the ,earth1 associated with other facts given below1 would rather seem to indicate a terrestrial than a celestial origin4 ,if the aerolites belong to the same class of bodies as the falling stars1 differing from them only in size and mass1 it is difficult to see why so very few should fall upon the ,earth during the great meteoric showers1 when thousands of shooting-stars traverse our atmosphere4 ,in ,prof4 ,kirkwood's ,meteoric ,astronomy are given catalogues of all the falls of aerolites and fire-balls which have been observed at the time of the periodic meteoric showers of the #ajth of ,august and the #acth of ,november1 during a period of #bba years for the ,perseids1 or ,august showers1 and of #cah years for the ,leonids1 or ,november showers4 ,during #bba years1 #aj falls of aerolites have been witnessed simultaneously with the fall of the ,perseids2 while during #cah years1 only #d such falls have been recorded as having occurred at the time of the ,leonid shower4 ,if there is any close connection between the shooting-stars and the aerolites1 we should expect to find a maximum in their fall at the time of the great meteoric displays4 ,so far1 no maxima or minima have yet been discovered in the fall of aerolites2 they do not seem1 like meteoric showers1 to be governed by a law of periodicity4 ,a very remarkable peculiarity of the aerolites is that they seem to have a tendency to fall in certain regions4 ,such are the southern part of ,france1 the north of ,italy1 ,hindostan1 the central states of ,north ,america1 and ,mexico and ,brazil4 ,there is a curious contrast existing between the quick cometary motion of the aerolites before their explosion1 and the comparatively slow motion of their fragments as they reach the ,earth2 motion which seems to be no greater than that corresponding to their natural fall impeded by the resistance of the air4 ,in general1 their penetration into the soil upon which they fall does not at all correspond to the great velocity with which they move in the atmosphere4 ,the fragmentary structures of the aerolites1 their identity of substance with that of our globe1 their great resemblance to the volcanic minerals of the ,earth1 and the fractures and faults which some of them exhibit1 do not correspond at all with the idea that they are cometary particles fallen on the ,earth4 ,as far as their structure and appearance is concerned1 they seem rather to be a volcanic product of the interior of the ,earth than parts of disintegrated comets4 ,it must be admitted that their identity with the shooting-stars is far from established1 and that they are still involved in mystery4 ,the so-called meteoric dust gathered at sea and on high mountains may have various origins1 and may be partly furnished by volcanic dust carried to great distances in the atmosphere4 ,since millions of shooting-stars penetrate our atmosphere every year and remain in it1 becoming definitively a part of the ,earth1 it follows that1 no matter how small may be the quantity of matter of which they are composed1 they must gradually increase the volume and mass of our globe1 although the increase may be exceedingly slow4 ,supposing every one of the shooting-stars penetrating our atmosphere to contain one cubic millimeter of matter1 it has been calculated that it would take nearly #ce1jjj years to make a deposit one centimeter in thickness all over the surface of our globe4 ,insignificant as this may appear1 it is probable that the quantity of matter of meteoric origin which is added to our globe is much less than has just been supposed4 ,,the ,,milky-,,way ,,or ,,galaxy ,,plate ,,xiii ,during clear nights1 when the ,moon is below the horizon1 the starry vault is greatly adorned by an immense belt of soft white light1 spanning the heavens from one point of the horizon to the opposite point1 and girdling the celestial sphere in its delicate folds4 ,every one is familiar with this remarkable celestial object1 called the ,milky-way or ,galaxy4 ,seen with the naked eye1 the ,galaxy appears as an irregular1 narrow1 nebulous belt1 apparently composed of cloud-like luminous masses of different forms and sizes1 separated by comparatively dark intervals4 ,these cloud-like masses vary much in luminous intensity1 and while some among them are very bright and conspicuous1 others are so faint that they are hard to recognize4 ,in general1 the brightest parts of the ,milky-way are situated along the middle of its belt1 while its borders1 which are usually very faint1 gradually vanish in the sky4 ,some parts of the ,galaxy1 however1 show very little of the cloudy structure so characteristic of other parts1 being almost uniform throughout1 except towards the borders1 which are always fainter4 ,these parts showing greater uniformity are also the faintest4 ,such is the general appearance of the ,milky-way on ordinary nights1 but on rare occasions1 when the atmosphere is particularly pure1 it presents one of the grandest sights that can be imagined4 ,at such favorable moments ,i have seen the ,galaxy gleaming with light1 and appearing as if composed of star-dust or of precious stones4 ,the strange belt then appeared all mottled over and fleecy1 its large cloud-like masses being subdivided into numerous small1 irregular cloudlets of great brilliancy1 which appeared projected upon a soft luminous background4 ,the width of the ,galaxy is far from being uniform2 while in some places it is only #d or #e1 in others it is #ae and even more4 ,in some places it appears wavy in outline1 at others quite straight2 then it contracts1 to expand a few degrees distant2 while at other places it sends off branches and loops1 varying in form1 size and direction1 some of which are quite prominent1 while others are very faint4 ,although very irregular in form1 the general appearance of the galactic belt is that of a regular curve occupying one of the great circles of the celestial sphere4 ,the ,milky-way completely encircles the heavens1 but1 of course1 only one-half is visible at any one moment1 since our globe prevents the other half from being seen4 ,if1 for a moment1 we imagine ourselves left in space1 our globe having vanished from under our feet1 we should then see the whole ,galaxy forming a continuous belt in the heavens1 at the centre of which we should apparently be situated4 ,while only one-half of the galactic belt can be seen at once from any point on the ,earth1 yet1 according to the position of the observer1 a larger or smaller portion of the whole can be seen at different times4 ,in high northern or southern latitudes but little more than half can be seen even by continuous observations2 but as we approach the equatorial regions1 more and more of it becomes visible1 until the whole may be seen at different hours and seasons4 ,in the latitudes of the northern states1 about two-thirds of the ,galaxy is visible1 the rest remaining hidden below the horizon2 but from the southern states very nearly the whole can be seen4 ,the half of the ,milky-way visible at any one time from any latitude on the ,earth never entirely sets below the horizon1 although in some places it may be so near the horizon as to be rendered invisible by vapors4 ,in the latitude of ,cambridge1 when in its lowest position1 the summit of its arc is still about #ab or #ae above the northern horizon4 ,the great circle of the celestial sphere1 occupied by the galactic belt1 is inclined at an angle of about #fc to the celestial equator1 and intersects this great circle on one side in the constellation ,monoceros in #f;h4 #dgm41 and on the opposite side in the constellations ,aquila and ,ophiuchus in #ah;h4 #dgm4 of right ascension2 so that its northern pole is situated in the constellation ,coma ,berenices in ,r4 ,a4 #ab;h4 #dgm41 declination ,n4 #bg1 and the southern in the constellation ,cetus in ,r4 ,a4 #j;h4 #dgm41 declination ,s4 #bg4 ,according to the seasons and to the hours of the night at which it is observed1 the galactic arch presents different inclinations in the sky4 ,owing to its inclination to the equator of the celestial sphere1 its opposite parts exhibit opposite inclinations when they pass the meridian of a place4 ,that part of the ,galaxy which is represented on ,plate ,,xiii41 and which intersects the celestial equator in the constellation ,aquila1 is inclined to the left or towards the east1 when it is on the meridian2 while the opposite part1 situated in ,monoceros1 is inclined to the right1 or towards the west1 when it reaches the meridian4 ,the former passes the meridian in the evening in the summer and autumn months2 the latter1 in the winter and spring months4 ,,plate ,,xiii4--,,part ,,of ,,the ,,milky ,,way4 ,from a study made during the years #ahgd1 #ahge and #ahgf ,by beginning at its northernmost part1 represented at the upper part of ,plate ,,xiii41 situated in the chair of the constellation ,cassiopeia1 and descending southwardly1 and continuing in the same direction until the whole circle is completed1 the course of the ,milky-way through the constellations may be briefly described as follows3 ,from ,cassiopeia's chair1 the ,galaxy1 forming two streams1 descends south1 passing partly through ,lacerta on the left1 and ,cepheus on the right2 at this last point it approaches nearest to the polar star4 ,then it enters ,cygnus1 where it becomes very complicated and bright1 and where several large cloudy masses are seen terminating its left branch1 which passes to the right1 near the bright star ,deneb1 the leader of this constellation4 ,below ,deneb1 the ,galaxy is apparently disconnected and separated from the northern part by a narrow1 irregular dark gap4 ,from this rupture1 the ,milky-way divides into two great streams separated by an irregular dark rift4 ,an immense branch extends to the right1 which1 after having formed an important luminous mass between the stars and 1 continues its southward progress through parts of ,lyra1 ,vulpecula1 ,hercules1 ,aquila and ,ophiuchus1 where it gradually terminates a few degrees south of the equator4 ,the main stream on the left1 after having formed a bright mass around ,cygni1 passes through ,vulpecula and then ,aquila1 where it crosses the equinoctial just below the star after having involved in its nebulosity the bright star ,altair1 the leader of ,aquila4 ,in the southern hemisphere the ,galaxy becomes very complicated and forms a succession of very bright1 irregular masses1 the upper one being in ,scutum ,sobieskii1 while the others are respectively situated in ,sagittarius and in ,scorpio2 the last1 just a little above our horizon1 being always considerably dimmed by vapors4 ,from ,scutum ,sobieskii1 the ,galaxy expands considerably on the right1 and sends a branch into ,scorpio1 in which the fiery red star ,antares is somewhat involved4 ,continuing its course below our horizon1 the ,milky-way enters ,ara and ,norma1 and then1 passing partly through ,circinus1 ,centaurus and ,musca1 it reaches the ,southern ,cross1 after having been divided by the large dark pear-shaped spot known to navigators as the ,coal-,sack4 ,in ,ara and ,crux the ,milky-way attains its maximum of brightness1 which there surpasses its brightest parts in ,cygnus4 ,in ,musca1 it makes its nearest approach to the south pole of the heavens4 ,it then enters ,carina and ,vela1 where it spreads out like a fan1 and terminates in this last constellation1 before reaching 1 being once more interrupted by a dark and very irregular gap1 on a line with the two stars and 4 ,it is noteworthy that this second rupture of continuity of the ,galaxy in ,vela is very nearly opposite1 or at about #ahj from the break near ,deneb in ,cygnus4 ,continuing its course on the other side of the break1 the ,milky-way again spreads out into the shape of a fan1 grows narrower in entering ,puppis1 where it is longitudinally divided by darkish channels4 ,it then passes above our southern horizon1 becoming visible to us1 passing through part of ,canis ,major1 where its border just grazes the brilliant star ,sirius4 ,but from ,puppis it gradually diminishes in brightness and complication1 becoming faint and uniform4 ,it enters ,monoceros and ,orion1 where it again crosses the equator a little above 1 the northernmost of the three bright stars in the belt of ,orion4 ,continuing its northward course it passes through ,gemini1 extending as far as ,castor and ,pollux1 and then entering ,auriga1 where it begins to increase in brightness and in complication of structure4 ,it passes partly through ,camelopardus and into ,perseus1 where an important branch proceeds from its southern border4 ,this branch beginning near the star 1 advances towards the celebrated variable star ,algol1 around which it is quite bright and complicated4 ,continuing its course in the same direction1 the branch rapidly loses its brightness1 becoming very faint a little below ,algol1 and passing through ,persei1 it enters ,taurus1 leaving the ,pleiades on its extreme southern margin2 and after having passed through where it branches off1 it rapidly curves towards the main stream1 which it joins near ,tauri1 thus forming an immense loop4 ,the ramification projecting near ,tauri involves in its nebulosity the ruddy star ,aldebaran and the scattered group of the ,hyades4 ,it then advances towards the three bright stars 1 and of the belt of ,orion1 which1 together with the sextuple star ,orionis1 are involved in its faint nebulosity1 and joins the main stream on the equinoctial1 having thus formed a second loop1 whose interior part is comparatively free from nebulosity1 and contains the fine stars ,betelgeuse and ,bellatrix4 ,that portion of the main galactic stream which is comprised between the star ,deneb in ,cygnus1 and ,capella in ,auriga1 is divided longitudinally