,,auror3 ,,their ,,characters ,,and ,,spectra4 ,,by ,j4 ,,rand ,,capron1 ,f4,r4,a4,s4 8,and now the ,northern ,lights begin to burn1 faintly at first1 like sunbeams playing in the waters of the blue sea4 ,then a soft crimson glow tinges the heavens4 ,there is a blush on the cheek of night4 ,the colours come and go2 and change from crimson to gold1 from gold to crimson4 ,the snow is stained with rosy light4 ,twofold from the zenith1 east and west1 flames a fiery sword2 and a broad band passes athwart the heavens1 like a summer sunset4 ,soft purple clouds come sailing over the sky1 and through their vapoury folds the winking stars shine white as silver4 ,with such pomp as this is ,merry ,christmas ushered in1 though only a single star heralded the first ,christmas40--,,longfellow4 ,,london3 ,e4 ,f4 ,n4 ,,spon1 #df ,,charing ,,cross4 ,,new ,,york3 #ddf ,,broom ,,street4 #ahgi4 ,illustration ,,printed ,,by ,,taylor ,,and ,,francis1 ,,red ,,lion ,,court1 ,,fleet ,,street4 ,,to ,,prof4 ,,charles ,,piazzi ,,smyth1 ,f4,r4,s4,e41 ,,astronomer ,,royal ,,for ,,scotland1 ,,one ,,of ,,the ,,earliest ,,spectroscopic ,,observers ,,of ,,the ,,aurora ,,and ,,zodiacal ,,light1 ,,this ,,volume ,,is ,,respectfully ,,dedicated ,,by ,,the ,,author4 ,,preface4 ,probably few of the phenomena of ,nature so entirely charm and interest scientific and non-scientific observers alike as the ,aurora ,borealis1 or 8,northern ,lights0 as it is popularly called4 ,whether contemplated as the long low quiescent arc of silver light illuminating the landscape with a tender radiance1 as broken clouds and columns of glowing ruddy light1 or as sheaves of golden rays1 aptly compared by old writers to aerial spears1 such a spectacle cannot fail at all times to be a subject of admiration1 in some cases even of awe4 ,hence it is no wonder that the ,aurora has always received a considerable amount of attention at the hands of scientific men4 ,early explorers of the ,arctic ,regions made constant and important observations of it and its character2 and the list of references to works given in the ,appendix will show how often it formed the subject of monographs and communications to learned ,societies4 ,the early contributions seem relatively more numerous than those of a later date2 and the substance of them will be found well summed up in ,dr4 ,brewster's #8,edinburgh ,encyclopdia' 7#ahcj71 article 8,aurora40 ,a most complete and able epitome of our more recent experience and knowledge of the ,aurora and its spectrum has been contributed by my friend ,mr4 ,henry ,r4 ,procter to the present 7#ith7 edition of the #8,encyclopdia ,britannica1' article 8,aurora ,polaris40 ,it is1 however1 a drawback to ,encyclopdic articles that their matter is of necessity condensed1 and that they rarely have the very desirable aid of drawings and engravings to illustrate their subjects4 ,in spite1 therefore1 of the exhaustive way1 both as to fact and theory1 in which the contributor to the #8,encyclopdia ,britannica' has realized his task1 it seemed to me there was still room left for a popular treatise1 having for its object the description of ,auror1 their characters and spectra4 ,the question of the ,aurora spectrum seems the more worthy of extended discussion in that it still remains an unsolved problem4 ,in spite of the observations and researches of ngstrm1 ,lemstrm1 and ,vogel abroad1 and of ,piazzi ,smyth1 ,herschel1 ,procter1 ,backhouse1 and others at home1 the goal is not yet reached2 for while the faint and more refrangible lines are but doubtfully referred to air1 the bright and sharp red and green lines1 which mainly characterize the spectrum1 are as yet unassociated with any known analogue4 ,with these views1 and to incite to further and closer observations1 ,i have been induced to publish the present volume as a sort of ,auroral ,guide4 ,for much of the history of the ,aurora ,i am indebted to1 and quote from former articles and records1 including the two excellent ,encyclopdic ones before referred to4 ,mr4 ,procter1 ,mr4 ,backhouse1 and my friend ,mr4 ,w4 ,h4 ,olley have each kindly furnished me with much in the way of information and suggestion4 ,dr4 ,schuster has lent me tubes showing the true oxygen spectrum2 while ,herr ,carl ,bock1 the ,norwegian naturalist1 has enabled me to reproduce a veritable curiosity1 viz4 a picture in oil painted by the light of a ,lapland ,aurora4 ,the experiments detailed in ,part ,,iii4 were suggested by the earlier ones of ,de la ,rive1 ,varley1 and others1 and demonstrate the effect of the magnet on electric discharges4 ,for assistance in these ,i am indebted to my friend ,mr4 ,e4 ,dowlen4 ,the illustrations are mainly from original drawings of my own4 ,those from other sources are acknowledged4 ,messrs4 ,mintern have well reproduced in chromo-lithography the coloured drawings illustrating the ,auror1 moon-patches1 c4 ,,table ,,of ,,contents4 ,,part ,i4 ,,the ,,aurora ,,and ,,its ,,characters4 ,,chapter ,i4 ,the ,aurora as known to the ,ancients3 pp4 #a-e4 ,,chapter ,,ii4 ,some general ,descriptions of ,auror3 pp4 #f-ae4 ,by ,sir ,john ,franklin3 pp4 #f1 #g4 ,by ,rev4 ,james ,farquharson3 pp4 #g1 #h4 ,by ,mons4 ,lottin 7,lardner73 pp4 #h-aa4 ,by ,lieut4 ,weyprecht 7,payer73 pp4 #aa-ad4 ,article in #8,edinburgh ,encyclopdia3' pp4 #ad1 #ae4 ,,chapter ,,iii4 ,some specific ,descriptions of ,auror3 pp4 #af-cj4 ,capt4 ,sabine's ,auror3 p4 #af4 ,aurora seen at ,sunderland1 ,february #hth1 #ahag3 p4 #af4 ,dr4 ,hayes's ,aurora1 #fth ,january1 #ahfa3 pp4 #af1 #ag4 ,prof4 ,lemstrm's ,aurora1 #ast ,september1 #ahfh3 pp4 #ag1 #ah4 ,mr4 ,j4 ,r4 ,capron's ,aurora1 ,october #bdth1 #ahgj3 pp4 #ah1 #ai4 ,mr4 ,barker's red and white ,auror1 #ith ,november 7#ahgj873 p4 #ai4 ,mr4 ,j4 ,r4 ,capron's ,aurora1 ,february #dth1 #ahgb3 pp4 #ai1 #bj4 ,cardiff1 ,aurora seen at3 p4 #ba4 ,mr4 ,j4 ,r4 ,capron's ,aurora1 ,february #dth1 #ahgd3 pp4 #ba1 #bb4 ,mr4 ,herbert ,ingall's ,aurora1 ,july #ahth1 #ahgd3 pp4 #bb1 #bc4 ,mr4 ,j4 ,r4 ,capron's white ,aurora1 ,september #aath1 #ahgd3 pp4 #bc1 #bd4 ,dr4 ,allnatt's ,aurora1 ,june #ith1 #ahgf3 p4 #bd4 ,herr ,carl ,bock's ,lapland ,aurora1 ,october #crd1 #ahgg3 p4 #be4 ,rev4 ,t4 ,w4 ,webb's ,aurora3 pp4 #be1 #bf4 ,english ,arctic ,expedition1 #ahge-gf3 p4 #bf4 ,aurora ,australis3 pp4 #bf-bi4 ,prof4 ,piazzi ,smyth's typical ,auror3 pp4 #bi1 #cj4 ,,chapter ,,iv4 ,phenomena simulating ,auror3 pp4 #ca-cb4 ,auroric ,lights 7,kinahan73 pp4 #ca1 #cb4 ,luminous ,arch3 p4 #cb4 ,,chapter ,v4 ,some qualities of the ,aurora3 pp4 #cc-ea4 ,noises attending ,auror3 pp4 #cc1 #cd4 ,colours of ,aurora3 pp4 #ce-cg4 ,height of ,aurora3 pp4 #cg-dj4 ,phosphorescence attending ,aurora3 pp4 #da-dd4 ,aurora and ,ozone3 pp4 #dd1 #de4 ,polarization of ,aurora light3 pp4 #de1 #df4 ,number of ,auror3 p4 #df4 ,duration of ,aurora3 p4 #dg4 ,travelling of ,auror 7,donati73 pp4 #dg1 #dh4 ,geographical distribution of ,auror 7,fritz and ,loomis73 pp4 #dh1 #di4 ,extent and principal zone of the ,aurora3 pp4 #ej1 #ea4 ,,chapter ,,vi4 ,aurora in connexion with other ,phenomena3 pp4 #eb-fi4 ,auror and ,clouds3 pp4 #eb-ed4 ,aurora and ,thunder-storms3 pp4 #ed1 #ee4 ,aurora and ,magnetic ,needle3 pp4 #ee-eh4 ,auror1 ,magnetic ,disturbances1 and ,sun-spots3 pp4 #eh-fb4 ,aurora and ,electricity3 pp4 #fb-fd4 ,aurora and ,meteoric ,dust3 pp4 #fd1 #fe4 ,aurora and ,planets ,venus and ,jupiter3 pp4 #ff1 #fg4 ,aurora and ,zodiacal ,light3 pp4 #fg-fi4 ,,chapter ,,vii4 ,aurora-like patches on the partially-eclipsed ,moon3 pp4 #gj-gg4 ,,chapter ,,viii4 ,aurora and ,solar ,corona3 pp4 #gh-ha4 ,,chapter ,,ix4 ,supposed ,causes of the ,aurora3 pp4 #hb-hg4 ,prof4 ,lemstrm's ,theory3 pp4 #hg1 #hh4 ,theories of ,,mm4 ,becquerel and ,de la ,rive3 p4 #hh4 ,m4 ,plant's electric experiments3 pp4 #hi1 #ij4 ,,part ,,ii4 ,,the ,,spectrum ,,of ,,the ,,aurora4 ,,chapter ,x4 ,spectroscope adapted for the ,aurora3 pp4 #ia-ic4 ,spectrum of ,aurora described3 pp4 #id-ajj4 ,flickering of the green line3 p4 #ajj4 ,mr4 ,backhouse's graphical spectra of four ,auror3 p4 #aja4 ,lord ,lindsay's ,aurora-spectrum1 ,october #ba1 #ahgj3 p4 #ajb4 ,spectrum of the ,aurora ,australis3 pp4 #ajc1 #ajd4 ,professor ,piazzi ,smyth's ,aurora-spectra3 p4 #ajd4 ,author's ,catalogue of the ,auroral lines3 pp4 #ajd-ajf4 ,theories in relation to the ,aurora and its spectrum3 pp4 #ajf1 #ajg4 ,,chapter ,,xi4 ,the comparison of some ,tube and other ,spectra with the ,spectrum of the ,aurora3 pp4 #ajh-abj4 ,hydrogen-tube3 pp4 #ajh-aaj4 ,carbon- and oxygen-tubes3 pp4 #aaj-aad4 ,geissler mercury-tube and barometer mercurial vacuum3 pp4 #aad1 #aae4 ,air-tubes3 pp4 #aae1 #aaf4 ,phosphorescent tube3 pp4 #aaf1 #aag4 ,spark in air3 p4 #aag4 ,spark over water3 p4 #aag4 ,phosphoretted-hydrogen flame3 pp4 #aag1 #aah4 ,iron-spectrum3 p4 #aah4 ,spectrum of mercury3 p4 #aai4 ,table of coincidences3 p4 #aai4 ,,chapter ,,xii4 ,notes on ,professor ngstrm's ,theory of the ,aurora-spectrum3 pp4 #aba-abg4 ,,chapter ,,xiii4 ,the ,oxygen-spectrum in relation to the ,aurora 7,procter and ,schuster73 pp4 #abh-aca4 ,,part ,,iii4 ,,magneto-,,electric ,,experiments ,,in ,,connexion ,,with ,,the ,,aurora4 ,,introduction3 pp4 #acc-ace4 ,,chapter ,,xiv4 ,examination of ,geissler-tubes under action of the ,magnet3 pp4 #acf-adf4 ,nitrogen-tubes3 pp4 #acf1 #acg4 ,oxygen-tubes3 p4 #ach4 ,hydrogen-tubes3 pp4 #ach1 #aci4 ,water-gas tube3 p4 #aci4 ,ammonia-tube3 pp4 #aci1 #adj4 ,carbonic-acid tube3 p4 #adj4 ,chlorine-tubes3 pp4 #adj1 #ada4 ,iodine-tubes3 pp4 #ada-adc4 ,bromine-tubes3 pp4 #adc1 #add4 ,silicic fluoride-tubes3 p4 #add4 ,sulphuric-acid tubes3 pp4 #add1 #ade4 ,sulphur-tube3 pp4 #ade1 #adf4 ,,chapter ,,xv4 ,effect of ,magnet on a capillary ,glass ,tube3 pp4 #adg1 #adh4 ,action of magnet on a bar of heavy glass3 pp4 #adg1 #adh4 ,,chapter ,,xvi4 ,effect of ,magnet on wide ,air 7,aurora7 tube3 pp4 #adi-aec4 ,stratification 7note on73 pp4 #adi1 #aej4 ,effect of magnet on ,plcker 7air-7 tube3 pp4 #aej-aeb4 ,effect of magnet on ,plcker tube 7tin chloride73 pp4 #aeb1 #aec4 ,effect of magnet on tin-chloride ,geissler tube3 p4 #aec4 ,,chapter ,,xvii4 ,effect of ,magnet on bulbed ,phosphorescent ,tube3 pp4 #aed-aef4 ,effect of magnet on small phosphorescent 7powder7 tubes3 pp4 #aef1 #aeg4 ,lighting-up tubes with one wire only 7,marquis of ,salisbury's observations73 pp4 #aeg1 #aeh4 ,,chapter ,,xviii4 ,action of the ,magnet on the ,electric ,spark3 pp4 #aei1 #afj4 ,,chapter ,,xix4 ,the ,discharge in vacuo in ,larger ,vessels1 and ,magnetic ,effects thereon3 pp4 #afa-afe4 ,some of ,baron ,reichenbach's magnetic researches tested3 pp4 #afe1 #aff4 ,summary of the foregoing ,experiments and their ,results3 p4 #afg4 ,,chapter ,,xx4 ,some concluding ,remarks3 pp4 #afh-aga4 ,,appendices4 ,a4 ,references to some ,works and ,essays on the ,aurora3 pp4 #agc1 #agd4 ,b4 ,extracts from the ,manual and ,instructions for the 7,english7 ,arctic ,expedition1 #ahge3 pp4 #age-aha4 ,c4 ,extracts from ,parliamentary ,blue-book1 containing the 8,results derived from the ,arctic ,expedition1 #ahge-gf30 pp4 #ahb-ahh4 ,d4 ,aurora and ,ozone3 pp4 #ahi-aic4 ,e4 ,dr4 ,vogel's ,inquiries into the ,spectrum of the ,aurora3 pp4 #aid-bjg4 ,,list ,,of ,,plates4 ,plate4 ,i4 ,the ,aurora during the ,ice-pressure ,to face page #ad ,,ii4 ,aurora seen by ,dr4 ,hayes1 #fth ,january1 #ahfa 0 0 #af ,,iii4 ,aurora1 ,guildford1 ,oct4 #bd1 #ahgj 0 0 #ah ,,iv4 ,aurora1 ,guildford1 ,feb4 #d1 #ahgb2 ,eclipsed ,moon1 ,aug4 #bc1 #bd1 #ahgg 0 0 #bj ,v4 ,corona1 ,graphical ,auror1 ,zodiacal ,light1 c4 0 0 #ba ,,vi4 ,aurora1 ,guildford1 ,feb4 #d1 #ahgd2 ,spectrum des ,nordlichts 7,vogel7 0 0 #bb ,,vii4 ,aurora1 ,kyle ,akin1 ,isle of ,skye1 ,sept4 #aa1 #ahgd 0 0 #bd ,,viii4 ,herr ,carl ,bock's ,lapland ,aurora1 ,oct4 #c1 #ahgg 0 0 #be ,,ix4 ,compared ,aurora and other ,spectra4 ,loomis's curves of ,auroras1 ,magnetic ,declination1 and ,solar ,spots 0 0 #ei ,x4 ,spectroscope1 ,micrometer1 ,tubes 0 0 #ia ,,xi4 ,aurora-spectra1 ,candle-spectrum 0 0 #ajb ,,xii4 ,aurora-spectrum1 ,solar spectrum1 and ,candle-spectrum 0 0 #ajd ,,xiii4 ,vogel's ,aurora-lines1 ,aurora-lines near ,g1 and in the red and green 0 0 #ajh ,,xiv4 ,aurora1 ,hydrocarbons1 ,oxygen 0 0 #aaj ,,xv4 ,aurora and ,air-tubes1 c4 0 0 #aae ,,xvi4 ,aurora1 ,phosphoretted ,hydrogen1 ,iron1 c4 0 0 #aag ,,xvii4 ,effect of ,magnet on ,tubes and ,spark 0 0 #acd ,,xviii4 ,same1 and ,oxygen-spectrum 0 0 #aed ,,part ,i4 ,,the ,,aurora ,,and ,,its ,,characters4 ,,chapter ,i4 ,,the ,,aurora ,,as ,,known ,,to ,,the ,,ancients4 ,sidenote3 ,seneca's #8,qustiones ,naturales1' ,lib4 ,i4 c4 xiv4 ,description of ,auror4 ,in ,seneca's #8,qustiones ,naturales1' ,lib4 ,i4 c4 xiv41 we find the following3--8,tempus est1 alios quoque ignes percurrere1 quorum divers figur sunt4 ,aliquando emicat stella1 aliquando ardores sunt1 aliquando fixi et hrentes1 nonnunquam volubiles4 ,horum plura genera conspiciantur4 ,sunt ,bothyno#a1 quum velut corona cingente introrsus igneus cli recessus est similis effoss in orbem spelunc4 ,sunt ,pithit#b1 quum magnitudo vasti rotundique ignis dolio similis1 vel fertur vel in uno loco flagrat4 ,sunt ,chasmata#c1 quum aliquod cli spatium desedit1 et flammam dehiscens1 velut in abdito1 ostentat4 ,colores quoque omnium horum plurimi sunt4 ,quidam ruboris acerrimi1 quidam evanid ac levis flamm1 quidam candid lucis1 quidam micantes1 quidam qualiter et sine eruptionibus aut radiis fulvi4 ''' ,sidenote3 ,seneca1 c4 xv4 ,c4 xv4 8,inter hc ponas licet et quod frequenter in historiis legimus1 clum ardere visum3 cujus nonnunquam tam sublimis ardor est ut inter ipsa sidera videatur1 nonnunquam tam humilis ut speciem longinqui incendii prbeat4 8,sub ,tiberio ,csare cohortes in auxilium ,ostiensis coloni cucurrerunt1 tanquam conflagrantis1 quum cli ardor fuisset per magnam partem noctis1 parum lucidus crassi fumidique ignis40 ,sidenote3 ,translation4 ,we may translate this3--8,it is time other fires also to describe1 of which there are diverse forms4 8,sometimes a star shines forth2 at times there are fire-glows1 sometimes fixed and persistent1 sometimes flitting4 ,of these many sorts may be distinguished4 ,there are ,bothyno1 when1 as within a surrounding corona1 the fiery recess of the sky is like to a cave dug out of space4 ,there are ,pithit1 when the expanse of a vast and rounded fire similar to a tub 7dolium7 is either carried about or glows in one spot4 8,there are ,chasmata1 when a certain portion of the sky opens1 and gaping displays the flame as in a porch4 ,the colours also of all these are many4 ,certain are of the brightest red1 some of a flitting and light flame-colour1 some of a white light1 others shining1 some steadily and yellow without eruptions or rays4 ''' 8,amongst these we may notice1 what we frequently read of in history1 the sky is seen to burn1 the glow of which is occasionally so high that it may be seen amongst the stars themselves1 sometimes so near the ,earth 7humilis7 that it assumes the form of a distant fire4 ,under ,tiberius ,csar the cohorts ran together in aid of the colony of ,ostia as if it were in flames1 when the glowing of the sky lasted through a great part of the night1 shining dimly like a vast and smoking fire40 ,sidenote3 ,auror frequently read of in history4 ,from the above passages many striking particulars of the ,aurora may be gathered2 and by the division of the forms of ,aurora into classes it is evident they were1 at that period1 the subject of frequent observation4 ,the expression 8et quod frequenter in historiis legimus0 shows1 too1 that the phenomena of ,auroral displays were a matter of record and discussion with the writers of the day4 ,various forms of ,aurora may be recognized in the passages from ,chap4 xiv42 while in those from ,chap4 xv4 a careful distinction is drawn between the ,auror seen in the zenith or the upper regions of the sky1 and those seen on the horizon or apparently 7and no doubt in some cases actually7 near the ,earth's surface4 ,sidenote3 ,a spurious ,aurora4 ,the description of the cohorts running to the fire only to find it an ,aurora1 calls to mind the many similar events happening in our own days4 ,not1 however1 but that a mistake may sometimes occur in an opposite direction4 ,in the memoirs of ,baron ,stockmar an amusing anecdote is related of one ,herr von ,radowitz1 who was given to making the most of easily picked up information4 ,a friend of the ,baron's went to an evening party near ,frankfort1 where he expected to meet ,herr von ,radowitz4 ,on his way he saw a barn burning1 stopped his carriage1 assisted the people1 and waited till the flames were nearly extinguished4 ,when he arrived at his friend's house he found ,herr von ,radowitz1 who had previously taken the party to the top of the building to see an ,aurora1 dilating on terrestrial magnetism1 electricity1 and so forth4 ,radowitz asked ,stockmar's friend1 8,have you seen the beautiful ,aurora ,borealis80 ,he replied1 8,certainly2 ,i was there myself2 it will soon be over40 ,an explanation followed as to the barn on fire3 ,radowitz was silent some ten minutes1 then took up his hat and quietly disappeared4 ,sidenote3 ,auror as portents4 ,it is probable that many of the phantom combats which are recorded to have appeared in forms of fire in the air on the evenings preceding great battles might be traced to ,auror1 invested with distinct characteristics by the imagination of the beholders4 ,auror are said to have appeared in the shape of armies of horse and foot engaged in battle in the sky before the death of ,julius ,csar1 which they were supposed to foretell4 ,for more than a year before the siege and destruction of ,jerusalem by ,titus ,vespasian1 the ,aurora was said to have been frequently visible in ,palestine4 ,josephus1 in his #8,wars of the ,jews' 7,whiston's ,translation1 ,book ,,vi4 chap4 v4 sect4 #c71 in referring to the signs and wonders preceding the destruction of ,jerusalem1 speaks of a star or comet1 and that a great light shone round about the altar and the holy house1 which light lasted for half an hour1 and that a few days after the feast of unleavened bread a certain prodigious and incredible phenomenon appeared--8for before sunsetting chariots and troops of soldiers in their armour were seen running about among the clouds1 and surrounding of cities40 7,this1 if an ,aurora1 must have been an instance of a daylight one47 ,we find in ,book ,,ii4 of ,maccabees1 chap4 v4 verses #a1 #b1 #c1 #d 7,b4,c4 about #agf years73-- 8#a4 ,about this same time ,antiochus prepared his second voyage into ,egypt3 8#b4 ,and then it happened that through all the city1 for the space almost of forty days1 there were seen horsemen running in the air1 in cloth of gold1 and armed with lances like a band of soldiers4 8#c4 ,and troops of horsemen in array1 encountering and running one against another1 with shaking of shields and multitude of pikes1 and drawing of swords and casting of darts1 and glittering of golden ornaments and harness of all sorts4 8#d4 ,wherefore every man prayed that that apparition might turn to good40 ,sidenote3 ,early descriptions of ,auror4 ,in ,aristotle's #8,de ,meteoris1' ,lib4 ,i4 c4 iv4 and v41 the ,aurora is described as an appearance resembling flame mingled with smoke1 and of a purple red or blue colour4 ,pliny 7,lib4 ,,ii4 c4 xxvii47 speaks of a bloody appearance of the heavens which seemed like a fire descending on the earth1 seen in the third year of the #ajgth ,olympiad1 and of a light seen in the nighttime equal to the brightness of the day1 in the ,consulship of ,ccilius and ,papirius 7,lib4 ,,ii4 c4 xxxiii471 both of which may be referred to ,auror4 ,in the #8,annals of ,philosophy1' vol4 ix4 p4 #bej1 it is stated that the ,aurora among ,english writers is first described by ,matthew of ,westminster1 who relates that in ,a4,d4 #eee lances were seen in the air 78quasi species lancearum in are vis sunt a septentrionali usque ad occidentem074 ,in the article in the #8,edinb4 ,encyc4' vol4 iii4 7#ahcj71 the ,aurora 7known to the vulgar as 8streamers0 or 8merry dancers07 is distinguished in two kinds--the 8tranquil0 and the 8varying40 ,musschenbroek enumerates as forms3--trabs1 8the beam10 an oblong tract parallel to the horizon2 sagitta1 8the arrow20 faces1 8the torch20 capra saltans1 8the dancing goat20 bothyno1 8the cave10 a luminous cloud having the appearance of a recess or hollow in the heavens1 surrounded by a corona2 pithi1 8the tun10 an ,aurora resembling a large luminous cask4 ,the two sorts of ,auror distinguished as the 8bothyno0 and 8pithi0 are evidently taken from the passage in ,seneca's #8,qustiones' before quoted4 ,in #8,liberti ,fromondi ,meteorologicorum' 7,london1 #afef71 ,lib4 ,,ii4 cap4 v4 8,de ,meteoris suprem regionis aris10 art4 #a4 ,de ,capra1 ,trabe1 ,pyramide1 c41 these and other fantastic forms attributable to ,auror are more fully described4 ,in the article 8,aurora ,polaris10 ,encyc4 ,brit4 edit4 ix41 we find noted that from a curious passage in ,sirr's #8,ceylon and the ,cingalese1' vol4 ii4 p4 #aag1 it would seem that the ,aurora1 or something like it1 is visible occasionally in ,ceylon1 where the natives call it 8,buddha ,lights10 and that in many parts of ,ireland a scarlet ,aurora is supposed to be a shower of blood4 ,the earliest mentioned ,aurora 7in ,ireland7 was in #fhh1 in the #8,annals of ,cloon-mac-noise1' after a battle between ,leinster and ,munster1 in which ,foylcher ,o',moyloyer was slain4 ,in the article in the ,edinb4 ,encyc4 before referred to it is stated that it was not much more than a century ago that the phenomenon had been noticed to occur with frequency in our latitudes4 ,dr4 ,halley had begun to despair of seeing one till the fine display of #agaf4 ,sidenote3 ,early notices of ,auror not frequent in our latitudes4 ,the first account on record in an ,english work is said to be in a book entitled #8,a ,description of ,meteors by ,w4 ,f4 ,d4 ,d4' 7reprinted1 ,london1 #afed71 which speaks of 8burning spears0 being seen ,january #cj1 #aefj4 ,the next is recorded by ,stow as occurring on ,october #g1 #aefd2 and1 according to ,stow and ,camden1 an ,aurora was seen on two nights1 #adth and #aeth ,november1 #aegd4 ,twice1 again1 an ,aurora was seen in ,brabant1 #acth ,february and #bhth ,september1 #aege4 ,cornelius ,gemma compared these to spears1 fortified cities1 and armies fighting in the air4 ,auror were seen in #aehj and #aeha in ,wirtemberg1 ,germany4 ,then we have no record till #afba1 when an ,aurora1 described by ,gassendi in his #8,physics1' was seen all over ,france1 ,september #bnd of that year4 ,in ,november #afbc another1 described by ,kepler1 was seen all over ,germany4 ,from #afff to #agaf no appearance is recorded in the #8,transactions of the ,french ,academy of ,sciences2' but in #agjg one was seen in ,ireland and at ,copenhagen2 while in #agjg and #agjh the ,aurora was seen five times4 ,the ,aurora of #agaf1 occurring after an interval of eighty years1 which ,dr4 ,halley describes1 was very brilliant and extended over much country1 being seen from the west of ,ireland to the confines of ,russia and the east of ,poland1 extending nearly #cj of longitude1 and from about the #ejth degree of latitude1 over almost all the north of ,europe1 and in all places exhibiting at the same time appearances similar to those observed in ,london4 ,an ,aurora observed in ,bologna in #agbc was stated to be the first that had ever been seen there2 and one recorded in the #8,berlin ,miscellany' for #agig is called a very unusual phenomenon4 ,nor did ,auror appear more frequent in the ,polar ,regions at that time1 for ,clius states that the oldest inhabitants of ,upsala considered the phenomenon as quite rare before #agaf4 ,anderson1 of ,hamburg1 writing about the same time1 says that in ,iceland the inhabitants themselves were astonished at the frequent ,auror then beginning to take place2 while ,torfus1 the ,icelander1 who wrote in #agjf1 was old enough to remember the time when the ,aurora was an object of terror in his native country4 ,according to ,m4 ,mairan1 #adda ,auror were observed between ,a4,d4 #ehc and #agea1 of which #igb were observed in the winter half-years and #dfi during the summer half-years4 ,in our next ,chapter we propose to give some general descriptions of ,auror from comparatively early sources4 ,,chapter ,,ii4 ,,some ,,general ,,descriptions ,,of ,,auror4 ,sidenote3 ,sir ,john ,franklin's description4 ,sir ,john ,franklin 7#8,narrative of a ,journey to the ,shores of the ,polar ,sea in the years #ahai1 #ahbj1 #ahba1 #ahbb'7 describes an ,aurora in these terms3-- ,sidenote3 ,parts of the ,aurora3 beams1 flashes1 and arches4 8,for the sake of perspicuity ,i shall describe the several parts of the ,aurora1 which ,i term beams1 flashes1 and arches4 8,the beams are little conical pencils of light1 ranged in parallel lines1 with their pointed extremities towards the earth1 generally in the direction of the dipping-needle4 ,sidenote3 ,formation of the ,aurora4 8,the flashes seem to be scattered beams approaching nearer to the earth1 because they are similarly shaped and infinitely larger4 ,i have called them flashes1 because their appearance is sudden and seldom continues long4 ,when the ,aurora first becomes visible it is formed like a rainbow1 the light of which is faint1 and the motion of the beams undistinguishable4 ,it is then in the horizon4 ,as it approaches the zenith it resolves itself into beams which1 by a quick undulating motion1 project themselves into wreaths1 afterwards fading away1 and again and again brightening without any visible expansion or contraction of matter4 ,numerous flashes attend in different parts of the sky40 ,sidenote3 ,arches of the ,aurora4 ,sir ,john ,franklin then points out that this mass would appear like an arch to a person situated at the horizon by the rules of perspective1 assuming its parts to be equidistant from the earth2 and mentions a case when an ,aurora1 which filled the sky at ,cumberland ,house from the northern horizon to the zenith with wreaths and flashes1 assumed the shape of arches at some distance to the southward4 ,he then continues3--8,but the ,aurora does not always make its first appearance as an arch4 ,it sometimes rises from a confused mass of light in the east or west1 and crosses the sky towards the opposite point1 exhibiting wreaths of beams or coron boreales on its way4 ,an arch also1 which is pale and uniform at the horizon1 passes the zenith without displaying any irregularity or additional brilliancy40 ,sir ,john ,franklin then mentions seeing three arches together1 very near the northern horizon1 one of which exhibited beams and even colours1 but the other two were faint and uniform4 7,see example of a doubled arc ,aurora observed at ,kyle ,akin1 ,skye1 ,plate ,,vii47 ,he also mentions an arch visible to the southward exactly similar to one in the north4 ,it appeared in fifteen minutes1 and he suggests it probably had passed the zenith before sunset4 ,the motion of the whole body of the ,aurora from the northward to the southward was at angles not more than #bj from the magnetic meridian4 ,the centres of the arches were as often in the magnetic as in the true meridian4 ,a delicate electrometer1 suspended #ej feet from the ground1 was never perceptibly affected by the ,aurora4 ,sidenote3 ,aurora does not often appear until some hours after sunset4 ,sir ,john ,franklin further remarks that the ,aurora did not often appear immediately after sunset1 and that the absence of that luminary for some hours was in general required for the production of a state of atmosphere favourable to the generation of the ,aurora4 ,sidenote3 ,aurora seen in daylight4 ,on one occasion1 however 7,march #hth1 #ahba71 he observed it distinctly previous to the disappearance of daylight2 and he subsequently states that on four occasions the coruscations of the ,aurora were seen very distinctly before daylight had disappeared4 ,in the article 8,aurora ,polaris10 ,encyc4 ,brit4 edit4 ix41 the ,transactions of the ,royal ,irish ,academy1 #aghh1 are referred to1 where ,dr4 ,usher notices that the ,aurora makes the stars flutter in the telescope2 and that1 having remarked this effect strongly one day at #aa ,a4,m41 he examined the sky1 and saw an ,auroral corona with rays to the horizon4 ,instances are by no means rare of the principal ,aurora-line having been seen in waning sunlight1 and in anticipation of an ,aurora which afterwards appeared4 ,sidenote3 ,the ,rev4 ,james ,farquharson's observations4 ,auroral arch4 ,passage across the zenith4 ,the ,rev4 ,james ,farquharson1 from the observation of a number of ,auror in ,aberdeenshire in #ahbc 7#8,philosophical ,transactions1' #ahbi71 concluded3--that the ,aurora follows an invariable order in its appearance and progress2 that the streamers appear first in the north1 forming an arch from east to west1 having its vertex at the line of the magnetic meridian 7when this arch is of low elevation it is of considerable breadth from north to south1 having the streamers placed crosswise in relation to its own line1 and all directed towards a point a little south of the zenith72 that the arch moves forward towards the south1 contracting laterally as it approaches the zenith1 and increasing its intensity of light by the shortening of the streamers and the gradual shifting of the angles which the streamers near the east and west extremities of the arch make with its own line1 till at length these streamers become parallel to that line1 and then the arch is seen in a narrow belt #c or #d only in breadth1 stretching across the zenith at right angles to the magnetic meridian2 that it still makes progress southwards1 and after it has reached several degrees south of the zenith again enlarges its breadth by exhibiting an order of appearances the reverse of that which attended its progress towards the zenith from the north2 that the only conditions that can explain and reconcile these appearances are that the streamers of the ,aurora are vertical1 or nearly so1 and form a deep fringe which stretches a great way from east to west at right angles to the magnetic meridian1 but which is of no great thickness from north to south1 and that the fringe moves southward1 preserving its direction at right angles to the magnetic meridian4 ,sidenote3 ,m4 ,lottin's observations4 ,dr4 ,lardner1 in his #8,museum of ,science and ,art1' vol4 x4 p4 #ahi et seq41 alludes to a description of 8this meteor0 7sic7 supplied by ,m4 ,lottin1 an officer of the ,french ,navy1 and a ,member of the ,scientific ,commission to the ,north ,seas4 ,between ,september #ahch and ,april #ahci1 being the interval when the sun was constantly below the horizon1 this savant observed nearly #aej ,auror4 ,during this period sixty-four were visible1 besides many concealed by a clouded sky1 but the presence of which was indicated by the disturbances they produced upon the magnetic needle4 ,the succession of appearances and changes presented by these 8meteors0 is thus graphically described by ,m4 ,lottin3-- ,sidenote3 ,formation of the auroral bow4 8,between four and eight o'clock ,p4,m4 a light fog1 rising to the altitude of six degrees1 became coloured on its upper edge1 being fringed with the light of the meteor rising behind it4 ,this border1 becoming gradually more regular1 took the form of an arch1 of a pale yellow colour1 the edges of which were diffuse1 the extremities resting on the horizon4 ,this bow swelled slowly upwards1 its vertex being constantly on the magnetic meridian4 ,blackish streaks divided regularly the luminous arc1 and resolved it into a system of rays4 ,these rays were alternately extended and contracted1 sometimes slowly1 sometimes instantaneously1 sometimes they would dart out1 increasing and diminishing suddenly in splendour4 ,the inferior parts1 or the feet of the rays1 presented always the most vivid light1 and formed an arc more or less regular4 ,the length of these rays was very various1 but they all converged to that point of the heavens indicated by the direction of the southern pole of the dipping-needle4 ,sometimes they were prolonged to the point where their directions intersected1 and formed the summit of an enormous dome of light4 ,sidenote3 ,it ascends to the zenith4 ,reaches the zenith4 8,the bow then would continue to ascend toward the zenith4 ,it would suffer an undulatory motion in its light--that is to say1 that from one extremity to the other the brightness of the rays would increase successively in intensity4 ,this luminous current would appear several times in quick succession1 and it would pass much more frequently from west to east than in the opposite direction4 ,sometimes1 but rarely1 a retrograde motion would take place immediately afterward2 and as soon as this wave of light had run successively over all the rays of the ,aurora from west to east1 it would return in the contrary direction to the point of its departure1 producing such an effect that it was impossible to say whether the rays themselves were actually affected by a motion of translation in a direction nearly horizontal1 or if this more vivid light was transferred from ray to ray1 the system of rays themselves suffering no change of position4 ,the bow1 thus presenting the appearance of an alternate motion in a direction nearly horizontal1 had usually the appearance of the undulations or folds of a ribbon or flag agitated by the wind4 ,sometimes one1 and sometimes both of its extremities would desert the horizon1 and then its folds would become more numerous and marked1 the bow would change its character and assume the form of a long sheet of rays returning into itself1 and consisting of several parts forming graceful curves4 ,the brightness of the rays would vary suddenly1 sometimes surpassing in splendour stars of the first magnitude2 these rays would rapidly dart out1 and curves would be formed and developed like the folds of a serpent2 then the rays would affect various colours1 the base would be red1 the middle green1 and the remainder would preserve its clear yellow hue4 ,such was the arrangement which the colours always preserved4 ,they were of admirable transparency1 the base exhibiting blood-red1 and the green of the middle being that of the pale emerald2 the brightness would diminish1 the colours disappear and all be extinguished1 sometimes suddenly and sometimes by slow degrees4 ,after this disappearance fragments of the bow would be reproduced1 would continue their upward movement and approach the zenith2 the rays1 by the effect of perspective1 would be gradually shortened2 the thickness of the arc1 which presented then the appearance of a large zone of parallel rays1 would be extended2 then the vertex of the bow would reach the magnetic zenith1 or the point to which the south pole of the dipping-needle is directed4 ,at that moment the rays would be seen in the direction of their feet4 ,if they were coloured they would appear as a large red band1 through which the green tints of their superior parts could be distinguished1 and if the wave of light above mentioned passed along them their feet would form a long sinuous undulating zone2 while throughout all these changes the rays would never suffer any oscillation in the direction of their axis1 and would constantly preserve their mutual parallelisms4 ,sidenote3 ,multiple bows4 ,corona formed4 8,while these appearances are manifested new bows are formed1 either commencing in the same diffuse manner or with vivid and ready formed rays2 they succeed each other1 passing through nearly the same phases1 and arrange themselves at certain distances from each other4 ,as many as nine have been counted having their ends supported on the earth1 and in their arrangement resembling the short curtains suspended one behind the other over the scene of a theatre1 and intended to represent the sky4 ,sometimes the intervals between these bows diminish1 and two or more of them close upon each other1 forming one large zone traversing the heavens and disappearing towards the south1 becoming rapidly feeble after passing the zenith4 ,but sometimes also1 when this zone extends over the summit of the firmament from east to west1 the mass of rays appear suddenly to come from the south1 and to form1 with those from the north1 the real boreal corona1 all the rays of which converge to the zenith4 ,this appearance of a crown1 therefore1 is doubtless the mere effect of perspective2 and an observer placed at the same instant at a certain distance to the north or to the south would perceive only an arc4 8,the total zone1 measuring less in the direction north and south than in the direction east and west1 since it often leans upon the corona1 would be expected to have an elliptical form2 but that does not always happen3 it has been seen circular1 the unequal rays not extending to a greater distance than from eight to twelve degrees from the zenith1 while at other times they reach the horizon4 8,let it then be imagined that all these vivid rays of light issue forth with splendour1 subject to continual and sudden variations in their length and brightness2 that these beautiful red and green tints colour them at intervals2 that waves of light undulate over them2 that currents of light succeed each other2 and in fine1 that the vast firmament presents one immense and magnificent dome of light1 reposing on the snow-covered base supplied by the ground1 which itself serves as a dazzling frame for a sea calm and black as a pitchy lake4 ,and some idea1 though an imperfect one1 may be obtained of the splendid spectacle which presents itself to him who witnesses the ,aurora from the ,bay of ,alten4 ,sidenote3 ,duration of corona4 8,the corona when it is formed only lasts for some minutes2 it sometimes forms suddenly1 without any previous bow4 ,there are rarely more than two on the same night1 and many of the ,auroras are attended with no crown at all4 ,sidenote3 ,disappearance of ,aurora4 8,the corona becomes gradually faint1 the whole phenomenon being to the south of the zenith1 forming bows gradually paler and generally disappearing before they reach the southern horizon4 ,all this most commonly takes place in the first half of the night1 after which the ,aurora appears to have lost its intensity2 the pencils of rays1 the bands1 and the fragments of bows appear and disappear at intervals4 ,then the rays become more and more diffused1 and ultimately merge into the vague and feeble light which is spread over the heavens1 grouped like little clouds1 and designated by the name of auroral plates 7plaques aurorales74 ,their milky light frequently undergoes striking changes in the brightness1 like motions of dilatation and contraction1 which are propagated reciprocally between the centre and the circumference1 like those which are observed in marine animals called ,medus4 ,the phenomena become gradually more faint1 and generally disappear altogether on the appearance of twilight4 ,sometimes1 however1 the ,aurora continues after the commencement of daybreak1 when the light is so strong that a printed book may be read4 ,it then disappears1 sometimes suddenly2 but it often happens that1 as the daylight augments1 the ,aurora becomes gradually vague and undefined1 takes a whitish colour1 and is ultimately so mingled with the cirro-stratus clouds that it is impossible to distinguish it from them40 ,lieutenant ,weyprecht has grandly described forms of ,aurora in ,payer's #8,new ,lands within the ,arctic ,circle' 7vol4 i4 p4 #cbh et seq47 as follows3-- ,sidenote3 ,lieut4 ,weyprecht's description4 ,formation of arches4 8,there in the south1 low on the horizon1 stands a faint arch of light4 ,it looks as it were the upper limit of a dark segment of a circle2 but the stars1 which shine through it in undiminished brilliancy1 convince us that the darkness of the segment is a delusion produced by contrast4 ,gradually the arch of light grows in intensity and rises to the zenith4 ,it is perfectly regular2 its two ends almost touch the horizon1 and advance to the east and west in proportion as the arch rises4 ,no beams are to be discovered in it1 but the whole consists of an almost uniform light of a delicious tender colour4 ,it is transparent white with a shade of light green1 not unlike the pale green of a young plant which germinates in the dark4 ,the light of the moon appears yellow contrasted with this tender colour1 so pleasing to the eye and so indescribable in words1 a colour which nature appears to have given only to the ,polar ,regions by way of compensation4 ,the arch is broad1 thrice the breadth1 perhaps1 of the rainbow1 and its distinctly marked edges are strongly defined on the profound darkness of the ,arctic heavens4 ,the stars shine through it with undiminished brilliancy4 ,the arch mounts higher and higher4 ,an air of repose seems spread over the whole phenomenon2 here and there only a wave of light rolls slowly from one side to the other4 ,it begins to grow clear over the ice2 some of its groups are discernible4 ,the arch is still distant from the zenith1 a second detaches itself from the dark segment1 and this is gradually succeeded by others4 ,all now rise towards the zenith2 the first passes