by a very irregular1 narrow1 darkish cleft1 comparatively devoid of nebulosity1 which1 however1 is interrupted at some points4 ,this dark gap sends short branches north and south1 the most important of which are situated near ,cephei and ,cassiopei4 ,another branch runs from beyond of the constellation last mentioned4 ,the main stream of the ,galaxy after leaving ,perseus1 enters ,cassiopeia1 and sending short branches into ,andromeda1 it completes its immense circle in ,cassiopeia's chair1 where this description was begun4 ,when examined through the telescope1 the appearance of the ,milky-way completely changes1 and its nebulous light is resolved into an immense number of stars1 too faint to be individually seen with the naked eye4 ,when ,galileo first directed the telescope to the galactic belt1 its nebulous1 cloud-like masses were at once resolved into stars1 even by the feeble magnifying power of his instrument4 ,when1 much later1 ,sir ,william ,herschel undertook his celebrated star-gaugings of the ,galaxy1 millions of stars blazed out in his powerful telescopes4 ,the stars composing this great nebulous belt are so numerous that it is impossible to arrive at any definite idea as to their number4 ,from his soundings ,herschel estimated at #aaf1jjj the number of stars which1 on one occasion1 passed through the field of his telescope in #ae minutes1 by the simple effect of the diurnal motion of the heavens2 and on another occasion1 a number estimated at #bej1jjj crossed the field in #da minutes4 ,in a space of #ej1 comprised between and ,cygni1 shown on ,plate ,,xiii41 he found no less than #cca1jjj stars4 ,prof4 ,struve has estimated at #bj1ejj1jjj the number of stars seen in the ,milky-way through the twenty-foot telescope employed by ,herschel in his star-gaugings4 ,great as this number may seem1 it is yet far below the truth2 as the great modern telescopes1 according to ,professor ,newcomb1 would very probably double the number of stars seen through ,herschel's largest telescope1 and detect from thirty to fifty millions of stars in the ,milky-way4 ,although the telescope resolves the ,galaxy into millions of stars1 yet the largest instruments fail to penetrate its immense depths4 ,the forty-foot telescope of ,herschel1 and even the giant telescope of ,lord ,rosse1 have failed to resolve the ,milky-way entirely into stars1 the most distant ones appearing in them as nebulosities upon which the nearer stars are seen projected1 the galactic stratum being unfathomable by the largest telescopes yet made4 ,the stars composing the ,milky-way are very unevenly distributed1 as might easily be supposed from the cloud-like appearance of this belt4 ,in some regions they are loosely scattered1 forming long rows or streams of various figures1 while in others they congregate into star groups and clusters having all imaginable forms1 some being compressed into very dense globular masses4 ,the intervals left between the clustering masses are poorer in stars1 and indeed some of them are even totally devoid of stars or nebulosity4 ,such are the great and small coal-sacks in the southern ,galaxy4 ,i have myself detected such a dark space devoid of stars and nebulosity in one of the brightest parts of the ,milky-way1 in the constellation ,sagittarius1 in about #ag;h4 #dem4 right ascension1 and #bg #ce' south declination4 ,it is a small miniature coal-sack or opening in the ,galaxy1 through which the sight penetrates beyond this great assemblage of stars4 ,close to this1 is another narrow opening near a small1 loose cluster4 ,although lacking the optical resources which now enable us to recognize the structure of the ,milky-way1 some of the ancient philosophers had succeeded tolerably well in their speculations regarding its nature4 ,it was the opinion of ,democritus1 ,pythagoras and ,manilius1 that the ,galaxy was nothing else but a vast and confused assemblage of stars1 whose faint light was the true cause of its milky appearance4 ,before the invention of the telescope1 no well-founded theory in regard to the structure of the ,milky-way could1 of course1 be attempted4 ,although ,kepler entertained different ideas in regard to the structure of this great belt from those now generally admitted1 yet in them may be found the starting point of the modern conception of the structure of the ,galaxy and of the visible universe4 ,in the view of this great mind1 the ,milky-way1 with all its stars1 formed a vast system1 the centre of which1 and of the universe1 was occupied by our ,sun4 ,kepler reasoned that the place of the ,sun must be near the centre of the galactic belt1 from the fact this last object appears very nearly as a great circle of the celestial sphere1 and that its luminous intensity is about the same in all its parts4 ,half a century later1 another attempt to explain the ,milky-way was made by ,wright1 of ,durham1 who rejected the idea of an accidental and confused distribution of the stars as inconsistent with the appearance of the ,galaxy1 and regarded them as arranged along a fundamental plane corresponding to that of the ,milky-way4 ,these ideas which were subsequently developed and enlarged by ,kant1 and then by ,lambert1 constitute what is now known as ,kant's theory4 ,according to this theory1 the stars composing the ,galaxy are conceived as being uniformly arranged between two flat planes of considerable extension1 but which are comparatively near together1 the ,sun occupying a place not very far from the centre of this immense starry stratum4 ,as we view this system crosswise through its thinnest parts1 the stars composing it appear scattered and comparatively few in number1 but when we view it lengthwiser through its most extended parts1 they appear condensed and extremely numerous1 thus giving the impression of a luminous belt encircling the heavens4 ,in the conception of ,kant1 each star was a sun1 forming the centre of a planetary system4 ,these systems are not independent1 but are kept together by the bonds of universal gravitation4 ,the ,galaxy itself is one of these great systems1 its principal plane being the equivalent of the zodiac in our planetary system1 while a preponderant body1 which might be ,sirius1 is the equivalent of our ,sun1 and keeps the galactic system together4 ,in the universe there are other galaxies1 but as they are too distant to be resolved into stars1 they appear as elliptical nebul4 ,such are1 in brief1 the grand speculations of ,kant and ,lambert on the ,milky-way1 and the structure of the universe4 ,kant's theory rested more on conjectures than on observed facts1 and needed therefore the sanction of direct observations to be established on a firm basis4 ,with this view1 ,sir ,william ,herschel investigated the subject1 by a long and laborious series of observations4 ,his plan1 which was that of star-gauging1 consisted in counting all the stars visible in his twenty-foot telescope1 comprised in a wide belt cutting the ,galaxy at right angles1 and extending from one of its sides to the opposite one1 thus embracing #ahj of the celestial sphere4 ,in this belt he executed #c1djj telescopic star-gaugings of a quarter of a degree each1 from which he obtained #fhc mean gaugings giving the stellar density of the corresponding regions4 ,the general result derived from this immense labor was that the stars are fewest in regions the most distant from the galactic belt2 while from these regions1 which correspond to the pole of the ,galaxy1 they gradually increase in number in approaching the ,milky-way4 ,the star density was found to be extremely variable1 and while some of the telescopic gaugings detected either no star at all1 or only one or two1 other gaugings gave #ejj stars and even more4 ,the average number of stars in a field of view of his telescope1 obtained for the six zones1 each of #ae1 into which ,herschel divided up the portion of his observing belt1 extending from the ,galaxy to its pole1 is as follows3 ,in the first zone1 commencing at #ij from the galactic belt and extending towards it1 #d stars per telescopic field were found2 #e in the second2 #h in the third2 #ad in the fourth2 #bd in the fifth and #ec in the sixth1 which terminated in the ,galaxy itself4 ,very nearly similar results were afterwards found by ,sir ,john ,herschel1 for corresponding regions in the southern hemisphere4 ,from these studies1 ,herschel concluded that the stellar system is of the general form supposed by the ,kantian theory1 and that its diameter must be five times as extended in the direction of the galactic plane1 as it is in a direction perpendicular to it4 ,to explain the great branch sent out by the ,galaxy in ,cygnus1 he supposed a great cleft dividing the system edgewise1 about half way from its circumference to its centre4 ,from suppositions founded on the apparent magnitude and arrangement of stars1 he estimated that it would take light about #g1jjj years to reach us from the extremities of the ,galaxy1 and therefore #ad1jjj years to travel across the system1 from one border to the opposite one4 ,but ,herschel's theory concerning the ,milky-way rested on the erroneous assumption that the stars are uniformly distributed in space1 and also that his telescopes penetrated through the entire depth of the ,galaxy4 ,further study showed him that his telescope of twenty feet1 and even his great forty-foot telescope1 which was estimated to penetrate to a distance #b1cjj times that of stars of the first magnitude1 failed to resolve some parts of the ,galaxy into stars4 ,meanwhile1 the structure of the ,milky-way being better known1 the irregular condensation of its stars became apparent1 while the mutual relation existing between binary and multiple systems of stars1 as also between the stars which form clusters1 was recognized1 as showing evidence of closer association between certain groups of stars than between the stars in general4 ,herschel's system1 which rested on the assumption of the uniform distribution of the stars in space1 and on the supposition that the telescopes used for his gauges penetrated through the greater depths of the ,galaxy1 being thus found to contradict the facts1 was gradually abandoned by its author1 who adopted another method of estimating the relative distances of the stars observed in his gaugings4 ,this method1 founded on photometric principles1 consisted in judging the penetrating power of his telescope by the brightness of the stars1 and not1 as formerly1 by the number which they brought into view4 ,he then studied by this new method the structure of the ,milky-way and the probable distance of the clustering masses of which it is formed1 concluding that the portion of the ,galaxy traversing the constellation ,orion is the nearest to us4 ,this last result seems indicated by the fact that this portion of the ,milky-way is the faintest and the most uniform of all the galactic belt4 ,more recently ,otto ,struve investigated the same subject1 and arrived at very nearly similar conclusions1 which may be briefly stated as follows3 ,the galactic system is composed of a countless number of stars1 spreading out on all sides along a very extended plane4 ,these stars1 which are very unevenly distributed1 show a decided tendency to cluster together into individual groups of different sizes and forms1 separated by comparatively vacant spaces4 ,this layer where the stars congregate in such vast numbers may be conceived as a very irregular flat disk1 sending many branches in various directions1 and having a diameter eight or ten times its thickness4 ,the size of this starry disk cannot be determined1 since it is unfathomable in some directions1 even when examined with the largest telescopes4 ,the ,sun1 with its attending planets1 is involved in this immense congregation of suns1 of which it forms but a small particle1 occupying a position at some distance from the principal plane of the ,galaxy4 ,according to ,struve1 this distance is approximately equal to #bjh1jjj times the radius of the ,earth's orbit4 ,the ,milky-way is mainly composed of star-clusters1 two-thirds1 perhaps1 of the whole number visible in the heavens being involved in this great belt4 ,in conclusion1 our ,sun is only one of the individual stars which constitute the galactic system1 and each of these stars itself is a sun similar to our ,sun4 ,these individual suns are not independent1 but are associated in groups varying in number from a few to several thousands1 the ,galaxy itself being nothing but an immense aggregation of such clusters1 whose whole number of individual suns probably ranges between thirty and fifty millions4 ,in this vast system our globe is so insignificant that it cannot even be regarded as one of its members4 ,according to ,dr4 ,gould1 there are reasons to believe that our ,sun is a member of a small1 flattened1 bifid cluster1 composed of more than #djj stars1 ranging between the first and seventh magnitude1 its position in this small system being eccentric1 but not very far from the galactic plane4 ,the study of the ,milky-way1 of which ,plate ,,xiii4 is only a part1 was undertaken to answer a friendly appeal made by ,mr4 ,a4 ,marth1 in the ,monthly ,notices of the ,royal ,astronomical ,society1 in #ahgb4 ,i take pleasure in offering him my thanks for the suggestion1 and for the facility afforded me in this study by his ,list of ,co-ordinates of ,stars within and near the ,milky-way1 which was published with it4 ,,the ,,star-,,clusters ,,plate ,,xiv ,it is a well-known fact that the stars visible to the naked eye are very unequally distributed in the heavens1 and that while they are loosely scattered in some regions1 in others they are comparatively numerous1 sometimes forming groups in which they appear quite close together4 ,in our