beyond it1 then sinks slowly towards the northern horizon1 and as it sinks loses its intensity4 ,arches of light are now stretched over the whole heavens2 seven are apparent at the same time on the sky1 though of inferior intensity4 ,the lower they sink towards the north the paler they grow1 till at last they utterly fade away4 ,often they all return over the zenith1 and become extinct just as they came4 ,sidenote3 ,band of light appears4 ,second band and rays4 8,it is seldom1 however1 that an ,aurora runs a course so calm and so regular4 ,the typical dark segment1 which we see in treatises on the subject1 in most cases does not exist4 ,a thin bank of clouds lies on the horizon4 ,the upper edge is illuminated2 out of it is developed a band of light1 which expands1 increases in intensity of colour1 and rises to the zenith4 ,the colour is the same as in the arch1 but the intensity of the colour is stronger4 ,the colours of the band change in a never-ceasing play1 but place and form remain unaltered4 ,the band is broad1 and its intense pale green stands out with wonderful beauty on the dark background4 ,now the band is twisted into many convolutions1 but the innermost folds are still to be seen distinctly through the others4 ,waves of light continually undulate rapidly through its whole extent1 sometimes from right to left1 sometimes from left to right4 ,then1 again1 it rolls itself up in graceful folds4 ,it seems almost as if breezes high in the air played and sported with the broad flaming streamers1 the ends of which are lost far off on the horizon4 ,the light grows in intensity1 the waves of light follow each other more rapidly1 prismatic colours appear on the upper and lower edge of the band1 the brilliant white of the centre is enclosed between narrow stripes of red and green4 ,out of one band have now grown two4 ,the upper continually approaches the zenith1 rays begin to shoot forth from it towards a point near the zenith to which the south pole of the magnetic needle1 freely suspended1 points4 ,sidenote3 ,corona formed4 8,the band has nearly reached it1 and now begins a brilliant play of rays lasting for a short time1 the central point of which is the magnetic pole--a sign of the intimate connexion of the whole phenomenon with the magnetic forces of the earth4 ,round the magnetic pole short rays flash and flare on all sides1 prismatic colours are discernible on all their edges1 longer and shorter rays alternate with each other1 waves of light roll round it as a centre4 ,what we see is the auroral corona1 and it is almost always seen when a band passes over the magnetic pole4 ,this peculiar phenomenon lasts but a short time4 ,the band now lies on the northern side of the firmament1 gradually it sinks1 and pales as it sinks2 it returns again to the south to change and play as before4 ,so it goes on for hours1 the ,aurora incessantly changes place1 form1 and intensity4 ,it often entirely disappears for a short time1 only to appear again suddenly1 without the observers clearly perceiving how it came and where it went2 simply1 it is there4 ,sidenote3 ,single-rayed band4 8,but the band is often seen in a perfectly different form4 ,frequently it consists of single rays1 which1 standing close together1 point in an almost parallel direction towards the magnetic pole4 ,these become more intensely bright with each successive wave of light2 hence each ray appears to flash and dart continually1 and their green and red edges dance up and down as the waves of light run through them4 ,often1 again1 the rays extend through the whole length of the band1 and reach almost up to the magnetic pole4 ,these are sharply marked1 but lighter in colour than the band itself1 and in this particular form they are at some distance from each other4 ,their colour is yellow1 and it seems as if thousands of slender threads of gold were stretched across the firmament4 ,a glorious veil of transparent light is spread over the starry heavens2 the threads of light with which this veil is woven are distinctly marked on the dark background2 its lower border is a broad intensely white band1 edged with green and red1 which twists and turns in constant motion4 ,a violet-coloured auroral vapour is often seen simultaneously on different parts of the sky4 ,sidenote3 ,aurora in stormy weather4 ,fragments4 8,or1 again1 there has been tempestuous weather1 and it is now1 let us suppose1 passing away4 ,below1 on the ice1 the wind has fallen2 but the clouds are still driving rapidly across the sky1 so that in the upper regions its force is not yet laid4 ,over the ice it becomes somewhat clear2 behind the clouds appears an ,aurora amid the darkness of the night4 ,stars twinkle here and there2 through the opening of the clouds we see the dark firmament1 and the rays of the ,aurora chasing one another towards the zenith4 ,the heavy clouds disperse1 mist-like masses drive on before the wind4 ,fragments of the northern lights are strewn on every side3 it seems as if the storm had torn the ,aurora bands to tatters1 and was driving them hither and thither across the sky4 ,these threads change form and place with incredible rapidity4 ,here is one6 lo1 it is gone6 ,scarcely has it vanished before it appears again in another place4 ,through these fragments drive the waves of light3 one moment they are scarcely visible1 in the next they shine with intense brilliancy4 ,but their light is no longer that glorious pale green2 it is a dull yellow4 ,it is often difficult to distinguish what is ,aurora and what is vapour2 the illuminated mists as they fly past are scarcely distinguishable from the auroral vapour which comes and goes on every side4 ,sidenote3 ,bands4 ,rays reach the pole4 ,no noise4 8,but1 again1 another form4 ,bands of every possible form and intensity have been driving over the heavens4 ,it is now eight o'clock at night1 the hour of the greatest intensity of the northern lights4 ,for a moment some bundles of rays only are to be seen in the sky4 ,in the south a faint1 scarcely visible band lies close to the horizon4 ,all at once it rises rapidly1 and spreads east and west4 ,the waves of light begin to dart and shoot1 some rays mount towards the zenith4 ,for a short time it remains stationary1 then suddenly springs to life4 ,the waves of light drive violently from east to west1 the edges assume a deep red and green colour1 and dance up and down4 ,the rays shoot up more rapidly1 they become shorter2 all rise together and approach nearer and nearer to the magnetic pole4 ,it looks as if there were a race among the rays1 and that each aspired to reach the pole first4 ,and now the point is reached1 and they shoot out on every side1 to the north and the south1 to the east and the west4 ,do the rays shoot from above downwards1 or from below upwards8 ,who can distinguish8 ,from the centre issues a sea of flames3 is that sea red1 white1 or green8 ,who can say8 ,it is all three colours at the same moment6 ,the rays reach almost to the horizon3 the whole sky is in flames4 ,nature displays before us such an exhibition of fireworks as transcends the powers of imagination to conceive4 ,involuntarily we listen2 such a spectacle must1 we think1 be accompanied with sound4 ,but unbroken stillness prevails2 not the least sound strikes on the ear4 ,once more it becomes clear over the ice1 and the whole phenomenon has disappeared with the same inconceivable rapidity with which it came1 and gloomy night has again stretched her dark veil over everything4 ,this was the ,aurora of the coming storm--the ,aurora in its fullest splendour4 ,no pencil can draw it1 no colours can paint it1 and no words can describe it in all its magnificence40 ,a reproduction of the woodcut in ,payer's #8,austrian ,arctic ,voyages1' illustrating some of the features of the above description1 will be found on ,plate ,i4 ,in the #8,edinburgh ,encyclopdia1' article 8,aurora10 we find3-- ,sidenote3 ,descriptions of ,auror in high ,northern latitudes4 8,in high ,northern latitudes the ,auror ,boreales are singularly resplendent1 and even terrific4 8,they frequently occupy the whole heavens1 and1 according to the testimony of some1 eclipse the splendour of stars1 planets1 and moon1 and even of the sun itself4 ,sidenote3 ,in ,siberia4 8,in the south-eastern districts of ,siberia1 according to the description of ,gmelin1 cited and translated by ,dr4 ,blagden 7,phil4 ,trans4 vol4 lxxiv4 p4 #bbh71 the ,aurora is described to begin with single bright pillars1 rising in the north1 and almost at the same time in the north-east1 which1 gradually increasing1 comprehend a large space of the heavens1 rush about from place to place with incredible velocity1 and finally almost cover the whole sky up to the zenith1 and produce an appearance as if a vast tent were expanded in the heavens1 glittering with gold1 rubies1 and sapphires4 ,a more beautiful spectacle cannot be painted2 but whoever should see such a northern light for the first time could not behold it without terror40 ,sidenote3 ,maupertius's description at ,oswer-,zornea4 ,maupertius describes a remarkable ,aurora he saw at ,oswer-,zornea on the #ahth ,december1 #ahgf4 ,an extensive region of the heavens towards the south appeared tinged of so lively a red that the whole constellation of ,orion seemed as if dyed in blood4 ,the light was for some time fixed1 but soon became movable1 and1 after having successively assumed all the tints of violet and blue1 it formed a dome of which the summit nearly approached the zenith in the south-west4 ,sidenote3 ,red ,auror rare in ,lapland4 ,maupertius adds that he observed only two of the red northern lights in ,lapland1 and that they are of very rare occurrence in that country4 ,the observations of ,carl ,bock1 the ,norwegian naturalist1 kindly communicated by him to me1 and detailed in ,chapter ,,iii41 quite confirm this observation of ,maupertius as to the rare occurrence of red ,auror in ,lapland1 he having only seen one4 ,illustration3 ,plate ,i4 ,,chapter ,,iii4 ,,some ,,specific ,,descriptions ,,of ,,auror1 ,,including ,,results ,,of ,,the ,,english ,,arctic ,,expedition1 #ahge-gf4 ,captain ,sabine's ,auror4 ,sidenote3 ,captain ,sabine's ,auror4 ,captain ,sabine describes ,auror seen at ,melville ,island 7,parry's first voyage1 ,january #ae74 ,towards the southern horizon an ordinary ,aurora appeared4 ,the luminous arch broke into masses streaming in different directions1 always to the east of the zenith4 ,sidenote3 ,curvature of arches towards each other4 ,the various masses seemed to arrange themselves in two arches1 one passing near the zenith and a second midway between the zenith and the horizon1 both north and south1 but curving towards each other4 ,at one time a part of the arch near the zenith was bent into convolutions like a snake in motion and undulating rapidly4 ,aurora seen at ,sunderland1 ,february #hth1 #ahag4 7#8,annals of ,philosophy1' vol4 ix4 p4 #bej47 ,sidenote3 ,aurora seen at ,sunderland1 ,feb4 #h1 #ahag4 ,formation of corona4 ,it began about #g ,p4,m4 during a strong gale from the ,n4,w41 with single bright streamers in the ,n4 and ,n4,w41 which covered a large space and rushed about from place to place with amazing velocity1 and had a fine tremulous motion1 illuminating the hemisphere as much as the moon does eight or nine days from change4 ,about #aa o'clock part of the streamers appeared as if projected south of the zenith and looked like the pillars of an immense amphitheatre1 presenting a most brilliant spectacle and seeming to be in a lower region of the atmosphere1 and to descend and ascend in the air for several minutes4 7,this appears to have been the formation of a corona47 ,one streamer passed over ,orion1 but neither increased nor diminished its splendour4 ,description of ,aurora by ,dr4 ,hayes1 #fth ,january1 #ahfa4 ,sidenote3 ,dr4 ,hayes's ,aurora1 #fth ,january1 #ahfa4 #8,recent ,polar ,voyages' contains a narrative of the voyage of ,dr4 ,hayes1 who sailed from ,boston on the #fth of ,july1 #ahfj1 and wintered at ,port ,foulbe4 ,he witnessed a remarkable display of the ,aurora ,borealis on the morning of the #fth ,january1 #ahfa4 ,sidenote3 ,development of ,aurora4 ,the darkness was so profound as to be oppressive4 ,suddenly1 from the rear of the black cloud which obscured the horizon1 flashed a bright ray4 ,presently an arch of many colours fixed itself across the sky1 and the ,aurora gradually developed4 ,sidenote3 ,rays changed to glow4 ,the space within the arch was filled by the black cloud2 but its borders brightened steadily1 though the rays discharged from it were exceeding capricious1 now glaring like a vast conflagration1 now beaming like the glow of a summer morn4 ,more and more intense grew the light1 until1 from irregular bursts1 it matured into an almost uniform sheet of radiance4 ,towards the end of the display its character changed4 ,lurid fires flung their awful portents across the sky1 before which the stars seemed to recede and grow pale4 ,sidenote3 ,mixed colours4 ,colours change4 ,tongues of white flame formed4 ,the colour of the light was chiefly red2 but every tint had its turn1 and sometimes two or three were mingled2 blue and yellow streamers shot across the terrible glare1 or1 starting side by side from the wide expanse of the radiant arch1 melted into each other1 and flung a strange shade of emerald over the illuminated landscape4 ,again this green subdues and overcomes the red2 then azure and orange blend in rapid flight1 subtle rays of violet pierce through a broad flash of yellow1 and the combined streams issue in innumerable tongues of white flame1 which mount towards the zenith4 ,the illustration which accompanies this description in the work is reproduced on ,plate ,,ii41 and forcibly reminds one of the 8curtains0 of the ,aurora described in the preceding ,chapter by ,mons4 ,lottin4 ,illustration3 ,plate ,,ii4 ,prof4 ,lemstrm's ,aurora of #ast ,september1 #ahfh4 ,sidenote3 ,prof4 ,lemstrm's ,aurora1 #ast ,september1 #ahfh4 ,in the first ,swedish ,expedition1 #ahfh1 some remarkable observations were made on the appearance of luminous beams around the tops of mountains1 which ,m4 ,lemstrm showed by the spectroscope to be of the same nature as ,auror4 ,sidenote3 ,aurora from earth's surface4 ,yellow-green line seen4 ,on the #ast ,september1 #ahfh1 on the ,isle of ,amsterdam in the ,bay of ,sweerenberg1 there was a light fall of snow1 and the snowflakes were observed falling obliquely4 ,all at once there appeared a luminous phenomenon which1 starting from the earth's surface1 shot up vertically1 cutting the direction of the falling snowflakes1 and this appearance lasted for some seconds4 ,on examination with a spectroscope the yellow-green line was found by ,lemstrm 7but of feeble intensity7 when the slit of the instrument was directed towards a roof or other object covered with snow1 and even in the snow all round the observer4 ,sidenote3 ,lemstrm's conclusions4 ,m4 ,lemstrm concluded that an electric discharge of an auroral nature1 which could only be detected by means of the spectroscope1 was taking place on the surface of the ground all around him1 and that1 from a distance1 it would appear as a faint display of ,aurora4 ,it should1 however1 here be noted that the reflection of an ,aurora from a white or bright surface would give1 in a fainter degree1 the spectrum of the ,aurora itself2 and1 apart from the phenomena seen by the eye1 the case fails to be conclusive that an ,aurora on the surface of the ground was examined4 ,mr4 ,j4 ,r4 ,capron's ,aurora of ,october #bdth1 #ahgj4 ,sidenote3 ,mr4 ,j4 ,r4 ,capron's ,aurora1 ,oct4 #bd1 #ahgj4 ,silver glow in north4 ,phosphorescent cloud-streamers4 ,crimson masses on horizon4 ,coloured streamers4 ,corona formed4 ,aurora fades away4 ,the description1 from my notes made at the time of this fine display1 is as follows3--8,last evening 7,october #bd7 the ,aurora ,borealis was again most beautifully seen here 7,guildford74 ,at #f ,p4,m4 indications of the coming display were visible in the shape of a bright silver glow in the north1 which contrasted strongly with the opposite dark horizon4 ,for two hours this continued1 with the addition from time to time of a crimson glow in the north-east1 and of streamers of opaque-white phosphorescent cloud1 shaped like horse-tails 7very different from the more common transparent auroral diverging streams of light71 which floated upwards and across the sky from east and west to the zenith4 ,at about #h o'clock the display culminated2 and few observers1 ,i should think1 ever saw a more lovely sky-picture4 ,two patches of intense crimson light about this time massed themselves on the north-east and north-west horizon1 the sky between having a bright silver glow4 ,the crimson masses became more attenuated as they mounted upwards2 and from them there suddenly ran up bars or streamers of crimson and gold light1 which1 as they rose1 curved towards each other in the north1 and1 ultimately meeting1 formed a glorious arch of coloured light1 having at its apex an oval white luminous corona or cloud of similar character to the phosphorescent clouds previously described1 but brighter4 ,at this time the spectator appeared to be looking at the one side of a cage composed of glowing red and gold bars1 which extended from the distant parts of the horizon to a point over his head4 ,shortly after this the ,auroral display gradually faded away1 and at #i o'clock the sky was of its usual appearance1 except that the ordinary tint seemed to have more of indigo1 probably by contrast with the marvellous colours which had so lately shone upon it40 ,sidenote3 ,t4 ,f4's description of same at ,torquay4 ,mr4 ,gibbs's report in ,london4 ,t4 ,f41 describing the same ,aurora from ,torquay1 says it showed itself at sundown1 attained its maximum at #h1 and lasted until #aa4 ,at #h o'clock more than half the visible heavens was one sea of colour2 the general ground greenish yellow and pale rose1 with extensive shoals of deep rose in the east and west2 while from the north1 streaming upwards to and beyond the zenith1 were tongues and brushes of rosy red1 so deep that the sky between looked black4 ,mr4 ,gibbs reported that in ,london1 at about #h o'clock1 brilliant crimson rays shot up to the zenith1 and the sky seemed one mass of fire4 ,a facsimile of my water-colour sketch of this fine discharge is given on ,plate ,,iii4 ,illustration3 ,plate ,,iii4 ,mr4 ,barker's 7superposed7 red and white ,auror1 #ith ,november 7#ahgj874 ,sidenote3 ,mr4 ,barker's ,auror1 #ith ,november 7#ahgj874 ,red ,aurora4 ,white ,aurora4 ,on the #ith ,november 7#ahgj87 ,mr4 ,barker saw at ,new ,haven 7,u4 ,s47 a most magnificent crimson ,aurora4 ,at about a quarter to #f ,p4,m4 it consisted of a brilliant streamer shooting up from the north-western horizon4 ,this was continued in a brilliant red1 but rather nebulous1 mass of light passing upwards and to the north4 ,its highest points were from #cj to #dj in altitude4 ,a white ,aurora1 consisting of bright streamers1 appeared simultaneously and extended round to the north-east4 ,prof4 ,newton informed ,mr4 ,barker that he had observed an equally brilliant red patch of auroral light in the north-east five or ten minutes earlier4 ,sidenote3 ,red seen through white4 ,since the lower end of the red streamers was much lower than that of the white1 it would seem as if the red were seen through the white1 the red being most remote4 ,sidenote3 ,crimson line not seen in white ,aurora4 ,spectroscopic observations of this ,aurora were made4 ,the crimson ,aurora lasted less than half an hour1 and then disappeared4 ,in the white ,aurora1 which remained1 the crimson line could not be seen4 ,sidenote3 ,carl ,bock's vibrating rays4 ,it may be here noted that during the ,aurora seen by ,carl ,bock in ,lapland1 and painted by him by its own light 7described1 p4 #be71 he had the impression of sets of vibrating rays behind each other1 and in the drawing it looks as if streamers were seen behind an arc4 ,illustration3 ,plate ,,iv4 ,mr4 ,j4 ,r4 ,capron's ,aurora of ,february #dth1 #ahgb4 ,sidenote3 ,mr4 ,j4 ,r4 ,capron's ,aurora1 ,feb4 #d1 #ahgb4 ,masses of phosphorescent vapour4 ,rose tints appeared4 ,aurora from behind clouds4 ,formation of corona4 ,duration of corona4 ,streamers from corona4 ,rain during ,aurora4 ,wind during night4 ,phosphorescent clouds preceded the ,aurora in daylight4 ,my description of this ,aurora as seen at ,guildford1 and as given at the time1 is as follows3--8,last evening1 returning from church a little before #h ,p4,m41 the sky presented a weird and unusual aspect1 which at once struck the eye4 ,a lurid tinge upon the clouds which hung around suggested the reflection of a distant fire2 while scattered among these1 torn and broken masses of vapour1 having a white and phosphorescent appearance1 and quickly changing their forms1 reminded me of a similar appearance preceding the great ,aurora of #bdth ,october1 #ahgj4 ,shortly some of these shining white clouds or vapours partly arranged themselves in columns from east to west1 and at the same time appeared the characteristic patches of rose-coloured light which are often seen in an auroral display4 ,about #h o'clock the clouds had to a certain extent broken away1 and the ,aurora shone out from behind heavy banks of vapour1 which still rested on the eastern horizon1 the north-west horizon being free from cloud and glowing brightly with red light4 ,and now1 at about #h4ae1 was presented a most beautiful phenomenon4 ,while looking upwards1 ,i saw a corona or stellar-shaped mass of white light form in the clear blue sky immediately above my head#d1 not by small clouds or rays collecting1 but more in the way that a cloud suddenly forms by condensation in the clear sky on a mountain top1 or a crystal shoots in a transparent liquid1 having too1 as ,i thought1 an almost traceable nucleus or centre1 from which spear-like rays projected4 ,from this corona in a few seconds shot forth diverging streamers of golden light1 which descended to and mingled with the rosy patches of the ,aurora hanging about the horizon4 ,the spaces of sky between the streamers were of a deep purple 7probably an effect of contrast74 ,the display of the corona1 though lasting a few minutes only1 was equal to1 if not excelling in beauty1 the grand display of ,october #ahgj1 before described1 in which case1 however1 a ring or disk of white light of considerable size took the place of the stellar-shaped corona4 ,what struck me particularly was the corona developing itself as from a centre in the clear sky1 and the diverging streamers apparently shooting downwards1 whereas in general the streamers are seen to shoot up from the horizon and converge overhead4 ,the effect may have been an illusion2 but1 if so1 it was a remarkable one4 ,the general ,aurora lasted for some time1 till it was lost in a clouded sky2 and1 in fact1 rain was descending at one time while the ,aurora was quite bright4 ,strong wind prevailed during the night#e4 ,the ,aurora was probably very extensive1 as the evening1 notwithstanding the clouds1 was nearly as bright as moonlight4 ,the peculiar clouds referred to must have preceded the ,aurora in daylight1 as ,i recollect seeing them at #f4cj as we went to church40 ,sidenote3 ,aurora predicted4 ,they had even then a peculiarly wild1 ragged1 and phosphorescent appearance1 and so much resembled some ,i had seen to accompany the ,aurora of ,october #ahgj1 that ,i predicted 7as came to pass7 a display later in the evening4 ,a facsimile of my water-colour sketch of this ,aurora is given on ,plate ,,iv4 fig4 #a1 while the corona and rays are represented 7with rather too hard an outline7 on ,plate ,v4 fig4 #b4 ,illustration3 ,plate ,v4 ,description of an ,aurora seen at ,cardiff4 ,sidenote3 ,aurora seen at ,cardiff4 ,formation of corona4 ,an ,aurora was seen at ,cardiff4 ,a dusky red aspect of the sky towards the north1 and extending itself across the zenith westward1 made its appearance about half-past #e ,p4,m4 ,the lights reached their greatest intensity at #f o'clock1 when the sky was suffused with a rich crimson glow1 a broad band of colour reaching from ,n4,e4 to ,w4 ,a corona of deep hue1 having rugged sharply defined edges1 stood out prominently in the zenith1 apparently on a parallel plane to the earth1 and having its centre almost immediately over the head of the spectator4 ,sidenote3 ,radii thrown out from corona4 ,from this corona1 elliptic in form1 and in its broadest diameter about four times the size of the moon1 there were thrown out brilliant silvery blue radii1 extending to the ,n4,e4 and ,w4 horizon1 and presenting the appearance of a vast cupola of fire4 ,sidenote3 ,rain fell when ,aurora died out4 ,at half-past #f the lights died completely out1 leaving masses of cloud drifting up from the south1 and a shower of rain fell4 ,the corona was remarked upon as unusual4 ,at ,edinburgh the sky was brilliant for several hours4 7,the date of this ,aurora is uncertain1 as the account is from an undated newspaper cutting4 ,it is supposed to be in ,february #ahgb1 but could hardly have been on the #dth1 as the ,aurora of that date did not reach its maximum development at ,edinburgh till #h ,p4,m47 ,mr4 ,j4 ,r4 ,capron's ,aurora1 seen at ,guildown1 ,guildford1 ,february #dth1 #ahgd4 ,sidenote3 ,silvery brightness in ,n4,e4 ,light-cloud1 which moved from ,e4 to ,w4 ,formation of arc in ,n4 ,streamers4 ,horizontal clouds of misty light4 ,about #g ,p4,m4 my attention was drawn to a silvery brightness in the north-east4 ,above1 and still more to the east1 was a bright cloud of light1 which looked dense and misty1 and gave one the impression of an illuminated fog-cloud4 ,the edges were so bright that the adjacent sky1 but for the stars shining in it1 might1 by contrast1 have been taken for a dark storm-cloud4 ,the light-cloud expanded upwards until its apex became conical1 and then moved rapidly from east1 along the northern horizon1 until it reached the due west1 where it rested1 and formed for some time a luminous spot in the sky4 ,about the same time a long low arch of light formed along the northern horizon1 having a brighter patch at each extremity2 and these being higher in the sky1 the arch and turned-up ends were in shape like a ,tartar bow4 ,this bow was permanent2 and later on a cloud of rose-coloured light formed in the east1 looking like the reflection of a distant fire4 ,from the bow also shot up curved streamers of silver light towards the zenith1 which at one time threatened to form a corona4 ,this1 however1 did not happen1 and the ,aurora gradually faded away1 until1 when the moon rose about #h1 a silver tinge in the east alone remained4 ,i should also mention that fleecy horizontal clouds of misty light floated in the north above the bow across the streamers4 ,mr4 ,h4 ,taylor informed me he saw a similar ,aurora some three weeks before1 in which the bright horizontal light and short white streamers were the main characters4 ,i am not sure that the horizontal light-clouds were not actual mist-clouds illuminated by reflection of the ,aurora2 not so1 however1 ,i think1 the first-mentioned cloud1 which had more the appearance of the aura in the large end of an illuminated ,geissler tube4 ,sidenote3 ,spectrum of the ,aurora described4 ,i examined the ,aurora with a ,browning direct-vision spectroscope1 and found ngstrm's line quite bright1 and by the side of it three faint and misty bands towards the blue end of the spectrum upon a faintly illuminated ground4 ,i could also see at times a bright line beyond the bands towards the violet4 ,there was not light enough to take any measurements of position of the lines4 ,i made a pencil sketch of this ,aurora1 at the time when the light-cloud had moved ,w4 and the arc formed1 and of the spectrum4 ,these drawings are reproduced on ,plate ,,vi4 figs4 #a and #a;a4 ,illustration3 ,plate ,,vi4 ,mr4 ,herbert ,ingall's ,aurora1 ,july #ahth1 #ahgd4 ,sidenote3 ,mr4 ,herbert ,ingall's ,aurora1 ,july #ah1 #ahgd4 ,haze canopy formed4 ,bright bluish flames appeared4 ,beams and streamers appeared4 ,oscillatory motion of rays4 ,an ,aurora of ,july #ahth1 #ahgd1 seen by ,mr4 ,herbert ,ingall at ,champion ,hill1 ,s4,e41 was described by him as an extraordinary one4 ,about #aa the sky was clear2 at midnight the sky was covered by a sort of haze canopy1 sometimes quite obscuring the stars1 and then suddenly fading away4 ,mr4 ,ingall was shortly after remarking the sky in the ,s4,e4 and ,s4 horizon as being more luminous than usual1 when his attention was drawn to a growing brightness in the ,s4,w41 and a moment afterwards bright bluish flames 8swept over the ,s4,w4 and ,w4 horizon1 as if before a high wind4 ,they were not streamers1 but bright blue flames40 ,they lasted about a minute and faded2 but about two minutes afterwards a glowing luminosity appeared in the ,w4,s4,w41 and broke into brilliant beams and streamers4 ,the extreme rays made an angle of #ij with each other1 the central ray reaching an altitude of #ej4 ,the extreme divergence of the streamers 7indicating their height above the earth's surface71 and their direction 7from ,w4,s4,w4 to ,e4,n4,e47 at right angles to the magnetic meridian1 suggested to ,mr4 ,ingall a disturbance of an abnormal character4 ,the rays had an oscillatory motion for about fifteen seconds1 and then disappeared1 8as if a shutter had suddenly obscured the source of light40 ,sidenote3 ,mr4 ,ingall's remarks corroborated4 ,mr4 ,ingall's remarks were corroborated by an observer in lat4 #ed #df #fb ,n41 long4 #f;h #abm #ais#ge ,w4 ,the display1 however1 was more brilliant1 and the intensity of light at midnight illuminated the whole district as with an electric light4 ,the rays1 too1 bore tints differing from one another2 the largest seemed to partake of the nature of the blue sky1 while the smaller ones1 running parallel with the horizon1 were ever changing from blue to orange-red4 ,sidenote3 ,rev4 ,c4 ,gape saw flashes or streaks of a pale blue colour4 ,on ,june #be 7same year871 between #i and #aj o'clock1 the ,rev4 ,chas4 ,gape saw at ,rushall ,vicarage1 ,scole1 ,norfolk1 in the ,e4,s4,e41 very frequent flashes or streaks of a pale blue colour darting from the earth towards the heavens like an ,aurora4 ,the day had been dull and close1 with distant thunder4 ,in the ,e4,s4,e4 it was dark1 but overhead and everywhere else it was clear and starry4 ,mr4 ,j4 ,r4 ,capron's ,white ,aurora of ,september #aath1 #ahgd4 ,sidenote3 ,mr4 ,j4 ,r4 ,capron's white ,aurora of ,sept4 #aa1 #ahgd4 ,on ,september #aa1 #ahgd1 we were at ,kyle ,akin1 in the ,isle of ,skye4 ,the day had been wet and stormy1 but towards evening the wind fell and the sky became clear4 ,about #aj ,p4,m4 my attention was called to a beautiful ,auroral display4 ,sidenote3 ,double arc of pure white light in the ,n4 ,no crimson or rose tint was to be seen1 but a long low-lying arc of the purest white light was formed in the north1 and continued to shine with more or less brilliancy for some time4 ,the arc appeared to be a double one1 by the presence of a dark band running longitudinally through it4 ,sidenote3 ,white streamers4 ,auroral bow believed to be near the earth4 ,occasional streamers of equally pure white light ran upwards from either end of the bow4 ,the moon was only a day old1 but the landscape was lighted up as if by the full moon2 and the effect of ,kyle ,akin lighthouse1 the numerous surrounding islands1 and the still sea between was a true thing of beauty4 ,the display itself formed a great contrast to the more brilliant but restless forms of ,auror generally seen4 ,i particularly noticed a somewhat misty and foggy look about the brilliant arc1 giving it almost a solid appearance4 ,the space of sky between the horizon and the lower edge of the arc was of a deep indigo colour1 probably the effect of contrast4 ,i had a strong impression that the bow was near to the earth1 and was almost convinced that the eastern end and some fleecy clouds in which it was involved were between myself and the peaks of some distant mountains4 ,i have not seen any other account of this ,aurora1 of which ,i was able at the time to obtain a sketch4 ,this is reproduced on ,plate ,,vii4 ,it was a lovely sight1 and wonderfully unlike the cloud-accompanied and crimson ,auror which ,i had seen in the ,south4 ,it is noticed in ,parry's #8,third ,voyage' that the lower edge of the auroral arch is generally well defined and unbroken1 and the sky beneath it so exactly like a dark cloud 7to him often of a brownish colour71 that nothing could convince to the contrary1 if the stars1 shining through with undiminished lustre1 did not discover the deception4 ,sidenote3 ,no trace of brown colour in segment of sky below the arc4 ,i saw no trace of brown colour4 ,the segment below the arch resting on the horizon was of a deep indigo colour4 ,illustration3 ,plate ,,vii4 ,dr4 ,allnatt's ,aurora1 ,june #ith1 #ahgf4 ,sidenote3 ,dr4 ,allnatt's ,aurora1 ,june #i1 #ahgf4 ,band of auroral light appeared4 ,streaks of cirro-stratus divided the ,aurora4 ,want of electric manifestations attributed to absence of sun-spots4 ,dr4 ,allnatt1 writing to the #8,times' from ,abergele1 ,north ,wales1 near the coast of the ,irish ,channel1 reported an ,aurora on the night of the #ith ,june1 #ahgf4 ,after a cool and gusty day1 with a strong ,n4,e4 wind and a disturbed sea1 there appeared at #aa ,p4,m4 in the ,n4 horizon a broad band of vivid auroral light1 homogeneous1 motionless1 and without streamers4 ,about midnight a long attenuated streak of black cirro-stratus stretched parallel with the horizon1 and divided the ,aurora into nearly symmetrical sections4 ,on the preceding day the sky was covered with dark masses of electric cloud of weird and fantastic forms4 ,the season had been singularly unproductive of high electric manifestations1 which ,dr4 ,allnatt thought might be attributable to the comparative absence of spots on the solar disk4 ,it may here be noted how conspicuous the years #ahgg and #ahgh have been for absence of ,sun-spots and of ,auror4 ,illustration3 ,plate ,,viii4 ,herr ,carl ,bock's ,lapland ,aurora1 #crd ,october1 #ahgg4 ,sidenote3 ,herr ,carl ,bock's ,lapland ,aurora1 #crd ,oct4 #ahgg4 ,lapland ,auror generally of the yellow type4 ,in ,january #ahgh ,i had the pleasure to meet1 at the ,westminster ,aquarium1 ,herr ,carl ,bock1 the ,norwegian naturalist1 who accompanied four ,laplanders1 two men and two women1 with sledges1 tents1 c41 on their visit to this country4 ,the ,laplanders 7as mentioned elsewhere7 did not confirm the accounts of noises said to have been observed by ,greenlanders and others during the ,aurora4 ,carl ,bock mentioned to me that the displays he saw in ,lapland were most brilliant1 but generally of the yellow type 7the ,laplanders called the ,aurora 8yellow lights074 ,he saw only one red ,aurora4 ,he kindly lent me a picture 7probably in its way unique71 an oil-painting of an ,aurora ,borealis1 entirely sketched by the light of the ,aurora itself4 ,sidenote3 ,a picture painted by light of the ,aurora4 ,movement of the rays4 ,inner edge of arc fringed with rays4 ,the painting is remarkable for the tender green of the sky1 an effect probably due to a mixture of the ordinary sky colour with the yellow light of the ,aurora4 ,this picture was taken at ,porsanger ,fjord1 in lat4 #ga #ej1 on #crd ,october1 #ahgg4 ,it lasted from #i ,p4,m4 till about #aa ,p4,m4 ,the rays kept continually moving1 and certain of them seemed in perspective and behind the others4 ,it will be noticed that the inner edge of the arc is fringed with rays1 contrary to the sharp and definite margin which is usually presented4 ,probably two ,auror or auroral forms were seen--a quiescent arc in front1 and a set of moving streamers beyond4 ,two larger and brighter patches of light are seen at each extremity of the arc1 as in the case of the ,aurora seen by me at ,guildown1 ,february #dth1 #ahgd1 which1 indeed1 the display much resembles4 ,a reduced facsimile of ,herr ,bock's excellent picture is given on ,plate ,,viii4 ,sidenote3 ,aurora of longitudinal rays4 ,herr ,bock also acquainted me that on the following day he saw an ,aurora in which the lines of light1 instead of being vertical1 were longitudinal1 and were continually swept along in several currents4 ,they were not so strong as in the former case4 ,rev4 ,t4 ,w4 ,webb's ,aurora4 ,sidenote3 ,rev4 ,t4 ,w4 ,webb's ,aurora4 ,arc resolved into sets of streamers moving in opposite directions4 ,the ,rev4 ,t4 ,w4 ,webb has described to me in a letter an ,aurora very like that seen by ,carl ,bock in ,lapland1 and apparently the prevailing type in those regions4 ,an arc similar to that figured by ,carl ,bock appeared in the ,n4,w41 and seemed to resolve itself into two sets of streamers moving in opposite directions 7or the one set might be fixed and the other moving71 like the edges of two great revolving toothed wheels4 ,this lasted but for a few seconds2 but during that interval the tints were varied and brilliant1 including blue and green4 ,the ,english ,arctic ,expedition #ahge-gf1 under ,capt4 ,sir ,george ,nares4 ,sidenote3 ,english ,arctic ,expedition1 #ahge-gf4 ,instructions for use of officers4 ,appendix ,b4 ,capt4 ,sir ,g4 ,nares's report4 ,true ,auror seldom observed1 and displays faint4 ,citron-line observed on only two displays4 ,appendix ,c4 ,in anticipation of the starting of this ,expedition1 some instructions for the use of the officers in connexion with the hoped for display of brilliant ,auror were prepared3--as to general features of the ,auror1 by ,professor ,stokes2 as to ,polarization1 by ,dr4 ,william ,spottiswoode2 and as to ,spectrum work1 by ,mr4 ,norman ,lockyer and myself4 ,as these instructions were somewhat elaborate1 and will apply to all ,auroral displays1 ,i have supplied a copy of them in ,appendix ,b4 ,they were unfortunately not brought into requisition1 for want of the ,auror themselves4 ,capt4 ,sir ,george ,nares has reported to the ,admiralty1 under date #eth ,december1 #ahgg1 as follows3--8,although the auroral glow was observed on several occasions between #be ,october1 #ahge1 and #bf ,february1 #ahgf1 true ,auror were seldom observed2 and the displays were so faint1 and lasted so short a time1 and the spectrum observations led to such poor results1 that no special report has been considered necessary4 ,although the citron-line was observed occasionally1 on only two displays of the ,aurora was it well defined1 and then for so short a time that no measure could be obtained40 7,for ,sir ,george ,nares's further ,report see ,appendix ,c1 containing extracts from blue-book1 #8,results derived from the ,arctic ,expedition1 #ahge-f4'7 ,aurora ,australis4 ,sidenote3 ,aurora ,australis4 ,mr4 ,forster's description4 ,long columns of white light spreading over the whole sky4 ,in an article on ,auror in high ,southern latitudes 7,phil4 ,trans4 ,no4 #dfa1 and vol4 liv4 ,no4 #ec71 we find that ,mr4 ,forster1 who as naturalist accompanied ,capt4 ,cook on his second voyage round the world1 says3--8,on ,february #agth1 #aggc1 in south latitude #eh1 a beautiful phenomenon was observed during the preceding night1 which appeared again this1 and several following nights4 ,it consisted of long columns of a clear white light shooting up from the horizon to the eastward almost to the zenith1 and gradually spreading over the whole southern part of the sky4 ,these columns were sometimes bent sideways at their upper extremities2 and though in most respects similar to the northern lights of our hemisphere1 yet differed from them in being always of a whitish colour1 whereas ours assume various tints1 especially those of a fiery and purple hue4 ,the sky was generally clear when they appeared1 and the air sharp and cold1 the thermometer standing at the freezing point40 ,this account agrees very closely in particulars with ,capt4 ,maclear's notice of ,aurora ,australis after referred to1 and especially in the marked absence of red ,auror4 ,the height of the barometer does not appear to be mentioned1 the temperature being apparently much the same as in the more recent cases4 ,sidenote3 ,capt4 ,maclear's ,aurora ,australis1 #crd ,march1 #ahgd4 ,light of pale yellow tint only4 ,in a letter dated from ,h4,m4,s4 #8,challenger1' ,north ,atlantic1 ,april #ajth1 #ahgf1 ,capt4 ,maclear was good enough to communicate to me some particulars of an ,aurora ,australis seen #crd ,march #ahgd1 in lat4 #ed ,s41 long4 #ajh ,e4 ,the letter is mainly descriptive of the spectrum 7which will be described in connexion with the general question of the spectrum of the ,aurora74 ,it states that the red line was looked for in vain1 and that the light appeared of a pale yellow1 and had none of the rosy tint seen in the northern displays4 ,sidenote3 ,capt4 ,maclear's ,auror described in #8,nature4' ,capt4 ,maclear has since contributed to #8,nature1' of #ast ,november #ahgg1 a description of four ,auror seen from the #8,challenger' in high southern latitudes 7including the one communicated to me74 ,he speaks of the opportunity of observing as not frequent1 either from the rarity