northern sky are found a few such agglomerations of stars1 which are familiar objects to all observers of celestial objects4 ,in the constellation ,coma ,berenices1 the stars are small1 but quite condensed1 and form a loosely scattered1 faint group4 ,in ,taurus1 the ,hyades and the ,pleiades1 visible during our winter nights1 are conspicuous and familiar objects which cannot fail to be recognized4 ,in the last group1 six stars may be easily detected by ordinary eyes on any clear night1 but more can sometimes be seen2 on rare occasions1 when the sky was especially favorable1 ,i have detected eleven clearly and suspected several others4 ,the six stars ordinarily visible1 are in order of decreasing brightness1 as follows3 ,alcyone1 ,electra1 ,atlas1 ,maia1 ,taygeta and ,merope4 ,glimpses of ,celano and ,pleione are sometimes obtained4 ,when the sky is examined with some attention on any clear1 moonless night1 small1 hazy1 luminous patches1 having a cometary aspect1 are visible here and there to the naked eye4 ,in the constellation ,cancer is found one of the most conspicuous1 called ,prsepe1 which forms a small triangle with the two stars and 4 ,in ,perseus1 and involved in the ,milky-way1 is found another luminous cloud1 situated in the sword-handle1 and almost in a line with the two stars and of ,cassiopeia's ,chair4 ,in the constellation ,hercules1 another nebulous mass of light1 but fainter1 is also visible between the stars and where it appears as a faint comet1 in the depths of space4 ,in ,ophiuchus and ,monoceros are likewise found hazy1 luminous patches4 ,in the southern sky1 several such objects are also visible to the naked eye1 being found in ,sagittarius1 in ,canis ,major and in ,puppis2 but the most conspicuous are those in ,centaurus and ,toucan4 ,that in ,centaurus involves the star in its pale diffused nebulosity1 and that in ,toucan is involved in the lesser ,magellanic cloud4 ,when the telescope is directed to these nebulous objects1 their hazy1 ill-defined aspect disappears1 and they are found to consist of individual stars of different magnitudes1 which being more or less closely grouped together1 apparently form a system of their own4 ,these groups1 which are so well adapted to give us an insight into the structure and the vastness of the stellar universe1 are called ,star-clusters4 ,star-clusters are found of all degrees of aggregation1 and while in some of them1 such as in the ,pleiades1 in ,prsepe and in ,perseus1 the stars are so loosely scattered that an opera glass1 and even the naked eye1 will resolve them2 in others1 such as in those situated in ,hercules1 ,aquarius1 ,toucan and ,centaurus1 they are so greatly compressed that even in the largest telescopes they appear as a confused mass of blazing dust1 in which comparatively few individual stars can be distinctly recognized4 ,although only about a dozen ,star-clusters can be seen in the sky with the naked eye1 yet nearly eleven hundred such objects visible through the telescope1 have been catalogued by astronomers4 ,the stars composing the different clusters visible in the heavens vary greatly in number1 and while in some clusters there are only a few1 in others they are so numerous and crowded that it would be idle to try to count them1 their number amounting to several thousands4 ,it has been calculated by ,herschel that some clusters are so closely condensed1 that in an area not more than part of that covered by the ,moon1 at least #e1jjj stars are agglomerated4 ,when the group in the ,pleiades is seen through the telescope it appears more important than it does to the naked eye1 and several hundreds of stars are found in it4 ,in a study of ,tempel's nebula1 which is involved in the ,pleiades1 ,i have mapped out #bej stars1 mostly comprised within this nebula1 with the telescope of #f inches aperture1 which ,i have used for this study4 ,as a type of a loose1 coarse cluster1 that in ,perseus is one of the finest of its class4 ,it appears to the naked eye as a single object1 but in the telescope it has two centres of condensation1 around which cluster a great number of bright stars1 forming various curves and festoons of great beauty4 ,among its components are found several yellow and red stars1 which give a most beautiful contrast of colors in this gorgeous and sparkling region4 ,in a study which ,i have made of this twin cluster1 ,i have mapped out #ffd stars belonging to it1 among which are two yellow and five red stars4 ,while some clusters1 like those just described1 are very easily resolvable into stars with the smallest instruments1 others yield with the greatest difficulty1 even to the largest telescopes1 in which their starry nature is barely suspected4 ,owing to this peculiarity1 star-clusters are usually divided into two principal classes4 ,in the first class are comprised all the clusters which have been plainly resolved into stars1 and in the second all those which1 although not plainly resolvable with the largest instruments now at our disposal1 show a decided tendency to resolvability1 and convey the impression that an increase of power in telescopes is the only thing needed to resolve them into stars4 ,of course this classification1 which depends on the power of telescopes to decide the nature of these objects1 is arbitrary1 and a classification based on spectrum analysis is now substituted for it4 ,the star-clusters are also divided into globular and irregular clusters1 according to their general form and appearance4 ,the globular clusters1 which are the most numerous1 are usually well-defined objects1 more or less circular in their general outlines4 ,the rapid increase of brightness towards their centres1 where the stars composing them are greatly condensed1 readily conveys the impression that the general form of these sparkling masses is globular4 ,the irregular clusters are not so rich in stars as the former4 ,usually their stars are less condensed towards the centre1 and are1 for the most part1 so loosely and irregularly distributed1 that it is impossible to recognize the outlines of these clusters or to decide where they terminate4 ,the globular clusters are usually quite easily resolvable into stars1 either partly or wholly1 although some among them do not show the least traces of resolvability1 even in the largest instruments4 ,this may result from different causes1 and may be attributed either to the minuteness of their components or to their great distance from the ,earth1 many star-clusters being at such immense distances that they are beyond our means of measurement4 ,as has been shown in the preceding section1 the star-clusters are found in great number in the ,galaxy2 indeed1 it is in this region and in its vicinity that the greater portion of them are found4 ,in other regions1 with the exception of the ,magellanic clouds1 where they are found in great number and in every stage of resolution1 the clusters are few and scattered4 ,,plate ,,xiv4--,,star-,,cluster ,,in ,,hercules4 ,from a study made in ,june1 #ahgg ,the star-cluster in the constellation ,hercules1 designated as ,no4 #d1bcj in ,sir ,j4 ,herschel's catalogue1 and which is represented on ,plate ,,xiv41 is one of the brightest and most condensed in the northern hemisphere1 although it is not so extended as several others1 its angular diameter being only #g' or #h'4 ,this object1 which was discovered by ,halley in #agad1 is one of the most beautiful of its class in the heavens4 ,according to ,herschel1 it is composed of thousands of stars between the tenth and fifteenth magnitudes4 ,undoubtedly the stars composing this group are very numerous1 although those which can be distinctly seen as individual stars1 and whose position can be determined1 are not so many as a superficial look at the object would lead us to suppose4 ,from a long study of this cluster1 which ,i have made with instruments of various apertures1 ,i have not been able to identify more stars than are represented on the plate1 although the nebulosity of which this object mainly consists1 and especially the region situated towards its centre1 appeared at times granular and blazing with countless points of light1 too faint and too flickering to be individually recognized4 ,towards its centre there is quite an extended region1 whose luminous intensity is very great1 and which irresistibly conveys the impression of the globular structure of this cluster4 ,besides several outlying appendages1 formed by its nebulosity1 the larger stars recognized in this cluster are scattered and distributed in such a way that they form various branches1 corresponding with those formed by the irresolvable nebulosity4 ,at least six or seven of these branches and wings are recognized1 some of which are curved and bent in various ways1 thus giving this object a distant resemblance to some crustacean forms4 ,although ,i have looked for it with care1 ,i have failed to recognize the spiral structure attributed to this object by several observers4 ,among the six appendages which ,i have recognized1 some are slightly curved2 but their curves are sometimes in opposite directions1 and two branches of the upper portion make so short a bend that they resemble a claw rather than a spiral wing4 ,the spectrum of this cluster1 like that of many objects of its class1 is continuous1 with the red end deficient4 ,a little to the north-east of this object is found the cluster ,no4 #d1bid1 which1 although smaller and less bright than the preceding1 is still quite interesting4 ,it appears as a distinctly globular cluster without wings1 and much condensed towards its centre4 ,the stars individually recognized in it1 although less bright than those of the other cluster1 are so very curiously distributed in curved lines that they give a peculiar appearance to this condensed region4 ,a little to the north of ,centauri may be found the great ,centauri cluster1 ,no4 #c1eca1 already referred to above4 ,this magnificent object1 which appears as a blazing globe #bj' in diameter1 is1 according to ,herschel1 the richest in the sky1 and is resolved into a countless number of stars from the twelfth to the fifteenth magnitude1 which are greatly compressed towards the centre4 ,the larger stars are so arranged as to form a sort of net-work1 with two dark spaces in the middle4 ,the great globular cluster ,no4 #eb1 involved in the lesser ,magellanic cloud1 in the constellation ,toucan1 is a beautiful and remarkable object4 ,it is composed of three distinct1 concentric layers of stars1 varying in brightness and in degree of condensation in each layer4 ,the central mass1 which is the largest and most brilliant1 is composed of an immense number of stars greatly compressed1 whose reddish color gives to this blazing circle a splendid appearance4 ,around the sparkling centre is a broad circle1 composed of less compressed stars1 this circle being itself involved in another circular layer1 where the stars are fainter and more scattered and gradually fade away4 ,many other great globular clusters are found in various parts of the heavens1 among which may be mentioned the cluster ,no4 #d1fgh1 in ,aquarius4 ,this object is composed of several thousand stars of the fifteenth magnitude1 greatly condensed towards the centre1 and1 as remarked by ,sir ,j4 ,herschel1 since the brightness of this cluster does not exceed that of a star of the sixth magnitude1 it follows that in this case several thousand stars of the fifteenth magnitude equal only a star of the sixth magnitude4 ,in the constellation ,serpens the globular clusters ,no4 #d1jhc and ,no4 #d1aah are both conspicuous objects1 also ,no4 #d1fhg in ,capricornus4 ,in ,scutum ,sobieskii the cluster ,no4 #d1dcg is one of the most remarkable of this region4 ,the stars composing it1 which are quite large and easily made out separately1 form various figures1 in which the square predominates4 ,among the loose irregular clusters1 some are very remarkable for the curious arrangement of their stars4 ,in the constellation ,gemini the cluster ,no4 #a1cfj1 which is visible to the naked eye1 is a magnificent object seen through the telescope1 in which its sparkling stars form curves and festoons of great elegance4 ,the cluster ,no4 #a1dfg1 of the same constellation1 is remarkable for its triangular form4 ,in the constellation ,ara the cluster ,no4 #d1bcc1 composed of loosely scattered stars1 forming various lines and curves1 is enclosed on three sides by nearly straight single lines of stars4 ,in ,scorpio the cluster ,no4 #d1bbd is still more curious1 being composed of a continuous ring of loosely scattered stars1 inside of which is a round1 loose cluster1 which is divided into four parts by a dark cross-shaped gap1 in which no stars are visible4 ,among the #a1jcd objects which are now classified as clusters more or less resolvable1 #efe have been absolutely resolved into stars1 and #dfi have been only partly resolved1 but are considered as belonging to this class of objects4 ,in ,sir ,j4 ,herschel's catalogue there are #ajb clusters which are ,considered as being globular2 among them #cj have been positively resolved into stars4 ,the agglomeration of thousands of stars into a globular cluster cannot be conceived1 of course1 to be simply the result of chance4 ,this globular form seems clearly to indicate the existence of some bond of union1 some general attractive force acting between the different members of these systems1 which keeps them together1 and condenses them towards the centre4 ,herschel regards the loose1 irregular clusters as systems in a less advanced stage of condensation1 but gradually concentrating by their mutual attraction into the globular form4 ,although the stars of some globular clusters appear very close together1 they are not necessarily so1 and may be separated by great intervals of space4 ,it has been shown that the clusters are agglomeration of suns1 and that our ,sun itself is a member of a cluster composed of several hundreds of suns1 although1 from our point of observation1 these do not seem very close together4 ,so far as known1 the nearest star to us is a ,centauri1 but its distance from the ,earth equals #bba1jjj times the distance of the ,sun from our globe1 a distance which cannot be traversed by light in less than three years and five months4 ,it seems very probable that if the suns composing the globular clusters appear so near together1 it is because1 in the first place1 they are at immense distances from us1 and in the second1 because they appear nearly in a line with other suns1 which are at a still greater distance from us1 and on which they accordingly are nearly projected4 ,if one should imagine himself placed at the centre of the cluster in ,hercules1 for instance1 the stars1 which from our ,earth seems to be so closely grouped1 would then quite likely appear very loosely scattered around him in the sky1 and would resemble the fixed stars as seen from our terrestrial station4 ,judging by their loose and irregular distribution1 the easily resolvable clusters would appear1 in general1 to be the nearer to us4 ,it is probable that the globular clusters do not possess1 to a very great degree1 the regular form which they ordinarily present to us4 ,it seems rather more natural to infer that they are irregular1 and composed of many wings and branches1 such as are observed in the cluster in ,hercules2 but as these appendages would necessarily be much poorer in stars than the central portions1 they would be likely to become invisible at a great distance1 and therefore the object would appear more or less globular2 the globular form being simply given by the close grouping of the stars in the central portion4 ,it would seem1 then1 that in general1 the most loosely scattered and irregular clusters are the nearest to us1 while the smallest globular clusters and those resolvable with most difficulty are the most distant4 ,in accordance with the theory that the clusters are composed of stars1 the spectrum of these objects is in general continuous2 although1 in many cases1 the red end of the spectrum is either very faint or altogether wanting4 ,many objects presenting in a very high degree the principal characteristics exhibited by the true star-clusters1 namely1 a circular or oval mass1 whose luminous intensity is greatly condensed toward the centre1 have not yielded1 however1 to the resolving power of the largest telescopes1 although their continuous spectrum is in close agreement with their general resemblance to the star-clusters4 ,although such objects may remain irresolvable forever1 yet it is highly probable that they do not materially differ from the resolvable and partly resolvable clusters1 except by their enormous distance from us1 which probably reaches the extreme boundary of our visible universe4 ,,the ,,nebul ,,plate ,,xv ,besides the foggy1 luminous patches which have just been described1 a few hazy spots of a different kind are also visible to the naked eye on any clear1 moonless night4 ,these objects mainly differ from the former in this particular1 that when viewed through the largest telescopes in existence they are not resolved into stars1 but still retain the same cloudy appearance which they present to the unassisted eye4 ,on account of the misty and vaporous appearance which they exhibit1 these objects have been called ,nebul4 ,of the #bf nebulous objects visible to the naked eye in the whole heavens1 #ai belong to the class of star-clusters1 and #g to the class of nebul4 ,among the most conspicuous nebul visible to the unassisted eye1 are those in the constellations ,argo ,navis1 ,andromeda and ,orion4 ,besides the seven nebul visible to the naked eye1 a great number of similar objects are visible through the telescope4 ,in ,sir ,john ,herschel's catalogue of nebul and clusters1 are found #d1jec irresolvable nebul1 and with every increase of the aperture of telescopes1 new nebul1 invisible in smaller instruments1 are found4 ,notwithstanding their irresolvability it is probable1 however1 that many among them have a stellar structure1 which their immense distance prevents us from recognizing1 and are not therefore true nebul4 ,the giant telescope of ,lord ,rosse has shown nebul so remote that it has been estimated that it takes their light #cj million years to reach the ,earth4 ,the nebul are very far from being uniformly distributed in space4 ,in some regions they are rare1 while in others they are numerous and crowded together1 forming many small1 irregular groups1 differing in size and in richness of aggregation4 ,the grouping of the nebul does not occur at random in any part of the heavens1 as might naturally be supposed1 but1 on the contrary1 it is chiefly confined to certain regions4 ,outside of these regions nebul are rare and are separated from each other by immense intervals2 so that these isolated objects appear as if they were lost wanderers from the great nebulous systems4 ,the regions where the nebul congregate in great number are very extensive1 and in a general view there are two vast systems of nebular agglomeration1 occupying almost opposite points of the heavens1 whose centres are not very distant from the poles of the ,milky-way4 ,in the northern hemisphere1 the nebulous system is much richer and more condensed than in the southern hemisphere4 ,the northern nebul are principally contained in the constellations ,ursa ,minor and ,major1 in ,draco1 ,canes ,venatici1 ,bootes1 ,leo ,major and ,minor1 ,coma ,berenices1 and ,virgo4 ,in this region1 which occupies about of the whole surface of the heavens1 of the known nebul are assembled4 ,the southern nebul are more evenly distributed and less numerous1 with the exception of two comparatively small1 but very remarkable centres of condensation which1 together with many star-clusters1 constitute the ,magellanic clouds4 ,these two vast nebular groups are by no means regular in outline1 and send various branches toward each other4 ,they are separated by a wide and very irregular belt1 comparatively free from nebul1 which encircles the celestial sphere1 and whose medial line approximately coincides with that of the galactic belt4 ,the ,milky-way1 so rich in star-clusters1 is very barren in nebul2 but it is a very remarkable fact1 nevertheless1 that almost all the brightest1 largest1 and most complicated nebul of the heavens are situated either within it1 or in its immediate vicinity4 ,such are the great nebul in ,orion and ,andromeda2 the nebula of ,orionis2 the ,ring nebula in ,lyra2 the bifurcate nebula in ,cygnus2 the ,dumb-bell nebula in ,vulpecula2 the ,fan1 ,horse-shoe1 ,trifid and ,winged nebul in ,sagittarius2 the great nebula around ,argus ,navis1 and the ,crab nebula in ,taurus4 ,aside from the discovery of some of the largest nebul by different observers1 and their subsequent arrangement in catalogues by ,lacaille and ,messier1 very little had been done towards the study of these objects before #aggi1 when ,sir ,w4 ,herschel began to observe them with the earnestness of purpose which was one of the distinctive points of the character of this great man4 ,he successively published three catalogues in #aghf1 #aghi1 and #ahjb1 in which the position of #b1ejj nebulous objects was given4 ,this number was more than doubled before #ahfd1 when ,sir ,john ,herschel published his catalogue of #e1jgi nebul and star-clusters4 ,to this long list must be added several hundred similar objects1 since discovered by ,d',arrest1 ,stephan1 ,gould and others4 ,but1 as has been shown above1 among the so-called nebul are many star-clusters which do not properly belong to the same class of objects1 it being sometimes impossible in the present state of our knowledge to know whether a nebulous object belongs to one class or to the other4 ,the nebul exhibit a great variety of forms and appearances1 and1 in accordance with their most typical characters1 they are usually divided into several classes1 which are3 the ,nebulous stars1 the ,circular1 or ,planetary1 the ,elliptical1 the ,annular1 the ,spiral and ,irregular nebul4 ,,plate ,,xv4--,,the ,,great ,,nebula ,,in ,,orion4 ,from a study made in the years #ahge-gf ,the so-called nebulous stars consist of a faint nebulosity1 usually circular1 surrounding a bright and sharp star1 which generally occupies its centre4 ,the nebulosity surrounding these stars varies in brightness as well as in extent1 and while1 in general1 its light gradually fades away1 it sometimes terminates quite suddenly4 ,such nebulosities are usually brighter and more condensed towards the central star4 ,the stars thus surrounded do not seem1 however1 to be distinguished from others by any additional peculiarity4 ,some nebul of this kind are round1 with one star in the centre2 others are oval and have two stars1 one at each of their foci4 ,the nebulous star1 ,orionis1 represented at the upper part of ,plate ,,xv41 above the great nebula1 has a bright star at its centre and two smaller ones on the side4 ,the association of double stars with nebul is very remarkable1 and may in some cases indicate a mutual relation between them4 ,the so-called planetary nebul derive their name from their likeness to the planets1 which they resemble in a more or less equable distribution of light and in their round or slightly oval form4 ,while some of them have edges comparatively sharp and well defined1 the outlines of others are more hazy and diffused4 ,these nebul1 which are frequently of a bluish tint1 are comparatively rare objects1 and most of those known belong to the southern hemisphere4 ,when seen through large telescopes1 however1 they present a different aspect1 and their apparent uniformity changes4 ,the largest of these objects1 ,no4 #b1cdc of the ,general ,catalogue1 is situated in the ,great ,bear1 close to the star 4 ,its apparent diameter is1 according to ,sir ,j4 ,herschel1 #b'1 #dj1 and its light is equable1 except at the edge1 where it is a little hazy4 ,in a study which ,i made of this object in #ahgf1 with a refractor #f inches in aperture1 ,i found it decidedly brighter on the preceding side1 where the brightest part is crescent shaped4 ,in ,lord ,rosse's telescope its disk is transformed into a luminous ring with a fringed border1 and two small star-like condensations are found within4 ,another planetary nebula1 near ,andromed1 has also shown an annular structure in ,rosse's telescope4 ,the elliptical nebul1 as their name implies1 are elongated1 elliptical objects2 but while some of them are only slightly elongated ovals1 others form ellipses whose eccentricity is so great that they appear almost linear4 ,in all these objects the light is more or less condensed towards the centre2 but while in some of them the condensation is gradual and slight1 in others it is so great and sudden that the centre of the nebula appears as a large diffused star1 somewhat resembling the nucleus of a comet4 ,from the general appearance of these objects1 it is not unlikely that some of them are either flattish1 nebulous disks1 like the planetary nebul1 or nebulous rings1 seen more or less sidewise4 ,the condensation of light at their centres does not appear to be stellar1 but nebulous like the rest1 and it is a remarkable fact that very few1 if any1 of these objects are resolvable into stars4 ,several elliptical nebul are remarkable for having a star at or near each of their foci1 or at each of their extremities4 ,such are the elliptical nebul in ,draco1 ,centaurus1 and ,sagittarius1 ,nos4 #d1dai1 #c1gjf and #d1cie of the ,general ,catalogue1 the last of which is in the vicinity of the triple star ,sagitarii4 ,each of these nebul has a star at each of its foci1 while ,no4 #a1 in ,cetus1 has a star at each of its extremities4 ,among the most remarkable elliptic nebul may be mentioned ,nos4 #a1hfa and #b1cgc of ,sir ,j4 ,herschel's catalogue1 both situated in the constellation ,leo4 ,the first is one of ,lord ,rosse's spiral nebul1 and the last1 which is a very elongated object1 is formed of concentric oval rings1 which are especially visible towards its central part4 ,the constellation ,draco is particularly remarkable for the number of elliptical nebul found within its boundaries4 ,among them are ,nos4 #c1ici1 #d1jeh1 #d1jfd1 #d1jhg1 #d1dae1 etc41 which are quite remarkable objects of their class4 ,no4 #d1jeh1 of which ,i have made a study1 is bright1 and has a decided lenticular form with a condensation in the centre4 ,its following edge is better defined than the preceding4 ,in ,lord ,rosse's telescope this object exhibits a narrow1 dark1 longitudinal1 gap in its interior4 ,by far the largest and the finest object of this class is the great nebula in ,andromeda4 ,although this object belongs rather to the class of irregular nebul1 yet it is generally considered as an elliptic nebula1 since its complicated structure1 being less prominent1 was not recognized until #ahdh1 when it was perceived by ,george ,p4 ,bond1 ,director of the ,harvard ,college ,observatory4 ,this1 the first nebula discovered1 was found in #afab by ,simon ,marius4 ,it is situated in the constellation ,andromeda1 in the vicinity of the star 1 and almost in a line with the stars and of the same constellation4 ,it is visible to the naked eye1 and appears as a faint comet-like object4 ,it is represented at the upper left hand corner of ,plate ,,xiii41 on the border of the ,milky-way1 as it appears to the naked eye4 ,the nebula in ,andromeda is one of the brightest in the heavens1 and is closely attended by two smaller nebul4 ,perhaps it would be rather more correct to say