of the phenomena1 or because the dense masses of cloud prevalent in those regions prevented their being seen except when exceptionally bright4 ,there were four appearances described3-- ,sidenote3 ,feb4 #i1 #ahgd4 7#a47 ,at #a4cj on the morning of ,february #ith1 #ahgd1 preceded by a watery sunset1 lat4 #eg ,s4 and long4 #ge ,e41 bar4 #bij in41 ther4 #ce2 brilliant streaks to the westward4 ,day broke afterwards with high cirrus clouds and clear horizon4 ,sidenote3 ,feb4 #ba1 #ahgd4 7#b47 ,at #i4cj ,p4,m41 ,february #ba1 #ahgd1 lat4 #fd ,s41 long4 #hi ,e41 bar4 #bhh in41 ther4 #ca2 one bright curved streamer4 ,the ,aurora preceded a fine morning with cumulo-stratus clouds1 extending from ,jupiter 7which appeared to be near the focus7 through ,orion and almost as far beyond4 ,under this a black cloud1 with stars visible through it4 ,real cumuli hid great part of the remainder of the sky1 but there were two vertical flashing rays which moved slowly to the right 7west74 ,generally the ,aurora was still bright4 ,sidenote3 ,march #c1 #ahgd4 ,auroral line found in light to southward4 7#c47 ,at midnight1 ,march #crd1 #ahgd1 lat4 #ec #cj ,s41 long4 #aji ,e41 bar4 #bia1 ther4 #cf1 after some days' stormy weather1 a brilliant sunset1 followed by a fine morning4 ,soon after #h ,p4,m4 the sky began to clear and the moon shone out4 ,noticing the light to the southward to be particularly bright1 ,capt4 ,maclear applied the spectroscope1 and found the distinguishing auroral line4 ,sidenote3 ,brilliant white clouds seen4 ,about midnight the sky was almost clear1 but south were two or three brilliant light clouds1 colour very white-yellow1 shape cumulo-stratus4 ,from about west to near south extended a long feathery light of the same colour1 parallel with the horizon1 and between south and west there appeared occasionally brilliant small clouds4 ,the upper edges seemed hairy1 and gave one the idea of a bright light behind a cloud4 ,the forms changed1 but no particular order was noticed4 7,here follows a description of the spectrum1 and the mode in which a delineation by the lines was obtained47 ,sidenote3 ,march #f1 #ahgd4 ,capt4 ,maclear suggests whether a low barometer has to do with the absence of red4 7#d47 ,at #h ,p4,m41 ,march #fth1 #ahgd4 ,this was a slight ,aurora1 seen to the southward2 after this the clouds changed to high cirrus4 ,capt4 ,maclear suggests whether a low barometer has any thing to do with the absence of red in the spectrum1 the normal state of the barometer being an inch lower in those regions than in more temperate latitudes4 ,sidenote3 ,barometer falls after the ,aurora1 and strong gale from the ,s4 or ,s4,w4 follows4 ,edin4 ,encyc4 vol4 iii4 article 8,aurora40 ,dr4 ,kirwan observed that the barometer commonly falls after the ,aurora4 ,mr4 ,winn1 in the seventy-third volume of the ,phil4 ,trans41 makes the same remark1 and says that in twenty-three instances1 without fail1 a strong gale from the south or south-west followed the appearance of an ,aurora4 ,if the ,aurora were bright1 the gale came on within twenty-four hours1 but was of no long continuance2 if the light was faint and dull1 the gale was less violent1 longer in coming1 and longer in duration4 ,sidenote3 ,pale yellow glow rare in the ,aurora ,borealis4 ,the pale yellow-coloured glow referred to by ,capt4 ,maclear is1 in my experience1 rare in the ,aurora ,borealis4 ,it is probably the 8qualiter et sine eruptionibus aut radiis fulvi10 described by ,seneca 7ant1 p4 #a71 and may probably belong to more southern climes4 ,sidenote3 ,spectrum of ,auror ,australes extends more into the violet4 ,we shall see too1 by-and-by1 that these ,auror ,australes as to spectrum extend more into the violet than the ,aurora ,borealis4 ,the yellow1 as complementary to violet1 is likely thus to make 7in the absence of the red7 its appearance4 ,it is1 however1 somewhat singular that ,carl ,bock found almost exclusively yellow ,auror in ,lapland4 ,in ,proctor's #8,borderland of ,science1' article 8,the ,antarctic ,regions10 we find quoted a passage from a letter by ,capt4 ,howes1 of the #8,southern ,cross1' in which a graphic description is given of a ,southern ,aurora3-- ,sidenote3 ,capt4 ,howes's description of a ,southern ,aurora4 8,at about half-past one on the #bnd of last ,september the rare phenomenon of the ,aurora ,australis manifested itself in a most magnificent manner4 ,our ship was off ,cape ,horn1 in a violent gale1 plunging furiously into a heavy sea1 flooding her decks1 and sometimes burying her whole bows beneath the waves4 ,the heavens were as black as death1 not a star was to be seen1 when the brilliant spectacle first appeared4 ,sidenote3 ,balls of electric fire resting on mast-heads c4 8,i cannot describe the awful grandeur of the scene2 the heavens gradually changed from murky blackness till they became like vivid fire1 reflecting a lurid glowing brilliancy over every thing4 ,the ocean appeared like a sea of vermilion lashed into fury by the storm1 the waves dashing furiously over our side1 ever and anon rushed to leeward in crimson torrents4 ,our whole ship--sails1 spars1 and all--seemed to partake of the same ruddy hues4 ,they were as if lighted up by some terrible conflagration4 ,taking all together--the howling1 shrieking storm1 the noble ship plunging fearlessly beneath the crimson-crested ways1 the furious squalls of hail1 snow1 and sleet1 drifting over the vessel1 and falling to leeward in ruddy showers1 the mysterious balls of electric fire resting on our mast-heads1 yard-arms1 c41 and1 above all1 the awful sublimity of the heavens1 through which coruscations of auroral light would shoot in spiral streaks1 and with meteoric brilliancy1--there was presented a scene of grandeur surpassing the wildest dreams of fancy40 ,the foregoing picture presents a singular contrast to the yellow-white ,auror described as seen in high southern latitudes by ,capt4 ,maclear1 and is interesting as a southern ,aurora of a red or ruddy tint4 ,looking1 however1 at the extreme rarity of red ,auror in those latitudes1 and the description of 8mysterious balls of electric fire resting on our mast-heads1 yard-arms1 c40 7a phenomenon not often noticed in connexion with the ,aurora71 it suggests itself that the case in question may have been an instance not of a true ,aurora1 but of an electric display1 with conditions approaching those experienced by travellers who have found themselves in mountainous districts surrounded by storm-clouds charged with electricity#f4 ,prof4 ,piazzi ,smyth's ,typical ,auror4 ,sidenote3 ,prof4 ,piazzi ,smyth's typical ,auror4 ,prof4 ,piazzi ,smyth was kind enough lately to send me the fourteenth volume of the #8,astronomical ,observations made at the ,royal ,observatory1 ,edinburgh1 during the years #ahgj-ahgg4' ,this volume1 amongst its other interesting matter1 affords some valuable information on the subject of the ,aurora ,borealis4 ,the ,aurora plates are five in number1 three comprising some well-executed chromo-lithographs of typical ,auror1 from sketches made by ,prof4 ,smyth1 the other two plates being of the ,aurora spectrum4 ,the ,auror delineated are thus described3-- ,sidenote3 ,aug4 #f1 #ahga1 quiescent arc4 ,august #ba1 #ahga1 active arc4 ,plate #e4 7,august #f1 #ahga47 ,an example of a mild quiescent kind of auroral arc1 with dark cavernous substratum4 7,august #ba1 #ahga47 ,an example of a bright large active arc darting out rays4 ,sidenote3 ,sept4 #g1 #ahga1 arc streamers and clouds4 ,may #h1 #ahga1 double arc 7longitudinal74 ,plate #f4 7,september #g1 #ahga47 ,an auroral arc1 with streamers and dark clouds1 and maintaining a bright appearance though in proximity to the moon4 7,may #h1 #ahga47 ,a double-arched auroral arc 7the arches are longitudinally arranged74 ,sidenote3 ,april #bh1 #ahga1 multiple arc4 ,oct4 #be1 #ahgj1 coloured ,aurora4 ,plate #g4 7,april #bh1 #ahga47 ,a multiple-arched arc of ,aurora with moonlight4 7,october #be1 #ahgj47 ,a case of grandest coloured ,auror1 or ,aurora superb and almost universal4 ,all the foregoing drawings are very vivid and striking1 and form a most interesting set of typical forms of ,auror4 ,according to my own experience1 the ,aurora with arches arranged longitudinally1 thus1 ,illustration1 is the rarest of all the forms4 ,i have not met with it myself1 nor do ,i recollect an illustration of one other than ,prof4 ,smyth's4 ,,chapter ,,iv4 ,,phenomena ,,simulating ,,auror4 ,auroric ,lights 7,kinahan74 ,sidenote3 ,mr4 ,kinahan's ,auroric ,lights4 ,white and red4 ,white light appears in pencils radiating from a point4 ,mr4 ,g4 ,henry ,kinahan writes to #8,nature1' from ,ovoca1 under date ,january #bgth1 #ahgg1 and speaks of two distinct kinds of light so classed--one brilliant and transparent1 of a white yellowish-blue or yellowish-red colour1 while the other is semi-opaque and of a bloody red colour1 the latter being considered in ,ireland a forerunner of bad weather4 ,the first kind generally appears as intermittent pencils of light that suddenly appear and disappear4 ,sidenote3 ,frequently not stationary1 but jumping about4 ,usually they proceed or radiate from some point near the north of the horizon2 but ,mr4 ,kinahan has frequently seen them break from a point in the heavens1 not stationary1 but jumping about within certain limits4 ,sometimes these lights occur as suddenly flashing clouds of light of a white colour1 but at other times of blue and reddish yellow4 ,sidenote3 ,in daylight like sun-rays4 ,red light appears in clouds floating upwards or diffused4 ,if this class of lights is watched into daylight1 they appear somewhat like faint rays of a rising sun4 ,one morning1 while travelling in ,west ,galway in the twilight1 they were very brilliant1 and quite frightened ,mr4 ,kinahan's car-driver1 who thought the sun was going to rise in the north instead of the east4 ,the second1 or bloody red light1 usually occurs in clouds floating in one direction up into the heavens1 but often diffused over a portion of the sky4 ,mr4 ,kinahan has never seen them coming from the east1 and on only a few occasions from the south1 but generally from the west1 north-west1 or north4 ,sidenote3 ,red light appears as dirty misty clouds in daylight1 or as a mist or misty rays4 ,if both kinds of light appear at the same time1 the second while passing over the first dims it4 ,if the second class is watched into daylight1 they appear as dirty misty clouds that suddenly form and disappear without the spectator being able to say where they come from or where they go to1 or as a hazy mist over a portion of the sky1 that suddenly appears and disappears1 or as misty rays proceeding from a point in the horizon4 ,generally1 when these clouds occur1 there is a bank of black clouds to the westward4 ,sidenote3 ,season since ,october #ahgf prolific in auroric light4 ,mr4 ,kinahan then speaks of the season as having been prolific in auroric light1 as there had been few nights since the #ast ,october then last 7#ahgf7 in which they did not appear4 ,on many occasions they were late in the night1 being very common and brilliant during the dark days of ,december1 a few hours before dawn 7about #e o'clock74 ,each time there was a fine day they appeared also1 and the weather broke again4 ,sidenote3 ,mr4 ,j4 ,allan ,broun questions nature of these lights1 as ,aurora is seldom seen at #e ,a4,m4 in this country4 ,on #gg occasions seen only twice so early4 ,season was of marked infrequency elsewhere4 ,mr4 ,jno4 ,allan ,broun refers to this graphic account of ,mr4 ,kinahan's1 and concludes there must have been some mistake as to the nature of these 8auroric lights10 as the ,aurora ,borealis is very rarely seen at #e ,a4,m4 in this country4 ,in the years #ahdd and #ahde1 during which the ,aurora was sought for at ,makerstown every hour of the night1 it was observed in #gg nights on an average of nearly three hours each night2 but it was seen only twice so early1 and that with a bright or brilliant ,aurora1 which remained during five hours on the first occasion1 and from #f ,p4,m4 to #f ,a4,m4 on the second4 ,parts of the phenomenon seen by ,mr4 ,kinahan1 ,mr4 ,broun also could not say he had ever seen2 and if ,mr4 ,kinahan's observations could have been confirmed it would have been most important1 especially as made so frequently at the epoch of minimum4 ,the description is in many respects a sufficiently recognizable one of auroral discharges2 but the frequent appearance in early morning is certainly unusual1 and few if any ,auror seem to have been recorded as appearing elsewhere in ,great ,britain during the time which ,mr4 ,kinahan refers to as so prolific 7see1 however1 ,dr4 ,allnatt's1 ant1 p4 #bd74 ,in fact1 the season in question was one of marked infrequency 7see ,english ,arctic ,expedition ,report1 ant1 p4 #bf74 ,mr4 ,buchan furnished ,mr4 ,broun with a note of ,auror seen in the stations of the ,scottish ,meteorological ,society during the year #ahgf1 and they were #db in number1 #bf in the first half1 and #af in the second half of the year4 ,the greater part were seen in the most northerly stations1 including the ,orkney1 ,shetland1 and ,faroe ,islands1 and only #i south of the ,forth4 ,luminous ,arch4 ,sidenote3 ,luminous arch1 ,sept4 #aa1 #ahad4 ,height above horizon #f to #i miles4 ,in the #8,annals of ,philosophy1' vol4 iv4 p4 #cfb1 there is a minute description of a luminous arch which appeared in the sky on the night of ,sunday1 ,september #aath1 #ahad1 and was seen in the west of ,england opposite the ,irish ,sea1 the west part of the south of ,scotland1 and part of the west of ,ireland4 ,it was described as a part of either a body of dense greyish-white light1 or a mass of luminous matter in the shape of an arch4 ,its height above the horizontal line was estimated at not more than #i nor less than #f miles4 ,sidenote3 ,it moved southward1 and was assumed to differ from the ,aurora4 ,its direction when first seen was ,n4 #hj ,e41 and ,s4 #hj ,w4 ,it moved to the southward4 ,it was assumed to differ from the ,aurora ,borealis in wanting coruscations1 and in its having a much paler light4 ,,chapter ,v4 ,,some ,,qualities ,,of ,,the ,,aurora4 ,noises attending ,auror4 ,sidenote3 ,noises attending ,auror4 ,gmelin affirms them4 ,other testimony to them4 ,musschenbroek4 ,cavallo4 ,nairne4 ,belknap4 ,in the ,edinb4 ,encyc41 ,gmelin is stated1 in continuation of his description of an ,arctic ,aurora1 to add3--8,for however fine the illumination may be1 it is attended1 as ,i have heard from the relation of many persons1 with such a hissing1 cracking1 and rushing noise through the air1 as if the largest fireworks were playing off40 ,to describe what they then heard1 the natives are said to use the expression1 8,spolochi chodjat0--that is1 ,the raging host is passing4 ,the hunter's dogs1 too1 are also described as so much frightened when the ,auror overtake the hunters1 that they will not move1 but lie obstinately on the ground till the noise has passed4 ,this account of noises seems to be confirmed by other testimony4 ,they are stated to have been heard at ,hudson's ,bay and in ,sweden2 and ,musschenbroek mentions that the ,greenland whale-fishers assured him they had frequently heard the noise of the ,aurora ,borealis1 but adds that 8no person in ,holland had ever experienced this phenomenon40 ,mr4 ,cavallo declares he 8has repeatedly heard a crackling sound proceeding from the ,aurora ,borealis0 7,elements of ,nat4 or ,exper4 ,phil4 vol4 iii4 p4 #ddi74 ,mr4 ,nairne mentions that in ,northampton1 when the northern lights were very bright1 he is confident he perceived a hissing or whizzing sound4 ,mr4 ,belknap of ,dover1 ,new ,hampshire1 ,north ,america1 testifies to a similar fact 7,american ,trans4 vol4 ii4 p4 #aif74 ,sidenote3 ,sir ,john ,franklin negatives them4 ,sir ,john ,franklin mentions1 in his #8,journey to the ,shores of the ,polar ,sea'3--8,nor could we distinguish its 7the ,aurora's7 rustling noise1 of which1 however1 such strong testimony has been given to us that no doubt can remain of the fact40 ,sidenote3 ,march #aath4 ,hissing noise heard during ,aurora's passage4 ,explained to arise from the snow4 ,in detail1 he mentions he never heard any sound that could be unequivocally considered as originating in the ,aurora1 although he had had an opportunity of observing that phenomenon for upwards of #bjj nights 7the ,aurora was registered at ,bear ,lake #cdc times without any sound being heard to attend its motions72 but the uniform testimony of the natives and all the older residents in the country induced him to believe that its motions were sometimes audible4 ,on the #aath ,march1 at #aj ,p4,m41 a body of ,aurora rose ,n4,n4,w42 and after a mass had passed ,e4 by ,s41 the remainder broke away in portions1 which crossed about #dj of the sky with great rapidity4 ,a hissing noise1 like that of a bullet passing through the air1 was heard1 which seemed to proceed from the ,aurora2 but ,mr4 ,wentzel assured the party the noise was occasioned by severe cold succeeding mild weather1 and acting upon the surface of the snow previously melted in the sun's rays4 ,a similar noise was heard the next morning4 ,sidenote3 ,capt4 ,sabine also negatives noise4 ,in ,parry's first voyage1 ,captain ,sabine describes an ,aurora seen at ,melville ,island1 and adds that the ,aurora had the appearance of being very near the party1 but no sound could be heard4 ,sidenote3 ,article 8,aurora ,polaris10 ,encyc4 ,brit41 suggests noises as not improbable4 ,in the article 8,aurora ,polaris10 ,encyc4 ,brit1 edition ix41 the writer admits the evidence of scientific ,arctic voyagers having listened in vain for such noises2 but1 referring to the statements of ,greenlanders and others on the subject1 concludes there is no priori improbability of such sounds being occasionally heard1 since a somewhat similar sound accompanies the brush-discharge of the electric machine4 ,sidenote3 ,payer negatives and discredits noises4 ,payer1 of the ,austrian ,polar ,expedition 7#ahgb-ahgd71 states that the ,aurora was never accompanied by noise1 and discredits the alleged accounts of noises in the ,shetlands and ,siberia4 ,sidenote3 ,as also ,weyprecht4 ,lieut4 ,weyprecht1 of the same expedition1 says 7ant1 p4 #ad73--8;,involuntarily we listen2 such a spectacle must1 we think1 be accompanied with sound1 but unbroken silence prevails1 not the least sound strikes on the ear40 ,sidenote3 ,herr ,carl ,bock negatives noises in the case of ,lapland ,auror4 ,herr ,carl ,bock1 who accompanied the ,laplanders visiting this country 7at the ,westminster ,aquarium7 in #ahgg-gh1 and who witnessed many brilliant auroral displays in ,lapland1 assured me he could trace no noise1 except on one occasion1 when he heard a sort of rustling1 which he attributed to the wind4 ,the ,laplanders themselves did not associate any special noise with the ,aurora4 ,sidenote3 ,auroral noises in telephone4 ,ringing sound in vacuum-tube under influence of magnet4 ,it has been recently stated1 in an article on the ,telephone in #8,nature1' that ,professor ,peirce 8has observed the most curious sounds produced from a telephone in connexion with a telegraph wire during the ,aurora ,borealis20 but no further details are given4 ,in experimenting with a silicic fluoride vacuum-tube between the poles of an electro-magnet1 ,i found1 on the magnet being excited1 that the capillary stream of blue light was decreased in volume and brightness1 and at the same time from within the tube a peculiar whistling or slightly metallic ringing sound was heard4 ,sidenote3 ,adverse conclusion as to noises accompanying ,aurora4 ,i certainly have never met with an instance of noise accompanying an ,aurora and traced to it4 ,on the whole the balance of evidence seems quite adverse to any proof of noises proper ordinarily accompanying an ,aurora4 ,colours of the ,aurora4 ,sidenote3 ,colours of the ,aurora4 ,sir ,john ,franklin's views4 ,other observers have described all colours of spectrum4 ,violet rare4 ,crimson indicates coming ,aurora4 ,sir ,john ,franklin considered the colours in the ,polar ,aurora did not depend on the presence of any luminary1 but were generated by the motion of the beams1 and then only when that motion was rapid and the light brilliant4 ,the lower extremities1 he says1 quivered with a fiery red colour1 and the upper with orange4 ,he also saw violet in the former4 ,other observers have1 in their various descriptions of ,auror1 mentioned the colours of the rays or beams as red1 crimson1 green1 yellow1 c42 in fact1 comprising the range of the spectrum4 ,violet seems less frequently mentioned4 ,the red or crimson colour is frequently the first indication of the coming ,aurora1 and is usually seen on or near the horizon4 ,the colours have frequently been observed to shift or change4 ,sidenote3 ,prof4 ,piazzi ,smyth describes colours of ,aurora of ,feb4 #d1 #ahgb1 as seen at ,edinburgh4 ,prof4 ,piazzi ,smyth1 in a letter to #8,nature1' describing the ,aurora of ,february #dth1 #ahgb1 as seen at ,edinburgh1 says that when the maximum development was reached all the heavens were more or less covered with pink ascending streamers1 except towards the ,n41 which was dark and grey--first by means of a long low arch of blackness1 transparent to large stars1 and then by the streamers which shot up from this arch1 which were green and grey only for several degrees of their height1 and only became pink as they neared the zenith4 ,the red streamers varied from orange to rose-pink1 red rose1 and damask rose4 ,the ,professor pointed out that the spectroscope knew no variety of reds giving one red line only1 and attributed this to the mixing up of rays and streamers of blackness out of the long low arch4 ,when the ,aurora faded away a true starlight-night sky appeared2 so that evidently the dark arch and streamers were as much part of the ,aurora as the green and red lights4 ,sidenote3 ,dr4 ,allnatt at ,frant describes vivid colours of same ,aurora4 ,dr4 ,allnatt1 at ,frant1 found in the case of the same ,aurora the south-western part of the heavens tinged by a bright crimson band4 ,a dark elliptical cloud extending from ,s4 to ,s4,e4 was illuminated at its upper edge with a pale yellow light1 and sent up volumes of carmine radii interspersed with green and the black alternating matter characteristic of elemental electricity4 ,almost due ,e41 and of about #be degrees elevation1 was a bright insulated spot of vivid emerald-green1 which appeared almost sufficiently intense to cast a faint shadow from intercepting objects4 ,at #g o'clock the ,aurora had passed the zenith1 and the sky presented a weird and wonderful appearance4 ,a dark rugged cloud1 some #h degrees ,e4 of the zenith1 was surrounded by electric light of all hues--carmine1 green1 yellow1 blood-red1 white1 and black2 and the bright spot still existed in the south4 ,sidenote3 ,descriptions at ,blackburn and ,cambridge4 ,lapland ,auror yellow4 ,at ,blackburn1 in ,lancashire1 the rays were described as glowing in the ,n4,e4 from silvery white to deepest crimson2 and at ,cambridge the same ,aurora was described as of a brilliant carmine tint4 ,the ,auror seen in ,lapland by ,herr ,carl ,bock1 were1 he informed me1 almost invariably yellow2 he saw only one red one4 ,sidenote3 ,hydrogen vacuum-tube suggestive of ,aurora colours4 ,the behaviour of a hydrogen ,geissler vacuum-tube will be subsequently referred to in the ,chapter on the comparison of some tubes with the ,aurora spectrum1 and is suggestive as to ,aurora colours4 ,sidenote3 ,variation of tints in4 ,the capillary part of this tube1 when lighted by a small coil1 was found to vary in tint--silver-white1 bright green1 and crimson being each in succession the dominant colour1 according to the working of the break of the coil4 ,when a spectroscope was used1 the red1 blue1 and violet lines of the gas were seen to change in intensity in accordance with the light colour seen in the tube4 ,sidenote3 ,variation of colour in nitrogen tube under influence of magnet4 ,a ,geissler nitrogen vacuum-tube was also so arranged that the capillary part of it should be vertically between the conical extremities of the armatures of a large electro-magnet1 the armatures just being clear of the outside of the tube4 ,the tube was then lighted up by a small coil1 and the magnet excited by four large double-plate bichromate cells4 ,sidenote3 ,change from rosy to violet hue4 ,the stream of light was steady and brilliant1 and1 except at the violet pole1 of the rosy tint peculiar to a nitrogen vacuum-tube4 ,on excitation of the electro-magnet1 the discharge was seen to diminish in volume1 with an apparent increase in impetuosity2 and not only the capillary part1 but in a less degree the bulbs also of the tube1 changed from a rosy to a well-marked violet hue4 ,sidenote3 ,photographic plates taken4 ,difference in4 ,we several times connected and disconnected the magnet with its batteries1 but always with the same result4 ,of the spectrum of the capillary part of this tube we took photographic plates with quartz prisms and lenses1 taking care that all things should be as equal as possible1 the apparatus undisturbed1 and the time of exposure exactly the same4 ,one plate was taken with the tube in its normal condition1 the other while it was under the influence of the magnet4 ,the spectra were identical1 except that the plate of the tube influenced by the magnet was decidedly the brightest1 and was found to penetrate more into the violet region 7the ,author's #8,photographed ,spectra1' p4 #fj1 plate xxv474 ,these plates effectually corroborated the change of colour1 as the violet ray would have more photographic effect than the rosy4 ,the identity of the spectra of the capillary part proved that the change in colour could not have proceeded from an extension of the violet glow4 7,a similar experiment will be found also detailed in ,part ,,iii4 ,chapter ,,xii47 ,height of the ,aurora4 ,sidenote3 ,height of ,aurora4 ,sir ,john ,franklin considers it within the region of the clouds4 ,at no great elevation4 ,sir ,john ,franklin 7,narrative of a ,journey on the ,shores of the ,polar ,sea in the years #ahai1 '#bj1 '#ba1 '#bb7 says3--8,my notes upon the appearance of the ,aurora coincide with those of ,dr4 ,richardson in proving that that phenomenon is frequently seated within the region of the clouds1 and that it is dependent in some degree upon the cloudy state of the atmosphere40 ,and further3--8,the observations of ,dr4 ,richardson point particularly to the ,aurora being formed at no great elevation1 and that it is dependent upon certain other atmospheric phenomena1 such as the formation of one or other of the various modifications of cirro-stratus40 ,sir ,john ,franklin also refers to notes from the ,journal of ,lieut4 ,robert ,hood1 ,r4,n41 on an ,aurora3-- ,sidenote3 ,observations of ,lieut4 ,robert ,hood and ,dr4 ,richardson4 ,a beam not more than #g miles from the earth4 ,an arch #g miles from the earth4 ,the observations were made at ,basquian ,house1 and at the same time by ,dr4 ,richardson at ,cumberland ,house1 quadrants and chronometers having been prepared for the purpose4 ,on the #bnd ,april the altitude of a brilliant beam was #aj #j #j at #aj;h #am #js at ,cumberland ,house4 ,fifty-five miles ,s4,s4,w4 it was not visible4 ,it was estimated that the beam was not more than #g miles from the earth1 and #bg from ,cumberland ,house4 ,on the #fth ,april the ,aurora was for some hours in the zenith at that place1 forming a confused mass of flashes and beams2 and in lat4 #ec #bb #dh ,n41 long4 #ajc #g #ag1 it appeared in the form of an arch1 stationary1 about #i high1 and bearing ,n4 by ,e4 ,it was therefore #g miles from the earth4 ,sidenote3 ,an arch between #f and #g miles from the earth4 ,on the #gth ,april the ,aurora was again in the zenith before #aj ,p4,m4 at ,cumberland ,house1 and in lat4 #ec #cf #dj ,n41 long4 #ajb #ca #da4 ,the altitude of the highest of two concentric arches at #i;h ,p4,m4 was #i1 at #i;h #cjm it was #aa #cj1 and at #aj;h #jm #js ,p4,m4 #ae #j #j1 its centre always bearing ,n4 by ,e4 ,during this time it was between #f and #g miles from the earth4 ,the bearings are true1 not magnetic4 ,sidenote3 ,sir ,john ,franklin's remarks4 ,sir ,j4 ,franklin says this was opposed to the general opinion of meteorologists of that period3 he also noticed he had sometimes seen an attenuated ,aurora flashing across the sky in a single second1 with a quickness of motion inconsistent with the height of #fj or #gj miles1 the least that had hitherto been ascribed to it4 ,sidenote3 ,dr4 ,richardson's conclusions4 ,the needle was most disturbed1 ,february #ac1 #ahba1 ,p4,m41 at a time when the ,aurora was distinctly seen passing between a stratum of cloud and the earth2 and it was inferred from this and other appearances that the distance of the ,aurora from the earth varied on different nights4 ,dr4 ,richardson concludes that his notes prove1 independent of all theory1 that the ,aurora is occasionally seated in a region of the air below a species of cloud which is known to possess no altitude2 and is inclined to infer that the ,aurora ,borealis is constantly accompanied by1 or immediately precedes1 the formation of one or other of the forms of cirro-stratus4 ,sidenote3 ,captain ,parry observed ,auror near the ,earth's surface4 ,sir ,w4 ,r4 ,grove's observation at ,chester4 ,mr4 ,ladd's observation at ,margate4 ,the author's observation at ,kyle ,akin1 ,skye4 ,captain ,parry observed ,auror near the earth's surface2 and records that he and two companions saw a bright ray of the ,aurora shoot down from the general mass of light between him and the land1 which was distant some #cjjj yards4 ,sir ,w4 ,r4 ,grove 7#8,correlation of ,physical ,forces'7 saw an ,aurora at ,chester1 when the flashes appeared close1 so that gleams of light continuous with the streamers were to be seen between him and the houses--8he seemed to be in the ,aurora40 ,mr4 ,ladd1 of ,beak ,street1 ,regent ,street1 has related to me an appearance he was struck with1 and examined carefully4 ,standing in the evening in ,margate ,harbour1 he saw a white ray of the ,aurora1 which1 apparently shooting downwards1 was clearly placed between his eye and the opposite head of the pier1 which projected into the sea4 ,mr4 ,ladd also informed me that ,prof4 ,balfour assured him that such an appearance was not unusual4 ,in the double-arc ,aurora seen by me in the ,isle of ,skye1 ,september #aa1 #ahgd 7described ant1 p4 #bc71 ,i had a strong impression that the bow was near the earth1 and thought that the eastern end1 and some fleecy clouds in which it was involved1 were between myself and the peaks of the distant mountains4 ,sidenote3 ,dalton's calculation of #ajj miles4 ,backhouse's #ej to #ajj miles4 ,prof4 ,newton1 mean #acj miles4 ,elevation of ,auror cannot exceed a few miles4 ,in the article 8,aurora ,polaris10 ,encyc4 ,brit41 edition ix41 ,dalton is instanced as having calculated the height of an ,aurora in the north of ,england at #ajj miles2 and ,backhouse as having made many calculations1 with the result of an average height of #ej to #ajj miles4 ,prof4 ,newton1 too1 is quoted for the height of #bh ,auror 7calculated by one observation of altitude and amplitude of an arch7 as ranging from #cc to #bha miles1 with a mean of #acj miles4 ,it is1 however1 pointed out that a height of #fb miles above the earth's surface would imply a vacuum attainable with difficulty1 even with the ,sprengel pump4 ,this difficulty is then met by a reference to the observed altitude of some meteors1 and to a suggestion of ,prof4 ,herschel's that electric repulsion may carry air or other matter up to a great height4 ,dr4 ,lardner 7#8,museum of ,science and ,art1' vol4 x4 p4 #aib7 speaks of the height of ,auror as not certainly ascertained2 but considers them atmospheric phenomena scarcely above the region of the clouds1 and does not think it probable that their elevation in any case can exceed a few miles4 ,sidenote3 ,m',clintock's observations4 ,capt4 ,ross saw ,auror on an ice-cliff1 which he attributed to electric action4 ,m',clintock1 after noticing that the beams of the ,aurora were most frequently seen in the direction of open water1 says that in some cases patches of light could be plainly seen a few feet above a small mass of vapour over an opening in the ice4 ,captain ,ross1 in his ,antarctic voyage1 saw the bright line of the ,aurora forming a range of vertical beams along the top of an ice-cliff2 and suggested this was produced by electrical action taking place between the vaporous mist thrown upwards by the waves against the berg1 and the colder atmosphere with which the latter was surrounded4 ,sidenote3 ,bergman estimates height as #dfh miles4 ,bergman1 from a mean of #cj computations1 makes the height of the phenomenon to be #gb ,swedish 7about #dfh ,english7 miles4 ,sidenote3 ,boscovich #hbe miles4 ,father ,boscovich calculated the height of an ,aurora ,borealis observed on the #afth ,december1 #agbg1 to have been #hbe miles4 ,sidenote3 ,mairan #fjj miles4 ,euler several thousand miles4 ,dr4 ,blagden about #ajj miles4 ,mairan supposed the far greater number of ,auror to be at least #fjj miles above the surface of the earth4 ,euler assigned them an elevation of several thousands of miles4 ,dr4 ,blagden1 however1 limited their height to about #ajj miles1 which he supposed to be the region of fireballs--remarking that instances were upon record in which northern lights had been seen to join and form luminous balls1 darting about with great velocity1 and even leaving a train behind them like common meteors 7,phil4 ,trans4 vol4 lxxiv4 p4 #bbg74 ,sidenote3 ,dalton #aej miles4 ,mr4 ,dalton1 from an observation of the luminous arches on a base of #bb miles1 found the altitude of the ,aurora to be about #aej miles 7,dalton's #8,meteorological ,observations and ,essays1' #agic1 pp4 #ed1 #aec74 ,sidenote3 ,dr4 ,thompson assumes considerable height4 ,his table4 ,average of #ca observations1 #ejj miles4 ,dr4 ,thompson1 #8,annals of ,philosophy1' vol4 iv4 p4 #dbi 7#ahad71 assumes that the height of the beams above the surface of the earth was much greater than that of most other meteorological appearances1 and gives 7p4 #dcj7 a table of ,auror1 mainly taken from ,bergman1 ,opusc4 v4 p4 #bia1 of #ca ,auror observed in the years #afba to #agic1 with heights in ,english miles4 ,the lowest is1 #bcrd ,february1 #aghd1 ,london 7,cavendish71 #fb miles2 the highest1 #bcrd ,october1 #agea1 ,fournerius1 #ajjf miles6 ,the average of the #ca estimated observations gives a height of about #ejj miles4 ,it is not stated how these observations were obtained1 though methods are mentioned how they might be4 ,sidenote3 ,prof4 ,heis's instrument for determining height of ,auror4 ,prof4 ,heis1 of ,mnster1 exhibited at the recent ,scientific ,loan ,collection at ,south ,kensington 7#8,official ,catalogue1' #crd edit4 p4 #bif1 ,no4 #abca7 an instrument for the determination of the position of the point of convergence of the rays of the ,aurora1 and for determining the height of the ,aurora4 ,a ball resting in a pan was to be brought into position1 so that several diverging pencils of ,aurora1 when properly viewed1 were covered by the rod which passed through the centre of the ball4 ,the point of the rod 7which could be moved up and down in the ball71 when the instrument was set to the astronomical meridian1 showed the azimuth and altitude of the converging point of the pencils of light4 ,this point of convergence does not coincide with the point to which the inclination-needle directs4 ,from the deviation of the two points1 the height of the ,aurora could be calculated4 ,sidenote3 ,professor ,newton's method of calculating height4 ,professor ,h4 ,a4 ,newton 7,sil4 ,journ4 of ,science1 #bnd ser4 vol4 xxix4 p4 #bhf7 has proposed a method of calculating the height of ,auror by one observation of altitude and amplitude of an arch4 ,it assumes that the auroral arches are arcs of circles1 of which the centre is the magnetic axis of the earth1 or at least that they are nearly parallel to the earth's surface1 and probably also to the narrow belt or ring surrounding the magnetic and astronomical poles4 ,professor ,newton finds that1 d being the distance from the observer to the centre of curvature of the nearest part of this belt 7for ,england1 situated about #ge ,n4 lat41 #ej ,w4 long471 h the apparent altitude of the arch1 #b;a its amplitude on the horizon1 x its height1 ,r the earth's radius1 and c the distance of the observer from the ends of the arch3-- sin sin d cos a cosec7d h7 7#a7 tan c z sin h sin sec 7#b7 x ,r - 7sec c - #a7 7#c7 ,sidenote3 ,gave a height from #cc to #bha miles1 and a mean of #acj miles4 ,this method with #bh ,auror gave a height from #cc to #bha miles and a mean of #acj miles4 ,galle has suggested 7,pogg4 ,ann4 cxlvi4 p4 #acc7 that the height of ,auror might be calculated from the amount of divergence between the apparent altitude of the auroral corona and that indicated by the dipping-needle1 a principle which has been adopted in ,prof4 ,heis's apparatus before described4 ,the results do not differ materially from ,professor ,newton's4 ,the conclusions to be arrived at from the foregoing instances and opinions are certainly very puzzling4 ,the terrestrial character of some ,auror seems well established4 ,the height to which these phenomena may ascend is left almost a matter of conjecture1 and further observations are very desirable4 ,phosphorescence4 ,sidenote3 ,phosphorescence4 ,phosphorescent bands4 ,storm-clouds which threw out cirri4 ,shone with a sort of phosphorescence4 ,storm-cloud surrounded by glories of a phosphorescent whiteness4 ,in the voyage of the #8,hansa' 7#8,recent ,polar ,voyages1' p4 #dbj71 on the #ith ,september1 #ahfi1 at #aj ,p4,m41 ,aurora gleams appeared in the west1 shooting towards the south4 8,radiant sheaves and phosphorescent bands mounted towards the zenith10 but the phantasmagoria quickly vanished4 ,m4 ,silbermann 7#8,comptes ,rendus1' lxviii4 p4 #aabj7 mentions storm-clouds which threw out tufts of cirri from their tops1 which extended over the sky1 and resolved into1 first1 fine1 and afterwards more abundant rain4 7,i saw a fine day example of this on the ,lago di ,guarda1 ending in a copious discharge of rain attended with loud thunder and vivid lightning47 ,usually the fibres were sinuous2 but in much rarer cases they became perfectly rectilinear and surrounded the cloud like a glory1 and occasionally shone with a sort of phosphorescence4 ,on the night of #fth ,september1 #ahfe1 at #aa ,p4,m41 a stormy cloud was observed in the ,n4,n4,w41 and lightning was seen in the dark cumulous mass4 ,around this mass extended glories of a phosphorescent whiteness1 which melted away into the darkness of the starry sky4 ,round the cloud was a corona1 and outside this two fainter coron4 ,after the cloud had sunk below the horizon the glories were still visible4 ,sidenote3 ,sabine's luminous cloud at ,loch ,scavaig1 ,skye4 ,other observations of luminous clouds4 ,sabine mentions a cloud frequently enveloping ,loch ,scavaig1 in ,skye1 as being at night perfectly self-luminous1 and that he saw rays1 similar to those of the ,aurora1 but produced in the cloud itself4 ,sabine also refers to luminous clouds mentioned in ,gilbert's ,annals1 and to observations by ,beccaria1 ,deluc1 the ,abb ,rozier1 ,nicholson1 and ,colla2 and to luminous mists as observed by ,dr4 ,verdeil at ,lausanne in #agec1 and by ,dr4 ,robinson in ,ireland4 ,sidenote3 ,aurora at ,melville ,island4 ,he also describes 7,parry's ,first ,voyage7 an ,aurora seen at ,melville ,island1 and says the light was estimated as equal to that of the moon when a week old4 ,besides the pale light1 which resembled the combustion of phosphorus1 a slight tinge of red was noticed when the ,aurora was most vivid2 but no other colours4 ,this ,aurora was repeatedly seen on the following day4 ,sidenote3 ,procter suspects ,aurora is formed in a mist4 ,m',clintock3 ,aurora is never visible in a perfectly clear atmosphere4 ,mr ,procter1 in a letter to me1 suspects that the ,aurora is generally formed in a sort of 8mist or imperfect vapour20 and this mist or imperfect vapour seems in many instances to form part of the ,aurora1 and to partake of its self-luminous character4 ,m',clintock does not imagine that the ,aurora is ever visible in a perfectly clear atmosphere4 ,he has often observed it just silvering or rendering luminous the upper edge of low fog or cloud-banks1 and with a few vertical rays feebly vibrating4 ,sidenote3 ,aurora of ,feb4 #d1 #ahgd4 ,illuminated fog-cloud4 ,capt4 ,oliver's meteor-cloud4 ,auroral display1 #bdth ,oct41 #ahgj4 ,streamers of phosphorescent cloud4 ,an instance of apparent phosphorescence is supplied by the ,aurora of the #dth ,february1 #ahgd 7ant71 when a bright cloud of light was seen which gave the impression of an 8illuminated fog-cloud40 ,captain ,s4 ,p4 ,oliver saw at ,buncrana1 ,co4 ,donegal1 on ,february #d1 #ahgd1 what he describes as a meteor-cloud1 viz4 8a broad band of silvery white and luminous cloud40 ,this appearance1 as described by another correspondent1 was evidently an imperfectly formed 7perhaps actually forming7 ,auroral arc4 ,the great ,auroral display of the #bdth of ,october1 #ahgj1 as seen by me1 included1 according to my notes made at the time1 8streamers of opaque white phosphorescent cloud1 very different from the more common transparent ,auroral diverging streams of light40 ,sidenote3 ,aurora of ,feb4 #d1 #ahgb1 at ,frant4 ,radii of phosphorescent light4 ,describing the ,aurora of ,february #d1 #ahgb1 at ,frant1 ,dr4 ,allnatt says3--8,at a later hour of the night the canopy of cirro-stratus had separated1 and was transformed into luminous masses of radiant cumulus4 ,at #aj4dj the ,aurora reappeared in the ,n41 and sent luminous radii of white phosphorescent light from the periphery of a segment of a perfectly circular arch0#g4 ,sidenote3 ,the author's description of same ,aurora4 ,masses of phosphorescent vapour4 ,again1 ,february #dth1 #ahgb1 as described by me1 the first signs of the ,aurora were 7in dull daylight7 a lurid tinge upon the clouds1 which suggested the reflection of a distant fire2 while scattered among these1 8torn and broken masses of white vapour having a phosphorescent appearance0 reminded me of a similar observation in ,october #ahgj4 ,sidenote3 ,day ,auror must have a phosphorescent glow4 ngstrm considers yellow-green line due to fluorescence or phosphorescence4 ,oxygen and some of its compounds phosphorescent4 ,the day ,auror1 which are elsewhere described1 and are not very uncommon1 could1 we may presume1 hardly be seen without the presence of some phosphorescent glow4 ,professor ngstrm1 in his ,aurora ,memoir 7discussed elsewhere71 in discussing the yellow-green line1 considers the only probable explanation to be that it owes its origin to fluorescence or phosphorescence4 ,he says that some fluorescence is produced by the ultra-violet rays2 and adds1 8an electric discharge may easily be imagined1 which1 though in itself of feeble light1 may be rich in ultra-violet light1 and therefore in a condition to cause a sufficiently strong fluorescent light40 ,and he refers to the fact that oxygen and some of its compounds are phosphorescent4 ,sidenote3 ,a phosphoretted hydrogen spectrum-band is close to yellow-green auroral line4 ,phosphorescent or fluorescent after-glow of electric discharge4 ,in the examination of certain spectra connected with the ,aurora1 detailed in ,part ,,ii41 ,i have shown that the bright edge of one of the phosphoretted hydrogen bands is in close proximity to the yellow-green ,auroral line4 ,i have also referred to the peculiar brightening by reduction of temperature of one of the bands in the red end of the spectrum of phosphoretted hydrogen1 so that from almost invisible it became bright1 and to the peculiar brightening of a line in the yellow-green in certain 8,aurora0 and phosphorescent tubes4 ,it has also been observed that the electric discharge has a phosphorescent or fluorescent after-glow 7isolated1 ,i believe1 by ,faraday74 ,it seems difficult to avoid in some way connecting all these circumstances with the yellow-green line of the ,aurora1 if not also with the line in the red4 ,sidenote3 ,sorby's experiments on fluorescence and absorption4 ,bonelleine1 spectrum of4 ,coloured layer of fungi4 ,spectrum of ,oscillatori4 ,mr4 ,sorby1 in his experiments on the connexion between fluorescence and absorption 7#8,monthly ,microscopical ,journal'71 found in the spectrum of a solution in alcohol of a strongly fluorescent substance called bonelleine 7the green colouring-matter found in the ,aurelia ,bonellia-viridis7 two bright bands1 the one red and the other green1 with centres respectively at #fdcj and #ehhj1 and their limits towards the blue end at #fcbj and #ehbj4 ,on adding an acid the red band changed its place to #fadj4 ,the superficial membranous coloured layer of the fungi ,russula nitida and vesca in alcohol gave an absorption band with centre at #eedj1 while the spectrum of fluorescence extended to #ddjj4 ,a solution of ,oscillatori in water gave a spectrum of absorption with bands at #fbjj and #efij2 while the spectrum of fluorescence showed two bright bands having their centres at #fdgj and #ehjj1 and their limits towards the blue end at #fcbj and #egaj4 ,sidenote3 ,sea phosphorescence1 a continuous spectrum4 ,these instances of course cannot be connected with the ,aurora except as showing the spectrum region and lines of fluorescence4 ,the sea phosphorescence1 according to ,professor ,piazzi ,smyth1 has a continuous spectrum extending from somewhat below ,e to near ,f 7,plate ,v4 fig4 #c74 ,sidenote3 ngstrm finds the sky almost phosphorescent4 ngstrm1 on the occasion of the starry night when he found traces of the green line in all parts of the heavens1 speaks of the sky as being 8almost phosphorescent40 ,sidenote3 ,author of article in ,encyc4 ,brit4 suggests that the phosphorescent or fluorescent light may be due to chemical action4 ,herschel's observation of phosphorescence in ,geissler and 8garland0 tubes4 ,the author of the ,aurora article in the ,encyc4 ,brit4 suggests that the phosphorescent or fluorescent light attributed to the ,aurora may be due to chemical action4 ,he also questions ngstrm's assumption that water-vapour is absent in the higher atmosphere1 and thinks that it and other bodies may1 by electric repulsion1 be carried above the level they would attain by gravity4 ,he then continues that if discharges take place between the small sensible particles of water or ice in the form of cirri 7as ,silbermann has shown to be likely7 surface decomposition would ensue1 and it is highly probable the nascent gases would combine with emission of light4 ,he adds 8that it has been almost proved that in the case of hydrogen phosphide the very characteristic spectrum 7light87 produced by its combustion is due neither to the elements nor to the products of combustion1 but to some peculiar action at the instant of combination2 and it is quite possible that under such circumstances as above described water might also give an entirely new spectrum40 ,professor ,herschel has referred to the phosphorescent light which remains glowing in ,geissler tubes after the spark has passed1 and to the fact that one of the globes of a 8garland0 tube which was heated did not shine after the spark had passed1 apparently because of the action of heat on the ozone to which the phosphorescence might be due4 7,see experiments on ,mr4 ,browning's bulbed tube1 ,part ,,iii4 ,chap4 ,,xv47 ,aurora and ,ozone4 ,sidenote3 ,aurora and ,ozone4 ,smells of sulphur during ,auror attributed to ozone4 ,accounts are given by travellers in ,norway of their being enveloped in the ,aurora1 and perceiving a strong smell of sulphur1 which was attributed to the presence of ozone4 ,m4 ,paul ,rollier1 the aronaut1 descended on a mountain in ,norway #acjj metres high1 and saw brilliant rays of the ,aurora across a thin mist which glowed with a remarkable light4 ,to his astonishment1 an incomprehensible muttering caught his ear2 when this ceased he perceived a very strong smell of sulphur1 almost suffocating him 7#8,arctic ,manual1' p4 #gbf74 ,sidenote3 ,question whether the oxygen of the air may be changed into ozone4 ,in the case of the ,aurora1 the question naturally arises whether the oxygen of the air may be changed into ozone1 perhaps also whether the nitrogen may not be modified in some similar manner4 ,sidenote3 ,ozone destroyed by heat4 ,the absorption spectra of oxygen1 and of the same gas in its form of ozone1 may possibly differ2 but this can hardly happen in the case of incandescent oxygen1 for ozone is at once destroyed by heat at #cjj1 and slowly at #ajj1 and must be partially at least destroyed by the heat of the discharge4 ,if any lines were due to ozone in such a spectrum1 we should expect they would be weakened by heat and brightened by cold4 ,sidenote3 ,ozone in a large bell-receiver not manifested in spectrum4 ,in the case of a continued discharge in a large exhausted bell-receiver1 the presence of ozone in considerable quantities was manifested to us by its odour when the receiver was removed from the pump2 but the spectrum of the stream of light did not appear to differ from that in ,geissler tubes4 ,sidenote3 ,professor ,dewar demonstrates that ozone is condensed oxygen4 ,in a course of lectures at the ,royal ,institution in ,march #ahgh1 on the ,chemistry of the ,organic ,world1 ,prof4 ,dewar appears to have demonstrated1 by ,prof4 ,andrews' apparatus1 that ozone is really condensed oxygen1 and1 further1 that during this condensation heat is absorbed1 which is evolved during the decomposition or re-expansion4 ,sidenote3 ,refers to the silent discharge between the atmosphere and the earth4 ,he also exhibited the oxidizing power of ozone in its action on mercury1 and commented on its similar action upon organic matter in forming nitrates1 and on its remarkable bleaching properties1 but added there was as yet no proof of its combining with free nitrogen4 ,that peroxide of hydrogen accompanies the formation of ozone by the slow combustion of phosphorus1 and that this peroxide acts with ozone in decomposing organic bodies1 though in an inexplicable manner1 the ,professor considered to be proved4 ,he also referred to the silent discharge probably perpetually going on between the upper and lower strata of the atmosphere1 and also between these and the earth1 accounting1 as the ,professor considered1 for some of the chemical actions whereby nitrogenous compounds are formed in the soil4 ,sidenote3 ,no spectrum of ozone obtained4 ,as far as ,i am aware1 no information as to a possible spectrum of ozone1 or a modification of the oxygen or other spectra by its presence1 has1 up to the present time1 been obtained#h4 ,sidenote3 ,suggestion to subject electric discharge to influence of cold4 ,it has been suggested by ,mr4 ,procter and myself that the electric discharge in an exhausted moist tube1 if subjected to a considerable degree of cold1 might produce a modification of the air-spectrum1 perhaps even a spectrum analogous to that of the ,aurora4 ,for some further notes on this subject see ,appendix ,d 7,aurora and ,ozone74 ,polarization of the ,aurora ,light4 ,sidenote3 ,polarization of the ,aurora light4 ,mr4 ,ranyard found none4 ,in #8,nature1' vol4 vii4 p4 #bja1 is contained an account of observations of the polarization of the zodiacal light and of the ,aurora1 by ,mr4 ,a4 ,cowper ,ranyard1 who1 using both a double-image prism and a ,savart on the great ,aurora of ,february #dth1 #ahgb1 detected no trace of polarization4 ,he also examined a smaller one of #ajth ,november1 #ahga1 with a like result4 ,sidenote3 ,prof4 ,alexander found strong polarization in latitude #fj4 ,mr4 ,fleming 7who refers to these observations7 remarks that the only other account he had met with was contained in ,prof4 ,stephen ,alexander's ,report on his ,expedition to ,labrador1 given in ,appendix #ba of the ,u4,s4 ,coast ,survey ,report for #ahfj1 p4 #cj4 ,professor ,alexander found strong polarization with a ,savart's polariscope1 and thought that the dark parts of the ,aurora gave the strongest polarization4 ,this was in latitude about #fj1 at the beginning of ,july1 and near midnight4 ,it is not stated whether there was twilight or air-polarization at the time1 nor is the plane of polarization given4 ,sidenote3 ,mr4 ,shroeder found no polarization4 ,the question naturally arises1 especially as the darkest parts of the ,aurora are usually situated low down near the horizon1 whether the polarization in the latter case did not proceed from the atmosphere and not from the ,aurora itself4 ,mr4 ,shroeder found no traces of polarization in the ,aurora of ,february #dth1 #ahgb4 ,further examinations of the ,aurora with some delicate form of polariscope would seem very desirable4 ,sidenote3 ,polarization not found in the zodiacal light2 except faint traces by ,mr4 ,burton4 ,the evidence of polarization in the case of the zodiacal light seems also almost entirely negative--,mr4 ,ranyard pointing out observations of his own1 of ,captain ,tupman1 and of ,mr4 ,lockyer with this result4 ,mr4 ,burton1 using a ,savart set so as to give a black centre when the bands were parallel to the plane of polarization1 believed he detected faint traces of polarization in the brightest parts of the zodiacal light 7as seen in ,sicily71 the bands being black-centred when their direction coincided with the axis of the cone of light4 ,mr4 ,burton saw no trace of bands when examining the slight remaining twilight apart from the zodiacal light4 ,mr4 ,ranyard was not able to confirm ,mr4 ,burton's observations on the same evening and with the same instrument4 ,number of ,auror4 ,sidenote3 ,number of ,auror4 ,sir ,john ,franklin's observations4 ,sir ,john ,franklin saw in the ,arctic ,regions1 in the years #ahai1 #ahbj1 #ahba1 #ahbb3--;,in the month of ,september two ,auror1 in ,october three1 in ,november three1 in ,december two1 in ,january five1 in ,february seven1 in ,march sixteen1 in ,april fifteen1 and in ,may eleven4 ,sidenote3 ,periodicity as to days not established4 ,periodicity as to days seems to have no certain law2 and though certain days in ,february and ,march are marked as those of fine returning displays1 they must be looked on as accidental4 ,sidenote3 ,maxima and minima4 ,two well-marked annual maxima seem to occur in ,march and ,october 7the latter the greater71 and two minima in ,june and ,january1 the greater in ,june 7,encyc4 ,brit474 ,the #dth of ,february1 #ahgb1 and same day #ahgd1 are1 however1 curious instances of a recurring remarkable display4 ,sidenote3 ,kmtz's table4 ,a table by ,kmtz1 showing the number of ,auroras in each month of the year1 with the maxima and minima as above stated1 will be found on ,plate ,v4 fig4 #e4 ,sidenote3 ,dr4 ,hayes's observations in winter of #ahfj-fa4 ,dr4 ,hayes has observed that in the winter of #ahfj-fa 7when the ten or eleven years' inequality was at its maximum7 only three ,auror were seen and recorded1 and they were feeble and short in duration4 ,sidenote3 ,captain ,maguire's observations at ,point ,barrow as to number and time of appearances4 ,captain ,maguire1 at ,point ,barrow 7#aheb-ed71 reports that the ,aurora was seen six days out of seven1 and on #ajgi occasions1 being nearly one third of the hourly observations4 ,it was seldom seen between #i ,a4,m4 and #e ,p4,m41 not at all between #aj ,a4,m4 and #d ,p4,m4 ,it increased regularly and rapidly from #e ,p4,m4 until #a ,a4,m41 and then diminished in the same way until #i ,a4,m4 ,the winters of #ahgg and #ahgh and the springs of #ahgh and #ahgi have been singularly deficient in ,auror4 ,i have seen none at ,guildown4 ,duration of ,aurora4 ,sidenote3 ,duration of ,aurora4 ,sometimes a few minutes2 at other times the whole night or even days4 ,in the article in the #8,edinb4 ,encyc4' before referred to some remarks are made on the duration of the ,aurora4 ,sometimes it is formed and disappears in the course of a few minutes4 ,at other times it lasts for hours or during the whole night1 or even for two or three days together4 ,musschenbroek observed one in #agcd which he considered to have lasted ten days and nights successively1 and another in #agce which lasted from the #bbnd to the #cast ,march4 ,sidenote3 ,auror may run on into the day without being noticed4 ,with respect to ,captain ,maguire's observations 7ant7 it may be remarked that ,auror may doubtless frequently run on into and through the day without their being noticed 7instances1 however1 are known of ,auror seen in daylight72 and hence it is difficult to judge of the limit of duration of a particular ,aurora unless indications are sought for during the day 7by the shapes of clouds1 action of the magnet1 c47 as well as during the night4 ,probably ,auror seen during successive nights may be parts of a continuous discharge4 ,the ,travelling of ,auror4 ,sidenote3 ,travelling of ,auror4 ,donati's investigations4 ,donati undertook to study the ,aurora with reference to the mode of its extension2 and he arrived at the result that the ,aurora of ,february #d1 #ahgb1 was not observed in different regions of the earth in the same physical moment2 but everywhere at the same local hour1 as in the case of celestial phenomena1 which do not share in the earth's rotation4 ,sidenote3 ,questions sent to ,italian ,consuls4 ,the ,minister of ,foreign ,affairs sent a circular to all ,italian ,consuls1 asking them the necessary questions2 and in reply received reports from forty-two places in our hemisphere and from four in the southern1 the places embracing in one latitude the considerable extent of #bdj degrees of longitude4 ,an epitome of the tables 7in which the results are divided into three zones7 is as follows3-- ,sidenote3 ,table of results4 ---------------------------------------- ----------------------- ,zone4 ,mean longitude ,no4 of ,mean hour ,mean hour of zone4 stations4 of maximum4 of end4 ---------------------------------------- ----------------------- ,eastern #b hrs4 #e mins4 ,e4 #i #i hrs4 #ab hrs4 ,middle #j hr4 #bj mins4 ,e4 #ag #h hrs4 #aa hrs4 ,western #e hrs4 #ch mins4 ,w4 #ac #h hrs4 #i hrs4 ---------------------------------------- ----------------------- ,sidenote3 ,extensions of the ,aurora4 ,the ,aurora passed through four periods4 ,first period of origin1 light weak4 ,second period1 increase of intensity4 ,third period1 continuous brightness4 ,fourth period1 decrease4 ,donati summed up the facts3--,that the light phenomena of this ,aurora began to show themselves in the extreme east of the southern hemisphere in ,eden and ,melbourne2 shortly after1 they were observed in the east of our hemisphere in ,china 7but not in ,japan72 from ,china the ,aurora passed over the whole of ,asia and ,europe1 and crossed the ,atlantic and the ,american ,continent as far as ,california4 ,it was invisible in ,central and ,south ,america4 ,during these immense extensions it passed through four periods4 ,in the first 7called by ,donati the period of origin7 the light of the ,aurora was pretty weak1 and spread from ,shanghai to ,bombay2 in the second period1 during which it passed on from ,bombay to ,taganrog1 it acquired a sudden increase of intensity2 in the third period 7called by ,donati the normal7 the ,aurora passed over ,europe from east to west with regularity and a continuous brightness2 the fourth period1 that of decrease1 was observed in ,america4 ,the ,aurora had a tendency to end earlier in reference to the local hour in the western stations than in the eastern4 ,the acceleration on an average of the end of the phenomenon was twenty minutes for every hour of longitude4 ,sidenote3 ,donati's conclusions4 ,explanation of mode of propagation of same ,aurora4 ,donati concluded that these facts were not reconcilable with the theory of the ,aurora depending on meteorological and electro-magnetic phenomena of the globe4 ,since1 too1 we have not a yearly1 but a ten-yearly period of the ,aurora1 which coincides with that of sun-spots and terrestrial magnetism1 ,donati supposed that the cosmic causes of the polar lights were electro-magnetic currents between the sun and the earth4 ,this would explain the mode of propagation of the ,aurora of #dth ,february4 ,conceive an electric current going from the earth to the sun1 or vice vers2 certain phenomena of the ,aurora could only be observed in those parts of the atmosphere which have a determinate position or direction with reference to this current2 and consequently these phenomena would be successively visible on the different meridians1 as these meridians1 by reason of the earth's rotation1 assume the same position to the current4 ,for the ,aurora to be visible certain meteorological and telluric circumstances must1 however1 doubtless work together with the cosmical cause4 ,geographical ,distribution of ,auror 7,fritz and ,loomis74 ,sidenote3 ,geographical ,distribution of ,auror4 ,prof4 ,fritz's and ,prof4 ,loomis's line of frequency4 ,professors ,fritz and ,loomis have investigated this subject2 and ,petermann's #8,mittheilungen1' vol4 xx4 7#ahgd71 contains a paper by the former1 from which it appears that the northern limit of ,auror chosen by ,professor ,loomis nearly coincided1 except in ,england1 with a line of frequency in ,professor ,fritz's paper4 ,this line nearly passes through ,toronto1 ,manchester1 and ,st4 ,petersburg4 ,professor ,loomis places it as far north as ,edinburgh4 ,on a line across ,behring's ,straits1 and coming down below #fj ,n4 in ,america and the ,atlantic1 and just north of the ,hebrides1 to ,drntheim1 and including the most northern points of ,siberia1 the frequency is represented by #ajj4 ,sidenote3 ,within this another zone of greatest frequency and intensity4 ,within this is another zone of greatest frequency and intensity1 which passes just south of ,point ,barrow1 in lat4 #gb ,n41 on the northern coast of ,america1 and by the ,great ,bear ,lake to ,hudson's ,bay1 where it reaches a latitude of #fj1 then on to ,nain1 on the coast of ,labrador1 and to the south of ,cape ,farewell2 then bending sharper to the northward1 it passes between ,iceland and the ,faroe ,islands1 near to the ,north ,cape1 on by the northern ice-sea to ,nova-,zembla and ,cape ,tschejuskin1 and on just to the north of the ,siberian coast to the south of ,kellett ,land1 thence returning to ,point ,barrow4 ,sidenote3 ,lines on which annually nearly the same number of ,auror are seen4 ,more or less parallel with this line are the lines on which annually nearly the same number of ,auror are seen4 ,the line for one ,aurora annually went from ,bordeaux1 through ,switzerland1 past ,krakau1 south of ,moscow and ,tobolsk1 to the northern end of ,lake ,baikal1 on to the ,sea of ,ochotsk and to the ,southern ,aleutes1 thence through ,northern ,california to the mouth of the ,mississippi and to ,bordeaux4 ,the line for five ,auror annually went from ,brest through ,belgium1 ,stettin1 ,wologda1 between ,tobolsk and ,beresow1 parallel to the previous line to ,ochotsk1 and on to ,brest1 c4 ,almost exactly with the line of greatest frequency coincides the line forming the boundary of the direction of visibility of the ,northern ,light towards the ,pole or towards the ,equator2 while northwards of this line the ,polar ,light is seen in the direction towards the ,equator2 and from all stations the ,northern ,lights are seen in directions which are pretty much normal to that curve and the entire system of isochasms4 ,sidenote3 ,assumed connexion between ,aurora and ice-formation4 ,professor ,fritz has remarked that the curves of greater frequency tend towards the region of atmospheric pressure1 and also that they bear some relation to the limit of perpetual ice--tending most southward where1 as in ,north ,america1 the ice limit comes further south4 ,he also endeavours to show a connexion between the periods of maximum of ,auror and those of ice-formation1 and considers ice to be an important local cause influencing their distribution4 ,these being most frequently seen over open water in the ,arctic regions1 has been referred to as noticed by ,franklin and others4 ,extent and principal ,zone of the ,aurora4 ,sidenote3 ,extent and principal zone of ,aurora4 ,m4 ,moberg's ,finland observations 7#ahdf-ee7 compared by ,prof4 ,fritz with those in other regions4 ,the ,finland observations1 published by ,m4 ,moberg in his #8,polarlichter ,katalogue' of ,northern ,lights in the years #ahdf-ee1 numbering #aajj1 have been compared by ,prof4 ,fritz1 in his paper in the #8,wochenschrift fr ,astronomie1' with the auroral phenomena of the same period in all other regions4 ,the ,table shows that of #bjce days of the months ,august to ,april on which ,northern ,lights were seen1 #aajg days were those of ,northern ,lights for ,finland4 ,on #gid they were visible simultaneously in ,america1 and mostly also in ,europe2 on #aja days in ,europe only1 and on #bab days in ,finland only4 ,on #ieh days ,northern ,lights were visible in ,europe and ,america which were not visible in ,finland4 ,all these numbers refer only to the months ,august to ,april1 as in the remaining months the brightness of the night in ,finland makes such observations impossible4 ,the conclusion is arrived at that a large portion of ,auror have no very great extension1 or that the causes producing the phenomena must often be of a very local character2 while in another portion of the phenomena the extent1 or the regions of simultaneous appearance are very considerable4 ,sidenote3 ,number limited to ,finland only small4 ,the number limited to ,finland1 for which hitherto corresponding observations from other lands are wanting1 is very small--#bab1 or #ai per cent4 of the whole number seen in ,finland4 ,with the increase of frequency of the phenomena at the time of maximum1 the number observed in ,finland and ,america on the same day increases2 while those observed in ,finland and ,europe only1 or in ,finland only1 decreased1 in accordance with the known law that with the frequency the intensity and extent also increase4 ,sidenote3 ,one third of ,auror seen in ,america and ,europe simultaneously4 ,between #ahbf and #ahee1 of #bhgh days on which1 in ,america1 the ,northern ,lights were seen1 there were #ajfe on which they were also visible in ,europe2 so that at least every third day of ,auror was common to both these portions of the globe4 ,in the years #ahdf to #ahee1 and #ahfh to #ahgb1 there were in the first period #feg ,northern-,light days common to ,america and ,europe out of #afia1 and in the second #cig out of #gae4 ,sidenote3 ,local occurrence of the ,aurora not in favour of its assumed cosmical nature4 ,the comparison by ,prof4 ,fritz of ,m4 ,moberg's ,finland observations has been lately reviewed in #8,nature' 7,march #h1 #ahgh7 and the result arrived at that1 8,after ten years1 in spite of the vastly accumulated material of careful observations1 there appears no necessity to change ,herr ,fritz's system of curves in any essential detail2 indeed certain parts of the same1 which were at first only based on probability and supposition 7the part of the principal zone between the north of ,norway and ,nishen ,kolynisk as an instance71 we now know with perfect certainty to be correct40 ,it has been remarked that the local occurrence of ,auror is not in accordance with the hypothesis of the phenomenon being one of a cosmical nature4 ,the winter of #ahgj was remarkable for brilliant displays2 and the displays of ,october #bdth and #beth1 #ahgj1 were remarkably brilliant in ,england and in ,america also1 and the ,aurora ,australis was seen on the same days at ,madras4 ,these displays were seen in ,england and ,america in the daytime as patches or coron of white light1 with streamers stretching upward from them4 ,,chapter ,,vi4 ,,the ,,aurora ,,in ,,connexion ,,with ,,other ,,phenomena4 ,auror and ,clouds4 ,sidenote3 ,auror and clouds4 ,dr4 ,richardson's observations4 ,aurora constantly accompanied by or immediately precedes the formation of cirro-stratus4 ,dr4 ,richardson 7#8,sir ,john ,franklin's ,narrative'71 so long ago as the years #ahai-ahbb1 made many recorded observations on the connexion of clouds with the ,aurora ,borealis in the ,polar regions4 ,some of these are alluded to in ,chapter ,v41 section 8,height of the ,aurora10 for the purpose of showing the moderate distance he found it to be above the earth2 and his inference is there mentioned1 8that the ,aurora ,borealis is constantly accompanied by or immediately precedes the formation of one or other of the various kinds of cirro-stratus40 ,on the #acth ,november and #ahth ,december1 #ahbj1 the connexion of an ,aurora with a cloud intermediate between cirrus and cirro-stratus is mentioned4 ,it is1 however1 also mentioned that the most vivid coruscations of the ,aurora were observed when there were only a few attenuated shoots of cirro-stratus floating in the air1 or when that cloud was so rare that its existence was only known by the production of a halo round the moon4 7,an instance of attenuated streaks of cirro-stratus in connexion with an auroral arc will be found in the ,aurora seen at ,guildown on the #dth ,february #ahgd1 a sketch of which is reproduced on ,plate ,,vi4 fig4 #a47 ,sidenote3 ,polarity discerned in cirro-stratus clouds4 ,dr4 ,richardson goes on to express his opinion that he1 on some occasions1 discerned a polarity in the masses of clouds belonging to a certain kind of cirro-stratus 7approaching cirrus71 by which their long diameters1 having all the same direction1 were made to cross the magnetic meridian nearly at right angles4 ,sidenote3 ,apparent polarity of ,aurora might perhaps be ascribed to the clouds themselves4 ,dr4 ,richardson further suggests that if it should be thereafter proved that the ,aurora depends upon the existence of certain clouds1 its apparent polarity might perhaps be ascribed to the clouds themselves which emit the light2 or1 in other words1 the clouds might assume their peculiar arrangement through the operation of one cause 7magnetism1 for instance71 while the emission of light might be produced by another--a change in their internal constitution perhaps connected with a motion of the electric fluid4 ,dr4 ,richardson further remarks that1 generally speaking1 the ,aurora appeared in small detached masses for some time before it assumed that convergency towards the opposite parts of the horizon which produced the arched form4 ,sidenote3 ,sir ,john ,franklin's observations4 ,sir ,john ,franklin says in his ,polar expeditions he often perceived the clouds in the daytime disposed in streams and arches such as the ,aurora assumes4 ,sidenote3 ,dr4 ,low's4 ,dr4 ,low 7#8,nature1' iv4 p4 #aba7 considers he witnessed a complete display of auroral motions in cirrus cloud1 and considers all clouds subject to magnetic or diamagnetic polarization2 he states that when the lines converge towards the magnetic pole fine weather follows1 and when at right angles to it wet and stormy4 ,sidenote3 ,m4 ,silbermann's observations1 #aeth ,april1 #ahfi4 ,cirrus clouds took the place of the ,aurora4 ,in the ,encyc4 ,brit4 edition #i1 article 8,aurora ,polaris10 after referring to the evidence of ,franklin1 ,richardson1 and ,low1 ,m4 ,silbermann 7#8,comptes ,rendus1' lxviii4 p4 #ajea7 is quoted in detail for observed connexion between the ,aurora and cirrus cloud4 #aeth ,april1 #ahfi1 at #aa;h #afm1 an ,aurora appeared and disappeared2 but it seemed as if the columns were still visible1 and it soon became obvious that fan-like cirrus clouds1 with their point of divergence in the north1 had taken the place of the ,aurora4 ,between #a and #b ,a4,m4 the clouds had passed the zenith1 and let fall a little fine frozen rain4 ,at #d ,a4,m4 the cirrus of the false ,aurora was still visible1 but deformed towards the top1 and presenting a flaky aspect4 ,the cirrus never appeared to replace the ,aurora either from right or left1 but to substitute itself for it like the changes of a dioramic view4 ,sidenote3 ,payer thinks the transition of ,aurora into clouds not proved4 ,payer1 in his #8,austrian ,arctic ,voyages1' thinks that the occurrence of the ,aurora during the day 7i4 e4 light clouds with its characteristic movement7 had been rather imagined than actually observed1 and that the transition of white clouds into auroral forms at night has never been satisfactorily proved4 ,he1 however1 mentions the mist-like appearance of the ,aurora4 ,sidenote3 ,dr4 ,allnatt's observations1 #dth ,february1 #ahgb1 at ,frant4 ,aurora passed into cirro-stratus4 ,dr4 ,allnatt observed the splendid ,aurora of #dth ,february1 #ahgb1 at ,frant1 and noticed the weird and wonderful appearance of the phenomena4 ,at #f ,p4,m4 the ,aurora commenced by the ,s4,w4 portion of the heavens being tinged with a bright carmine hue1 and in a short time the whole visible hemisphere was lighted up4 ,a dark elliptical cloud extending from ,s4 to ,s4,e4 and ,s4,w4 sent up volumes of coloured radii4 ,at #g the ,aurora had passed the zenith1 and a dark1 broken1 rugged cloud some #h ,e4 of zenith was surrounded by electric light of all hues4 ,at #g4dj the ,aurora began to wane1 and passed into a homogeneous cirro-stratus of sufficient density to obscure the stars1 disappearing at #g4de4 ,sidenote3 ,later1 cirro-stratus was transformed into luminous cumulus4 ,at a later hour of the night the canopy of cirro-stratus had separated and was transformed into luminous masses of radiant cumulus2 so that1 as ,dr4 ,allnatt observes1 there were called in requisition almost all the most prominent cloud-modifications during the progress of the phenomena4 ,the succession of formation1 transformation1 and reformation from ,aurora to cloud and from cloud to ,aurora was1 ,dr4 ,allnatt concluded1 conclusive of the theory before advanced of the electric origin of the recurrent rayed cloud-modifications in the place of the magnetic meridian1 over which so much mystery had been cast4 ,aurora and ,thunder-storms4 ,sidenote3 ,aurora and thunder-storms4 ,silbermann's theory4 ,silbermann asserts that ,auror are produced by the same general phenomena as thunder-storms1 and concludes that the ,auror of #ahei and #ahfi assumed the character of thunder-storms which1 instead of bursting in thunder1 had been drawn into the upper parts of the atmosphere1 and their vapour being crystallized in tiny prisms by the intense cold1 the electricity became luminous in flowing over these icy particles4 ,sidenote3 ,prof4 ,piazzi ,smyth on monthly frequency of ,auror and storms4 ,professor ,piazzi ,smyth has observed that the monthly frequency of ,auror varies inversely with that of thunder-storms4 ,his ,table of comparisons is as follows3-- ,sidenote3 ,his table of observations4 ,month4 ,lightning4 ,auror4 ,january #bdj #big ,february #add #dbe ,march #gj #cej ,april #aed #bge ,may #cgd #dh ,june #dhj #jj ,july #eeb #je ,august #chd #abf ,september #bbd #cff ,october #bjh #did ,november #aej #cbd ,december #aej #bhh ---- ---- ,mean of whole year #bdj #bja ,sidenote3 ,silbermann's observations #aeth ,april1 #ahfi4 #cjth ,april1 #ahfe4 ,silbermann1 on #aeth ,april1 #ahfi1 observed a fall of rain 7tiny crystals of ice7 on the disappearance of an ,aurora and its change into cloud forms 7see section1 8,auror and ,clouds10 p4 #ec74 ,he also observed a rain of little sparkling ice-prisms on #cjth ,april1 #ahfe1 at ,paris1 the city being then enveloped in a cirrus of vertical fibres similar to that which frequently accompanies the ,aurora4 ,on the occasion of the ,aurora seen by me at ,guildown1 #dth ,february1 #ahgb1 rain fell immediately succeeding the formation of the corona4 ,the falling of rain as an immediate sequence of an ,aurora seems1 however1 to be rather the exception than the rule2 but possibly this may vary with the character of the ,aurora itself--whether it be of the crimson class1 passing into cloud and accompanied with much electric disturbance1 or of the more quiescent white4 ,sidenote3 ,a falling barometer observed to follow ,auror4 ,a falling barometer following a display of ,auror has been noticed by ,sir ,john ,franklin and others2 and in some cases 7notably one in ,sicily before referred to7 storms and floods have accompanied this4 ,sidenote3 ,professor ,christison's observations4 ,in a paper read before the ,royal ,society of ,edinburgh in #ahfh1 ,prof4 ,christison mentioned1 as a fact of importance to agriculturists1 that the first great ,aurora after autumn is well advanced1 and following a period of fine weather1 is a sign of a great storm of rain and wind in the forenoon of the second day afterwards4 ,mr4 ,c4 ,l4 ,prince1 in his #8,climate of ,uckfield1' p4 #bah1 remarks that displays of ,auror are almost invariably followed by very stormy weather1 after an interval of from #aj to #ad days4 ,aurora and the ,magnetic ,needle4 ,sidenote3 ,aurora and the magnetic needle4 ,sir ,john ,franklin's observations4 ,motion communicated to the needle was neither sudden nor vibratory4 ,return of needle to its former position very gradual4 ,different positions of the ,aurora had considerable influence on the direction of the needle4 ,needle disturbed when ,aurora not visible4 ,quiescent yellow ,aurora produced no perceptible effect on needle4 ,return of needle more speedy after formation of a second arch4 ,slow when disturbance was considerable4 ,sir ,john ,franklin1 in his #8,narrative' 7before referred to71 gives ,lieutenant ,robert ,hood1 ,r4,n41 the credit of being 8the first who satisfactorily proved1 by his observations at ,cumberland ,house 7before mentioned71 the important fact of the action of the ,aurora upon the compass-needle10 and also 8to have proved the ,aurora to be an electrical phenomenon1 or at least that it induces a certain unusual state of electricity in the atmosphere40 ,sir ,john ,franklin then mentions that the motion communicated to the needle was neither sudden nor vibratory4 ,sometimes it was simultaneous with the formation of arches1 prolongation of beams1 or certain other changes of form or of activity of the ,aurora4 ,but generally the effect of these phenomena upon the needle was not visible immediately2 but in about half an hour or an hour the needle had obtained its maximum of deviation4 ,from this its return to its former position was very gradual1 seldom regaining it before the following morning1 and frequently not until the afternoon1 unless it was expedited by another arch of the ,aurora operating in a direction different from the former one4 ,the magnetic needle in the open air was disturbed by the ,aurora whenever it approached the zenith4 ,its motion was not vibratory 7as observed by ,mr4 ,dalton71 perhaps owing to the weight of the card4 ,it moved slowly to the ,e4 or ,w4 of the magnetic meridian1 and seldom recovered its original direction in less than eight or nine hours4 ,the greatest extent of its aberration was #de4 ,the arches of the ,aurora were remarked commonly to traverse the sky nearly at right angles to the magnetic meridian2 but deviation was not rare1 and it was considered that the different positions of the ,aurora had considerable influence on the direction of the needle4 ,when an arch was nearly at right angles to the magnetic meridian1 the motion of the needle was towards the ,w4 ,this motion was greater when the extremity of the arch approached from the west towards the magnetic north4 ,a westerly motion also took place when the extremity of an arch was in the true north1 or about #cf to the west of the magnetic north4 ,the motion of the needle was towards the east when the same end of an arch originated to the southward of the magnetic west1 and when of course its opposite extremity approached nearer to the magnetic north4 ,in one case only a complete arch was formed in the magnetic meridian4 ,in another the beam shot up from the magnetic north to the zenith4 ,in both these cases the needle moved towards the west4 ,the needle was most disturbed on ,february #ac1 #ahba1 at a time when an ,aurora was distinctly seen passing between a stratum of clouds and the earth4 ,sometimes the needle deviated though no ,aurora was visible2 but it was uncertain whether there might not have been a concealed ,aurora at the time4 ,clouds were sometimes observed during the day to assume the form of the ,aurora1 and deviations of the needle were occasionally remarked at such times4 ,an ,aurora sometimes approached the zenith without producing any change of position of the needle2 while at other times a considerable alteration took place1 though the beams or arches did not come near the zenith4 ,the ,aurora was frequently seen without producing a perceptible effect on the needle4 ,at such times it was generally an arch or a horizontal stream of dense yellowish light with little or no internal motion4 ,the disturbance of the needle was not always proportionate to the agitation of the ,aurora1 but was always greater when the quick motion and vivid light were observed to take place in a hazy atmosphere4 ,in a few instances the needle commenced at the instant a beam started from the horizon upwards2 and its return was according to circumstances4 ,if an arch formed immediately afterwards1 having its extremities placed on opposite sides of the magnetic north and south to the former one1 the return of the needle was more speedy1 and it generally went beyond the point from which it first started4 ,when the disturbance was considerable1 it seldom regained its usual position before #c or #d ,p4,m4 on the following day4 ,on one occasion only the needle had a quick vibratory motion 7between #cdc #ej and #cdd #dj74 ,the disturbance produced by the ,aurora was so great that no accurate deductions as to diurnal variation could be made4 ,sidenote3 ,magnetic observations on board the #8,tegetchoff4' ,payer1 in his #8,new ,lands within the ,arctic ,circle' 7vol4 i4 pp4 #cbg1 #cbh71 gives the result of the magnetic observations on board the ,austrian ship #8,tegetchoff' in the years #ahgb-gd1 made by means of a magnetic theodolite1 a dipping-needle1 and three variation instruments4 ,the extraordinary disturbances of the needle rendered the determination of exact mean values for the magnetic constants impossible4 ,the following were the principal results of these observations3-- ,sidenote3 ,disturbances great4 7#a7 ,the magnetic disturbances were of extraordinary magnitude and frequency4 ,sidenote3 ,greater as the rays were rapid4 ,quiescent arches exercised no influence4 7#b7 ,they were closely connected with the ,aurora1 and they were greater as the motion of the rays was more rapid and fitful and the prismatic colours more intense4 ,quiescent and regular arches1 without changing rays or streamers1 exercised mostly no influence on the needle4 ,sidenote3 ,declination-needle1 effects on4 7#c7 ,in all the disturbances the declination-needle moved towards the east1 and the horizontal intensity decreased while the inclination increased4 ,sir ,john ,franklin sums up his information as to the needle to much the same effect1 viz4 that brilliant and active coruscations cause a deflection almost invariably if they appear through a hazy atmosphere and if the prismatic colours are exhibited in the beams or arches4 ,on the contrary1 when the air is clear and the ,aurora presents a steady dense light of a yellow colour and without motion1 the needle is often unaffected by its appearance4 ,sidenote3 ,parry's experience4 ,parry 7,third ,voyage7 found his variation-needle 7extremely light and delicately suspended7 in no instance affected by the ,auror2 but he seems to have principally met with the quiescent form of that phenomenon4 ,m4 ,lottin1 the ,french savant 7whose description of an ,auroral display has been given in ,chapter ,,ii471 observed in the ,north ,sea1 between ,september #ahch and ,april #ahci1 while the sun was below the horizon1 #aej ,auror4 ,during this period #fd were visible1 8besides many which a cloudy sky concealed1 but the presence of which was indicated by the disturbances they produced upon the magnetic needle0 7,lardner's #8,museum of ,science and ,art1' vol4 x4 p4 #ahi74 ,sidenote3 ,grand displays accompanied by motion of needle to the west4 ,it has been remarked by some observers that grand displays of the ,aurora are frequently preceded or accompanied by an extraordinary motion of the needle to the westward4 ,captain ,maguire found at ,point ,barrow 7#aheb-ed7 that the appearance of the ,aurora in the south was connected with the motion of the magnet to the east of the magnetic north1 and if in the north to the west of the same4 ,sidenote3 ,solar disturbances and ,aurora4 ,on an occasion in #ahei great solar disturbances were observed1 the ,greenwich magnets were much disturbed1 and a fine ,aurora was visible4 ,sidenote3 ,cipoletti's observation4 ,cipoletti1 of ,florence1 remarks on the strong magnetic disturbances at ,vienna and ,munich during the ,auror of #dth ,february1 #ahgb1 and #dth ,february1 #ahgd4 ,sidenote3 ,dr4 ,thompson concludes that cylinders of ,aurora cannot be doubted to be magnets4 ,dr4 ,thompson1 in his #8,annals of ,philosophy1' vol4 iv4 p4 #dca 7#ahad71 mentions as an authenticated fact that during the prevalence of the ,aurora the magnetic needle was frequently observed to become unsteady1 and 7p4 #dcb7 concludes that cylinders of ,aurora cannot be doubted to be magnets4 ,the only three bodies capable of assuming magnetic properties are iron1 nickel1 and cobalt4 ,when meteors are considered1 it is not altogether extravagant to conjecture that bodies similar in their nature to some of the solid bodies which constitute our globe may exist in some unknown state in the atmosphere4 ,during the ,aurora of #acth ,may1 #ahfi1 the declination at ,greenwich varied #a #be1 while the vertical force experienced four successive maxima1 and the greatest oscillation amounted to #jjd of the total mean value4 ,the horizontal force varied only #jjad of its mean value4 ,during the ,aurora of #aeth ,april1 #ahfi1 the declination at ,stonyhurst varied #b #bc #ad in nine minutes4 ,illustration3 ,plate ,,ix4 ,auror1 ,magnetic ,disturbances1 and ,sun-spots4 ,sidenote3 ,auror1 magnetic disturbances1 and sun-spots in ,italy4 ,auror were frequent in ,italy in ,april #ahga4 ,on the #ajth a remarkable one was seen1 with declinometer deflected towards the east1 and #fc sun-spots were counted4 ,on the morning of the #ajth the deflection continued1 and at midday #ig sun-spots were counted4 ,on the #ahth a brilliant ,aurora lasted to #aj o'clock at night4 ,from this time till the #bcrd the ,aurora appeared constantly1 giving a reddish tinge in the north and north-west4 ,a brilliant display took place on the evening of the #bcrd4 ,on the evenings when the ,aurora appeared the magnetometers were disturbed throughout ,italy1 and ended by a violent agitation during the whole of the #bdth4 ,sun-spots were observed at ,rome1 ,palermo1 and ,moncalieri1 but the greater number on the days of the ,auror4 ,a brilliant display at ,moncalieri on ,june #ah was accompanied by very violent magnetic disturbance4 ,sidenote3 ,proctor's sun-spots and ,aurora4 ,september #be1 #ahgj1 ,mr4 ,proctor counted #ajb spots on the solar disk2 and on the night of the #bdth and morning of the #beth an ,aurora of unwonted magnificence was visible at various stations in ,england1 ,france1 and ,germany4 ,sidenote3 ,sun-spots and the magnet4 #aa years' period4 ,schwabe's sun-spot period4 ,with respect to sun-spots and the magnet1 the frequency of magnetic storms1 causing oscillation of the needle1 gradually increased from a minimum in #ahdc to a maximum in #ahdh1 giving a variation of something near #aa years altogether4 ,schwabe observed the sun-spots for #bd years1 and found they had a regular maximum and minimum every five years1 and that the years #ahdc and #ahdh were minimum and maximum years coinciding with the magnetic variation at those periods4 ,sidenote3 ,prof4 ,loomis considers connexion established between magnetic declination1 auroral displays1 and sun-spots4 ,professor ,loomis 7#8,american ,journal of ,science1' vol4 v4 ,april #ahgc7 considers that a comparison between the mean daily range of the magnetic declination and the number of ,auroras observed in each year1 and also with the extent of the black spots on the surface of the sun1 establishes a connexion between these phenomena1 and indicates that auroral displays 7at least in the middle latitudes of ,europe and ,america7 are subject to a law of periodicity1 that their grandest displays are repeated at intervals of about #fj years1 and that there are also other fluctuations1 less distinctly marked1 which succeed each other at an average interval of about #aj or #aa years1 the times of maxima corresponding quite remarkably with the maxima of solar spots4 ,sidenote3 ,illustrative table of coincidences4 ,an illustration of the result of these observations is given on ,plate ,,ix4 fig4 #b4 ,the curves are in close correspondence1 and the coincidence at the times of maximum and minimum is remarkable4 ,the auroral maximum generally occurs a little later than the magnetic maximum2 and the connexion between the auroral and magnetic curves appears somewhat more intimate than between the auroral and sun-spot curves4 ,sidenote3 ,prof4 ,loomis considers a sun-spot a solar disturbance affecting the earth's magnetism4 ,professor ,loomis contends 8that the black spot is a result of a disturbance of the sun's surface1 which is accompanied by an emanation of some influence from the sun1 which is almost instantly felt upon the earth in an unusual disturbance of the earth's magnetism1 and a flow of electricity1 developing the auroral light in the upper regions of the earth's atmosphere40 ,sidenote3 ,carrington and ,hodgson's observations of bright spots on the sun1 accompanied by magnetic disturbance at ,kew1 and followed by wide-spread ,auror4 ,this connexion between the sun's spots and the earth's magnetism has been considered as proved2 and one instance at least of an intense disturbance and outbreak of the sun's surface having been observed simultaneously with the occurrence of a terrestrial magnetic storm is a matter of record4 ,this will be found detailed in the #8,monthly ,notices of the ,royal ,astronomical ,society1' vol4 xx4 pp4 #ac and #ae1 and is so interesting in its character that it may be briefly referred to here4 ,mr4 ,r4 ,c4 ,carrington1 ,september #a1 #ahei1 #aa;h #ahm1 while observing and drawing a group of solar spots1 saw suddenly two patches of intense bright light break out in the middle of the group4 ,the brilliancy was fully equal to that of direct sunlight4 ,seeing the outbreak was on the increase1 ,mr4 ,carrington left the telescope1 to call some one to witness it4 ,on his return within sixty seconds it was nearly concluded4 ,the spots travelled from their first position1 and vanished as two rapidly fading dots of white light4 ,in five minutes the two spots traversed a space of about #ce1jjj miles4 ,mr4 ,carrington found no change in the group itself4 ,his impression was that the phenomena took place at an elevation considerably above the general surface of the sun1 and above and over the great group of spots on which it was seen projected4 ,it broke out at #aa;h #ahm1 and vanished at #aa;h #bcm4 ,mr4 ,r4 ,hodgson independently on the same day1 and at close upon the same time1 saw a very brilliant star of light1 much brighter than the sun's surface1 most dazzling to the protected eye1 illuminating the upper edges of the adjacent spots and streaks4 ,the rays extended in all directions1 and the centre might be compared to ,lyr when seen in a large telescope4 ,it lasted for some five minutes4 ,at the very moment of this solar disturbance the instruments at ,kew indicated a magnetic storm2 and ,proctor1 in his volume on the ,sun1 page #bjf1 details how this magnetic storm was accompanied by very widely-spread indications of electrical disturbance in many parts of the globe4 ,vivid ,auror were seen not only in both hemispheres1 but in latitudes and places where they are seldom witnessed4 ,rome1 ,cuba1 and the ,west ,indies1 the tropics within #ah of the equator1 and even ,south ,america and ,australia1 are thus referred to for displays4 ,at ,melbourne1 on the night of ,september #bnd1 the greatest ,aurora ever seen there made its appearance4 ,it was observed1 too1 that magnetic communication was at the same time disturbed all over the earth4 ,strong currents1 continually changing their direction1 swept along the telegraphic wires4 ,at ,washington and ,philadelphia the signal-clerks received severe shocks1 and the wires had to give up work4 ,at a station in ,norway the transmitting apparatus was set fire to2 and at ,boston1 in ,north ,america1 a flame of fire followed the pen of ,baine's electric telegraph4 ,sidenote3 ,mr4 ,john ,allan ,broun's magnetic oscillation-curves2 showing that the sun's magnetic action has lately become more constant4 ,in diagram1 curves gradually flatten4 ,in an interesting communication to #8,nature' 7,january #crd1 #ahgh71 entitled 8,the ,sun's ,magnetic ,action at the ,present ,time10 ,mr4 ,john ,allan ,broun has contributed some magnetic oscillation-curves1 deduced from observations made in the ,trevandrum ,observatory 7nearly on the magnetic equator71 by which1 if confirmed by other observations1 it would appear that the sun's magnetic action has lately become gradually more constant4 ,the curves are three in number1--no4 #a for the years #ahee-eh1 no4 #b for the years #ahfe-fh1 no4 #c for the years #ahgd-gg4 ,in no4 #a curve the minimum is very clearly marked by two points corresponding to ,april #a and ,may #a1 #ahef1 and there is little difference in the rapidity with which the curve descends to and ascends from the minimum4 ,in no4 #b curve the epoch of minimum is by no means so well marked2 it occurs between the points for ,april #a and ,september #a1 #ahff4 ,there is also a considerable difference in the rapidity of variation in the descending and ascending branches of the curve4 ,the descent is nearly as rapid as in curve no4 #a2 but the ascent is very much slower4 ,in curve no4 #c the lowest point is that for ,december #a1 #ahge2 but it is even now1 with points a year and a half later1 difficult to say whether this is the minimum or not1 the point for ,january #a1 #ahgg1 being only #jjb 7two hundredths of a minute of arc7 higher4 ,in this curve the change of range in diurnal oscillation is quite insignificant from ,november #a1 #ahgd1 to ,april #a1 #ahgg1 an interval of three years and five months4 ,in the diagram given by ,mr4 ,broun the curves show themselves gradually flattening1 no4 #c being almost a straight line4 ,sidenote3 ,mr4 ,broun never found an ,aurora without a corresponding irregularity in the declination-needle4 ,mr4 ,broun remarks upon the report of ,sir ,george ,nares as to the insignificant nature of the ,auror seen in the ,arctic ,expedition in the winter of #ahge-gf1 and the accompanying statement that1 as far could be discovered1 they were totally unconnected with any magnetic or electric disturbance2 and states1 as the result of his own experience in the south of ,scotland1 that several of the ,auror observed by him were of the very faintest kind1 8were traces0 which he could never have remarked had he not been warned by very slight magnetic irregularities to examine the sky with the greatest attention4 ,again1 in no case had he seen the faintest trace of an ,aurora without finding at the same time a corresponding irregularity in the movement of the force or declination-magnet4 ,sidenote3 ,prof4 ,piazzi ,smyth comments on variance in the cycles4 ,prof4 ,piazzi ,smyth1 commenting on this article1 makes the inquiry how the sun-spot cycle and the terrestrial magnetic oscillation cycle can be considered as agreeing1 the sun-spot cycle1 according to ,prof4 ,wolf1 being #aaaaa years1 and the magnetic cycle #aje years according to ,mr4 ,broun4 ,sidenote3 ,m4 ,faye's remarks to a similar effect4 ,another correspondent writes and quotes ,m4 ,faye1 in #8,la ,mtorologie ,cosmique1' for the remark1 8,la priode des taches porte #aa ans #a par ,m4 ,wolf n'tant pas gale celle des variations magntiques 7#aj ans #de71 ces deux phnomnes n'ont aucun rapport entre eux40 ,sidenote3 ,mr4 ,broun's rejoinder and explanation4 ,mr4 ,broun1 in a further letter1 rejoins that if we could accept ,dr4 ,wolf's view we should find that the mean duration of a cycle for both phenomena since #aghg would be #aaid years1 while the sun-spot results for eight cycles determined by ,dr4 ,wolf during eighty years before #aghg give #ajbc or1 if we take nine cycles1 #ajdc years for the mean duration4 ,it is by mixing these two very different means that the ,zurich philosopher finds #aaa years1 a mean which ,mr4 ,broun considers can evidently have no weight given to it4 ,on the other hand1 if ,dr4 ,wolf is in error 7as ,mr4 ,broun believes he is7 as to the existence of a maximum in #agig1 the mean durations for the eighty years after and for the eighty years before #aghg agree as nearly as the accuracy of the determinations for the beginning of the eighteenth century will permit4 ,mr4 ,broun then repeats his conviction that the sun-spot maxima and minima are really synchronous with those of the magnetic diurnal observations4 ,sidenote3 ,mr4 ,jenkins's explanation of ,prof4 ,loomis's chart4 ,mr4 ,b4 ,g4 ,jenkins1 in a letter to #8,nature1' refers ,prof4 ,smyth to ,prof4 ,loomis's chart of magnetic oscillations given in ,prof4 ,balfour ,stewart's paper in #8,nature' 7vol4 xvi4 p4 #aj71 for the purpose of showing that there are exactly seven minimum periods from #aghg to #ahga1 the mean of which is twelve years1 the mean of the seven corresponding maximum periods being #aah years4 ,the true magnetic declination-period is1 then1 the mean of these1 viz4 #aai years4 ,in exactly the same manner he finds that the mean period of sun-spots is #aai years4 ,sidenote3 ,jupiter's suspected connexion with sun-spots4 ,the auroral displays also have the same period4 ,mr4 ,jenkins also refers to ,wolf1 ,de ,la ,rue1 ,stewart1 and ,loewy1 as having stated their belief that ,jupiter is the chief cause in the production of sun-spots1 and draws attention to the period of #aai years as being ,jupiter's anomalistic year1 or the time which elapses between two perihelion passages4 ,sidenote3 ,infrequency of ,auror and absence of sun-spots in #ahgf-gh4 ,the infrequency of ,auror during the years #ahgf-gh1 and a corresponding comparative absence of sun-spots1 may be added to the evidence on the subject4 ,i have seen no account of important ,auror during the years mentioned1 and day after day has recently 7#ahgh7 passed with a perfectly clean sun-disk4 ,aurora and ,electricity4 ,sidenote3 ,aurora and electricity4 ,sir ,john ,franklin's experience with electrometer4 ,sir ,john ,franklin failed to get indications of electricity connected with the ,aurora with a pith-ball electrometer2 but with another form of electrometer specially constructed for the purpose he seems to have got some1 though not very strong or regular1 indications of repulsion between the needle of the instrument and the conductor when ,auror were seen4 ,he does not decide whether the electricity was received from or summoned into action by the ,aurora4 ,sidenote3 ,parry's experience4 ,parry1 at ,fort ,bowen1 with a gold leaf electroscope connected with a chain attached by glass rods to the skysail mast-head1 #aae feet above sea-level1 found no effect4 ,sidenote3 ,dr4 ,allnatt's experience1 ,february #d1 #ahgb4 ,dr4 ,allnatt1 at ,frant1 during the display of #dth ,february1 #ahgb1 found the earth's electricity so powerful that the gold leaves of the electrometer remained divergent for a considerable time4 ,sidenote3 ,m',clintock found electroscope affected in ,baffin's ,bay and ,port ,kennedy4 ,m',clintock observes that on six occasions of ,aurora in ,baffin's ,bay1 the electroscope was strongly affected1 and on three occasions of ,aurora at ,port ,kennedy4 ,the electricity was always positive4 ,dec4 #ah4--;,dr4 ,walker called him to see the electroscope4 ,the charge was at first weak1 but afterwards strong enough to keep the leaves diverged4 ,dr4 ,walker found two periods of minimum electrical disturbance about #i ,p4,m4 and noon4 ,sidenote3 ,electric currents in telegraphic wires during ,auror4 ,electric currents have been reported as produced in telegraph wires during ,auror4 ,though transient they are said to be often very powerful1 and to interrupt the ordinary signals4 ,loomis 7,sillim4 ,journ4 vol4 xxxii47 mentions cases where wires have been ignited1 brilliant flashes produced1 and combustible materials kindled by their discharge4 ,here1 too1 we may note the account of electric phenomena in the case of the ,aurora ,australis described 7ant1 p4 #bh7 by ,mr4 ,proctor4 ,sidenote3 ,mr4 ,george ,draper's report as to disturbed condition of the ,indian ,submarine and other cables during ,aurora of ,february #d1 #ahgb4 ,mr4 ,george ,draper1 of the ,british-,indian ,submarine ,telegraph ,company1 speaking of the ,aurora of ,february #d1 #ahgb 7and writing to the #8,times' under date ,february #eth71 states that the ,aurora visible in ,london was also visible at ,bombay1 ,suez1 and ,malta1 and that the ,company's electrician at ,suez reported that the earth-currents there were equal to #agj cells 7,daniell's battery71 and that sparks came from the cable4 ,the electrical disturbances lasted until midnight1 and interrupted the working of both sections of the ,british ,indian ,cable between ,suez and ,aden1 and ,aden and ,bombay4 ,for some days previously the signals on the ,british ,indian cables had been much interfered with by electrical and atmospheric disturbances4 ,at ,malta there was a severe storm on the morning of the #dth1 so that it was necessary to join the cable to earth for some hours1 and the ,aurora was very large and brilliant there4 ,the electrical disturbances on the cables in the ,mediterranean and on those between ,lisbon and ,gibraltar1 and ,gibraltar and the ,guadiana1 were also very great4 ,the signals on the land line between ,london and the ,land's ,end were interrupted for several hours on the night of the #dth by atmospheric currents4 ,similar effects accompanied the displays of ,oct4 #bd and #be1 #ahgj4 ,aurora and ,meteoric ,dust4 ,sidenote3 ,aurora and meteoric dust4 ,theories of ,dr4 ,zeyfuss and ,m4 ,grneman4 ,a theory has been propounded independently by ,dr4 ,zeyfuss and by ,m4 ,grneman1 of ,grningen1 according to which the light of the ,aurora is caused by clouds of ferruginous meteoric dust ignited by friction with the atmosphere4 ,grneman shows that these might be arranged along the magnetic curves by the action of the earth's magnetic force during their descent1 and that their influence might produce the observed magnetic disturbances4 ,sidenote3 ,ferruginous dust in the ,polar ,regions4 ,the arches might be accounted for by the effects of perspective2 and the iron spectrum shows correspondence with some of the lines of the ,aurora4 ,ferruginous particles have been found in the dust of the ,polar regions according to ,professor ,nordenskild1 but whether derived from stellar space or from volcanic eruption is uncertain4 ,a difficulty has been suggested that while meteors are more frequent in the morning1 or on the face of the earth which is directed forward on its orbit1 the reverse prevails in the case of ,auror4 ,grneman meets this by supposing that in the first case the velocity may be too great to allow of arrangement by the earth's magnetic force4 ,he accounts for the infrequency of the ,aurora in equatorial regions by the weakness of the earth's magnetic force1 and the fact that when it does occur the columns must be parallel to the earth's surface4 ,sidenote3 ,baumhauer's proposition4 ,baumhauer 7,compt4 ,rend4 vol4 lxxiv4 p4 #fgh7 advances1 as regards ,polar ,auror1 the proposition1 that not only solid masses large and small1 but clouds of 8uncondensed0 7meteoric7 matter probably enter our atmosphere4 ,if from our knowledge of the meteoric stones which fall to the earth's surface we may draw any conclusion respecting the chemical constitution of these clouds of matter1 it would appear that they may contain a considerable portion of the magnetic minerals iron and nickel4 ,let such a cloud approach our earth1 regarded as a great magnet1 it would be attracted towards the ,pole1 and1 penetrating our atmosphere1 the particles which have not been oxidized1 and are in a state of extremely fine division1 would by their oxidation generate light and heat1 producing the polar ,auror4 ,baumhauer suggests it would be interesting in support of this theory to detect in the soil of polar areas the presence of nickel4 ,the presence of iron and nickel in meteoric masses in considerable quantities is frequent2 and cases are also on record by ,eversmann of hailstones containing crystals of a compound of iron and sulphur1 by ,pictet of hailstones containing nuclei which proved to be iron1 and by ,cozari of hailstones containing nuclei of an ashy-grey colour1 the larger ones of which were attracted by the magnet1 and found to contain iron and nickel4 ,nickel was found by ,reichenbach in parts of ,austria on hills consisting of beds of sandstone and limestone1 and quite free from metallic veins4 ,sidenote3 ,mr4 ,lefroy's description of a phenomenon ascribed by him to streams of cosmic dust4 ,mr4 ,j4 ,w4 ,n4 ,lefroy1 in #8,nature1' describes a phenomenon seen by him at ,fremantle1 ,west ,australia1 in the month of ,may1 which he designates 8,a ,lunar ,rainbow1 or an ,intra-lunar convergence of ,streams of slightly illuminated ,cosmic ,dust80 ,it lasted about three quarters of an hour1 and consisted of one grand central feather1 of very bright white cloud1 springing out of the horizon at ,w4,n4,w41 and crossing the meridian at about #bj north of the zenith1 with a width of #g to #h4 ,on either side of this was a system of seven or eight minor beams of light1 extending from the ,w4 to the ,e4 horizon1 subtending a chord common to themselves and to the main stream1 and converging towards the axis of the central stream so as to intersect it at a point about #cj or #dj below the western horizon1 at which the whole system subtended an azimuth of about #bj4 ,near the zenith1 where its transverse section was a maximum1 that section subtended an angle of about #dj4 ,the idea strongly suggested itself to ,mr4 ,lefroy of converging streams of infinitely minute particles of matter passing through space at a distance from the earth at which its aerial envelope may have still a density sufficient by its resistance to give cosmic dust passing through it that illumination which it possessed4 ,in about twenty minutes the streams of light had attained their maximum brightness4 ,their apparent figure was that of a nearly circular 7slightly flattened7 arc of an amplitude of #ae or #bj1 as viewed from the middle point of its chord4 ,the brightness and the convergence of the streams were both more marked towards the western horizon than the eastern4 ,this same phenomenon was described in the #8,south-,australian ,register' as a beautiful lunar rainbow visible in the western heavens4 ,mr4 ,lefroy and other observers concurred in the impression that the minor lateral streams on the ,n4 side of the main one intervened between the earth and the moon1 and that one or more of them in their slow vibrations swept the surface of the moon and sensibly obscured its light4 ,there can be hardly any question that the phenomenon observed was in fact an ,aurora4 ,sidenote3 ,suggestion as to collecting iron and nickel particles from the atmosphere4 ,it may be a question whether iron and nickel particles of meteoric origin do not ordinarily exist in the atmosphere in a greater degree than we suspect1 and might be detected if special means1 such as magnets1 plates of glass covered with glycerine1 c41 were adopted for the purpose of collecting and examining the cosmic dust4 ,larger gatherings than usual of iron and nickel particles during the presence of ,auror would be in support of ,mr4 ,lefroy's theory4 ,the ,aurora and the ,planets ,venus and ,jupiter4 ,sidenote3 ,the ,aurora and planets ,venus and ,jupiter4 ,the planet ,venus's halo during ,aurora4 ,during a brilliant ,aurora seen at ,sunderland1 ,february #h1 #ahag 7#8,annals of ,philosophy1' p4 #bej71 about #h o'clock1 ,venus was about #h above the horizon1 and displayed a very peculiar appearance4 ,her rays passed through a thin mist or cloud1 probably electric1 of a deep yellow tint4 ,her apparent magnitude seemed increased1 and a halo was formed round her as sometimes appears round the moon in moist weather2 but the stars that were in that part of the heavens shone with their accustomed brilliancy4 ,sidenote3 ,dr4 ,miles's observation of ,venus during an ,aurora4 ,the ,rev4 ,t4 ,w4 ,webb1 in his #8,celestial ,objects' 7#ahei71 p4 #dc1 quoting from the ,philosophical ,transactions1 mentions that1 8,january #bcrd1 #agdi-ej1 there was a splendid ,aurora ,borealis about #f ,p4,m4 ,the ,rev4 ,dr4 ,miles1 at ,tooting1 had been showing ,jupiter and ,venus to some friends with one of ,short's reflectors1 greatest power #bjj1 when a small red cloud of the ,aurora appeared1 rising up from the ,s4,w4 7as one of a deeper red had done before71 which proceeded in a line with the planets and soon surrounded both4 ,venus appearing still in full lustre1 he viewed her again with the telescope without altering the focus1 and saw her much more distinctly than ever he had done upon any occasion4 ,his friends were of the same opinion4 ,they all saw her spots plain 7resembling those in the moon71 which he had never seen before1 and this while the cloud seemed to surround it as much as ever40 ,i think this effect might perhaps have arisen from the ,aurora acting as a screen1 and removing the glare with which so bright an object as ,venus is always accompanied2 but the case is a singular one1 and one would be glad of further experience4 ,i suggested observations on this head during ,sir ,geo4 ,nares's ,arctic ,expedition2 but the suggestion1 for some reason of which ,i am not aware1 was not included in the official instructions issued4 ,sidenote3 ,brightness of stars during ,auror4 ,remarks are frequent of the brightness of stars as seen through ,auror4 ,payer1 of the ,austrian ,expedition1 remarks that falling stars passed through the ,aurora without producing any perceptible effect or undergoing any change4 ,sidenote3 ,aurora of ,oct4 #bd1 #ahgj1 and ,jupiter4 ,a grand display of the ,aurora took place #bdth ,october1 #ahgj4 ,about this time the belts of ,jupiter were observed to be highly coloured4 ,as observed by me on the night of ,november #b1 #ahgj1 at #i ,p4,m41 with an #h-;in4 ,browning reflector1 achromatic eyepieces #add1 #cje1 and #dej1 the equatorial zone was of a distinctly dark ochre colour1 deepening to red-brown as it approached the lower 7,n47 edge4 ,two thin belts above were slate-purple1 and a darker belt below was of a deep purple colour4 ,sidenote3 ,according to ,lassell and others1 ,jupiter's belts exhibit the brightest colours at period of ,auror4 ,lassell1 ,proctor1 and others have reported ,jupiter's belts to exhibit the brightest colours at the period of ,auror4 ,mr4 ,browning gives a drawing of ,jupiter as seen on ,january #ca1 #ahgj 7a year noted for ,auror71 with the belts brightly coloured4 ,the finest view of ,jupiter ,i ever had was on the #hth ,february1 #ahgb 7a fine ,aurora was on the #dth71 when1 with the #h-;inch ,browning reflector1 ,i saw the whole surface of the planet 7by glimpses7 cloud-mottled4 ,the equatorial belt was1 however1 then slightly tinted only4 ,in ,dr4 ,miles's observation 7p4 #ff7 he does not seem to have noticed the colouring of ,jupiter's belts4 ,sidenote3 ,infrequency of ,auror and lightness in tint of ,jupiter's belts4 ,the three past years1 #ahgf1 #ahgg1 and #ahgh1 have been distinguished by the infrequency of ,auror2 and ,jupiter's equatorial zone and belts have been mainly reported of light tints4 ,the subject apparently deserves more attention than it has hitherto received4 ,the ,aurora and the ,zodiacal ,light4 ,sidenote3 ,the ,aurora and the ,zodiacal ,light4 ngstrm's observation on spectrum4 ngstrm in #ahfg found the spectrum of the ,zodiacal ,light to be monochromatic1 consisting of a single line in the green1 to which he assigned approximately the position #abei on ,kirchhoff's scale1 the same that he had determined for the green line of the ,aurora ,borealis2 and ,respighi1 on the ,red ,sea1 on the evening of the #aath and the morning of the #abth ,january #ahgb1 perceived in the ,zodiacal ,light not only this green line1 but near it1 towards the blue1 a band or zone of apparently continuous spectrum4 ,sidenote3 ,respighi's at ,campidoglio4 ,at the ,observatory of the ,royal ,university of ,campidoglio1 ,february #eth1 #ahgb1 ,respighi1 at #g ,p4,m41 was able to discern the same spectrum2 and on directing the spectroscope to other points he found that this spectrum showed itself in all parts of the heavens from the horizon to the zenith1 more or less defined in different parts1 but everywhere as bright as in the ,zodiacal ,light4 ,the ,observatory ,assistant1 ,dr4 di ,legge1 likewise observed this spectrum distinctly in various parts of the heavens4 ,respighi's observations corroborating ngstrm's in #ahfg1 appeared to him to demonstrate the identity of the ,zodiacal ,light with the ,aurora1 and to establish the identity of their origin4 ,sidenote3 ,pringle thinks the ,aurora may be considered as allied to the ,zodiacal ,light4 ,pringle1 in a letter to #8,nature' from ,south ,canara1 ,october #c1 #ahga1 alludes to the ,aurora as being considered by many allied to the ,zodiacal ,light1 and does not think the evidence then hitherto adduced against the theory at all conclusive4 ,he says3--8,assume the auroral light to consist of solid particles of matter1 planet dust1 shining by reflected light1 and it is not difficult to imagine the ,aurora playing amongst these tiny worlds1 each of which would have its own small magnetic system swayed like our own by the monster magnet the sun40 ,sidenote3 ,phosphorescence of sky when ,zodiacal ,light has been seen bright4 ,he notices he has never found it to have a decided outline1 nor traced it east or west to #ahj from the sun4 ,he also refers to others having noticed that when the ,zodiacal ,light has been seen unusually bright1 a 8phosphorescence0 of the sky was everywhere visible4 ,sidenote3 ,pringle failed to find bright lines or bands in the ,zodiacal ,light4 ,he does not seem at that time to have examined the matter spectroscopically2 and on ,june #bc1 #ahgb1 he writes again1 pointing out the peculiarity in ,respighi's observation that the green line was seen everywhere as bright as in the ,zodiacal ,light1 and suggesting that it was due to a concealed ,aurora present at the time of ngstrm's and ,respighi's observations4 ,he further states he had examined the ,zodiacal ,light with a ,browning #e-prism spectroscope 7,i presume a compound direct-vision form is meant7 since the last ,december1 and1 brilliant as the phenomenon had frequently been1 failed to detect the slightest appearance of bright lines or bands4 ,a faint diffuse spectrum about as intense as that of a bright portion of the ,milky ,way was all he had obtained4 ,sidenote3 ,prof4 ,piazzi ,smyth confirms this4 ,professor ,piazzi ,smyth1 in the clear sky of ,italy1 and with an instrument specially designed for showing faint spectra1 found no lines or bands1 but only a faint continuous spectrum extending from about midway between ,d and ,e in the solar spectrum to nearly ,f 7see ,plate ,v4 fig4 #c1 in which the continuous spectrum is graphically shown1 white on a black ground74 ,sidenote3 ,colour of the ,zodiacal ,light4 ,it may here be mentioned that the ,zodiacal ,light is usually described as1 in these latitudes1 of a golden yellow or pale lemon tinge4 ,sidenote3 ,rev4 ,mr4 ,webb's observation1 ,february #b1 #ahfb4 ,he found no green line of the ,aurora4 ,on one occasion1 however1 it has been described as not having this tinge1 but rather resembling the light of the ,milky ,way1 but brighter4 ,on another occasion ,i saw the whole cone of a crimson hue without any mixture of yellow4 ,the ,rev4 ,mr4 ,webb thought that a display seen at ,hardwick ,vicarage1 ,february #bnd1 #ahfb1 showed a ruddy tinge not unlike the commencement of a crimson ,aurora--8it was certainly redder or yellower than the galaxy40 ,he examined it with a pocket spectroscope which would show distinctly the green line of the ,aurora 7probably ,browning's miniature71 but nothing of the kind was visible1 nor could any thing be traced beyond a slight increase of general light1 which1 on closing the slit1 was extinguished long before the auroral band would have become imperceptible4 ,sidenote3 ,a4 ,w4 ,wright's observations and conclusions4 ,a4 ,w4 ,wright examined the ,zodiacal ,light with a ,duboscq single-prism spectroscope1 the telescope and collimator having a clear aperture of #bd centimetres1 magnifying-power of telescope #i diameters4 ,special precautions were taken about the observations1 and the conclusions arrived at were3-- 7#a7 ,the spectrum of the ,zodiacal ,light is continuous1 and is sensibly the same as that of faint sunlight or twilight4 7#b7 ,no bright line or band can be recognized as belonging to this spectrum4 7#c7 ,there is no evidence of any connexion between the ,zodiacal ,light and the ,polar ,aurora4 ,sidenote3 ,polarization of ,zodiacal ,light4 ,burton's observation confirmed by ,wright and ,tacchini4 ,the ,polarization of the ,zodiacal ,light has been already referred to under the head of 8,polarization of the ,aurora30 but it may be here noted that ,mr4 ,burton's observation of polarization of the light there mentioned has been confirmed by ,wright and ,tacchini1 and the presence of reflected sunlight established4 ,in this respect it differs from the ,aurora1 in which no trace of polarization has hitherto been detected2 and looking at this1 and at the weight of evidence in the spectroscopic observations1 the theory of a connexion between the ,aurora and the ,zodiacal ,light must1 as the matter stands1 be given up4 ,,chapter ,,vii4 ,,aurora-,,like ,,patches ,,on ,,the ,,partially-,,eclipsed ,,moon4 ,sidenote3 ,aurora-like patches on the partially-eclipsed moon1 ,feb4 #bg1 #ahgg4 ,in anticipation of the total eclipse of the ,moon on the #bgth ,february1 #ahgg1 several articles appeared in the leading journals of the day describing1 for the public benefit1 the appearances which might be expected during the occurrence of the phenomenon4 ,sidenote3 ,formerly it was thought the moon was illuminated by auroral light4 ,among these was one by ,mr4 ,r4 ,a4 ,proctor1 in which the following passage occurs3--8,that dull1 or occasionally glowing red colour1 shown by the moon when she is fully and even deeply immersed in the shadow of the earth1 is a phenomenon whose explanation is not without interest4 ,formerly it was thought that the moon possessed an inherent light1 or perhaps was illuminated by auroral light1 which only became discernible at the time of total eclipse4 ,indeed even ,sir ,w4 ,herschel fell into the mistake of supposing this the only available explanation1 having miscalculated the efficiency of the true cause40 ,sidenote3 ,author's notes of the eclipse4 ,colour-tints described4 ,a crimson-scarlet tint reminded author of an auroral glow4 ,this passage was only pointed out to me by a friend after the eclipse had actually taken place1 and ,i had sent him some notes of what ,i then saw4 ,my notes on the occasion comprised1 amongst others1 the following remarks3--8,the tints of colour also during partial eclipse1 owing1 no doubt1 to the moon's considerable altitude1 were singularly bright and well contrasted4 ,silver-grey1 dusky copper-red1 and the same tint clearer and brighter were ranged side by side with a lovely jewel effect4 ,we noticed also at times a crimson-scarlet tint1 deeper and less mixed with yellow than the copper colour4 ,this last tint reminded me much of a crimson glow common to the ,aurora1 and which ,i also once distinctly remarked 7of course in a weaker degree7 in the zodiacal light0 7ant1 p4 #fh74 ,sidenote3 ,eclipse1 ,aug4 #bc-bd1 #ahgg4 ,sky clear1 but eclipsed moon misty and indistinct until total obscuration4 ,succession of colours4 ,on the occasion of the eclipse of ,august #bc-bd1 #ahgg1 we were favoured at ,guildown1 in common with many other places1 by a singularly clear sky during the progress of the moon's obscuration and subsequent clearing4 ,in the early part of the evening1 however1 the moon1 from some cause 7possibly atmospheric vapour71 seemed to have1 as the earth's shadow advanced on its disk1 an unexpectedly misty and indistinct appearance1 which lasted up to and including total obscuration4 ,golden yellow1 yellow copper1 dull copper1 ruddy copper1 and dull red were successively the principal colours observed at different times and at various portions of the moon's surface4 ,sidenote3 ,as shadow passed off1 indistinctness gave way to a sharpness of the moon's features as seen through shadow4 ,two patches of crimson light described4 ,after referring to some spectroscopic appearances1 my notes then ran on thus3--8,as the shadow began to pass off1 and the bright sharp crescent of the illuminated portion of the moon to appear1 the general aspect of the moon's disk seemed to me to greatly change4 ,the certain amount of indistinctness noticeable during approach and continuance of totality1 gave way to a considerable sharpness of the moon's features as seen through the shadow4 ,the shadowed part glowed with a richer copper tint1 on which were seen dark1 almost black1 spots and patches40 ,then follows a description of these2 and the notes continue3--8,two features here struck me--the one a continuation of the upper limb of the illuminated crescent1 so that it seemed to form a bead of light just on the centre of the upper edge of the moon2 the other two patches of crimson light1 similar to those ,i described as having been seen in the last total eclipse4 ,one of these1 quite a small one1 was just under the elongated bead before described2 the other1 a much larger and more diffused one1 was seen towards the south-west limb of the moon1 about midway between it and the centre4 ,the spots or patches were of a decidedly crimson-red1 in contrast to the ordinary copper-red of the disk1 and were noticed by my friend as well as by myself40 ,sidenote3 ,patches well seen in field-glass2 lost in small refractor4 ,they gradually deepened in tint4 ,these were eye observations4 ,the patches were quite well seen 7but not so brightly as with the eye7 with a double achromatic field-glass4 ,with a #c-;inch ,cooke refractor and low power1 they seemed lost in the general moon tint2 but they were then diminishing in brightness4 ,from a comparison of my two sketches1 the patches seem to have gradually deepened in tint1 and we considered them to have disappeared in a like gradual manner4 ,sidenote3 ,two sketches taken4 ,my first sketch was taken