that it has three centres of condensation1 as the two small nebul referred to are entirely involved in the same faint and extensive nebulosity4 ,its general form is that of an irregular oval1 upwards of one degree in breadth and two and a half degrees in length4 ,its brightest and most prominent part1 which alone was seen by the earlier observers1 consists in a very elongated lenticular mass1 which gradually condenses towards its centre into a blazing1 star-like nucleus1 surrounded by a brilliant nebulous mass4 ,at a little distance to the south of this central condensation is found one of the lesser centres of condensation noted above1 which is globular in appearance1 with a bright1 star-like nucleus like the former4 ,the other centre of condensation is found to the north-west of the centre of the principal mass1 and is quite elongated1 with a centre of condensation towards its southern extremity1 but it is not so bright as the others4 ,close to the western edge of the bright lenticular mass first described1 and making a very slight angle with its longer axis1 are found two narrow and nearly rectilinear dark rifts1 running almost parallel to each other1 and both terminating in a slender point in the south4 ,these dark rifts1 which are almost totally devoid of nebulous matter1 are quite rare in nebul1 and afford a good opportunity to watch the changes which this part of the nebul may undergo4 ,this nebula has never been positively resolved into stars1 although ,prof4 ,geo4 ,bond and others have strongly suspected its resolvability4 ,in a study which ,i have made of it1 with the same instrument employed by ,bond1 and also with the great ,washington telescope1 ,i detected a decided mottled appearance in several places1 which might be attributable to a beginning of resolvability2 but ,i do not consider this a conclusive indication that the nebula is resolvable4 ,the continuous spectrum given by this nebula1 showing that it is not in the gaseous state which its appearance seems to indicate1 warrants the conclusion1 however1 that it will ultimately be found to be resolvable4 ,this object1 being situated on the edge of the ,galaxy and involved in its diffused light1 has a great number of small stars belonging to this belt projected upon it4 ,during my observations ,i have mapped out #a1cbc of these stars1 none of which seems to be in physical connection with the nebula4 ,among the circular and elliptical nebul a few exhibit a very remarkable structure1 being apparently perforated1 and forming either round1 slightly oval1 or elongated rings of great beauty4 ,these ,annular nebul are among the rarest objects in the heavens4 ,in ,scorpio1 two such nebul are found involved in the ,milky-way1 and also one in ,cygnus4 ,one of those in ,scorpio has two stars involved within its ring1 at the extremities of its smallest interior diameter4 ,a very elongated nebula in the vicinity of the fine triple star ,andromed is also annular1 and has two stars symmetrically placed at the extremities of its greatest interior axis4 ,another elongated annular nebula is also found north of ,pegasi4 ,the grandest and most remarkable of the annular nebul is found in the constellation ,lyra1 about midway between the two stars and 4 ,it is slightly elliptical in form1 and according to ,prof4 ,e4 ,s4 ,holden1 its major axis is #gg4c and the minor #eh4 ,from a study and several drawings which ,i have made of this object1 with instruments of various apertures1 ,i have found it decidedly brighter towards its outer border1 at the extremities of its minor axis1 than at the ends of the major axis4 ,on very favorable occasions1 some of its brightest parts have appeared decidedly1 but very faintly mottled1 and ,i have recognized three small centres of condensation4 ,its interior1 in which ,professor ,holden has detected a very faint star1 is quite strongly nebulous4 ,in ,lord ,rosse's telescope1 this nebula is completely surrounded by wisps and appendages of all sorts of forms1 which ,i have failed to trace1 however1 both with the refractor of the ,harvard ,college ,observatory and with that of the ,naval ,observatory at ,washington2 ,rosse1 ,secchi and ,chacornac1 have seen this nebula glittering as if it were a heap of star dust1 although its spectrum indicates that it is gaseous4 ,the nebula ,no4 #a1eda1 in ,camelopardus1 of which ,i have also made a study and a drawing1 is closely allied to the class of annular nebul4 ,this object1 which is quite bright1 has a remarkable appearance4 ,it consists principally of somewhat more than half of an oval ring1 surrounding a bright1 nebulous mass which condenses around a star2 this mass being separated from the imperfect ring by a dark interval4 ,upon the bright portion of the ring1 and on opposite points1 are found two bright stars1 between which lies the star occupying the central mass4 ,the central mass extends at some distance outside of the ring on its open side4 ,several stars are involved in this object4 ,the ,spiral nebul are very curious and complicated objects1 but they are visible only in the largest telescopes4 ,prominent above all is the double spiral nebula ,no4 #c1egb1 in ,canes ,venatici1 which is not far from ,ursa ,majoris4 ,in ,lord ,rosse's telescope1 this object presents a wonderful spiral disposition1 looking somewhat like one of the fire-works called pin-wheels1 and forming long1 curved wisps1 diverging from two bright centres4 ,the spectrum of this object1 however1 is not that of a gas4 ,in the constellation ,virgo1 ,rosse has detected another such nebula4 ,in ,cepheus1 ,triangulum1 and ,ursa ,major1 are found other spiral nebul of smaller size4 ,lord ,rosse has recognized #dj spiral nebul and suspected a similar structure in #cj others4 ,the class of the ,irregular nebul1 which will be now considered1 differs greatly in character from the others1 and includes the largest1 the brightest and the most extraordinary nebul in the heavens4 ,the nebul of this class differ from those belonging to the other classes by a want of symmetry in their form and in the distribution of their light1 as well as by their capricious shapes1 and their very complicated structure4 ,another and perhaps the principal difference between them and the objects above described1 consists in the remarkable fact already stated1 that they are not1 except in rare cases1 to be found in the regions where the other nebul abound4 ,on the contrary1 they are found in or very near the ,milky-way1 precisely where the other nebul are the most rare4 ,this fact1 recognized by ,sir ,j4 ,herschel1 led him to consider them as outlying1 very distant1 and as it were detached fragments of the great stratum of the ,galaxy4 ,it seems very probable that the reason why these objects differ so greatly from the other nebul in size1 brightness and complication of structure1 is simply because they are much nearer to us than are most of the others4 ,they are perhaps nebulous members of our ,galaxy4 ,the same remark which has been made of star-clusters may be applied to nebul4 ,the nearer they are to us1 the larger1 the brighter and the more complicated they will appear1 while the farther they are removed1 the more simple and regular and round they will appear1 only their brightest and deepest parts being then visible4 ,the ,crab ,nebula of ,lord ,rosse1 near ,tauri1 ,no4 #a1aeg1 is one of the interesting objects of this class4 ,it has curious appendages streaming off from an oval1 luminous mass1 which give it a distant resemblance to the animal from which it derives its name4 ,the ,bifid nebula in ,cygnus1 ,nos4 #d1djj and #d1faf1 is another object of this class4 ,it consists of a long1 narrow1 crooked streak1 forking out at several places1 and passing through ,cygni4 ,observers1 having failed to recognize the connection existing between its different centres of brightness1 have made distinct nebul of this extended object4 ,the ,dumb-bell nebula in ,vulpecula1 ,no4 #d1ecb1 is a bright and curious object1 with a general resemblance to the instrument from which it derives its name4 ,lord ,rosse's telescope has shown many stars in it1 projected on a nebulous background1 and ,prof4 ,bond seems to have thought that it showed traces of resolvability1 although in the study which ,i made of this nebula with the same instrument used by the latter observer1 ,i failed to perceive any such traces4 ,dr4 ,huggins finds its spectrum gaseous4 ,the star-cluster1 ,no4 #d1djj1 in ,scutum ,sobieskii1 which is described by ,sir ,j4 ,herschel as a loose cluster of at least #ajj stars1 ,i have found to be involved in an extensive1 although not very bright1 nebula1 which would seem to have escaped his scrutiny4 ,in a study and drawing of this nebula made in #ahgf1 its general form is that of an open fan1 with the exception that the handle is wanting1 with deeply indented branches on the preceding side1 where the brightest stars of the cluster are grouped4 ,from its peculiar form1 this object might appropriately be called the ,fan nebula4 ,the ,omega or ,horse-shoe nebula1 in ,sagittarius1 ,no4 #d1djc1 of which ,i have made a study and two drawings1 one with a refractor #f inches in aperture1 and the other conjointly with ,prof4 ,holden1 with the great telescope of the ,naval ,observatory1 is a bright and very complicated object4 ,its general appearance in small instruments1 with low power1 is that of a long1 narrow pisciform mass of light1 from which proceeds on the preceding side1 the great double loop from which it derives its name4 ,but in the great ,washington refractor its structure becomes very complicated1 forming various bright nebulous masses and wisps of great extension4 ,prof4 ,holden1 who has made a careful1 comparative study of the published drawings of this object1 thinks there are reasons to believe that its western branch has moved relatively to the stars found within its loop4 ,the spectrum of this nebula is gaseous4 ,the ,trifid nebula1 ,no4 #d1cee1 in the same constellation1 is also a very remarkable object1 although it is not so bright as the last4 ,this nebula1 which ,i have studied with the refractor of the ,cambridge ,observatory1 consists of four principal masses of light1 separated by a wide and irregular gap branching out in several places4 ,these masses1 which are brighter along the dark gap1 gradually fade away externally4 ,a group of stars1 two of which are quite bright1 is found near the centre of the nebula1 on the inner edge of the following mass1 and close to the principal branch of the dark channel4 ,a little to the north1 and apparently forming a part of this nebula1 is a globular-looking nebula1 having a pale yellow star at its centre4 ,prof4 ,holden's studies on this nebula show that the triple star1 which was centrally situated in the dark gap from #aghd to #ahcc1 was found involved in the border of the nebulous mass following it1 from #ahci to #ahgg2 the change1 he thinks1 is attributable either to the proper motion of the group of stars or to that of the nebula itself4 ,in the same vicinity is found the splendid and very extensive nebula ,no4 #d1cfa1 in which is involved a loose1 but very brilliant star-cluster4 ,this nebula and cluster1 which ,i have studied and drawn with a #f inch telescope1 is very complicated in structure1 and divided by a dark irregular gap into three principal masses of light1 condensing at one point around a star1 and at others forming long1 bright1 gently-curved branches1 which give to this object a strong resemblance to the wings of a bird when extended upwards in the action of flying4 ,from this peculiarity this object might appropriately be called the ,winged nebula4 ,its spectrum is that of a gas4 ,the variable star ,argus is completely surrounded by the great nebula of the same name1 ,no4 #b1aig1 first delineated by ,sir ,j4 ,herschel1 during his residence at the ,cape of ,good ,hope1 in #ahch4 ,this object1 which covers more than of a square degree1 is divided into three unequal masses1 separated by dark oval spots1 comparatively free from nebulosity1 and is suspected to have undergone changes since ,herschel's time4 ,in the same field with the double star1 ,orionis1 the most easterly of the three bright stars in the belt of ,orion1 is found another irregular nebula of the ,trifid type4 ,from the drawings which ,i have made of this object1 it appears to be composed of three principal unequal masses1 separated by a wide1 irregular1 dark channel1 two of the masses being quite complicated in structure1 and forming curved1 nebulous streams of considerable length and breadth4 ,this nebula1 like the next to be described1 seems to be connected with the ,galaxy by the great galactic loop described in another section4 ,by far the most conspicuous irregular nebula visible from our northern ,states1 is the great nebula in ,orion1 ,no4 #a1agi1 represented on ,plate ,,xv4 ,this object1 visible to the naked eye1 is the brightest and the most wonderful nebula in the heavens4 ,it is situated a little to the south of the three bright stars in the belt of ,orion1 and may be readily detected surrounding the star 1 situated between and in a line with two faint stars1 the three being in a straight line which points directly towards 1 the middle star of the three in ,orion's belt4 ,the area occupied by this nebula is about equal to that occupied by the ,moon4 ,in its brightest parts the nebula in ,orion appears as a luminous cloud of a pentagonal form1 from which issue many luminous appendages of various shapes and lengths4 ,this principal mass is divided into secondary masses1 separated by darkish1 irregular intervals4 ,these secondary masses in their turn appear mottled and fleecy4 ,towards the lower part of the pentagonal mass is found a roundish dark space1 comparatively devoid of nebulosity1 in which are involved four bright stars forming a trapezium1 and several fainter ones4 ,the four bright stars of the trapezium constitute the quadruple star ,orionis1 from which the nebula has received its name4 ,the cloud-like pentagonal form is brightest on the north-west of the trapezium1 and is surrounded on three sides by long1 soft1 curved wisps1 fading insensibly into the outer nebulous mass in which they are involved4 ,on the east a broad1 wavy wing spreads out1 and sends an important branch southward4 ,south-east of the trapezium are found several curious dark spaces1 comparatively devoid of nebulosity1 especially those on the east1 which give to this nebula a singular character4 ,close to the north-eastern part of the nebula1 or rather in contact with it1 is found a small1 curiously-shaped nebula1 condensing around a bright star into a blazing nucleus4 ,from this centre it continues northward in a narrow diffused stream1 which spreads out in passing over the stars c#a and c#b2 and after having sent short branches northward1 it curves back to the south and joins the main nebula on the west of its starting point1 having thus formed a great loop which is not shown on the ,plate4 ,the nebula also forms a loop towards the south1 which is partly shown on ,plate ,,xv41 a small branch of which1 passing through ,orionis1 the nebulous star shown at the top of the ,plate1 and extending southward1 is not here represented4 ,on ordinary nights the nebula in ,orion is a splendid object1 and inspires the observer with amazement2 but this is as nothing compared with the grand and magnificent sight which it presents during the very rare moments when our atmosphere is perfectly clear and steady4 ,i have seen this nebula but once under these favorable circumstances1 and ,i was surprised by the grandeur of the scene4 ,then could be detected features to be seen at no other time1 and its fleecy1 floculent1 cloud-like masses glittered with such intensity that it seemed as if thousands of stars were going to blaze out the next moment4 ,although ,i observed the nebula under such favorable conditions1 and with the fifteen-inch refractor of the ,cambridge ,observatory1 yet ,i was disappointed in my expectations1 and distinguished no new stars or points of light1 and nothing more than a very bright mass1 finely divided into minute blazing cloudlets4 ,although ,i failed to resolve this nebula into stars1 yet ,lord ,rosse1 ,bond and ,secchi thought they had caught glimpses of star dust4 ,its spectrum1 however1 proves to be mainly that of incandescent gases1 probably hydrogen and nitrogen4 ,in the curved wisps found in this nebula1 ,lord ,rosse and others saw indications of a spiral structure4 ,several bright stars are found scattered over this nebula1 and besides those forming the trapezium1 there are three in a row1 a little to the south-east of that group1 which are quite bright and remarkable4 ,among the stars involved in this nebula1 few show signs of having a physical connection with it1 although it seems probable that the group of the trapezium is so connected4 ,some of these stars are variable4 ,the small stars represented on this ,plate1 as on others of the series1 are somewhat exaggerated in size1 as was unavoidable with any process of reproduction which could be adopted4 ,in #ahaa1 ,w4 ,herschel was led to suspect that some changes had occurred in this nebula1 but changes in such complicated and delicate objects are not easily ascertained1 since1 for the most part1 we have for comparison with our later observations only coarse drawings made by hands unskilled in delineation4 ,although comparatively rare1 double and multiple nebul may be found in the sky4 ,when this occurs1 their constituents most commonly belong to the class of spherical nebul4 ,sometimes the components are separated and distinct1 at other times one of them is projected upon the other1 either really or by the effect of perspective4 ,sometimes one is round and the other elongated4 ,it is probable that while some of these nebul are physically associated and form a system1 others appear to be so only because they happen to be almost in a line with the observer4 ,a double nebula in ,draco1 ,nos4 #d1abg and #d1abh1 which ,i have drawn1 is a fair type of those which are separated4 ,the first is a globular nebula1 and the last an oval one1 with a star at its centre4 ,the double nebula1 ,nos4 #heh and #hei1 in ,taurus1 which ,i have also studied1 is a type of the cases in which one nebula is partly projected on another4 ,in this instance both the nebul are globular4 ,the nebul in general show very little color in their light1 which is ordinarily whitish and pale4 ,some1 however1 present a decided bluish or greenish tint4 ,the great nebula in ,orion has a greenish cast1 and we have seen that some planetary nebul are bluish4 ,it has been a question whether nebul are changing4 ,it has already been stated that ,prof4 ,holden believes there is ground to suspect that the ,trifid and ,horse-shoe nebul have undergone some changes4 ,a nebula near ,tauri has been lost and found again several times4 ,two other nebul in the same constellation have presented curious variations4 ,one1 near a star of the tenth magnitude1 exhibited variations of brightness like those of the star itself1 and for a time disappeared4 ,the other1 near ,tauri1 increased in brightness for three months1 after which it disappeared4 ,in #ahei ,tempel discovered a nebula in the ,pleiades1 which has shown some fluctuations4 ,in #ahge ,i made a long study of this object1 and drew it carefully a dozen times1 but ,i was not able to see any changes in it within the two or three months during which my observations were continued4 ,but on ,nov4 #bd1 #ahgf1 it was found of a different color1 being purplish and very faint4 ,on ,dec4 #bc1 #ahhj1 it was found just as bright and visible as when ,i drew it in #ahge1 and on ,oct4 #bj1 #ahha1 it appeared faint and purplish again1 as in #ahgf4 ,on this last night1 and on those which followed it1 it was impossible for me to trace the nebulosity as far as in #ahge4 ,i consider this as due to a variation in the light of this object1 which in #ahge was bright enough to be well seen while the ,moon after her ,first ,quarter was within ten or fifteen degrees from the ,pleiades4 ,from the observations of ,m4 ,laugier1 it appears that some nebul have a proper motion1 comparable to that of stars4 ,from the displacement of the lines of their spectra by their motion in the line of sight1 ,dr4 ,huggins found that no nebula observed by him has a proper motion surpassing #be miles per second4 ,the ,ring nebula in ,lyra appears to move from us at the rate of #c miles per second1 and that in ,orion recedes about #ag miles per second4 ,the important question arises1 are all the irresolvable nebul in the heavens to be considered as so many star-clusters1 differing only from them by the minuteness of their components1 or their immense distance from us2 or are they cosmical clouds1 composed of luminous vapors1 similar to the matter composing the heads and tails of comets8 ,originally1 ,w4 ,herschel1 with many astronomers1 thought that all these objects were stellar aggregations1 too distant to be resolved into stars2 but he subsequently modified his opinion1 and accepted the idea that some of them are of a gaseous nature4 ,no direct proof that the nebul are gaseous could be obtained1 however1 before the spectroscope was known4 ,the attempt to analyze the light of the nebul with this instrument was made in #ahfd1 by ,dr4 ,huggins1 who directed his spectroscope to the planetary nebula1 ,no4 #d1cgc1 in ,draco4 ,its spectrum was found to consist of three bright1 distinct lines1 the brightest of which corresponded with the strongest nitrogen line1 and the feeblest with the hydrogen ,c line4 ,besides these lines1 it gave also a very faint1 continuous spectrum1 apparently due to a central point of condensation4 ,by this observation1 the gaseous nature of a nebula was for the first time demonstrated4 ,dr4 ,huggins thus analyzed #gj nebul1 of which one-third gave a gaseous spectrum1 consisting of several bright lines1 the brightest of which invariably corresponded with the lines of nitrogen4 ,the others gave a continuous spectrum1 with the red end usually deficient4 ,these results indicate that if some of the so-called nebul are due to an aggregation of stars1 either too minute or too remote in space to be individually resolved1 others are in a gaseous state4 ,yet the faint1 continuous spectrum1 given by some nebul1 in addition to their gaseous spectra1 seems to show that these nebul have some stars or matter in a different state1 either involved in them or projected on their surface4 ,the idea of diffused matter distributed here and there in space1 and gradually condensing into stars1 is by no means new4 ,as early as #aegb1 ,tycho ,brah proposed such an hypothesis1 to explain the sudden apparition of a new star in ,cassiopeia1 which he considered as formed by the recent agglomeration of the celestial matter diffused in space4 ,kepler adopted the same idea to explain the new star which appeared in ,ophiuchus1 in #afjd4 ,halley1 ,lacaille1 ,mairan and others1 entertained the same opinion4 ,the hypothesis of a self-luminous1 nebulous matter diffused in space1 and forming here and there immense masses1 has been proposed from the origin of the telescope1 and was adopted by ,sir ,william ,herschel1 who in his grand speculations on the universe considered the nebul as immense masses of phosphorescent vapors1 gradually condensing around one or several centres into stars or clusters of stars4 ,the evidence afforded by the spectroscope seems to be in favor of such an hypothesis1 and shows us that gaseous agglomerations exist in space4 ,according to our modern conception1 the visible universe is but an infinitely small portion of the infinite universe perceived by our mind4 ,the great blazing centre around which our little1 non-luminous globe pursues its endless journey1 is only an humble member of a cluster comprising four hundred equally powerful suns1 as they are believed to be1 although they appear to us as little twinkling stars4 ,the nearest of these stars is #bba1jjj times as far from the ,sun as the ,sun is from the ,earth1 and yet this entire cluster is only one among the several hundred ,star-clusters composing the great galactic nebula in which we are involved1 comprising thirty or fifty millions of such suns4 ,among the #d1jjj irresolvable nebul in the sky1 perhaps over one-half are supposed to be galaxies1 like our own galaxy1 composed of star-clusters1 and millions of stars4 ,besides these remote galaxies1 vast agglomerations of yet uncondensed1 nebulous matter exist in space1 and form the nebul proper1 in which the genesis of suns is slowly elaborated4 ,although the visible universe is limited by the penetrating power of our instruments1 yet we see in imagination the infinite universe stretching farther and farther2 but we know not whether this invisible universe is totally devoid of matter1 or whether it also is filled with millions and millions of suns and galaxies4 ,,appendix ,,key ,,to ,,the ,,plates ,,plate ,i4--,,group ,,of ,,sun-,,spots ,,and ,,veiled ,,spots4 ,observed ,june #ag1 #ahge1 at #g;h4 #cjm4 ,a4 ,m4 ,the background shows the sun's visible surface1 or photosphere1 as seen with a telescope of high power at the most favorable moments1 composed of innumerable light markings1 or granules1 separated by a network of darker gray4 ,the granules1 each some hundreds of miles in width1 are thought to be the flame-like summits of the radial filaments or columns of gas and vapor which compose the photospheric shell4 ,the two principal sun-spots of the group here represented show the characteristic dark umbra in the centre1 overhung by the thatch-like penumbra1 composed of whitish gray filaments4 ,the penumbral filaments are not supposed to differ in their nature from those constituting the ordinary photosphere1 save that they are seen here elongated and violently disturbed by the force of gaseous currents4 ,both spots are traversed partly or wholly by bright overlying facul1 or so-called luminous bridges1 depressed portions of which1 in the left-hand spot1 form the gray and rosy veils commonly attendant upon this class of spots4 ,in each of these spots1 also1 the inner ends of projecting penumbral filaments have fallen so far within the umbra as to appear much darker than the rest4 ,at the right of the upper portion of the left-hand spot1 is a mass of white facular clouds1 honey-combed by dark spaces1 through which are seen traces of the undeveloped third spot of the triple group first observed4 ,if seen upon the sun's limb1 this would have presented the appearance of a lateral spot4 ,above the right-hand spot is a small black dot1 or incipient spot1 without distinct penumbra4 ,the irregular dark rift below the two large spots and connecting them is a spot of the crevasse type1 with very slight umbra1 a still better example of which is seen in a westward prolongation of the penumbra of the left-hand spot4 ,in the upper left-hand corner of the ,plate are seen several small facul1 appearing as irregular whitish streaks amongst the granules4 ,in the pear-shaped darkening of the solar surface below and at their left1 is seen a veiled spot1 two of which attended this group4 ,approximate scale1 #bejj miles--#a inch4 ,,plate ,,ii4--,,solar ,,protuberances4 ,observed ,may #e1 #ahgc1 at #i;h4 #djm4 ,a4 ,m4 ,a view of an upheaval of the chromosphere1 or third outlying envelope of the sun1 as observed with the tele-spectroscope1 or telescope with spectroscope attached4 ,the method of the observation requires a word of explanation4 ,save