shortly after end of total phase2 the second about ten minutes later4 ,i have reproduced the original sketches in preference to any drawing prepared from them 7,plate ,,iv4 figs4 #b and #c74 ,the patches did not last long1 but were lost as the shadow swept off the moon4 ,i saw nothing of the sort during the approach of or pending totality1 nor until a small crescent of the moon began to appear behind the shadow4 ,i have looked for other accounts of these patches1 but cannot find any4 ,most observers have described the deeper colour of the shadowed moon by the word 8copper40 ,some extend this colour to red2 but there is probably much in the state of the atmosphere affecting this4 ,sidenote3 ,dec4 #c1 #agjc1 moon's colour described4 ,at ,avignon1 ,december #c1 #agjc1 the moon appeared1 pending eclipse1 8extraordinarily illuminated and of a very bright red10 while other and different features were seen at ,montpelier4 ,on ,march #ai1 #ahdh1 observers in ,england1 ,ireland1 and ,belgium described the moon's disk as 8intensely bright coppery red40 ,on the occasion of ,august #bc-bd1 #ahgg1 before mentioned1 an article in one of the public papers described the moon's disk1 during totality1 as of a 8dull copper colour40 ,sidenote3 ,mr4 ,keye's observation4 ,mr4 ,henry ,keye1 in the ,engadine1 at a height of #dejj feet above sea-level1 and with the purest air1 saw the partially covered moon 7before totality7 as a 8dull copper colour40 ,sidenote3 ,prof4 ,pritchard's4 ,m4 ,faye's4 ,dr4 ,allnatt's at ,frant4 ,prof4 ,pritchard1 writing from the ,oxford ,university ,observatory1 says that at #ab;h #ajm 7about the time my sketches were taken7 there was a good deal of light on the moon's following limb1 and the colour was 8more red than copper10 and apparently redder than it had been at a similar distance of time before totality4 ,mons4 ,faye reported to the ,french ,academy of ,sciences that 8a striking phenomenon not previously noticed was that the reddish tinge1 resembling that of a fine sunset1 was deepest at the margin of the disk1 a circumstance which he could not explain40 ,dr4 ,allnatt1 writing from ,frant1 says3--8,at totality the moon's disk presented a most extraordinary appearance3 the western limb was comparatively transparent1 but the main body appeared as though enveloped in a semi-opaque clot of coagulated blood1 through which the lunar features were dimly visible40 ,sidenote3 ,observations as to the patches4 ,the observations of ,prof4 ,pritchard and ,mons4 ,faye point more immediately to redness2 and this is the nearest approach ,i can find to the patches ,i noticed4 ,these patches do not seem to me easy of explanation4 ,they could not well be colours or details due to the actual surface of the moon itself4 ,the moon1 we are aware1 has only a certain portion of the visible disk slightly tinted4 ,the ,mare ,serenitatis is certainly of a slight green tinge2 and to the ,palus ,somni and certain other districts is attributed a pale red or pink2 but these tints could hardly have sufficed to produce the effect seen1 as the patches were conspicuous for a bright and decided colour4 ,the positions1 moreover1 did not correspond2 while the ease with which other details of the surface were seen at the time would1 if the tints had arisen from the surface itself1 probably have enabled the circumstance to be detected4 ,sidenote3 ,refraction of sun's rays not a satisfactory explanation4 ,the refraction of the sun's rays by passage through the earth's atmosphere is1 too1 not a satisfactory explanation4 ,this1 as judged by the appearance of the covered moon immediately before and at totality1 gives a disk of shadow deeper in tone in the centre and lightening towards the edges1 but in other respects fairly uniform1 so that the whole disk seems to partake of the same tint and its graduations2 and this is what might have been expected under the circumstances4 ,the patches1 on the other hand1 were quite local4 ,sidenote3 ,question of lunar atmosphere4 ,the theory of the moon's possessing no atmosphere whatever is now very generally1 but perhaps too readily1 received 7mainly upon the evidence of the spectroscopic observations of occulted stars#i71 as there still seems a reasonable doubt whether our satellite may not possess an atmosphere1 possibly rarefied1 but yet sufficiently dense to permit of the formation of cloud or vapour4 ,sidenote3 ,instance of patch of vapour or cloud on moon's surface4 ,a curious case1 in which a patch of vapour or cloud was supposed to be detected on the moon's surface1 is reported by the ,rev4 ,j4 ,b4 ,emmett in a communication to the #8,annals of ,philosophy' 7,new ,series1 vol4 xii4 p4 #ha74 ,it is dated 8,great ,ouseburn1 near ,boroughbridge1 ,july #e1 #ahbf10 the observation being made with 8the greatest care with a very fine telescope40 ,on the #abth ,april #h;h1 while observing the part of the moon called ,palus ,motis by ,nevelius1 with an excellent ,newtonian reflector of #f inches aperture1 at a particular part of the ,palus1 which he minutely describes1 he saw1 with powers #gj and #acj1 8a very conspicuous spot wholly enveloped in black nebulous matter1 which1 as if carried forward by a current of air1 extended itself in an easterly direction1 inclining a little towards the south1 rather beyond the margin of ,motis40 ,april #acth #h;h to #i;h1 the cloudy appearance was reduced both in extent and intensity1 and the spot from which it seemed to issue had become more distinctly visible4 ,on ,april #agth scarcely a trace of the nebulous matter remained2 but so long after as ,june #ajth #h;h 8a little blackness0 remained about the spot4 ,mr4 ,emmett suggested 8smoke of a volcano or cloudy matter40 ,a copy of the drawing annexed to the paper is given on ,plate ,x4 fig4 #aj 7black patch on moon74 ,if this observation was 7as it certainly appears to be7 critical and exact1 there must have been a disturbance of the moon's surface1 indicating some sort of cloud- or vapour-supporting atmosphere2 and probably1 for the purposes of ,auror1 an atmosphere of a very rarefied condition would suffice#aj4 ,sidenote3 ,prof4 ,alexander's evidence in favour of a lunar atmosphere4 ,according to the #8,new ,york ,tribune1' at a recent semi-annual meeting of the ,american ,academy of ,sciences1 ,professor ,alexander 8brought forward a variety of evidence tending to indicate some envelope like an atmosphere for the moon4 ,the evidence was principally drawn from observations during eclipses4 ,the explanations usually offered for the bright band seen around the moon at such times was fully considered1 and shown to be inadequate1 though good as far as they would apply4 ,the ruddy band of light is much too broad to be the sun's chromosphere4 ,it was most apparent in those instances where the moon was nearest the earth4 ,it would best be accounted for by supposing an atmosphere to the moon1 a thin remnant of ancient nebulosity1 comparable to that which accompanies the earth and gives rise to the appearance of the ,aurora ,borealis40 ,is it not1 however1 possible that the appearance might have arisen from ,auror in action within the region of the earth's own atmosphere during the passage of the sun's rays through it at the time of the eclipse8 ,the whole subject is difficult of explanation1 and should be one of the points for attention on the occasion of the next total ,lunar eclipse4 ,it seemed to me appropriate for introduction into the present history of the ,aurora1 whatever its solution may ultimately be4 ,sidenote3 ,mars and ,jupiter4 ,in the case of ,mars and ,jupiter1 whose atmospheres are sufficiently recognized1 red- and scarlet-tinted patches are frequently noticed4 ,in ,mars this is generally attributed to the geological character of the surface of the planet itself2 but ,i have observed on ,mars's surface during the recent opposition a local rosy tint of a more diffused and indefinite character2 and in the case of ,jupiter the appearances seem almost always connected with the clouds' belts1 as distinguished from the regions lying nearer to the planet's surface4 ,sidenote3 ,prof4 ,dorna's 8,lunar ,aurora40 ,professor ,dorna1 of ,turin1 ascribed a flickering light seen on the reddened disk of the moon during the ,lunar eclipse of ,february #ahgg to the action of a ,lunar ,aurora1 holding that the refraction of the sun's rays within the cone of the earth's shadow was not an adequate explanation 7#8,l',opinione ,nazionale1' ,march #c1 #ahgg74 ,sidenote3 ,spectroscopic observations bearing on the subject4 ,mr4 ,christie's observations at ,greenwich4 ,the spectroscope might have afforded some information on the question2 but my own telescopes 7#h and #c in47 were not of sufficient aperture to give a sensible spectrum of a portion of the moon's eclipsed surface1 and my observations were chiefly made on the entire disk with hand-spectroscopes without a slit4 ,mr4 ,christie1 at the ,royal ,observatory1 ,greenwich1 made a set of observations during totality1 and also during subsequent partial phase1 with a single-prism spectroscope4 ,during totality a strong absorption band was seen in the yellow1 and the red and blue ends of the spectrum were completely cut off1 while the orange was greatly reduced in intensity4 ,the yellow and green were comparatively bright1 and seemed to constitute the whole visible spectrum4 ,the absorption band became narrowed as the end of the total phase approached1 and during partial phase was reduced to a mere line4 ,the red end of the spectrum was cut off by a dark band commencing about halfway from ,d to ,c1 in which a black line was suspected4 ,the bands observed were characteristic of the spectrum of light which has passed through a thick stratum of air4 ,in the description of the spectrum of the ,aurora in ,part ,,ii41 it will be seen that the conspicuous red and green lines of the ,aurora are either coincident with1 or very close to1 some of these atmospheric lines4 ,it does not appear that ,mr4 ,christie examined the crimson patches specifically1 nor that he saw bright lines on any part of the moon's eclipsed disk4 ,sidenote3 ,mr4 ,pratt's notes of ,lunar ,eclipse1 ,august #bc1 #ahgg4 ,mr4 ,henry ,pratt has also kindly handed me for use his notes of the ,lunar eclipse of ,august #bc1 #ahgg1 as seen at ,brighton on a splendid night4 ,they were made as the phenomenon progressed1 are #eh in number1 and in many instances only a few minutes1 or even seconds1 apart4 ,a selection of them is here given3--#i;h #acm #ejs1 first contact of shadow4 #i;h #cjm1 shadow very dark2 no details of disk easily seen4 #i;h #djm1 first appearance of red4 #i;h #ejm1 red all over disk1 except margin bluish and ,s4 part green tint4 #aj;h #bm1 a sudden brightening of whole disk1 in strong contrast to two minutes previously4 #aj;h #aem1 ,e4 limb much darker4 #aj;h #cem1 south pole decidedly brightest4 #aj;h #ddm1 ,s4,e4 limb much brighter4 #aj;h #dhm1 whole disk much darker4 #aj;h #eam1 ,s4,e4 limb brightening again4 #aa;h #am1 ,n4,e4 limb brightening4 #aa;h #cm1 ,n4,e4 limb has darkened and brightened three times during last two minutes4 #aa;h #bjm1 ,n4 pole has darkened4 #aa;h #bam1 ,n4 pole has brightened4 #aa;h #bdm #cjs1 ,n4 pole darker red4 #aa;h #cem1 ,n4 pole bright4 #aa;h #cem #cjs1 same dark and red4 #aa;h #dbm1 ,n4,e4 limb especially bright for a few seconds1 and then reddened and shaded again4 #aa;h #dim1 ,s4 pole reddened4 #ab;h #am1 ,s4,w4 limb reddest part2 ,s4 pole red2 ,n4 pole paler red4 #ab;h #cm #ejs1 first appearance of ,e4 limb 7my first sketch was made shortly after this1 and my second about ten minutes later74 #ab;h #bam1 a bright patch on ,n4,n4,w4 separated from ,n4 pole4 #ab;h #bdm1 ,s4,w4 region is reddest part of eclipse4 #ab;h #djm1 redness of shadow fading out4 ,with a small ,browning star-spectroscope ,mr4 ,pratt saw the red and blue ends of the spectrum cut off1 but nothing else4 ,mr4 ,pratt adds that the red colour was not an effect of contrast or an optical delusion in any way1 as was proved by using at times a limited field containing only the red portion under examination4 ,in reference to the curious brightening and darkening of the disk1 and the change from time to time of local colour1 he says that with much experience he has seen nothing of the same marked character on other occasions1 and that 8the whole matter was at the time astonishing to me1 but none the less real40 ,the local red patches seen by me seem also to have been observed by ,mr4 ,pratt4 ,sidenote3 ,mr4 ,pratt's observation on the floor of ,plato4 ,as an addition to the instances of ,tycho1 ,picard1 c41 mentioned in the note on p4 #gc1 ,mr4 ,pratt has also sent me his notes of some observations by him1 of 8local obscuration of the floor of ,plato40 ,as somewhat condensed1 they are as follows3--#ahgb1 ,july #af4 ,while in other parts of the floor spots and streaks were well visible1 8the ,n4,w4 portion was in such a hazy condition that nothing could be defined upon it40 #ahgc1 ,nov4 #a4 #bg light streaks seen 7#g new73 the brightness of the streaks was in excess of their usual character1 as compared with the craterlets2 8an obliteration or invisibility of all the light streaks in the neighbourhood of craterlet no4 #a was very noticeable20 and also 8a similar obliteration of the ,n4 end of the streak called the ,sector1 near craterlet #c40 #ahgd1 ,january #a4 #ah light streaks seen1 including #c new1 8some of which outshone other longer known ones4 ,this was curious2 for had they been as bright within the last two years as on this occasion ,i must have noticed them40 ,mr4 ,pratt points out1 as worthy of remark1 that some months previous to ,november #ast1 #ahgc1 neither craterlets nor streaks on the floor of ,plato 8had maintained their previous characteristic brightness10--a fact which he thinks ought to be considered together with the outbreak of brilliancy of both orders on that day1 as well as the apparently sudden existence of new ones4 ,sidenote3 ,observation by ,mr4 ,hirst of a dark shade on the moon4 ,the #8,observatory1' ,march #a1 #ahgi1 p4 #cge1 contains an account1 by ,mr4 ,h4 ,c4 ,russell1 of some ,astronomical ,experiments made on the ,blue ,mountains1 near ,sydney1 ,n4 ,s4 ,w4 ,among these it is noticed that on #bast ,october1 #ahgh1 at #i ,a4,m41 when looking at the moon1 ,mr4 ,hirst found that a large part of it was covered with a dark shade1 quite as dark as the shadow of the earth during an eclipse of the moon4 ,its outline was generally circular1 and fainter near the edges4 ,conspicuous bright lunar objects could be seen through it2 but it quite obliterated the view of about half the moon's terminator1 while those parts of the terminator not in the shadow were distinctly seen4 ,no change in the position of the shade could be detected after three hours' watching4 ,the observation is made1 8,one could hardly resist the conviction that it was a shadow2 yet it could not be the shadow of any known body4 ,if produced by a comet1 it must be one of more than ordinary density1 although dark bodies have been seen crossing the sun which were doubtless comets40 ,the diameter of the shadow from the part of it seen on the moon was estimated at about three quarters that of the moon#aa4 ,,chapter ,,viii4 ,,aurora ,,and ,,the ,,solar ,,corona4 ,sidenote3 ,aurora and the solar corona4 ,mr4 ,norman ,lockyer's #8,solar ,physics4' ,mr4 ,norman ,lockyer1 in his #8,solar ,physics1' a work of #fff pages1 gives but little space to the ,aurora4 ,the index comprises3--8,aurora ,borealis1 connexion with sun-spots1 pp4 #hb-ajb40 8,affirmed coincidence of spectrum with that of the corona1 pp4 #bdd1 #bef40 ,sidenote3 ,extracts from as to ,aurora's connexion with sun-spots and with solar corona4 ,page #hb4 ,after referring to ,gen4 ,sabine as having shown that there are occasional disturbances in the magnetic state of the earth1 and that these disturbances have a periodical variation1 coinciding in period and epoch with the variation in frequency and magnitude of the solar spots as observed by ,schwabe1 the author proceeds to state1 8and the same philosopher has given us reason to conclude that there is a similar coincidence between the outburst of solar spots and of the ,aurora ,borealis40 ,page #ajb4 8,we have also shown that sun-spots or solar disturbances appear to be accompanied by disturbances of the earth's magnetism1 and these again by auroral displays40 ,sidenote3 ,evidence of ,american observers on nature of the corona considered4 ,page #bdc4 8,what1 then1 is the evidence furnished by the ,american observers on the nature of the corona 7solar78 ,it is bizarre and puzzling to the last degree4 ,the most definite statement on the subject is that it is nothing more nor less than a permanent ,solar ,aurora6 the announcement being founded on the fact that three bright lines remained visible after the image of a prominence had been moved away from the slit1 and that one 7if not all7 of these lines is coincident with a line 7or lines7 noticed in the spectrum of the ,aurora ,borealis by ,professor ,winlock40 ,mr4 ,lockyer then adds1 that amongst the lines he had observed up to that time1 some forty in number1 this line was among those which he had most frequently recorded1 and was1 in fact1 the first iron line which made its appearance in the part of the spectrum he generally studied1 when the iron vapour is thrown into the chromosphere4 ,sidenote3 ,mr4 ,lockyer's conclusion adverse to the question being settled4 ,hence he thought he should always see it if the ,aurora were a permanent solar corona1 and gave out this as its brightest line1 and on this ground alone should hesitate to regard the question as settled4 ,sidenote3 ,prof4 ,young's communication to #8,nature4' ,page #bef is an extract from a communication by ,prof4 ,young to #8,nature1' ,march #bd1 #ahgj1 in which the ,professor refers to the bright line #adgd as being always visible with proper management4 ,he also thinks it probable that this line coincides with the ,aurora line reported by ,prof4 ,winlock at #aeej of ,dr4 ,huggins's scale1 though he is by no means sure of it4 ,he had only himself seen it thrice1 and then not long enough to complete a measurement4 ,he was only sure that its position lay between #adfj and #adij of ,kirchhoff4 ,sidenote3 ,he does not abandon his hypothesis1 it having other elements of probability4 ,for this reason he did not abandon the hypothesis1 which appeared to have other elements of probability1 in the general appearance of the corona1 the necessity of immense electrical disturbances in the solar atmosphere as the result of the powerful vertical currents known to exist there1 as well as the curious responsiveness of our terrestrial magnets to solar storms2 yet he did not feel in a position to urge it strongly1 but rather awaited developments4 ,father ,secchi was disposed to think the line hydrogen1 while ,mr4 ,lockyer still believed it to be iron4 ,sidenote3 ,dr4 ,schellen reviews the subject in eclipse of #ahfi4 ,dr4 ,schellen1 in his #8,spectrum ,analysis1' treats the matter more in detail4 ,referring to the eclipse of #ahfi as confirming the previous observations that the coronal spectrum was free from dark lines1 he points out that ,pickering1 ,harkness1 ,young1 and others were agreed that with the extinction of the last rays of the sun all the ,fraunhofer lines disappeared at once from the spectrum4 ,he further says3-- ,sidenote3 ,young observed three bright lines in the spectrum of the corona4 ,coincidence of these lines with three bright lines observed by ,winlock in the ,aurora4 ,corona self-luminous1 and probably of a gaseous nature4 ,corona supposed to be a permanent polar light existing in the sun4 ,polar light in the sun attributed to electricity4 ,dr4 ,schellen thinks nature of the corona still a problem4 8,the small instruments employed by ,pickering and ,harkness1 with a large field of view1 exhibited a spectrum obtained at once from the corona1 the prominences1 and the sky in the neighbourhood of the sun4 ,these instruments showed during totality a faint continuous spectrum free from dark lines1 but crossed by two or three bright lines4 ,young1 with a spectroscope of five prisms1 observed the three bright lines in the spectrum of the corona1 and deduced the following positions according to ,kirchhoff's scale3--#abej #bj1 #acej #bj1 and #adgd4 ,it had been already explained why the last and brightest of these lines was thought to belong to the corona and not to that of the prominences1 and it seemed probable that the other two lines belonged also to the light of the corona1 from the fact that they were both wanting in the spectrum of the prominences when observed without an eclipse4 ,but what invested these three lines with a peculiar interest was the circumstance that they appeared to coincide exactly with the first three of the five bright lines observed by ,professor ,winlock in the spectrum of the ,aurora ,borealis4 ,these lines of the ,aurora were determined by ,winlock according to ,huggins's scale2 and if these be reduced to ,kirchhoff's scale1 the positions of the lines would be #abdg1 #acea1 and #adgc1 while the lines observed by ,young were #abej1 #acej1 and #adgd40 ,dr4 ,schellen then points out that if it be borne in mind that ,young found the positions of the two fainter lines more by estimation than by measurement1 the coincidence between the bright lines of the corona and those of the ,aurora would be found very remarkable4 ,the brightest of the lines1 #adgd1 was the reversal of a strongly marked ,fraunhofer line1 ascribed by ,kirchhoff and ngstrm to the vapour of iron4 ,dr4 ,schellen then details ,professor ,pickering's observations with the polariscope1 showing that the corona must be self-luminous1 and that from the bright lines seen in its spectrum it is probably of a gaseous nature1 and forms a widely diffused atmosphere round the sun2 and then adds1 8,it has been supposed1 from the coincidence of the three bright lines of the corona with those of the ,aurora ,borealis1 that the corona is a permanent polar light existing in the sun analogous to that of our earth40 ,dr4 ,schellen here adds3--8,lockyer1 however1 justly urges against this theory the fact that although the brightest of these three lines1 which is due to the vapour of iron1 is very often present among the great number of bright lines occasionally seen in the spectrum of the prominences1 it is by no means constantly visible1 which ought to be the case if the corona were a permanent polar light in the sun40 7,professor ,young's answer to this1 on the ground of line #adgd being always visible1 has been already given47 8,a yet bolder theory is the ascription of such a polar light in the sun to the influence of electricity1 which has been proved1 it is well known1 by the relation of the magnetic needle1 and the disturbance of the electric current in the telegraph wires1 to play an important part in the phenomenon of the ,aurora ,borealis20 and ,dr4 ,schellen then concludes with an opinion that the nature of the corona was still a problem#ab4 ,sidenote3 ,various places of wave-length assigned to these lines4 ,on reference to the #8,american ,journal of ,science1' vol4 xlviii4 pp4 #abc and #djd1 it seems that the auroral observations before referred to were made on #aeth ,april1 #ahfi1 by ,c4 ,s4 ,pierce1 with 8an ordinary chemical spectroscope1 with the collimator pointed directly to the heavens10 and were reported by ,winlock4 ,the lines were #abhj1 #adjj1 and #aeej of ,huggins's scale1 and were reduced to ,kirchhoff's scale by ,young4 ,these lines have had all sorts of places of wave-length assigned to them by different writers4 ,proctor gives #eegj1 #edjj1 #ebjj2 ,pickering and ,alvan ,clarke1 #ecbj 7assumed to be #ecaf1 coronal line72 ,barker1 #eagj1 #ebjj1 #ejbj2 ,backhouse1 #ecbj1 #dfdj1 and #dcaj4 ,in my #8,aurora ,spectrum1' ,plate ,,xii41 ,i have assigned two1 with a81 to #ecbj 7,alvan ,clarke7 and #ejbj 7,barker74 ,the third might perhaps be placed at #dfdj 7,backhouse and ,winlock74 ,sidenote3 ,doubts raised as to closeness of the observations for the purpose of comparison4 ,the coincidences relied on in the foregoing observations depend1 of course1 upon 7#a7 the accuracy of the observations themselves1 and 7#b7 the subsequent reduction of the lines for comparison4 ,assuming the correctness of the latter1 what have we as to the former8 ,two of ,professor ,young's positions of coronal lines1 as stated1 seem to have far too much of the element to make them sufficiently accurate4 ,pierce's auroral observation does not state how the lines were positioned4 ,as they all end with a cypher1 the suspicion naturally arises that the measurements did not extend beyond the first three places of the figures1 and1 if so1 could not be used for accurate comparison4 ,the auroral lines1 too1 are generally rather wide and nebulous1 and not easy of comparison with sharper ones4 ,,chapter ,,ix4 ,,supposed ,,causes ,,of ,,the ,,aurora4 ,sidenote3 ,supposed causes of the ,aurora4 ,sulphurous vapours4 ,magnetic effluvia4 ,at first the ,aurora was described to be sulphurous vapours issuing from the earth2 and ,musschenbroek pointed out that certain chemical mixtures sent forth a phosphorescent vapour1 in some respects resembling the ,aurora4 ,dr4 ,halley originally proposed a similar theory1 but ultimately concluded that the ,aurora might be occasioned by the circulation of the magnetic effluvia of the earth from one pole to another4 ,sidenote3 ,zodiacal light4 ,m4 de ,mairan1 in #agba1 in a treatise1 ascribed the ,aurora to the impulse of the zodiacal light upon the atmosphere of the earth4 ,sidenote3 ,luminous particles of our atmosphere4 ,euler combated this theory1 and ascribed the ,aurora to the luminous particles of our atmosphere driven beyond its limits by the light of the sun1 and sometimes ascending to the height of several thousand miles4 ,sidenote3 ,electric fluid in vacuo resembles ,aurora4 ,mr4 ,hawksbee very early showed that the electric fluid assumes1 in vacuo or in highly rarefied atmosphere1 an appearance resembling the ,aurora4 ,mr4 ,canton contrived an imitation of the ,aurora by means of electricity transmitted through the ,torricellian vacuum in a long glass tube1 and showed that such a tube would continue to display strong flashes of light for #bd hours and longer without fresh excitation4 ,sidenote3 ,experiment with electrical machine and exhausted receiver4 ,in the #8,edinburgh ,encyclopdia1' date #ahcj1 is mentioned an experiment in which an electrical machine and air-pump are so disposed that strong sparks pass from the machine to the receiver of the air-pump4 ,sidenote3 ,dr4 ,franklin's theory4 ,as the exhaustion proceeds the electricity forces itself through the receiver in a visible stream1 at first of a deep purple colour2 8but as the exhaustion advances it changes to blue1 and at length to an intense white1 with which the whole receiver becomes completely filled40 ,it will be noticed that this experiment bears a close resemblance to ,prof4 ngstrm's exhausted flask referred to later in treating of the spectrum of the ,aurora4 ,dr4 ,franklin gave a different form to the electric theory of the ,aurora1 supposing that the electricity which is concerned in the phenomenon passes into the ,polar regions from the immense quantities of vapour raised into the atmosphere between the tropics 7,exper4 and ,observ4 #agfi1 p4 #dc74 ,sidenote3 ,mr4 ,kirwan's theory4 ,mr4 ,kirwan 7,irish ,trans4 #aghh7 supposed that the light of the ,aurora ,borealis and ,australis was occasioned by the combustion of inflammable air kindled by electricity4 ,sidenote3 ,mons4 ,monge's4 ,mons4 ,monge proposed the theory that the ,auror were merely clouds illuminated by the sun's light falling upon them after numerous reflections from other clouds placed at different distances in the heavens 7,leons de ,physique par ,prejoulz1 #ahje1 p4 #bcg74 ,sidenote3 ,mons4 ,libes'4 ,mons4 ,libes propounded a theory that the electric fluid1 passing through a mixture of azote and oxygen1 produced nitric acid1 nitrous acid or nitrous gas1 and that these substances1 acted upon by the solar rays1 would exhibit those red and volatile vapours which form the ,aurora ,borealis 7,trait de ,physique1 ou ,dictionnaire de ,physique1 par ,libes2 ,rozier's ,journal1 ,june #agij1 ,february #agia1 and vol4 xxxviii4 p4 #aia74 ,sidenote3 ,mr4 ,dalton's4 ,mr4 ,dalton considered the ,aurora a magnetic phenomenon whose beams were governed by the magnetism of the earth4 ,he observed that the luminous arches were always perpendicular to the magnetic meridian 7,dalton's ,meteorological ,observations and ,essays1 #agic1 pp4 #ed1 #aec74 ,sidenote3 ,abb ,bertholon's4 ,the ,abb ,bertholon ascribed the ,aurora ,borealis to a phosphorico-electric light 7,encyc4 ,mthod4 art4 ,auror74 ,sidenote3 ,dr4 ,thompson concluded the arches to be an optical deception4 ,dr4 ,thompson 7,annals of ,philosophy1 vol4 iv4 p4 #dbi71 from the observations of ,mr4 ,cavendish and ,mr4 ,dalton1 concluded there was no doubt that the arched appearance of the ,aurora was merely an optical deception1 and that in reality it consisted of a great number of straight cylinders parallel to each other and to the dipping-needle at the place where they were seen4 ,sidenote3 ,artificial ,auror produced in exhausted tubes4 ,with many of us 7at least it was so in my own case7 our first viewed ,auror have been artificial ones1 devised by electricians and having their locus at the ,royal ,polytechnic in ,regent ,street or in some scientific lecture-room4 ,the effects in these cases are produced in tubes nearly exhausted by means of an air-pump1 and then illuminated by some form of electric or galvanic current4 ,sidenote3 ,tubes described4 ,in one instance the tube is usually of the form shown on ,plate ,x4 fig4 #i1 supported on a base with a brass ball electrode at the lower end1 and a pointed wire at the upper4 ,in another case the tube is of the form shown on same ,plate1 fig4 #h4 ,after exhaustion it is permanently closed1 the current passing through it by means of the platinum-wire electrodes introduced into each end of the tube4 ,the first form of tube is usually excited by a frictional plate machine2 the second by a galvanic current from a ,grove or bichromate battery1 which1 by the aid of a ,ruhmkorff coil1 has had its character changed from quantity to intensity4 ,in each instance1 upon connexion with the source supply of the electric current1 a very similar effect is produced4 ,sidenote3 ,effects described4 ,brilliant streams of rose-coloured light pass between the electrodes1 sometimes as a single luminous misty band1 sometimes in divided vibrating sprays or streams1 and sometimes in a flaky column of stri4 ,all this1 before the spectroscope took its part in the investigation1 we were content to accept as a very fair and probable explanation of the ,aurora accompanied by a mimic representation of the phenomenon4 ,these appearances may1 of course1 be produced at will in tubes having electrodes2 but it is1 moreover1 possible to produce them1 though with less effect1 in certain other forms of tube having no such direct communication with the external electric machine4 ,one electrode only may be connected with the coil or electrical machine4 ,the appearance is then a faint representation of what happens when the current entirely passes 7but see experiments with a single wire detailed in ,part ,,iii474 ,sidenote3 ,tube without electrodes4 ,in the case of an exhausted tube having no electrodes1 the wires from the coil may be made into a little helix and placed at each end of the tube1 and the induced currents within will show themselves in flashes and streams of light1 varying in colour and tint according to the gaseous or other contents of the tube4 ,sidenote3 ,tube excited by friction4 ,in some cases the ordinary forms of galvanic or electrical machine for supplying the current of electricity may be dispensed with4 ,a long straight tube exhausted and closed at each end1 and without electrodes1 ,plate ,x4 fig4 #f1 being slightly warmed and then excited by friction with the dry hand or a piece of flannel1 silk handkerchief1 or the like1 is soon filled with the most brilliant flashes of light playing in the interior1 and when once thoroughly charged needs but little further excitation to keep up the effect4 ,sidenote3 ,geissler's mercury tube4 ,geissler has introduced a form of tube in which electricity in its form of flashes and glow of light is produced by the friction of mercury4 ,the outer tube is strong1 and contains within it a smaller tube of uranium glass with balls blown upon it 7,plate ,x4 fig4 #g74 ,the tubes are exhausted and a small quantity of mercury is introduced which has access to both surfaces of the inner tube1 as well as to the inner surface of the outer tube4 ,upon the tube being reversed end for end or shaken1 the mercury runs up or down the tube and causes a very considerable display of whitish light4 ,the before-described tubes are also referred to1 and their spectra described1 in the section 8,on the comparison of some tube and other ,spectra with the ,aurora0 7,part ,,ii474 ,the aura or brush from the electrical machine has been considered as resembling the ,aurora1 while the hissing and crackling accompanying it has been supposed to corroborate the reports of similar noises having been heard during an auroral display4 ,sidenote3 ,prof4 ,lemstrm's instrument to demonstrate the nature of ,auror4 ,prof4 ,lemstrm1 of the ,university of ,helsingfors1 has devised an instrument for the purpose of demonstrating that ,auror are produced by electrical currents passing through the atmosphere4 ,an illustration of this instrument 7for which ,i am indebted to the ,editor of #8,nature'7 is introduced 7fig4 #a74 ,the instrument was exhibited at the recent ,scientific ,loan ,collection at ,south ,kensington1 and a full description of it1 together with an essay by ,prof4 ,lemstrm1 8,on the ,theory of the ,polar ,light10 will be found in the third edition of the ,official ,catalogue1 p4 #chf4 no4 #agea4 ,the apparatus is intended to show that an electric current passing from an insulated body does not produce light in air of normal pressure2 but as it rises to the rarefied air in the ,geissler tubes a phenomenon very like the real ,polar ,light is produced4 ,illustration3 ,fig4 #a4 ,a is an electrical machine1 the negative pole being connected with a copper sphere and the positive with the earth4 s s is of ebonite as well as ,r ,r d1 so that ,b is quite insulated as the earth is in space4 ,b is surrounded by the atmosphere4 a a a a a a are a series of ,geissler tubes with copper ends above and below4 ,all the upper ends are connected with a wire which goes to the earth2 consequently a current runs in the direction of the arrows through the air1 and the ,geissler tubes become luminous when the electrical machine is set into operation4 ,the ,geissler tubes represent the upper part of the atmosphere which becomes luminous when the ,aurora ,borealis is observed in the northern hemisphere4 ,the phenomena produced by the ,lemstrm apparatus are considered consistent with the theory advocated by ,swedish observers that electrical currents emanating from the earth and penetrating into the upper regions produce ,auror in both hemispheres4 ,the experiment differs from the apparatus of ,m4 de la ,rive1 who placed his current in vacuo1 and did not show the property of ordinary atmospheric air1 in allowing to pass unobserved1 at the pressure of #gfj millims41 a stream of electricity which illuminates a rarefied atmosphere4 ,sidenote3 ,m4 de la ,rive's apparatus described4 ,de la ,rive's apparatus was also exhibited at the same time1 and will be found described at p4 #che of the ,catalogue1 ,no4 #agdi4 ,a large sphere of wood represented the earth1 and iron cylinders the two extremities of the terrestrial magnetic axis4 ,these penetrated into two globes filled with rarefied air1 simulating the higher regions of the ,polar atmosphere4 ,the electric discharge turned around a point situate in the prolongation of the axis1 in a different direction at either pole1 when the two cylinders were charged by means of a horseshoe electro-magnet1 in accordance with observations on the rotation of the rays of the ,aurora4 ,sidenote3 ,de la ,rive's magnet in an electric egg4 ,de la ,rive placed an electro-magnet in an electric egg4 ,as soon as the magnet was set in action the discharge which had before filled the egg was concentrated into a defined band of light1 which rotated steadily round the magnet4 ,sidenote3 ,gassiot's experiment with #djj ,grove cells and exhausted receiver between poles of magnet4 ,gassiot describes an experiment with his great ,grove's battery of #djj cells1 in which an exhausted receiver was placed between the poles of the large electro-magnet of the ,royal ,institution4 8,on now exciting the magnet with a battery of #aj cells1 effulgent strata were drawn out from the positive pole1 and passed along the under or upper surface of the receiver according to the direction of the current4 8,on making the circuit of the magnet and breaking it immediately1 the luminous strata rushed from the positive pole and then retreated1 cloud following cloud with a deliberate motion1 and appearing as if swallowed up by the positive electrode40 ,mr4 ,marsh considered this bore a very considerable resemblance to the conduct of the auroral arches1 which almost invariably drift slowly southward4 ,sidenote3 ,mr4 ,marsh considered the ,aurora an electric discharge between the magnetic poles of the earth4 ,he considered it probable that the ,aurora was essentially an electric discharge between the magnetic poles of the earth1 leaving the immediate vicinity of the north magnetic pole in the form of clouds of electrified matter1 which floated southward1 bright streams of electricity suddenly shooting forth in magnetic curves corresponding to the points from which they originated1 and then bending southward and downward until they reached corresponding points in the southern magnetic hemisphere1 and forming pathways by which the electric currents passed to their destination2 and1 further1 that the magnetism of the earth caused these currents and electrified matter composing the arch to revolve round the magnetic pole of the earth1 giving them their observed motion from east to west or from west to east4 ,sidenote3 ,varley's observation on a glow-discharge in vacuo4 ,spark surrounded by an aura which could be separated4 ,varley showed that when a glow-discharge in a vacuum tube is brought within the field of a powerful magnet1 the magnetic curves are illuminated beyond the electrodes between which the discharge is taking place1 as well as in the path of the current1 and also thought that this illumination was caused by moving particles of matter1 as it deflected a balanced plate of talc on which it was caused to infringe4 ,it has also been shown that in electrical discharges in air at ordinary pressure1 while the spark itself was unaffected by the magnet1 it was surrounded by a luminous cloud or aura which was driven into the magnetic curve1 and which might also be separated from the spark by blowing upon it4 ,most of the foregoing interesting results and experiments will be found repeated and verified in ,part ,,iii4 ,prof4 ,lemstrm's ,theory4 ,sidenote3 ,prof4 ,lemstrm's theory4 ,prof4 ,lemstrm thinks that terrestrial magnetism plays only a comparatively secondary part in the phenomena of the ,polar ,light1 this part consisting essentially in a direct action upon the rays4 ,that the experiments of ,m4 de la ,rive do not all furnish the proof that the rays of the light are really united under this influence4 ,sidenote3 ,character of the ,polar ,light4 ,that the ,polar ,light considered as an electrical discharge gives the following results3-- 7#a7 ,an electric current arising from the discharge itself1 which takes place slowly4 7#b7 ,rays of light consisting of an infinite number of sparks1 each spark giving rise to two induction currents going in opposite directions4 7#c7 ,a galvanic current going in an opposite direction to that of the discharge1 and having its origin in the electromotive force discovered by ,m4 ,edlund in the electric spark4 ,that these currents require a closed circuit2 but this is not necessary in the case of the ,aurora1 as the earth and rarefied air of the upper regions are immense reservoirs of electricity producing the same effect as if the circuit were closed4 ,that permanent moisture in the air1 a good conductor of electricity1 is the cause of a slow and continuous discharge assuming the form of an ,aurora1 instead of suddenly producing lightning as in equatorial regions and mean latitudes4 ,sidenote3 ,polar ,light due to electric discharges only4 ,he sums up1 that the electric discharges which take place in the ,polar regions between the positive electricity of the atmosphere and the negative electricity of the earth are the essential and unique cause of the formation of the ,polar ,light1 light the existence of which is independent of terrestrial magnetism1 