on the rare occasions of a total solar eclipse1 no direct telescopic view of the solar prominences or flames is possible1 owing to the fact that the intense white light from the sun's main disk entirely obscures the feeble pink light of the chromosphere4 ,a few years ago ,messrs4 ,jannsen and ,lockyer found that a spectroscope of high dispersive power so weakens the spectrum of ordinary sun-light as to show the spectrum of bright lines given by the chromosphere1 on any clear day4 ,the telescope is adjusted so that a portion of the sun's limb1 usually near a group of active sun-spots1 shall be presented before the opened slit of the spectroscope4 ,the light of the chromosphere thus admitted along with some diffused sun-light from the earth's atmosphere1 produces a spectrum of intensely bright lines1 widely separated1 on the fainter background of the strongly dispersed spectrum of sun-light4 ,the most prominent of these bright lines are those known as the ,c line 7scarlet71 ,f line 7blue71 which with several others are due to the hydrogen present in the chromosphere1 the ,d#c line 7orange7 ascribed to a little known substance called helium1 and occasionally the sodium lines ,d#a1 ,d#c1 7yellow74 ,by adjusting the slit upon the scarlet ,c line1 the appearances represented in ,plate ,,ii4 were observed as through an atmosphere of scarlet light3 in the ,d or ,f lines identical appearances may be seen1 but somewhat less clearly defined1 as through yellow or blue light respectively4 ,hence the solar times1 as here observed with the spectroscope in the hydrogen ,c line1 are seen through a portion only 7the scarlet rays7 of the light coming from but one substance 7hydrogen7 of the companion incandescent substances present in the chromosphere4 ,the color of the collective chromospheric light is seen directly with the telescope during an eclipse 7,see ,plate ,,iii47 to be a delicate rosy pink4 ,description of the ,plate4--,the black background represents the general darkness of the eye-piece to the spectroscope4 ,the broad red stripe stretching from top to bottom of the ,plate is a portion of the red band of the spectrum1 magnified about #ajj times as compared with the actual spectroscopic view4 ,the upper and lower edges of the cross-section of dusky red correspond with the edges of the slit1 opened widely enough to admit a view of the chromospheric crest and of the whole height of the protuberances at once4 ,with a narrower opening of the slit this background would have been nearly black1 its reddish cast increasing with the amount of opening and consequent admission of diffused sun-light4 ,rising above the lower edge of the opening is seen a small outer segment of the chromosphere1 which1 as a portion of the sun's eastern limb1 should be imagined as moving directly towards the beholder4 ,the seams and rifts by which its surface is broken1 as well as the distorted forms of the huge protuberances show the chromosphere to be in violent agitation4 ,some of the most characteristic shapes of the eruptive protuberances are presented1 as also cloud-like forms overtopping the rest4 ,in the immediate foreground the bases of two towering columns appear deeply depressed below the general horizon of the segment observed1 showing an extraordinary velocity of motion of the whole uplifted mass toward the observer4 ,the highest of these protuberances was #abf1jjj miles in height at the moment of observation4 ,the triple protuberance at the left with two drooping wings and a tall swaying spire tipped with a very bright flame1 shows by its more brilliant color the higher temperature 7and possibly compression7 to which its gases have been subjected4 ,the irregular black bands behind this protuberance indicate the presence there of less condensed and cooler clouds of the same gases4 ,the dimmer jets of dame rising from the chromosphere are either vanishing protuberances1 or1 as in the case of the smallest jet shown at the extreme right of the horizon1 are the tops of protuberances just coming into view4 ,approximate scale1 #fjjj miles--#a inch4 ,,plate ,,iii4--,,total ,,eclipse ,,of ,,the ,,sun4 ,observed ,july #bi1 #ahgh1 at ,creston1 ,wyoming ,territory4 ,a telescopic view of the sun's corona or extreme outer atmosphere and of the solar flames or prominences during a total eclipse4 ,at the moment of observation the dark disk of the moon1 while still hiding the sun's main body1 had passed far enough eastward to allow the rosy pink chromospheric prominences to be seen on its western border4 ,on all sides of the sun's hidden disk1 the corona shows its pale greenish light extending in halo-like rays and streamers1 and two very remarkable wings stretch eastward and westward very nearly in the plane of the ecliptic and in the direction of the positions of ,mercury and ,venus respectively at the time of observation4 ,the full extent of these wings could not be shown in the ,plate without reducing its scale materially1 since the westerly wing extended no less than twelve times the sun's diameter1 and the easterly wing nearly as far1 or over ten million miles4 ,a circlet of bright light immediately bordering the moon's disk is the so-called inner corona1 next to which the wings and streamers arc brightest1 thence shading off imperceptibly into the twilight sky of the eclipse4 ,other noteworthy peculiarities of the corona1 as observed during this eclipse1 are the varying angles at which the radiating streamers are seen to project1 the comparatively dark intervals between them1 and the curved1 wisp-like projections seen upon the wings4 ,an especially noticeable gap appears where the most westerly of the upward streamers abruptly cuts off the view of the long wing4 ,the largest and brightest of the curving streamers on the westerly wing coincides with the highest flame-like protuberance4 ,to some observers of this eclipse the upward and downward streamers seemed pointed at their outer extremities and less regular in form4 ,approximate scale1 #ace1jjj miles--#a inch4 ,,plate ,,iv4--,,aurora ,,borealis4 ,as observed ,march #a1 #ahgb1 at #i;h4 #bem4 ,p4 ,m4 ,the view presents the rare spectacle of an aurora spanning the sky from east to west in concentric arches4 ,the ,polar ,star is nearly central in the background1 the constellation of the ,great ,bear on the right and ,cassiopeia's chair on the left4 ,the large star at some distance above the horizon on the right is ,arcturus4 ,the almost black inner segment of the aurora resting upon the horizon1 has its summit in the magnetic meridian1 which was in this case a little west of north1 its arc being indented by the bases of the ascending streamers4 ,both streamers and arches were1 when observed1 tremulous with upward pulsations and there was also a wave-like movement of the streamers from west to east4 ,the prevailing color of this aurora is a pale whitish green and the complementary red appears especially at the west end of the auroral arch4 ,the summits of the streamers are from four hundred to live hundred miles above the earth and the aurora is therefore a phenomenon of the terrestrial atmosphere rather than of astronomical observation proper4 ,,plate ,v4--,,the ,,zodiacal ,,light4 ,observed ,february #bj1 #ahgf4 ,an observation of the cone of light whose axis lies along the ,zodiac1 whence it derives its name4 ,it is drawn as seen in the west1 with its base in the constellation ,pisces1 and its apex near the familiar group of the ,pleiades in the constellation ,taurus4 ,the first bright star above the horizon in the base of the cone is the planet ,venus and at some distance above is the reddish disk of ,mars1 the two being in rare companionship as evening stars4 ,above the constellation ,pisces1 two bright stars of ,aries lie just outside the cone at the right4 ,the nearest bright star above these at the right is ,beta1 the leading star of the constellation ,triangula4 ,further at the right the three prominent stars nearly in a line are1 in ascending order1 ,delta1 ,beta and ,gamma of the constellation ,andromeda4 ,above these at the left1 the brightest star of a quadrangular group of four is the remarkable variable star ,algol 7,beta7 of the constellation ,perseus1 which changes from the second to the fourth magnitude in a period of less than three days4 ,at the left and a little above the ,pleiades is the ruddy star ,aldebaran1 one of the ,hyades and chief star in the constellation ,taurus4 ,these are the principal stars visible in this portion of the sky at the time of the observation4 ,their relative positions are represented as seen in the sky and not by the common method of star-atlases1 which allows for the change from a spherical to a plane surface4 ,their magnitude in the order of brightness is indicated only approximately4 ,,plate ,,vi4--,,mare ,,humorum4 ,from a study made in #ahge4 ,a view of one of the lunar plains1 or so-called seas 7,maria71 with an encircling mountainous wall consisting of volcano-like craters in various stages of subsidence and dislocation4 ,the sun-light coming from the west casts strong shadows from all the elevations eastward1 and is just rising on the terminator1 where the rugged structure of the ,moon's surface is best seen4 ,the lighter portions are the more elevated mountainous tracts and crater summits4 ,the detailed description of this ,plate given in the body of the ,manual is repeated here for convenience of reference3 ,the ,mare ,humorum1 or sea of moisture1 as it is called1 is one of the smaller gray lunar plains4 ,its diameter1 which is very nearly the same in all directions1 is about #bgj miles1 the total area of this plain being about #ej1jjj square miles4 ,it is one of the most distinct plains of the ,moon1 and is easily seen with the naked eye on the left-hand side of the disk4 ,the floor of the plain is1 like that of the other gray plains1 traversed by several systems of very extended but low hills and ridges1 while small craters are disseminated upon its surface4 ,the color of this formation is of a dusky greenish gray along the border1 while in the interior it is of a lighter shade1 and is of brownish olivaceous tint4 ,this plain1 which is surrounded by high clefts and rifts1 well illustrates the phenomena of dislocation and subsidence4 ,the double-ringed crater ,vitello1 whose walls rise from #d1jjj to #e1jjj feet in height1 is seen in the upper left-hand corner of the gray plain4 ,close to ,vitello at the east is the large broken ring-plain ,lee1 and farther east1 and a little below1 is a similarly broken crater called ,doppelmayer4 ,both of these open craters have mountainous masses and peaks on their door1 which is on a level with that of the ,mare ,humorum4 ,a little below1 and to the left of these objects1 is dimly seen a deeply imbedded oval crater1 whose walls barely rise above the level of the plain4 ,on the right-hand side of the great plain is a long fault1 with a system of fracture running along its border4 ,on this right-hand side may be seen a part of the line of the terminator1 which separates the light from the darkness4 ,towards the lower right-hand corner is the great ring-plain ,gassendi1 #ee miles in diameter1 with its system of fractures and its central mountains1 which rise from #c1jjj to #d1jjj feet above its floor4 ,this crater slopes towards the plain1 showing the subsidence to which it has been submitted4 ,while the northern portion of the wall of this crater rises to #aj1jjj feet1 that on the plain is only #ejj feet high1 and is even wholly demolished at one place where the floor of the crater is in direct communication with the plain4 ,in the lower part of the sea1 and a little to the west of the middle line1 is found the crater ,agatharchides1 which shows below its north wall the marks of rills impressed by a flood of lava1 which once issued from the side of the crater4 ,on the left-hand side of the plain is seen the half-demolished crater ,hippalus resembling a large bay1 which has its interior strewn with peaks and mountains4 ,on this same side can be seen one of the most important systems of clefts and fractures visible on the ,moon1 these clefts varying in length from #aej to #bjj miles4 ,approximate scale1 #ae miles--#a inch4 ,,plate ,,vii4--,,partial ,,eclipse ,,of ,,the ,,moon4 ,observed ,october #bd1 #ahgd4 ,a view of the ,moon partially obscured by the ,earth's shadow1 whose outline gives ocular proof of the earth's rotundity of form4 ,the shadowed part of the ,moon's surface is rendered visible by the diffused sun-light refracted upon it from the earth's atmosphere4 ,its reddish brown color is due to the absorption1 by vapors present near the earth's surface1 of a considerable part of this dim light4 ,on both the obscured and illuminated tracts the configurations of the ,moon's surface are seen as with the naked eye4 ,the craters appear as distinct patches of lighter color1 and the noticeably darker areas are the depressed plains or ,maria4 ,the large crater ,tycho1 at the lower part of the disk1 is the most prominent of these objects1 with its extensive system of radiating streaks4 ,the largest crater above is ,copernicus1 at the left of which is ,kepler and still above are ,aristarchus and ,herodotus appearing as if blended in one4 ,above and at the left of the great crater ,tycho1 the first dark tract is the ,mare ,humorum of ,plate ,,vi41 seen in its natural position1 with the crater ,gassendi at its northern 7upper7 extremity and ,vitello on its southern 7lower7 border4 ,the advancing border of the shadow appears1 as always1 noticeably darker than the remainder1 an effect probably of contrast4 ,the illuminated segment of the ,moon's disk has its usual appearance1 the lighter portions being the more elevated mountainous surfaces1 and the dark spaces the