which contributes only to give to the ,polar ,light a certain direction1 and in some cases to give it motion4 ,this ,prof4 ,lemstrm maintains contrary to those who believe they see in terrestrial magnetism1 or rather in the induction currents1 what is capable of developing the origin of the ,polar ,light4 ,theories of ,,mm4 ,becquerel and ,de la ,rive4 ,sidenote3 ,theories of ,,mm4 ,becquerel and ,de la ,rive4 ,m4 ,becquerel's theory is that solar spots are cavities by which hydrogen and other substances escape from the sun's protosphere4 ,that the hydrogen takes with it positive electricity which spreads into planetary space1 even to the earth's atmosphere and the earth itself1 always diminishing in intensity because of the bad conducting-power of the successive layers of air and of the earth's crust4 ,that would then only be negative1 as being less positive than the air4 ,the diffusion of electricity through planetary space would be limited by the diffusion of matter1 since it cannot spread in a vacuum4 ,that gaseous matter extends further than the limits usually assigned to the earth's atmosphere1 is proved by the observation of ,auror at heights of #ajj and #bjj kilometres1 where some gaseous matter must exist4 ,m4 de la ,rive agrees with ,m4 ,becquerel as to the electric origin of the ,aurora1 but considers the earth is charged with negative electricity and is the source of the positive atmospheric electricity1 the atmosphere becoming charged by the aqueous vapour rising in tropical seas4 ,the action of the sun he considers is an indirect one1 varying with the state of the sun's surface1 as shown by coincidences in the periods of ,aurora and sun-spots4 ,m4 ,plant's ,electric ,experiments4 ,sidenote3 ,m4 ,plant's experiments4 ,effects produced resembling ,auror4 ,m4 ,plant has performed some experiments with a very considerable series of secondary batteries4 ,by inserting the positive electrode after the negative in a vessel of salt water1 luminous and other effects were observed which were considered to have a strong resemblance to those of ,auror4 ,m4 ,plant advocates the theory that the imperfect vacuum of the upper regions1 acting like a large conductor1 plays the part of the negative electrode in his experiments1 while the positive electricity flows towards the planetary spaces1 and not towards the ground1 through the mists and ice-clouds which float above the ,poles4 ,sidenote3 ,m4 ,plant's experiments producing a corona1 an arc1 or a sinuous line4 ,in an article in #8,nature1' ,march #ad1 #ahgh1 a further account is given of ,m4 ,plant's experiments1 under the head of 8,polar ,auror20 and it is stated that1 in these experiments1 the electric current1 in presence of aqueous vapour1 yielded a series of results altogether analogous to the various phases of ,polar ,auror4 ,if the positive electrode of the secondary battery was brought into contact with the sides of a vessel of salt water1 there was observed1 according to the distance of the film 7electrode87 from the liquid1 either a corona formed of luminous particles arranged in a circle round the electrode 7fig4 #b1 p4 #ij71 an arc bordered with a fringe of brilliant rays 7fig4 #c71 or a sinuous line which rapidly folded and refolded on itself 7fig4 #d74 ,this undulatory movement1 in particular1 formed a complete analogy with what had been compared in ,auror to the undulations of a serpent1 or to those of drapery agitated by the wind4 ,the rustling noise accompanying the experiment was analogous to that sometimes said to accompany ,auror1 and was caused by the luminous electric discharge penetrating the moisture4 ,as in ,auror1 magnetic perturbations were produced by bringing a needle near the circuit1 the deviation increasing with the development of the arch4 ,the ,auror were produced by positive electricity1 the negative electrode producing nothing similar4 ,illustrations of these miniature ,auror are given in #8,nature1' and reproduced on p4 #ij4 ,no mention of any spectroscopic observations is made4 ,sidenote3 ,mr4 ,holden's views4 ,in a communication to the ,metropolitan ,scientific ,association 7#8,observatory1' ,march #a1 #ahgi1 p4 #chi71 ,mr4 ,a4 ,p4 ,holden1 after supporting the theory of a connexion between the waxing and waning of the solar corona and sun-spots1 adopts ,mr4 ,f4 ,pratt's hypothesis 8that the ,aurora is simply light filmy cirrus cloud1 first deposited at the base of a vast upper body of highly rarefied vapour1 and illuminated by the free electricity escaping in the condensation through the very rarefied medium above1 towards the north or south4 ,the ,aurora would1 according to this theory1 have its origin in a vast electrical storm1 resulting from a violent condensation of vapour which causes a flow of electricity from the pole to restore equilibrium40 ,the ,aurora would thus1 in ,mr4 ,holden's opinion1 8depend on storm phenomena of an intense character2 and the frequency of ,auror at the sun-spot maxima would indicate the connexion of the latter with the weather40 ,illustration3 ,fig4 #b4 ,the corona4 ,fig4 #c4 ,the arc and rays4 ,fig4 #d4 ,the sinuous line4 ,,part ,,ii4 ,,the ,,spectrum ,,of ,,the ,,aurora4 ,,chapter ,x4 ,,spectroscope ,,adapted ,,for ,,the ,,aurora4 ,sidenote3 ,must be of moderate dispersion1 with ready mode of measuring line-positions4 ,any form of spectroscope of moderate dispersion will suffice for observations of the spectrum of the ,aurora2 but1 for sake of convenience1 a hand or direct-vision spectroscope is to be preferred1 and it is desirable also to have some quick and ready mode of measuring the position of the lines while the ,aurora lasts4 ,sidenote3 ,mr4 ,browning's instrument described4 ,mr4 ,john ,browning arranged for me a form of instrument which ,i have found very convenient for observations by hand of the ,aurora-lines1 and also1 when fixed on a stand1 for tube and chemical investigations4 ,a representation of this instrument is given on ,plate ,x4 fig4 #a4 ,a brass tube carries a large compound 7#e7 direct-vision prism 7shown dark in the drawing74 ,an arrangement is made so that a second prism can at will be slipped into the tube 7shown in outline in the drawing74 ,with one prism and a fine slit the ,d lines are widely separated1 and the field of view extends at one glance from near ,c to near ,g4 ,when the second prism is inserted and used in combination1 the nickel line can be seen between the two ,d lines1 and the instrument may be used for solar work4 ,a photograph of the sun's spectrum1 taken with one prism only1 shows a great number of the dark solar lines and many of the bright ones1 ascribed by ,prof4 ,draper to oxygen and nitrogen4 ,illustration3 ,plate ,x4 ,sidenote3 ,diaphragm micrometer described4 ,mode of use of the micrometer4 ,the collimator and observing telescope are respectively #f inches in length1 and carry achromatic lenses of one inch aperture4 ,the telescope traverses the field so that the extremities of the spectrum may be observed4 ,the dispersion of the instrument was ascertained by a set of observations of the principal solar and some metallic lines1 made with an excellent filar micrometer4 ,for the ,auroral observations1 ,dr4 ,vogel has described an instrument 7see ,appendix ,e7 in which the usual spider's-web wires are replaced by a needle-point1 as being easily seen upon a faint spectrum4 ,illuminated wires may also be used2 but ,i was led ultimately to employ1 in preference1 a diaphragm micrometer which the spectrum itself illuminates1 as being adapted for speedy1 yet fairly accurate1 observations4 ,it was made in this manner3--,a card was first of all prepared 7,plate ,x4 fig4 #b71 and within a circle described on this1 a scale was drawn of moderately wide white spaces1 with black divisions between1 short and long1 so as to read off easily by eye4 ,the upper half of the circle was then entirely filled in with black2 and from the card as thus prepared a reduced negative photograph was made4 ,in this the spaces and lower half of the circle were opaque1 and the upper half of the circle and the lines between the spaces were transparent 7,plate ,x4 fig4 #d74 ,this photograph was about the size of a shilling 7fig4 #c1 same ,plate74 ,it was mounted carefully in ,canada balsam1 with a thin glass cover1 and then placed in the focus of the eyepiece4 ,in use1 the spectrum is brought upon the scale so that the upper half shows above the scale without any interruption at all2 while the lower half illuminates the scale and renders the divisions visible1 showing the spectrum-lines falling either upon them or the spaces between4 ,the photographed scale was next enlarged to a considerable size and printed upon faintly ruled paper2 and the enlargement was so arranged as to comprise five of the faint ruled lines between each division of the scale4 ,each of these faint lines in turn represented a certain portion of the spectrum as read off with the filar micrometer2 so that the scales as constructed with the filar micrometer and with the photographed micrometer corresponded for all parts of the spectrum included in the field of the eyepiece4 ,sidenote3 ,advantage of the method4 ,one of the photographed enlargements being laid on the table under the spectroscope1 the observed lines were marked off with ease and accuracy upon it2 and as the photograph was an exact copy of the scale1 any want of exactitude in the divisions was of no moment4 ,one great advantage of this method was1 that all the lines seen could be recorded at one time and with all in view1 and without the risk of slight shift in the instrument1 which frequently happens when lines are read off seriatim4 ,i found this plan most effective for the rapid and correct recording of a faint and evanescent spectrum1 and it gave close results when compared with traversing-micrometer measured spectra4 ,the records1 too1 admitted of subsequent examination at leisure4 ,sidenote3 ,double-slit plate arrangement4 ,mr4 ,browning subsequently constructed for me a double-slit plate 7lately in the ,scientific ,loan ,collection at ,south ,kensington7 for the same instrument 7,plate ,x4 fig4 #e74 ,the lower half of the plate is fixed4 ,the upper half traverses the lower by the aid of a micrometer-screw4 ,the slit is widened or closed at pleasure by loosening the small screws by which the jaw-plates are attached4 ,a scale is engraved on the fixed lower half of the plate for an approximate measurement1 while the division of the micrometer-screw-head completes it4 ,in use1 one half of the spectrum slides along the other1 and a bright line in the upper spectrum is selected as an index4 ,the distances between the lines of the lower half of the spectrum are read off by means of the bright line above4 ,this form of micrometer was suggested by ,mr4 ,procter 7in #8,nature'7 many years ago as a substitute for a more complicated apparatus by ,zllner4 ,other instruments on a similar principle have been lately introduced1 but for ,aurora purposes ,i prefer a fixed scale4 ,sidenote3 ,photographed spectrum suggested4 ,in #8,photographed ,spectra' ,i have pointed out that we shall probably obtain no spectrum of the ,aurora to be absolutely depended upon for comparison with other spectra until we succeed in a photographed one4 ,from experiments made with a special prism of the ,rutherfurd form1 constructed for me by ,mr4 ,browning 7with which many gas-spectra have been already photographed71 ,i see no reason1 should an unusually bright ,aurora favour us with a visit1 why its spectrum may not be recorded in a permanent form1 and with lines sufficiently well marked to be compared with other spectra4 ,rapid dry plates would be especially useful for such a purpose1 and some ,auror1 if wanting in brilliancy1 would doubtless compensate by their period of endurance4 ,sidenote3 ,mr4 ,hilger's half-prism spectroscope4 ,mr4 ,adam ,hilger has also made for me one of his 8half-prism0 spectroscopes1 in which considerable dispersion is obtained with but very little loss of light4 ,this instrument has a simple and rapid micrometer arrangement1 with a bright line as an index4 ,i have 7for want of ,auror7 had no opportunity of trying it1 but ,i doubt not it is well adapted for such a purpose4 ,spectrum of the ,aurora described4 ,sidenote3 ,lines or bands and continuous spectrum4 ,the spectrum of the ,aurora consists of a set of lines or bands upon a dark ground at each extremity of the spectrum1 but with more or less of faint continuous spectrum towards the centre4 ,the extreme range of the spectrum1 as observed up to the present time1 is from 8a0 7between ,c and ,d7 in the red to 8h0 7hydrogen7 in the violet4 ,sidenote3 ,lines nine in number4 ,the lines have been classified and arranged by ,lemstrm and others as nine in number1 but ,i believe not more than seven have ever been seen simultaneously4 ,the author of the article 8,aurora ,polaris10 in the #8,encyclopdia ,britannica1' classes the lines as nine1 and gives a table with the following results 7to these ,i have added ,herr ,vogel's lines1 for the purpose of identification and comparison73-- ,sidenote3 ,table from ,encyc4 ,brit4 ---------------------------------------- ,no4 of ,number of ,mean ,probable,vogel's line4 observations4 ,w4,l4 error4 lines4 ---------------------------------------- #a4 #e #fcjc #ha #fbig #b4 #aj #eefi #bi #eefi #c4 #d #ecdb #af #ecij #d4 #f #ebad #ed #ebcc #e4 #d #eafa #ig #eahi #f4 #f #dihd #aa #ejjd #g4 #d #dhbc #ic #h4 #h #dffg #ih #dffc #i4 #h #dbii #ic ---------------------------------------- ,the probable errors are large1 and it is a question whether any thing is gained by thus endeavouring to average the lines4 ,sidenote3 ngstrm's line4 ,zllner's line in the red4 ,other ,lines of the spectrum4 ,the principal and brightest line1 in the yellow-green1 is generally called 8ngstrm's10 and his 7probably the first7 measurement of its position at #eefg adopted4 ,this was in the winter of #ahfg-fh1 and he saw in addition1 by widening the slit1 traces of three very feeble bands situated near to ,f4 ,zllner is credited with the first observation of the line in the red4 ,these two lines are generally described as with similar characteristics1 and in about the same respective positions1 by all observers1 and have never been remarked to spread into bands4 ,the other lines in the spectrum are difficult to position1 owing to the many discordant observations of them4 ,they seem also variable in intensity as well as in number 7sometimes even in the same ,aurora71 and are not unfrequently observed to have their places supplied by bands4 ,sidenote3 ,second ,german expedition observations4 ,austro-,hungarian4 ,the spectroscope was used in the second ,german expedition1 but only the one brightest line seen--,dr4 ,brgen stating he had never seen a trace of the weak lines in the blue and red1 which were observed so distinctly with the same spectroscope on #beth ,october1 #ahgj1 after the return of the expedition4 ,lieutenant ,weyprecht used a small spectroscope during the ,austro-,hungarian ,expedition1 and saw only the well-known yellow-green line4 ,sidenote3 ,swedish expedition1 #ahfh4 ,lemstrm's observations4 ,in the ,swedish ,expedition1 #ahfh1 ,lemstrm mentions that in the ,aurora spectrum there are nine lines 7he does not say he saw them simultaneously71 which he considers to agree with lines belonging to the air-gases4 ,he also thinks the ,aurora could be referred to three distinct types1 depending on the character of the discharge4 ,sidenote3 ,spectrum or ,aurora seen at ,tronsa4 ,at ,tronsa an ,aurora was seen ,october #bast1 #ahfh1 which commenced in the north and became very brilliant4 ,the spectroscope showed3-- #a4 ,a yellow line at #gdi4 #b4 ,a very clear line in the blue at #feij4 #c4 ,two lines of hair's breadth1 with very pronounced 7horizontal87 stri on the side of the yellow1 one at #abe and the other about #aje4 ,i presume the stri were really vertical1 and that the explanation intended to convey that these lines shaded off towards the yellow4 ,from a comparison of the figures they must have been in the red1 and are the only instance recorded of two auroral lines in that region4 ,they are subsequently spoken of as 8shaded rays40--,j4 ,r4 ,c4 ,sidenote3 ,,mm4 ,wijkander and ,parent's observations4 ,m4 ,auguste ,wijkander and ,lieut4 ,parent1 of the ,swedish ,expedition in #ahgb-gc1 under ,professor ,nordenskild1 used a direct-vision spectroscope1 with a micrometer-screw movement of the prisms1 the reading being afterwards reduced to wave-lengths upon ngstrm's line-values4 ,the following ,table gives the results1 with ,dr4 ,vogel's lines added for the sake of comparison3-- ---------------------------------------- -------------------------- ,observations1 ,wijkander4 ,observations1 ,parent4 ---------------------------------------- ---,mean of ,lines4 ,probable ,probable both4 ,vogel4 ,number4,w4,l4 error4 ,number4,w4,l4 error4 ---------------------------------------- ---------------------- 44 44 44 44 44 44 44 44 #fbig 44 44 44 44 44 44 44 44 #eefi 7#a7 #e #ecei #c 44 44 44 #ecei #ecij 7#b7 #f #ebhi #e #c #ebhj #a #ebhf 44 7#c7 #f #ebci #d #b #ebjg #aa #ebca #ebcc 44 44 44 44 44 44 44 44 #eahi 7#d7 #e #diif #i 44 44 44 #diif #ejjd 7#e7 #a #dhga 44 #a #dhgc 44 #dhgb 44 7#f7 #h #dfib #b #aj #dgjh #e #dgja #dffc 7#g7 #a #dcff 44 44 44 44 #dcff 44 7#h7 #d #dbhj #c #c #dbhf #af #dbhd 44 ---------------------------------------- ---------------------- ,the brightest line in all ,auror1 #eefg1 was intentionally not included in the ,tables4 ,the red line was not seen4 ,nos4 #e and #g were only seen once1 and not in the same ,aurora4 ,sidenote3 ,spectrum of ,aurora of ,october #bdth1 #ahgj4 ,the ,aurora of ,october #bdth1 #ahgj1 came at a time when spectroscopes of a direct-vision form were being introduced1 and a number of observations were communicated at the time to #8,nature4' ,sidenote3 ,t4 ,f4's observations4 ,w4 ,b4 ,gibbs's observation4 ,elger's observation4 ,a correspondent1 ,t4 ,f41 writing from ,torquay1 saw1 with a direct-vision spectroscope1 one strong red line near ,c1 one strong pale yellow line near ,d1 one paler near ,f1 and a still paler one beyond1 with a faint continuous spectrum from about ,d to beyond ,f4 ,the ,c line was very conspicuous and the brightest of the whole4 ,it was intermediate in position and colour to the red lines of the lithium and calcium spectra4 ,plainly there were two spectra superposed1 for while the red portions of the ,aurora showed the four lines with a faint continuous spectrum1 the greenish portions showed only one line near ,d on a faint ground4 ,w4 ,b4 ,gibbs saw1 in ,london1 only two bright lines1 one a greenish grey1 situate about the middle of the spectrum1 and the other a red line very much like ,c 7hydrogen74 ,thomas ,g4 ,elger1 at ,bedford1 on the #bdth and #beth1 saw3--7#a7 a broad and well-defined red band near ,c2 7#b7 a bright white band near ,d 7same as ngstrm's ,w4,l4 #eefg71 on #beth visible in every part of the sky2 7#c7 a faint and rather nebulous line1 roughly estimated to be near ,f2 7#d7 a very faint line about halfway between #b and #c4 ,the red band was absent from the spectrum of the white rays of the ,aurora1 but the other lines were seen4 ,sidenote3 ,j4 ,r4 ,capron's observation4 ,with a small ,browning direct-vision spectroscope on the #bdth1 ,i found no continuous spectrum1 but two bright lines1 one in the green 7like that from the nebul1 but more intense1 and considerably flickering71 the other in the red 7like the lithium line1 but rather duskier3 ,plate ,v4 fig4 #f74 ,the latter was only well seen when the display was at its height2 it could1 however1 be faintly traced wherever the rose tint of the ,aurora extended4 ,the line in the green was well seen in all parts of the sky1 but was specially bright in the ,auroral patches of white light4 ,sidenote3 ,mr4 ,browning's observation4 ,alvan ,clarke's1 jun41 observations4 ,mr4 ,browning also saw the red line1 but found comparison difficult4 ,on the evening of the #bdth ,october1 ,mr4 ,alvan ,clarke1 jun41 at ,boston1 used a chemical spectroscope of the ordinary form1 with one prism and a photographed scale illuminated with a lamp4 ,four ,auroral lines were seen at points of his scale numbered #fa1 #fh1 #hj1 and #ih4 ,these were reduced to wave-lengths by ,professor ,pickering1 with the following results3-- ---------------------------------------- ---------------- ,line4 ,reading ,wave- ,assumed ,comments4 ,probable on scale4lengths4 line4 error4 ---------------------------------------- ---------------- #a4 #fa #efij #eegj ,common ,aurora-line4 -#bj #b4 #fh #ecbj #ecaf ,corona line4 #a #c4 #hj #dhej #dhfj ,f1 hydrogen4 - #c #d4 #ih #dcej #dcdj ,g1 hydrogen4 #f ---------------------------------------- ---------------- #fa is evidently wrong1 and was probably a mistake for #fc4 ,sidenote3 ,g4 ,f4 ,barker's observations4 ,george ,f4 ,barker1 observing at ,new ,haven 7,u4,s4,a471 saw1 on ,november #ith1 a crimson and white ,aurora1 which he examined with a single glass-prism spectroscope1 by ,duboscq1 of ,paris4 ,the line positions were obtained by an illuminated millimetre scale4 ,in the white ,aurora were four lines 7the red one being absent72 in the red ,aurora five4 ,the wave-lengths of the ,aurora-lines were run out as follows3-- 7#a47 ,between ,c and ,d1 #fbcj 7,zllner's #fbgj74 7#b47 0 ,d and ,e1 #efbj 7ngstrm's #eegj74 7#c47 0 ,e and b1 #eagj 7,winlock's #ebjj74 7#d47 0 b and ,f1 #ejbj4 7#e47 0 ,f and ,g1 #dhbj 7,alvan ,clarke's1 jun41 #dhej74 ,sidenote3 ,spectrum of ,aurora of ,feb4 #d1 #ahgb4 ,prof4 ,piazzi ,smyth's observations4 ,mr4 ,procter's ,aurora-lines will be found noticed in connexion with the spectrum of oxygen2 and ,lord ,lindsay's lines1 with a comparison scale drawing1 are separately described further on in this ,chapter4 ,the ,aurora of ,february #dth1 #ahgb1 had many observers2 some of whom communicated at the time spectroscopic notes4 ,professor ,piazzi ,smyth minutely describes the display as seen in ,edinburgh1 and saw 8ngstrm's green ,aurora-line perpetually over citron acetylene#ac at ,w4,l4 #eegi1 and the red ,aurora-line between lithium a and sodium a1 but nearer to the latter1 say at ,w4,l4 #fcgj40 ,extremely faint greenish and bluish lines also appeared at ,w4,l4 #ecjj1 #eajj1 and #dijj nearly4 ,sidenote3 ,rev4 ,t4 ,w4 ,webb's observations4 ,the ,rev4 ,t4 ,w4 ,webb1 with a very fine slit1 saw the green ,auroral line even in the light reflected from white paper4 ,with a wider slit he saw a crimson band in the brighter patches of that hue1 and beyond an extent of greenish or bluish light1 which he suspected to be composed of contiguous bands4 ,sidenote3 ,r4 ,j4 ,friswell's observations4 ,r4 ,j4 ,friswell1 coming up the ,channel at #i4dj1 with a ,hoffman's direct-vision spectroscope 7the observing telescope removed71 saw the green line1 a crimson line near ,c1 and faint traces of structure in the blue and violet4 ,sidenote3 ,the ,rev4 ,s4 ,j4 ,perry's observations4 ,the ,rev4 ,s4 ,j4 ,perry observed at ,stonyhurst four lines1 and1 on examining one of the curved streamers1 found the red line even more strongly marked than the green4 ,a magnetic storm was observed to be at its height from #d to #i ,p4,m4 of the same day4 ,sidenote3 ,j4 ,r4 ,capron's observations4 ,with a ,browning #g-prism direct-vision spectroscope ,i saw the green line in all parts of the ,aurora1 attended with a peculiar flickering movement4 ,i did not see the other lines4 ,sidenote3 ,his catalogue of lines up to ,nov4 #i1 #ahgb4 ,in a letter to #8,nature1' dated ,november #ith1 #ahgb1 ,i catalogued the lines observed up to that date as follows3-- #a4 ,a line in the red between ,c and ,d4 ,w4,l41 ngstrm1 #fbgi4 #b4 ,a line 7the principal one of the ,aurora7 in the yellow-green1 between ,d and ,e4 ,w4,l41 ngstrm1 #eefg4 #c4 ,a line in the green1 near ,e 7corona line874 ,w4,l41 ,alvan ,clarke1 jun41 and ,backhouse1 #ecbj4 #d4 ,a faint line in the green1 at or near b4 ,w4,l41 ,barker1 #eagj4 #e4 ,a faint line or band in the green1 between b and ,f4 ,w4,l41 ,barker1 #ejbj 7chromospheric874 #f4 ,a line in the green-blue1 at or near ,f4 ,w4,l41 ,alvan ,clarke1 jun41 #dhej4 #g4 ,a line in the indigo1 at or near ,g4 ,w4,l41 ,alvan ,clarke1 jun41 #dcej4 #h4 ,the continuous spectrum from about ,d to beyond ,f4 ,sidenote3 ,dr4 ,h4,c4 ,vogel's observations of ,auroral lines4 ,spectrum described4 ,dr4 ,h4 ,c4 ,vogel1 formerly of the ,bothkamp ,observatory1 near ,kiel1 and since of the ,astrophysical ,observatory1 ,potsdam1 made several observations of the ,auroral lines1 ,october #beth1 #ahgj4 ,besides the bright line between ,d and ,e1 he found several other fainter lines stretching towards the blue end of the spectrum on a dimly-lighted ground4 ,february #aath1 #ahga1 he observed the same set of lines1 and an average of six readings gave #eegb as the ,w4,l4 of the ngstrm line4 ,february #abth gave #eegf as ,dr4 ,vogel's reading1 and #eefi as ,dr4 ,lohse's4 ,april #ith gave #eefi1 and ,april #adth #eefi4 ,the ,aurora of ,april #ith1 #ahga1 was exceedingly brilliant1 so that micrometer measurements of the lines were taken4 ,the spectrum consisted of one line in the red1 five in the green1 and a somewhat indistinct broad line or band in the blue4 ,the lines are thus described3-- ,sidenote3 ,table of lines4 ,table of ,dr4 ,vogel's lines4 ,aurora1 ,april #ith1 #ahga4 ---------------------------------------- --------------------- ,w4,l4 ,probable ,remarks4 error4 ---------------------------------------- --------------------- #fbig #ad ,very bright stripe4 #eefi #b ,brightest line of the spectrum1 became noticeably fainter at ,on a faintly appearance of the red line4 lighted ground4 #ecij 44 ,extremely faint line2 unreliable observation4 #ebcc #d ,moderately bright4 #eahi #i ,this line was very bright when the red line appeared at the same time2 otherwise equal in brilliancy with the preceding one4 #ejjd #c ,very bright line4 #dfid ,broad band of light1 somewhat less brilliant #dffc #c in the middle2 very faint in those parts of #dfbi the ,aurora in which the red line appeared4 ---------------------------------------- --------------------- ,a translation of ,dr4 ,vogel's interesting paper will be found printed in extenso in ,appendix ,e1 and his lithographed drawings of the spectrum in the green and red portions of the ,aurora respectively on ,plate ,,vi4 figs4 #b and #c4 ,the observations of ,april #ith by ,dr4 ,vogel are probably1 up to the present time1 the most exact of any one ,aurora1 and ,i have therefore in most cases used them for comparison4 ,sidenote3 ,mr4 ,backhouse's catalogue of lines4 ,mr4 ,backhouse1 in a letter to #8,nature1' commenting upon my catalogue of lines1 gave the following as the latest determinations from his own observations3-- ,no4 #a4 ,wave-length #fjfj #b4 0 #effj #c4 0 #eafe #d4 0 #ejae #f4 0 #dfbe #g4 0 #dcje 7#fjfj must be a mistake for #fbfj1 and #effj for #eefj4--;,j4 ,r4 ,c47 ,mr4 ,backhouse never saw a line at #ecbj again4 ,he found the continuous spectrum to reach from ,no4 #b to ,no4 #g1 being brightest from a little beyond ,no4 #b to ,no4 #f4 ,this part of the spectrum did not give him so much the idea of a true 8continuous spectrum0 as of a series of bright bands too close to be distinguished4 ,sidenote3 ,subsequent full catalogue of ,auroral lines4 ,i have subsequently1 in another section of this ,chapter1 added a full catalogue of the ,auroral lines1 prepared by myself from the foregoing and other sources and observations2 and ,i also append to it a ,plate ,plate ,,xii41 in which these lines are positioned and the wave-lengths and names of observers are given4 ,the numbers of the lines on the ,plate correspond with those in the catalogue4 ,the solar spectrum and the spectrum of the blue base of a candle-flame are added for purposes of comparison4 ,the telluric bands in the solar spectrum are shown more distinctly than they actually appear1 and do not profess to give details4 ,flickering of the ,green ,line4 ,sidenote3 ,flickering of the green line4 ,herschel's observation4 ,j4 ,r4 ,capron's observation4 ,a4 ,s4 ,herschel noticed this1 ,april #ith 7#ahga874 ,he says3--8,a remarkable circumstance connected with the appearance of the single line observed on this occasion was the flickering and frequent changes with which it rose and fell in brightness2 apparently even more rapidly than the swiftly travelling waves1 or pulsations of light1 that repeatedly passed over the streamers1 near the northern horizon1 towards which the spectroscope was directed40 ,in the spectrum of the ,aurora of #bjth ,october1 #ahgj1 ,i saw and noted the green line as 8considerably flickering20 and in the ,aurora of #dth ,february1 #ahgb1 ,i again saw and noted 8the peculiar flickering0 ,i had remarked in #ahgj4 ,i have not seen the peculiarity noted by other observers4 ,mr4 ,backhouse's graphical ,spectra of four ,auror4 ,sidenote3 ,mr4 ,backhouse's graphical spectra of ,auror4 ,mr4 ,backhouse has been good enough to supply me with some details of four several ,auror seen by him at ,sunderland1 accompanied by drawings1 showing in a graphical way the spectrum of each display as seen with a spectroscope with rather a wide slit and as drawn by eye4 ,i have reduced the four drawings to the same scale1 and in this way they are extremely interesting for comparison 7,plate ,v4 fig4 #d74 ,the line on the left in each spectrum is ngstrm's bright ,auroral line1 and is supposed to be considerably prolonged4 ,the height of the lines denotes intensity4 ,sidenote3 ,april #ah1 #ahgc4 ,april #ahth1 #ahgc1 was a bright ,aurora4 ,no4 #c is a faint band1 which ,mr4 ,backhouse had not perceived before4 ,no4 #e had not been visible lately1 and ,mr4 ,backhouse thought it must belong to ,auror of a different type from those which had appeared latterly4 ,sidenote3 ,feb4 #d1 #ahgd4 ,february #dth1 #ahgd4 ,in the spectrum of this ,aurora ,mr4 ,backhouse saw seven lines1 all that he had ever seen4 7,the red line1 not shown in the diagram1 makes the seventh47 ,the spectrum is represented as seen between #f4ej and #g4e ,p4,m4 ,mr4 ,backhouse had only once before seen ,no4 #d1 and it became quite invisible between #g4de and #g4ee1 though the other lines were as bright as before and the red line had appeared4 ,sidenote3 ,oct4 #c1 #ahgd4 ,october #crd1 #ahgd4 ,this spectrum was examined1 and diagram made between #aj and #aj4be ,p4,m4 ,five lines only are indicated4 ,it is mainly distinguished from the two preceding spectra by the brightness of the continuous spectrum on which the lines #b1 #c1 and #d lie1 and by the weakness of ,no4 #e4 ,sidenote3 ,oct4 #d1 #ahgd4 ,october #dth1 #ahgd4 ,taken between #aa4aj and #aa4bj ,p4,m42 distinguished1 like the last1 by a considerable amount of continuous spectrum and by a faint line 7,no4 #c71 not seen in the last spectrum1 while ,no4 #c in the last is missing in this spectrum4 ,sidenote3 ,mr4 ,backhouse's remarks as to comparative frequency of some of the ,auroral lines4 ,mr4 ,backhouse1 as to both these last spectra1 remarks that the lines were very variable in intensity1 and sometimes some were visible and sometimes others4 ,they varied also in relative brightness in different parts of the sky at the same time4 ,mr4 ,backhouse1 in a communication to #8,nature1' referring to a statement of ,mr4 ,procter's1 that the bands of the ,auroral spectrum are seldom visible1 except the bright line at #eegj1 says that he always found two bands1 8doubtless ,winlock's #dfdj and #dcaj10 to be invariably visible when the ,aurora was bright enough to show them4 ,of thirty-four ,auror examined by ,mr4 ,backhouse1 fourteen showed the lines #dfdj and #dcaj1 and three others at least one of these1 while eight showed the red line4 7ngstrm only once saw this line47 ,in five ,auror1 all more or less red1 he saw a faint band1 the wave-length of which he placed at #ejjj or #eajj4 ,he never saw the line #ecbj 7also ,winlock's coronal line71 unless it were once1 probably from want of instrumental power4 ,with regard to these observations1 ,i may say that with a ,browning's miniature spectroscope ,i saw only two lines 7the red and the green7 in the grand display of the #bdth ,october1 #ahgj2 and with an instrument of larger aperture the green line only on the #dth ,february1 #ahgb2 while ,i saw the green line and three others towards the violet with the same instrument during the ,aurora of #dth ,february1 #ahgd4 7,see description of this ,aurora1 ant p4 #ba1 and drawing of spectrum1 ,plate ,,vi4 fig4 #a a47 ,lord ,lindsay's ,aurora-,spectrum1 #bast ,october1 #ahgj4 ,sidenote3 ,lord ,lindsay's ,aurora of #bast ,oct41 #ahgj4 ,lord ,lindsay observed a fine ,aurora at the ,observatory at ,dun ,echt on the night of the #bast ,october1 #ahgj4 ,it commenced about #i4cj1 reached its maximum about #aa1 and faded away suddenly about #aa4cj ,p4,m4 ,sidenote3 ,spectrum described4 ,a spectrum obtained in the north-west gave five bright lines with a ,browning's direct-vision spectroscope--two strong1 one medium1 two very faint4 ,a tallow candle was used to obtain a comparison spectrum of sodium and carburetted hydrogen4 ,a drawing of the spectrum obtained is given on ,plate ,,xi4 fig4 #b4 ,no4 #a is a sharp well-formed line visible with a narrow slit4 ,no4 #b1 a line very slightly more refrangible than ,f4 ,the side towards ,d is sharp and well defined1 while on the other side it is nebulous4 ,no4 #c1 slightly less refrangible than ,g1 is a broad ill-defined band1 seen only with a wide slit4 ,no4 #d1 a line near ,e1 woolly at the edges1 but rather sharp in the centre4 ,this1 says ,lord ,lindsay1 should be at or near the position of the line #adgd of the solar corona4 ,no4 #e1 a faint band1 coincident with b1 extending equally on both sides of it4 ,the lines are numbered in order of intensity4 ,it is questionable1 from observations with instruments carrying a scale1 whether the line-positions are exact2 but the description of their characters is valuable4 ,sidenote3 ,candle-spectrum4 ,as a candle blue-base spectrum is at times a ready and handy mode of reference in ,auroral observations 7as was found in this instance71 ,i have1 on ,plate ,,xi4 fig4 #e1 given a representation of it as seen with my ,auroral spectroscope4 ,dr4 ,watts's corresponding carbon-spectrum is added on the lower margin4 ,the numbers on the upper margin refer to my scale4 ,illustration3 ,plate ,,xi4 ,spectrum of the ,aurora ,australis4 ,sidenote3 ,captain ,maclear's spectra of ,aurora ,australis4 ,captain ,maclear1 on examining the streamer seen by him ,feb4 #ith1 #ahgd 7ant1 p4 #bg71 with the spectroscope1 found three prominent lines in the yellow-green1 green1 and blue or purple1 but not the red line4 ,in the ,aurora of ,march #crd1 #ahgd 7p4 #bg71 he could trace four lines1 three bright and one rather faint4 ,they must have been exceedingly bright to show so plainly in full-moon light4 ,sidenote3 ,instrument used1 and mode of registering lines4 ,the spectroscope used was a ,grubb single-prism with long collimator4 ,a needle-point in the eyepiece marked the position of the lines2 and a corresponding needle-point1 carried on a frame by a screw movement in concord with the point of the eyepiece1 scratched the lines on a plate of blackened glass4 ,two plates were taken4 ,on the first were scratched the auroral lines and the solar lines as seen in the moonlight2 on the second plate were scratched the auroral lines1 the ,solar lines from the moon1 and the carbon lines in a spirit-lamp4 ,sidenote3 ,copies of the two spectra obtained4 ,discrepancy in the spectra4 ,remarks on the spectra4 ,the next morning the solar lines were verified in sunlight4 ,i subjoin 7,plate ,,xi4 fig4 #c7 copies of the two spectra as printed in #8,nature1' the auroral lines being marked ,a1 the solar lines by the usual designating letters1 and the carbon by ,car4 ,to these spectra ,i have added for comparison ,dr4 ,vogel's spectrum of the ,aurora ,borealis4 ,captain ,maclear could not account for the different positions of the auroral lines in the two plates2 for the prism1 as far as he was aware1 was not moved during the observations4 ,as the solar lines are indicated in the same place in both spectra1 the case would seem one of actual change of position of the auroral lines during observation4 ,a comparison of the two spectra gives the impression that the lower one is the same as the upper1 except that the dispersion is greater1 the lines remaining relatively in position4 ,one does not1 however1 see how the dispersion could have so varied in a single-prism instrument1 and the position of the solar lines is adverse to such an explanation4 ,there is a suspicion that ,auror are not always identical in position of some of the lines2 but the line in the green 7considerably out of place in the lower ,australis spectrum7 has always1 within small limits1 the same position4 ,it will be noticed how much further the ,australis spectrum runs into the violet than ,vogel's ,borealis1 the latter having no lines much beyond ,f4 ,the faint line 7,no4 #b7 mentioned by ,captain ,maclear possibly corresponds with ,dr4 ,vogel's band4 ,the absence of the four lines of the ,aurora ,borealis in the green part of the spectrum of the ,australis is peculiar2 and in this respect1 too1 the two ,australis spectra agree4 ,sidenote3 ,comparison of the lines4 ,the nearest approaches to ,captain ,maclear's lines 7of the upper spectrum7 which ,i can find are3-- ,line ,corresponding line4 #a4 #eefg1 ngstrm4 #b4 7,the faint line47 ,vogel's band1 #dfid-dfbi4 #c4 ,i find no approximately corresponding line4 #d4 #dcej1 ,alvan ,clarke4 ,but the comparisons are not by any means close4 ,further observations of the ,australis spectrum are very desirable4 ,prof4 ,piazzi ,smyth's ,aurora-,spectra4 ,sidenote3 ,prof4 ,piazzi ,smyth's chemical and auroral spectra4 ,prof4 ,piazzi ,smyth1 in volume xiv4 of the #8,edinburgh ,astronomical ,observations1' #ahgj-gg1 has compared simultaneously the ,aurora-spectrum with the sets of bright lines seen in the blue base of flame--the lines of potassium1 lithium1 sodium1 thallium1 and indium being also introduced for comparison4 ,the spectra are drawn as seen under small dispersion1 and will prove most useful in cases where an ,aurora is not bright enough to admit of the lines being measured by micrometer1 and the eye and comparison spectrum are obliged to be resorted to4 ,illustration3 ,plate ,,xii4 ,author's ,catalogue of the ,auroral ,lines4 7,see ,plate ,,xii47 #a4 ,w4,l4 #fbig1 ,vogel4 ,very bright stripe2 first noticed by ,zllner4 ,seen only in red ,auror2 stands out on a dark ground1 without other lines near it4 ,character of line sharp and well defined2 varies in colour from dusky red to bright crimson4 ,intensity1 ,herschel1 #j to #d or #h4 ,according to same1 position coincident with atmospheric absorption-group 8a0 in solar spectrum 7between ,c and ,d74 ,i confirm this position according to my scale of solar lines1 and a drawing of the coincidence 7in which1 and in ,plate ,,xii41 the absorption-lines are drawn too dark7 is given on ,plate ,,xiii4 fig4 #b4 ,herschel says this line coincides with a red band in the negative glow-discharge1 but its identity is doubtful4 ,its isolation and want of adjacent lines seem to separate it from the air-spectrum and gas-spectra in general4 ,at the appearance of this line1 #eefi 7,no4 #b7 becomes noticeably fainter4 ,when this line is bright1 #eahi 7,no4 #e7 is bright also 7,vogel74 ,if we propose to assign to this line1 as well as to #eefi1 a phosphorescent origin1 it would be strongly confirmatory of such a theory 7in connexion with the phosphoretted-hydrogen spectrum7 to find it brighten at low temperatures4 ,note4--,sir ,john ,franklin says1 in his #8,polar ,expeditions1' that a low state of temperature is favourable for the production of brilliant coruscations4 ,it was seldom witnessed that the ,auror were much agitated1 or that the prismatic tints were very apparent1 when the temperature was above zero4 #b4 ,line in the yellow-green4 ,brightest of all lines in the ,aurora-spectrum4 ,w4,l4 #eefg1 ngstrm2 #eefi1 ,vogel4 ,intensity #be1 ,herschel4 ,to me more pale green than yellow1 sometimes flickering and changing in brightness 7,herschel and ,capron74 ,seen in all ,auror usually sharp and bright1 but ,procter has once recorded it nebulous4 ,its character as to width1 sharpness1 and intensity1 if carefully observed1 might indicate height and structure of ,aurora4 ,becomes noticeably fainter at appearance of red line 7,vogel74 ,found by me to correspond in position with a faint atmospheric absorption-band 7see ,plate ,,xiii4 fig4 #b74 ,according to ngstrm and ,herschel1 arising from a phosphorescent and fluorescent light1 emitted when air is subjected to the action of electrical discharge4 #c4 ,line in green near last4 ,w4,l4 #ecij4 ,an extremely faint and unreliable observation 7,vogel74 ,seen only by him1 unless ,alvan ,clarke's #ecbj 7coronal87 be the same4 #d4 ,line in green-blue4 ,w4,l4 #ebcc1 moderately bright 7,vogel72 #ebjj1 ,winlock4 ,intensity1 #b or #j8 to #f1 ,herschel4 ,coincides with line in the negative glow according to same4 ,frequently