floors of extensive plains4 ,approximate scale1 #adj miles--#a inch4 ,,plate ,,viii4--,,the ,,planet ,,mars4 ,observed ,september #c1 #ahgg1 at #aa;h4 #eem4 ,p4 ,m4 ,a view of the southern hemisphere of ,mars1 when in the most favorable position for observation1 and when exceptionally free from the clouds1 which very frequently hide its surface configurations4 ,since1 of all the planets1 ,mars is most like the earth1 ,plate ,,viii4 may give a fair idea of the appearance of our globe to a supposed observer on ,mars4 ,the dark gray and black markings1 are regarded as tracts of water1 or of some liquid with similar powers of absorbing light2 and1 for the same reason1 the lighter portions1 of a prevailing reddish tint1 are supposed to be bodies of land1 while the bright white portions are variously due to clouds1 to polar snow or ice1 and the bright rim of white along the limb1 to the depth of the atmosphere through which the limb is seen4 ,the chief permanent features of the planet's surface have been named in honor of various astronomers4 ,the large dark tract on the left is ,de ,la ,rue ,ocean1 the isolated oval spot near the centre is ,terby ,sea1 and on the right is the western end of ,maraldi ,sea1 with strongly indented border4 ,directly north of 7below7 ,de ,la ,rue ,ocean1 is ,maedler ,continent2 above it stretches ,jacob ,land2 and surrounding ,terby ,sea is ,secchi ,continent4 ,extending into the centre of ,de ,la ,rue ,ocean is a curious double peninsula1 called1 in consequence of the dimness of former observations1 ,hall ,island4 ,the sharply defined1 white-crested northern borders of ,de ,la ,rue ,ocean and ,maraldi ,sea may indicate the existence there of lofty coast ranges1 more or less constantly covered with opaque clouds strongly reflecting light4 ,the white spot in the centre of ,maedler ,continent1 of a temporary nature1 has a similar explanation4 ,the intervals of olivaceous gray on ,secchi ,continent and elsewhere may perhaps be ascribed to the flooding and drying up of marshes and lowlands1 as these markings have been observed to vary somewhat in connection with the change of seasons on ,mars4 ,the greenish tints observed along the planet's limb1 alike on the darker and lighter surfaces1 are probably due to an optical effect1 the green being complementary to the prevailing red of the disk4 ,the brilliant oval white spot near the southern 7upper7 pole of the planet is a so-called polar spot1 in all probability consisting of a material similar to snow or ice and here observed in the midst of a dark open sea4 ,approximate scale1 #cjj miles--#a inch4 ,,plate ,,ix4--,,the ,,planet ,,jupiter4 ,observed ,november #a1 #ahhj1 at #i;h4 #cjm4 ,p4 ,m4 ,this planet is perpetually wrapped in dense clouds which hide its inner globe from view4 ,the drawing shows ,jupiter's outer clouded surface with its usual series of alternate light and dark belts1 the disk as a whole appearing brighter in the centre than near the limb4 ,the darker gray and black markings indicate in general the lower cloud-levels2 that is1 partial breaks or rifts in the cloudy envelope1 whose prevailing depth apparently exceeds four thousand miles4 ,while the deepest depression in the cloudy envelope is within the limits of the ,great ,red ,spot1 the vision may not even here penetrate very deeply4 ,two of ,jupiter's four moons present bright disks near the planet's western limb1 and cast their shadows far eastward on the disk1 that of the second satellite falling upon the ,red ,spot4 ,on the ,red ,spot are seen in addition two small black spots1 no explanation of which can yet be offered4 ,the broad white ring of clouds bordering the ,red ,spot appeared in constant motion4 ,the central1 or equatorial belt1 shows brilliant cloudy masses of both the cumulus and stratus types1 and the underlying gray and black cloudy surfaces are pervaded with the pinkish color characteristic of this belt4 ,the dark circular spots on the wide white belt next north showed in their mode of formation striking resemblances to sun-spots4 ,they afterward coalesced into a continuous pink belt4 ,the diffusion of pinkish color over the three northernmost dark bands1 as here observed1 is unusual4 ,about either pole is seen the uniform gray segment or polar cap4 ,the equatorial diameter is noticeably longer than the polar diameter1 a consequence of the planet's extraordinary swiftness of rotation4 ,to the same cause may also be due chiefly the distribution of the cloudy belts parallel to the planet's equator1 though the analogy of the terrestrial trade-winds fails to explain all the observed phenomena4 ,approximate scale1 #e1ejj miles--#a inch4 ,,plate ,x4--,,the ,,planet ,,saturn4 ,observed ,november #cj1 #ahgd1 at #e;h4 #ejm4 ,p4 ,m4 ,saturn is unique amongst the planets in that its globe is encircled by a series of concentric rings1 which lie in the plane of its equator1 and consist1 according to present theories1 of vast throngs of minute bodies revolving about the planet1 like so many satellites1 in closely parallel orbits4 ,the globe of ,saturn1 like that of ,jupiter1 is surrounded by cloudy belts parallel to its equator4 ,the broad equatorial belt1 of a delicate pinkish tint1 is both brighter and more mottled than the narrower yellowish white belts1 which alternate with darker belts of ashy gray on both the north and south sides1 but are seen here only on the northern side4 ,the disk has an oval shape1 owing to the extreme polar compression of the globe4 ,the outer1 middle and inner rings1 with their various subdivisions1 are clearly shown in ,plate ,x41 and are best seen on the so-called ans1 or handles1 projecting on either side4 ,the gray outer ring is separated by the dusky pencil line into two divisions1 both of which appear slightly mottled on the ans1 as if with clouds4 ,the middle ring has three sub-divisions which are clearly distinguishable1 although separated by no dark interval1 viz41 a brilliant white outer zone1 distinctly mottled1 as seen on the extremities of the ans1 and two interior zones of gradually diminishing brightness4 ,the gauze or dusky ring is seen at its full width on the ans1 but on the background of the strongly illuminated globe only its outer and presumably denser border is visible4 ,the shadow of the globe on the rings is seen on the lower portion of the eastern ans4 ,the shadow on the dusky ring is with difficulty perceptible2 the shadow on the middle ring is slightly concave toward the planet1 which concavity is abruptly increased on the outer zone of this ring2 while the shadow on the outer ring slants away from the globe4 ,these appearances are fully accounted for by supposing a general increase of level from the inner edge of the dusky ring to the outer margin of the middle ring1 and a uniform lower level on the outer ring4 ,other observers have regarded the deflection of the shadow as an effect of irradiation4 ,the inner margin of the double outer ring presents on both ans a number of slight indentations1 which1 if not actual irregularities in the contour of this ring1 may be explained as shadows caused by elevations on the outer border of the middle ring1 or possibly by over-hanging clouds4 ,approximate scale1 #f1ejj miles--#a inch4 ,,plate ,,xi4--,,the ,,great ,,comet ,,of #ahha4 ,observed on the night of ,june #be-bf1 at #a;h4 #cjm4 ,a4 ,m4 ,a view of the comet #ahha1 ,,iii41 drawn as if seen with the naked eye1 the minute details1 however1 being reproduced as seen with the telescope4 ,the star-like nucleus is attended by four conical wings which cause it to appear diamond-shaped4 ,the coma appears double1 the brilliant inner coma1 immediately enveloping the nucleus1 being surrounded by a fainter exterior coma1 which has a noticeable depression corresponding to that of the inner edge of the principal coma4 ,the tail is divided lengthwise by a dark rift and is brightest on its convex or forward side4 ,an inner portion of the tail1 brighter than the rest1 is more strongly curved1 as if by solar repulsion4 ,stars are seen through the brighter parts of the tail1 as they may be seen even through the coma and nucleus1 with little diminution of their light4 ,,plate ,,xii4--,,the ,,november ,,meteors4 ,as observed on the night of ,november #ac-ad1 #ahfh4 ,a partially ideal view of the ,november ,meteors1 combining forms observed at different times during the night of ,nov4 #acth1 #ahfh4 ,it is not1 however1 a fanciful view1 since a much larger number of meteors were observed falling at once during the shower of ,november1 #ahcc1 and at other times4 ,the locality of the observation is shown by the ,polar ,star seen near the centre of the ,plate1 and ,cassiopeia's ,chair at the left4 ,the general direction of the paths of the meteors is from the north-east1 the radiant point of the shower having been in the constellation ,leo1 beyond and above ,ursa ,major4 ,while the orbits of the meteors are1 in general1 curved regularly and slightly1 several are shown with very eccentric paths1 among them one which changed its course at a sharp angle4 ,in the upper left-hand corner appear two vanishing trails of the ring-form1 and several others still further transformed into faint luminous patches of cloud4 ,red1 yellow1 green1 blue and purple tints were observed in the meteors and their trails1 as represented in the ,plate4 ,,plate ,,xiii4--,,part ,,of ,,the ,,milky ,,way4 ,from a study made during the years #ahgd1 #ahge and #ahgf4 ,the course of the portion of the ,galaxy represented in ,plate ,,xiii4 is as follows3 ,from ,cassiopeia's chair1 three bright stars of which appear at the upper edge of the ,plate1 the ,galaxy1 forming two streams1 descends south1 passing partly through ,lacerta on the left1 and ,cepheus on the right2 at this last point it approaches nearest to the ,polar ,star1 which is itself outside of the field of view4 ,then it enters ,cygnus1 where it becomes very complicated and bright1 and where several large cloudy masses are seen terminating its left branch1 which passes to the right1 near the bright star ,deneb1 the leader of this constellation4 ,below ,deneb1 the ,galaxy is apparently disconnected and separated from the northern part by a narrow1 irregular dark gap4 ,from this rupture1 the ,milky-way divides into two great streams1 separated by an irregular dark rift4 ,an immense branch extends to the right1 which1 after having formed an important luminous mass between the stars ,gamma and ,beta1 continues its southward progress through parts of ,lyra1 ,vulpecula1 ,hercules1 ,aquila and ,ophiuchus1 where it gradually terminates a few degrees south of the equator4 ,the main stream on the left1 after having formed a bright mass around ,epsilon ,cygni1 passes through ,vulpecula and then ,aquila1 where it crosses the equinoctial just below the star ,eta1 after having involved in its nebulosity the bright star ,altair1 the leader of ,aquila4 ,in the southern hemisphere the ,galaxy becomes very complicated and forms a succession of very bright1 irregular masses1 the upper one being in ,scutum ,sobieskii1 while the others are respectively situated in ,sagittarius and in ,scorpio2 the last1 just a little above our horizon1 being always considerably dimmed by vapors4 ,from ,scutum ,sobieskii1 the ,galaxy expands considerably on the right1 and sends a branch into ,scorpio1 in which the fiery red star ,antares is somewhat involved4 ,in the upper left-hand corner of the ,plate1 at some distance from the ,milky-way1 is seen dimly the ,nebula in ,andromeda1 which becomes so magnificent an object to telescopic view4 ,,plate ,,xiv4--,,star-,,cluster ,,in ,,hercules4 ,from a study made in ,june1 #ahgg4 ,in the constellation ,hercules1 a small nebulous mass is faintly visible to the eye1 a telescopic view of which is presented in ,plate ,,xiv4 ,it is one of the most beautiful of the easily resolvable globular clusters4 ,the brilliancy of the centre gives the cluster a distinctly globular appearance1 while the several wings curving in various directions1 have suggested to some observers an irregularly spiral structure4 ,the large stars of the cluster are arranged in several groups which correspond1 in a general way1 with the faintly luminous wings4 ,,plate ,,xv4--,,the ,,great ,,nebula ,,in ,,orion4 ,from a study made in the years #ahge-gf4 ,this nebula1 which is one of the most brilliant and wonderful of telescopic objects1 readily visible to the naked eve as a patch of nebulous light immediately surrounding the middle star of the three which form the sword of ,orion1 and a little south of the three well-known stars forming the belt4 ,the small stars in this1 as in other ,plates of the series1 are somewhat exaggerated in size1 as was unavoidable with any mode of reproduction that could be employed4 ,the bright pentagonal centre of the nebula is traversed by less luminous rifts1 the several subdivisions thus outlined being irregularly mottled as if by bright fleecy clouds4 ,toward the lower part of this bright pentagonal centre is a comparatively dark space containing four bright stars which form a trapezium and together constitute the quadruple star ,theta ,orionis1 which1 to the naked eye1 appears as the single star in the centre of the sword4 ,on three sides of the central mass extend long bright wisps1 whose curves fail1 however1 to reveal the spiral structure often attributed to this nebula4 ,on the east a broad wing1 with wave-shaped inner border1 stretches southward4 ,east of the trapezium are two especially noticeable dark spaces4 ,close to the main nebula on the north-east1 a small faint nebula surrounds a bright star1 and a branch from another faint stream of nebulous matter forming a loop to the southward1 encloses the nebulous star 7,iota ,orionis7 shown at the top of the ,plate4