observed4 #e4 ,line in green-blue4 ,w4,l4 #eahi4 ,this line is very bright when the red line appears at the same time2 otherwise equal in brilliancy with ,no4 #c 7,vogel72 ,winlock1 #ebjj4 ,not so frequently observed as ,no4 #c4 ,barker gives a band extending from #eccj to #ebjj4 ,intensity of #eahi1 #j to #h1 ,herschel1 who considers it coincident with a constant strong line in the spark-discharge4 #f4 ,line in blue4 ,w4,l4 #ejjd4 ,very bright line1 ,vogel2 #ejbj1 ,barker 7coronal874 ,intensity #b or #j8 to #h1 ,herschel4 ,coincides with line of nitrogen in the nebul according to same4 ,barker gives a band extending from #ejej to #diij4 #g4 ,line in the blue not found by ,vogel in ,aurora1 ,april #ith1 #ahga4 ,w4,l4 #dhej1 ,alvan ,clarke2 #dhbj1 ,backhouse and ,barker4 ,intensity1 ,herschel1 of #dhbj-dhgj1 #j to #d8 ,herschel suspects this and ,no4 #d to be seen only in ,auroral streamers of low elevation4 ,barker gives a band extending from #dicj to #dhej4 #h4 #dfid1 #dffc1 #dfbi4 ,broad band of light1 somewhat less bright in the middle2 very faint in those parts of the ,aurora in which the red line appears 7,vogel74 ,intensity #c-f 7,herschel74 ,a double band1 consisting of two lines1 the first rather more frequently noted than the second in ,auroral spectra1 agrees well in position with the principal band in the negative glow-spectrum 7same74 ,barker gives a band extending from #dgdj to #dfgj2 ,backhouse and ,winlock give a line at #dfdj1 situate within the same4 #i4 ,there seems a good deal of confusion about a fairly bright line 7intensity #j-f1 ,herschel7 seen in most ,auror 7not1 however1 by ,vogel1 ,april #ith1 #ahga71 and situate somewhere near ,g in the solar spectrum4 ,alvan ,clarke places it at #dcej1 on the less refrangible side of ,g2 ,backhouse and ,barker at or very near to ,g2 while ,lemstrm and others position it on the more refrangible side of ,g4 ,accurate observations1 for which a quartz spectroscope might be useful1 are much wanted4 ,herschel makes this line1 at #dbhe1 correspond with a strong band in the violet in the negative glow-spectrum4 ,herschel also refers to an apparently additional line near the hydrogen-line1 or between ,g and ,h1 in the solar spectrum1 as mentioned once by ,lemstrm at ,helsingfors4 ,i am not aware of any other observation of this line1 which must be considerably beyond that at or near ,g1 and would probably be difficult to detect1 except in instruments specially adapted for examination of the violet end of the spectrum4 ,theories in relation to the ,aurora and its ,spectrum4 ,sidenote3 ,lemstrm's4 ,lemstrm 7#a73--,that the ,polar light is caused by an electric current passing from the upper rarefied layers of the air to the earth1 producing light-phenomena that do not arise in the denser layers of the air4 7#b7 ,that there are nine rays 7lines or bands7 in the ,aurora-spectrum1 which in all probability agree with lines which belong to the gases of the air4 7#c7 ,that the ,aurora-spectrum can be referred to three distinct types1 which depend on the character of the discharge4 ,sidenote3 ,vogel's4 ,dr4 ,vogel3--7#a7 ,that the ,auror are electric discharges in rarefied-air strata of very considerable thickness4 7#b7 ,that the ,aurora-spectrum is a modification of the air-spectrum1 involving the question of alteration of the spectrum by conditions of temperature and pressure4 ,sidenote3 ngstrm's4 ngstrm3--7#a7 seems to adopt the hypothesis that the ,aurora has its final cause in electrical discharges in the upper strata of the atmosphere1 and that these1 whether disruptional or continuous1 take place sometimes on the outer boundary of the atmosphere1 and sometimes near the surface of the earth4 7#b7 ,that the ,aurora has two different spectra4 7#c7 ,that the green line is due to fluorescence or phosphorescence1 and that there is no need to resort to ,dr4 ,vogel's variability of gas-spectra according to circumstances of pressure and temperature4 7#d7 ,that an agreement exists between the lines of the ,aurora 7except the red and green before mentioned7 and the lines or bands of the violet light which proceed from the negative pole in dry air4 ,sidenote3 ,zllner's remark as to temperature of ,aurora and character of spectrum4 ,zllner has pointed out that the temperature of the incandescent gas of the ,aurora must be exceedingly low1 comparatively1 and concludes that the spectrum does not correspond with any known spectrum of the atmospheric gases--only because1 though a spectrum of our atmosphere1 it is one of another order1 and one which we cannot produce artificially4 ,,chapter ,,xi4 ,,the ,,comparison ,,of ,,some ,,tube ,,and ,,other ,,spectra ,,with ,,the ,,spectrum ,,of ,,the ,,aurora4 ,in part from an ,article in the #8,philosophical ,magazine' for ,april #ahge4 ,sidenote3 ,testing ngstrm's ,aurora theory4 ,battery and spectroscope described4 ,vogel's spectrum selected for comparison4 ,in order to test ,professor ngstrm's theory of the ,aurora1 referred to in the last ,chapter1 in an experimental way1 ,i examined1 in the winter of #ahgd1 some tube and other spectra1 not only for line-positions1 but also for general resemblance to an ,aurora-spectrum4 ,it did not seem desirable to use powerful currents4 ,a -inch-spark coil1 worked by a quart bichromate-cell1 was found sufficient to illuminate the tubes steadily4 ,the spectroscope used was one made for me by ,mr4 ,browning specifically for ,auroral purposes1 and of the direct-vision form1 being the same instrument as is described ant1 p4 #ia1 and figured in ,plate ,x4 fig4 #a4 ,the micrometer was the diaphragm one1 also before described and figured on same ,plate1 figs4 #b1 #c1 and #d4 ,i selected ,dr4 ,vogel's spectrum for comparison1 it being1 so far as ,i am aware1 the most accurately mapped1 with regard to wave-length1 at one observation1 of any ,auroral spectrum4 ,it seemed an unsafe plan to attempt to obtain an average ,aurora by comparison of different observations made at various times by different observers with all sorts of instruments--the difficulty1 too1 being increased by the suspicion that the spectrum itself at times varies in number and position as well as intensity of its lines4 ,sidenote3 ,central part only of spectrum mapped4 ,in most cases the central part of the spectrum only 7corresponding to the central lines of the ,aurora7 was mapped1 the red line in the ,aurora not being found to correspond with any prominent line in the gas-spectra examined1 and the ,auroral line near solar ,g being so indefinitely fixed as to render comparison almost valueless4 7,see ,plate ,,xiii4 fig4 #a47 ,dr4 ,vogel's spectrum does not comprise the line near ,g2 but ,i have added this 7in an approximate place only7 in order to complete the set of lines4 ,for drawing of ,dr4 ,vogel's spectrum1 with its scales attached1 see ,plate ,,xiii4 ,illustration3 ,plate ,,xiii4 ,hydrogen-tube4 ,sidenote3 ,hydrogen-tube4 ,colour of glow varied with intensity of current4 ,this tube was one of ,geissler's and of rather small calibre4 ,on illumination the wide ends were easily lighted with a silver-grey glow1 having a considerable amount of stratification4 ,the capillary part glowed brilliantly with silver-white1 bright green1 and crimson light1 according to the intensity of the current4 ,with the commutator slowly working1 white running into green and bright green were the main features of the thread of light2 on the current passing more rapidly1 the capillary thread became of an intense crimson1 at the same time apparently increasing in diameter 7an effect probably due to irradiation74 ,sidenote3 ,spectrum described4 ,the spectrum was very brilliant1 consisting of the three bright lines usually distinguished as ,h1 ,h1 and ,h1 and a number of shaded bands and fainter lines between these1 with a bright continuous spectrum as a background to the whole4 ,sidenote3 ,lines 1 1 and varied in intensity with colour as seen by eye4 ,fainter lines or bands described4 ,the lines ,h1 ,h1 and ,h were found to vary in intensity with the current1 and in accordance with the colour of the light as seen by the eye--a fact1 as ,i think1 not without bearing on the question of the ,aurora1 the varying tints of which are so well known4 ,the fainter lines or bands were mostly stripes of pretty equal intensity throughout1 and all about the width of the ,h line4 ,i did not trace any marked degrading on either side of the lines1 though the edges were not uniformly so sharp as ,h and ,h4 ,some of the lines were found coincident in position with lines of the air-spectrum4 ,sidenote3 ,purity of subsidiary lines questioned4 ,it is a question whether these subsidiary lines are hydrogen1 or are due to some tube impurity4 ,a photograph ,i have taken of this tube-spectrum shows #ag lines in the part of the spectrum between ,f and ,h1 some of which are repeated in the hydrocarbon-tube spectra4 ,sidenote3 ,coincidence of lines with ,aurora-spectrum4 ,no principal line1 and one subsidiary line only1 actually coincide with the ,aurora-spectrum1 this last being that to which ,dr4 ,vogel assigns an identical wave-length1 viz4 #eahi4 ,other of the subsidiary lines1 however1 fall somewhat near the ,aurora-lines #eefi1 #ecij1 #ebcc1 and #ejjd1 two faint lines also falling within the band #dfid to #dfbi4 ,sidenote3 ,comparison of the lines4 ,the lines 7adopting ,dr4 ,vogel's wave-lengths for the ,h lines7 were1 when compared1 as under3-- #dfid ,aurora #eefi #ecij #ebcc #eahi #ejjd to band4 #dfbi ,hydrogen #eeee #edbb 444 #eahi #ejjh #dfcb ,i remarked that a line 7#eeif7 described by ,dr4 ,vogel as 8very bright0 in his ,h spectrum does not appear in my tube1 though in most other respects our ,h spectra agree4 ,sidenote3 ,effect of distance on the spectrum4 ,i thought this tube afforded a good opportunity for testing the effect of distance upon the spectrum4 ,the slit was made rather fine4 ,at #f inches distance from it the line in the blue-green 7,f solar7 was very bright4 ,the lines marked 1 1 1 1 and also survived1 but were faint4 ,at #ab inches from the slit and were alone seen1 and at #bd inches stood by itself upon a dark ground4 ,i also noticed that the red and yellow parts of the spectrum first lost their light on the tube being withdrawn from the slit2 and this appeared to account for disappearing while survived4 ,for drawing of the hydrogen-tube spectrum see ,plate ,,xiv4 spectrum #a4 ,the question of effect of distance upon the spectroscopic appearance of a glowing light1 as tested for this and other tubes1 seems an important one4 ,it may possibly account for the generally faint aspect of the lines in the more refrangible part of the ,auroral spectrum4 ,illustration3 ,plate ,,xiv4 ,carbon- and ,oxygen-tubes4 ,sidenote3 ,carbon- and oxygen-tubes4 ,tubes described4 ,carbon-tubes lighted up4 ,spectra of the carbon-tubes described4 ,the following tube-observations were taken together1 because my friend ,mr4 ,henry ,r4 ,procter 7to whom ,i am indebted for many profitable hints and suggestions in ,auroral work7 was disposed to regard the spectra found in the carbon-tubes and in those marked 8,o0 as identical1 suggesting that pure ,o1 with the ordinary non-intensified discharge1 gives only a continuous spectrum2 and that the ,o tubes are in fact generally lighted up by a carbon-spectrum1 as the result of impurity from accidental causes4 ,the tubes examined for the purpose of comparison were as follows3--,a coal-gas tube1 a tube marked 8,c4,a410 three ,o tubes 7two of1 ,i believe1 ,london make1 and the third from ,geissler71 and an ,,oh tube1 also from ,geissler4 ,the carbon-tubes were both brilliantly and steadily lighted by the current4 ,the ,c4,a4 tube glowed with a peculiar silvery-grey green light in the capillary part1 and with a grey glow1 considerably stratified1 in the bulbs4 ,the coal-gas tube illumination was whiter and still more brilliant than the ,c4,a41 and with even finer stratification in the bulbs4 ,the spectra of both tubes were conspicuous for the same three well-known principal bright lines or bands in the yellow1 green1 and blue 7with one fainter in the violet71 all shading off towards the violet1 and in both cases with fainter intervening bands or lines4 ,these last bands or lines only partially coincided when the two tubes were compared4 ,the spectra in both cases were rich and glowing1 with a certain amount of continuous spectrum between the lines2 and the three principal bands or lines showed well and distinctly their respective place-colours4 ,sidenote3 ,tubes tested for distance4 ,tubes tested for distance4--,in the case of the ,c4,a4 tube1 at #ah inches from the slit the continuous spectrum and fainter lines disappeared1 while the four principal lines still shone out1 that in the green being the strongest4 ,at #bd inches the same lines were still visible1 though somewhat faintly4 ,in the case of the coal-gas tube1 at #bd inches the whole spectrum was quite brilliant1 the four principal lines being very bright and even preserving their distinctive colours4 ,the ,h line1 near the line or band in the blue1 was also plainly seen4 ,sidenote3 ,o tubes lighted up4 ,the ,o tubes1 when treated by the same current as the carbon-tubes1 were found to be all three identical in general features4 ,the discharge lighted up each of the tubes feebly and somewhat intermittently4 ,grey in the bulbs and a faint but decidedly pinkish white in the capillary part were the distinguishing light colours2 while nothing could be more marked than the difference in brilliancy between these and the preceding carbon-tubes4 ,sidenote3 ,,oh tubes lighted up4 ,o tubes spectra described4 ,the ,,oh tube presented very much the same character2 but the discharge occasionally varied from a pinkish white to a yellow colour1 somewhat like that which artists call brown-pink1 and reminding one of the 8golden rays0 in certain ,auror4 ,these ,o spectra presented1 in common with the carbon-tubes1 three principal bright lines or bands in the yellow1 green1 and blue1 with a fainter one in the violet1 all shading off towards the violet4 ,the bands1 however1 showed but very little trace of local colour1 and the whole spectrum had a faint and washed-out look1 very different from the carbon-spectra4 7,i certainly1 by a little management1 subsequently succeeded in getting the same look to the ,c4,a4 spectrum2 but it was only by removing the tube to some distance from the slit1 and thus depriving the spectrum of very much of its brightness47 ,the hydrogen line 7solar ,f7 was bright1 more so than any of the ,o lines4 ,the intensity of the three principal lines seemed to me to run in the following order3-- ,yellow4 ,green4 ,blue4 ,coal-gas ,oxygen ,between the lines and in the ,geissler ,o tube ,i found a rather bright line1 which ,i shall have occasion to refer to hereafter4 ,at #ab inches distance from the slit the ,o spectrum lost nearly all its light2 the ,h line1 and the three lines 1 1 and 1 alone faintly remaining1 being decidedly the brightest4 ,at #bd inches no spectrum at all was to be seen4 ,sidenote3 ,comparison of spectra of coal-gas and ,o tubes4 ,i carefully compared together the three principal lines of the two spectra of coal-gas and ,o by means of3-- #ast1 the photographed micrometer before described2 #bnd1 a comparison-prism on the slit plate2 #crd1 a piece of very fine brass foil cut as a pointer and fixed in the focus of a positive eyepiece4 ,the lines or bands in both tubes were found to be slightly nebulous towards the less-refrangible end 7where they were measured71 and the ,o tube was not bright under a moderately high power 7positive eyepiece74 ,subject to these remarks1 the three principal lines in both tubes were found to correspond in position within the limits of my instrument4 ,the spectra did not1 however1 ,i am bound to say1 look alike4 ,sidenote3 ,dr4 ,vogel's ,o spectrum reduced and compared4 ,puzzled by these observations1 it then occurred to me to reduce ,dr4 ,vogel's spectrum of ,o1 given in his memoir1 to the same scale with my own4 ,this ,i did independently1 and ,i then compared the result with my own spectrum as mapped out4 ,from the comparison1 ,i judge that if my ,o tubes1 one and all1 showed a carbon-spectrum1 the learned ,doctor's tube must have been subject to a similar infirmity1 as the tubes all agreed in main features4 ,there is1 however1 one point to which ,i desire to draw attention1 which is this1 that common to both the ,doctor's and my own ,geissler spectrum ,i found the before-mentioned rather bright line between and 4 ,this line ,i found no equivalent for in either of the carbon-tubes4 ,for spectra of coal-gas and oxygen-tubes1 see ,plate ,,xiv4 spectra #b1 #c1 #d4 ,sidenote3 ,tube- and flame-spectra of carbon do not correspond4 ,in comparing the spectra1 it should be remembered that the tube- and flame-spectra of carbon do not correspond4 ,compare1 for instance1 the spectrum of coal-gas or ,,co in tube1 and the well-known lines or bands in the blue base of a candle-flame4 ,the sharper edge of the yellow line or band of the carbon-tubes will be found about midway between the two bright yellow candle-lines or bands4 ,the first of the very beautiful group of lines or bands in the green in the candle-flame falls considerably behind the sharper edge of the green line or band in the tube1 while the third bright band in the tube1 alone of the three1 corresponds with a very faint band in the candle-flame4 ,a line or band in the violet in the tube-spectrum finds no equivalent in the candle-spectrum4 ,for comparison of the carbon-tube and flame spectra 7the principal lines of the tube being alone shown71 see ,plate ,,xvi4 spectra #f #g4 ,sidenote3 ,prof4 ,piazzi ,smyth's measurements of the components of the citron-band in a coal-gas flame4 ,note4--,prof4 ,piazzi ,smyth has been good enough1 at my instance1 to measure the components of the citron band of the carbo-hydrogen spectrum 7near ngstrm's ,aurora-line71 as seen in a coal-gas blowpipe-flame urged with common air4 ,the spectroscope used had prisms giving #bb of dispersion between ,a and ,h1 and the observing telescope magnified #aj times4 ,the following is a table of the results communicated to me by the ,professor3-- ,reading of ,intensity4 ,micrometer4 ,reference line1 lithium #d #afee 0 sodium1 #a #aj #ahde 0 0 #b #aj #ahea ,citron band4 ,carbo-hydrogen4 ,line #a1 exquisitely clear #f #babh #b1 0 #e #bahh #c1 0 #c #bbdd #d1 faint but clear #b #bbie #e1 faint #a #bcch #f1 faint and hazy #a #bcgj #g1 doubtful 8 #bcib ,reference line1 thallium #aj #bejh ,sidenote3 ,comparison of ,dr4 ,vogel's ,o lines and ,dr4 ,watts's carbon-lines4 ,from ,dr4 ,watts's #8,index of ,spectra' ,i have extracted the three principal carbon-tube bands or lines2 and they compare with ,dr4 ,vogel's oxygen-tube as under3-- ,yellow4 ,green4 ,blue4 ,dr4 ,vogel's oxygen-lines #efjc #eahi #dhbi ,dr4 ,watts's carbon-tube bands or lines #efjb #eaie #dhcd ,now these wave-length differences are so small that they raise a presumption of the possibility of the spectra being identical4 ,on the other hand1 assuming the spectra are not identical1 the comparison tells the other way1 viz4 that the differences are so minute as to escape detection in instruments of moderate dispersion4 ,with my own instrument ,i found the ,o spectrum too faint to increase the dispersive power with advantage4 ,considering the extremely different character of the two discharges1 the identity of all the ,o tubes1 and the presence of the line found between and in the ,o spectrum1 ,i think the two spectra are independent1 though ,i admit there is room for doubt4 ,sidenote3 ,o and ,,co spectra photographed4 ,note4--,since this examination ,i have photographed both spectra side by side 7see #8,photographed ,spectra1' ,plate ,,xxxi41 text1 pp4 #fi1 #gj74 ,the pictures include1 of course1 only the blue and violet parts of the spectrum2 but they are widely different in aspect1 and show that1 photographically at least1 in this part of the spectrum there is a complete want of identity4 ,subsequent investigations1 however1 by ,schuster and others 7detailed later in this ,chapter71 go to establish that the principal lines shown in mine and ,dr4 ,vogel's tubes were due to 7probably hydrocarbon7 impurity4 ,the exception is the single line common to mine and ,dr4 ,vogel's tubes1 but absent from the coal-gas spectrum4 ,this line proves to be oxygen4 ,compare oxygen-tube spectra 7,plate ,,xiv4 spectra #c and #d7 with ,schuster's oxygen-tube spectrum 7,plate ,,xviii4 fig4 #ae74 ,the line in question is found identical in the three tubes4 ,the tube ,,oh was found to give the principal lines of the ,o and ,h spectra combined on a faint continuous spectrum4 ,geissler ,mercury-tube 7,plate ,x4 fig4 #g7 and ,barometer ,mercurial vacuum4 ,sidenote3 ,mercury- and barometer-tubes examined4 ,mercury-tube described4 ,barometer-tube4 ,i next examined two vacuum-tubes of an entirely different character4 ,the one was a tube from ,geissler of stout glass1 some fifteen inches long1 without electrodes1 and an inch across4 ,within this tube was a second of uranium glass1 with bulbs blown in it4 ,in contact with both tubes a quantity of fluid mercury ran loose 7,plate ,x4 fig4 #g74 ,upon shaking this tube with the hand brilliant flashes of blue-white light1 like summer lightning1 flashed out4 ,these were discernible 7though faintly7 even in daylight4 ,the fine terminal wires of the coil being wrapped round each end of this tube1 when the current passed1 a bright and white induced discharge1 with a considerable amount of stratification1 was seen in the tube4 ,the other tube was that of a mercurial siphon-barometer4 ,this being placed in a stand1 one terminal wire was placed in the mercury in the short leg of the siphon1 while the other terminal was made into a little coil and placed on the upper closed extremity of the barometer-tube4 ,on passing the current1 the entire short space above the mercury was filled with a grey-white light1 not stratified1 but showing a conspicuous bright ring just above the level of the mercury4 ,sidenote3 ,spectrum of both these tubes described4 ,both these tubes1 when examined with the spectroscope1 showed four bright rather uniform bands 7the central one being the brightest71 which ,i assigned to the carbon-spectra 7see ,plate ,,xiv4 spectra #e and #f74 ,the ,geissler tube was probably filled designedly with coal-gas4 ,in the case of the barometer-tube the spectrum must be assumed to be the result of some carbon impurity4 ,no lines of mercury could be detected in either case4 ,an effort was made to examine the light of the ,geissler mercury-tube as excited by motion only1 but the spectrum could not be kept in the field2 the four lines were1 however1 seen to flash out as the light passed before the slit4 ,illustration3 ,plate ,,xv4 ,air-tubes4 ,sidenote3 ,air-tube illuminated4 ,the first tube ,i examined was an ordinary ,geissler tube charged with rarefied air4 ,the bulbs1 on passing the discharge1 were filled with the well-known rose-tinged light like to the ,aurora-streams4 ,this in the capillary part was condensed into a brighter and whiter thread1 while the platinum wire of the negative pole was surrounded by its characteristic mauve or violet glow4 ,sidenote3 ,spectrum described4 ,the spectrum1 even with a weak current1 was quite bright1 and consisted mainly of the nitrogen-lines and bands1 with the lines ,h1 ,h1 and ,h1 and some of the intermediate lines of the ,h tube4 ,the double line was undoubtedly the brightest in the spectrum when taken in the capillary part of the tube4 ,after this followed 1 and then 7,h71 1 and 4 ,i was1 however1 uncertain as to the relative brightness of the last three1 and marked their intensities with hesitation4 ,i tested them several times independently with differing results1 and suspected them of variability with the current4 ,the rest of the lines were very much of the same intensity4 7,for drawing of spectrum of air-tube in capillary part see ,plate ,,xv4 spectrum #a47 ,violet negative ,pole1 same tube4 ,sidenote3 ,violet 7negative7 pole3 spectrum described4 ,i next turned my attention to the violet or negative-pole glow2 and here a remarkable change took place in the spectrum1 not only in the position of the principal bands or lines1 but in their relative intensity 7see ,plate ,,xv4 spectrum #b74 ,the double line in the capillary part was replaced in the violet glow by a shaded band of second intensity 1 the sharp edge of which was extended towards the red1 and formed 7except for some faint indications7 the limit of the spectrum in that direction4 ,the somewhat faint line next in the capillary tube had its faint representative in the violet pole2 but the next two lines 7capillary7 were represented by the bright band in the violet pole lying in a position between them4 ,next in the violet pole came three faint lines1 representing 1 1 and in the capillary spectrum2 and then the bright band 1 which was the brightest of the violet-pole group1 and represented a medium-intensity band in the capillary spectrum4 ,after this was a faint band near 1 representing two rather bright ones in the capillary spectrum1 this last being succeeded by other bands in the violet4 1 1 and in the violet pole were examined carefully for relative brightness1 and were1 ,i believe1 correctly marked4 ,red positive ,pole4 ,sidenote3 ,red 7positive7 pole3 spectrum described4 ,the red positive pole was next examined1 but presented no peculiar features4 ,it appeared as a fainter representation of the capillary air-spectrum1 with some few lines or bands absent1 and 7as will be seen after7 was also a fair representation of a diffused air-spectrum 7see ,plate ,,xv4 spectrum #c74 ,examined for comparative intensity1 at #bd inches from the slit1 the whole capillary air-spectrum showed faintly4 ,the marked lines in the centre of the spectrum generally retained their prominence2 but after ,i judged next in brightness4 ,on examining the violet pole at #ab inches from the slit1 the whole spectrum was faint and the bands and were alone distinctly seen4 ,aurora 7air7-tube4 7,plate ,,xv4 spectrum #d47 ,sidenote3 ,aurora-tube3 discharge described4 ,spectrum described4 ,next to the ,geissler air-tube ,i examined an 8aurora0-tube1 about #ae inches long and #a inch across1 with platinum terminals1 and of the same diameter throughout 7,plate ,x4 fig4 #h74 ,the discharge was of a rosy-red colour1 and the long flickering stream from pole to pole certainly much reminded one optically of an auroral streamer4 ,spectroscopically examined1 the discharge presented a faint banded air-spectrum similar to that of the positive pole 7see ,plate ,,xv4 spectrum #d72 but the relative intensity of the lines was somewhat altered1 while a very bright line in the green 7seen also in the tube next described7 was characteristic of the spectrum1 and in this respect distinguished it from the ordinary air-spectrum4 ,phosphorescent tube4 ,sidenote3 ,phosphorescent tube described4 ,discharge described4 ,spectrum described4 ,following this last tube ,i examined one purchased as 8phosphorescent40 ,it was rather short 7#f inches71 of equal calibre1 and about the size of the bulb of a ,geissler tube4 ,it was filled with a white powder 7probably one of the ,becquerel compounds74 ,on passing the current between the electrodes1 a bright rose-coloured stream appeared2 and wherever this was in contact with the powder1 the tube glowed with a brilliant green light4 ,on stopping the current1 the tube still continued to shine1 but with a fainter green glow1 which gave only a continuous spectrum4 ,when examined in full glow1 the tube-spectrum was also in the main continuous and of a green tinge2 but upon it were bright lines in the blue and violet portions of the spectrum1 while in the red1 yellow1 and green a faint but distinct air-spectrum was seen2 and with this was also found the same bright line in the green which distinguished the 8aurora0-tube4 ,five out of six of the lines in the blue and violet will be also found in ,schuster's oxygen-tube1 violet pole 7,plate ,,xviii4 fig4 #ae74 ,the air-spectrum probably arose from impurity4 ,illustration3 ,plate ,,xvi4 ,spark in ,air4 ,sidenote3 ,spark in air3 spectrum described4 ,i next took a -inch spark in air between platinum terminals 7see ,plate ,,xv4 spectrum #f74 ,the principal lines in this spectrum were the line 7by far the brightest71 corresponding to in the violet pole2 next was 1 a line in the yellow1 not appearing in the tube-spectrum1 and then other lines of less intensity4 ,in the 8aurora0 and 8phosphorescent0 tubes was found1 as before mentioned1 a line in the green prominent for its brightness1 and1 indeed1 in the 8aurora0-tube the only one which survived when it was moved away from the slit4 ,this line also appeared in the spark-spectrum1 but there only of an average brightness4 ,i examined it carefully for position in the respective tubes2 and on comparing them by means of a pointer in the eyepiece1 found it coincident with the ridge or centre of the wedge-like bright-green broad band which is so conspicuous in the air-tube spectrum4 ,i think this edge-like centre has actually a line coincident with the line ,i refer to2 but if so1 its intensity little exceeds that of the band itself4 ,spark over ,water4 ,sidenote3 ,spark over water3 spectrum described4 ,to complete the set of air-experiments1 ,i examined the same spark taken from the surface of a small meniscus of water1 placed in a glass cup upon the lower platinum wire4 ,in this case the air-spectrum was plainly1 but not brightly1 seen at the violet end of the spectrum--the red1 yellow1 green1 and blue being filled with a continuous spectrum1 through which some of the air-lines faintly showed 7see ,plate ,,xv4 spectrum #g74 ,phosphoretted-,hydrogen ,flame4 ,sidenote3 ,phosphoretted-hydrogen flame4 ,this was obtained from a hydrogen-bottle fitted with glass tubing1 two or three minute pieces of phosphorus being placed with the zinc4 ,the flame was of a bright yellow colour1 with a cone of vivid green light in its centre4 ,sidenote3 ,spectrum described4 ,the spectrum was found to consist mainly of three bright bands in the yellow1 green1 and green-blue respectively 7see ,plate ,,xvi4 spectrum #c74 ,sidenote3 ,mons4 ,lecoq de ,boisbaudran's remarks on the spectrum increasing in brilliancy when the flame is cooled4 ,the central band was very striking in its emerald-green colour1 while all the bands were remarkable as being very broad in proportion to the slit 7which1 however1 was not fine74 ,the yellow band had a rich glow of colour4 ,my spectrum was mapped out at ordinary temperature1 and ,i found the bands sufficiently bright2 but ,mons4 ,lecoq de ,boisbaudran1 in his #8,spectres ,lumineux' 7texte1 p4 #ahh71 has described how the brilliancy of these bands is increased when the flame is artificially cooled 7refroidie74 ,the idea of cooling the flame was due to ,m4 ,salet1 who effected it either by a jet of water or by an air-blast4 ,the less refrangible bands seem the most susceptible to increase of brilliancy4 ,mons4 ,boisbaudran also makes the important remark that the relative intensities of the bands are in such case altered1 adding3--8,la plus importante de ces modifications consiste en un renforcement trs-considrable de la bande rouge #igjc 7,w4,l4 #eiid7 qui devient vive de presque invisible qu'elle tait en l'absence du refroidissement artificiel de la flamme40 ,full details of the changes are given by ,m4 de ,boisbaudran4 ,the bearing of these observations as connected with the variable character of the red line in the ,aurora-spectrum seems to me in the highest degree noteworthy4 ,iron-,spectrum4 ,sidenote3 ,iron-spectrum4 ,a comparison of this spectrum suggested itself1 partly from the suspected relations between the ,aurora and solar corona1 and partly from a consideration of the views expressed by ,m4 ,gronemann and others in favour of the ,aurora having its origin in the fall of an incandescent meteoric powder4 ,sidenote3 ,how obtained4 ,spectrum described4 ,mons4 ,lecoq de ,boisbaudran's spectra also given4 ,the spectrum was obtained from a spark taken over a solution of perchloride of iron in a small glass cup1 and was remarkable for its brightness in and about the green region4 ,the lines varied considerably in intensity1 and with a fine slit the principal ones were sharp1 distinct1 and clear4 ,a group of three lines 77 stood out boldly in the green as the most marked1 and next to these a group of three others more towards the violet end of the spectrum 7see ,plate ,,xvi4 spectrum #d74 ,by the side of my phosphoretted-hydrogen and iron spectra ,i have placed the principal lines of ,mons4 ,lecoq de ,boisbaudran's same spectra 7reduced to my scale71 and with figures of wave-lengths for comparison with the ,aurora-spectrum 7see ,plate ,,xvi4 spectra #a and #b74 ,sidenote3 ,comparison of iron- and ,aurora-spectrum4 ,a difficulty in comparing the iron-spectrum with that of the ,aurora arises from the large number of fine lines found in the former spectrum4 ,in a photograph 7taken with the same prism as before described7 of a small piece of meteoric iron fused in an electric arc by the aid of #dj ,grove cells1 about #aed lines are easily counted in the blue and violet parts of the spectrum4 ,double this number at least would be seen with a spectroscope of moderate dispersion in the region comprising the entire set of auroral lines4 ,spectrum of ,mercury4 ,sidenote3 ,mercury-spectrum4 ,how obtained4 ,this spectrum is given as useful for comparison with the bright and principal ,aurora-line4 ,it is easy to obtain with a small coil1 the metal being used as one electrode4 ,the yellow lines are distinct and steady2 but the green1 which is very bright1 is apt to flicker as the spark moves on the surface of the metal 7see ,plate ,,xvi4 spectrum #e74 ,the following ,table was compiled for the purpose of comparing the foregoing results with the ,aurora-spectrum4 ,sidenote3 ,table of coincidences4 ,,table showing comparative position of ,aurora-lines with the principal lines in the examined spectra4 ,c4 means coincident within the limits of my instrument and scale1 ,n4 near1 and ,,vn4 very near4 ---------------------------------------- ------------------------- #dfid ,aurora-lines #fbig #eefi #ecij #ebcc #eahj #ejjd to #dfbi #dcej8 4 4 4 4 4 4 4 4 ---------------------------------------- ------------------------- ,c41 ,band ,hydrogen-tube ,n4 ,n4 same includes ,w4,l4 #b lines4 ------------- -------------------------------------- ,band ,coal-gas ,n4 ,,vn4 includes tube #a line4 ------------- -------------------------------------- ,oxygen-tube ,,vn4 ------------- -------------------------------------- ,band ,band ,air1 includes ,n4 includes capillary #b lines4 ------------- -------------------------------------- ,band ,band ,air1 violet- 99 in- ,c4 includes 9999 pole cludes #a line4 ------------- -------------------------------------- ,air1 red-pole ,see ,air1 capillary4 ------------- ---------------------------------------- --- ,aurora-tube ,see ,air1 capillary2 and note bright line4 and phos- phorescent tube ------------- -------------------------------------- ,band ,air1 spark ,n4 ,n4 ,c4 includes #b lines4 ------------- -------------------------------------- ,air1 spark ,continuous spectrum and faint ,band over water air-lines4 includes #b lines4 ------------- -------------------------------------- ,phosphoretted ,n4 ,faint ,band hydrogen band4 in- cludes ------------- -------------------------------------- ,iron ,,vn4 ,n4 ,,vn4 ,,vn4 ---------------------------------------- ------------------------- 99 ,no results in the examined spectra2 but see ,plate ,,xiii4 fig4 #b4 9999 ,too uncertain in position for comparison 7see ,plate ,,xiii4 fig4 #a74 ,tested by coincidence1 or close proximity of lines to those of the ,aurora1 we arrange the spectra in the following order3--7#a7 iron1 7#b7 air-spark1 7#c7 hydrogen1 7#d7 air-tube1 7#e7 phosphoretted hydrogen1 7#f7 carbon and oxygen4 ,the air-tube spectrum might perhaps stand higher in the scale but for its broad bands1 which make comparison doubtful4 ,lines of oxygen possibly escape detection in the ,aurora from the faint character of its spectrum4 ,the phosphorus and iron spectra are especially interesting in connexion with ,professor ,nordenskild's 8metallic and magnetic cosmic dust in the ,polar regions0 7see ,phil4 ,mag4 ser4 #d1 vol4 xlviii4 p4 #edf74 ,sidenote3 ,additional ,table of compared spectra4 ,as an addendum to the foregoing1 on ,plate ,,ix4 fig4 #a will be found a ,table ,i have prepared1 in which a type ,aurora and also ,vogel's and ,barker's ,auror are compared with eight other spectra1 viz43-- ,s4 ,solar spectrum4 ,n4 ,nitrogen 7air73 ,watts4 ,o4 ,oxygen 7air73 ,watts4 ,c4,h4 ,carburetted-hydrogen vacuum-tube3 ,watts4 ,c4,i4 ,carburetted-hydrogen flame3 ,watts4 ,c4,c4 ,blue base of candle-flame3 ,capron4 ,o4,p4 ,oxygen vacuum-tube3 ,procter4 ,i4 ,iron3 ,watts4 ,the divisions and vertical lines will guide the eye in making comparison of the spectra4 ,,chapter ,,xii4 ,,some ,,notes ,,on ,,professor ,,ngstr,m',s ,,theory ,,of ,,the ,,aurora-,,spectrum4 ,the substance of these appeared in the #8,philosophical ,magazine' for ,april #ahge1 in conjunction with the 8,comparison of the ,tube and other ,spectra0 7,chapter ,,xi471 but they are now1 for the sake of convenience1 made a separate article4 ,sidenote3 ,professor ngstrm's propositions4 ,in a contribution by the late ,professor ngstrm to a solution of the problem of the ,aurora-spectrum 7an abstract of which appeared in #8,nature' of ,july #af1 #ahgd71 the ,professor is stated1 amongst other things1 to have laid down certain propositions in substance as follows3-- ,sidenote3 ,that the ,aurora has two spectra4 #ast4 ,that the ,aurora has two different spectra--the one comprising the one bright line in the yellow-green only1 and the other the remaining fainter lines4 ,sidenote3 ,that bright line does not coincide with ,,hc4 #bndly4 ,that the bright line falls within a group of hydrocarbon lines1 but does not actually coincide with any prominent line of such group1 and that ,dr4 ,vogel's finding this line to coincide with a not well-marked band in the air-spectrum must be regarded as a case of accidental coincidence4 ,sidenote3 ,that moisture is nil in ,aurora region4 #crdly4 ,that moisture in the region of the ,aurora must be regarded as nil1 and that oxygen and hydrogen must alone there act as conductors of electricity4 ,sidenote3 ngstrm's flask-experiment described4 ,professor ngstrm then details the examination of an exhausted dry air-flask filled with a discharge analogous to the glow of the negative pole of a vacuum air-tube4 ,sidenote3 ,flask-spectrum compared with ,aurora-spectrum4 ,the experiment is described as follows3--8,into a flask1 the bottom of which is covered with a layer of phosphoric anhydride1 the platinum wires are introduced1 and the air is pumped out to a tension of only a few millimetres4 ,if the inductive current of a ,ruhmkorff coil be sent through the flask1 the whole flask will be filled1 as it were1 with a violet light1 which otherwise only proceeds from the negative pole1 and from both electrodes a spectrum is obtained composed chiefly of shaded violet bands40 ,the comparison of the spectrum of this violet glow with that of the ,aurora gives1 according to ngstrm1 the following results3-- ,aurora-lines1 wave-lengths #dbhf #dgjc #ebbf ,violet light1 wave-lengths #dbgb #dgjg #ebbg ,two weak light bands1 found by ,dr4 ,vogel at #dffc and #dfbi1 are also compared with other lines in the violet light #dfed and #dfja2 and the ,professor then concludes that it may be in general assumed that the feeble bands of the ,aurora-spectrum belong to the spectrum of the negative pole1 possibly changed more or less by additions from the banded or the line air-spectrum4 ,sidenote3 ,bright line is due to fluorescence or phosphorescence4 #dthly4 ,that the only probable explanation of the bright line is1 that it owes its origin to fluorescence or phosphorescence4 ,the ,professor remarks on this point that 8an electric discharge may easily be imagined which1 though in itself of feeble light1 may be rich in ultra-violet light1 and therefore in a condition to cause a sufficiently strong fluorescence40 ,he notes also that oxygen and some of its compounds are fluorescent4 ,sidenote3 ,no need of ,dr4 ,vogel's theory of variability4 #ethly4 ,that there is no need1 in order to account for the spectrum of the ,aurora1 to have recourse to the 8very great variability of gas-spectra according to the varying circumstances of pressure and temperature0 7,dr4 ,vogel's theory74 ,professor ngstrm does not admit such variability1 and does not admit that the way a gas may be brought to glow or burn can alter the nature of the spectrum4 ,sidenote3 ,professor ngstrm's conclusions tested4 ,in order to test some of the ,professor's conclusions in an experimental way1 ,i examined some tube and other spectra not only for line-positions1 but also for general resemblance to an ,aurora-spectrum4 ,these experiments are detailed in the last ,chapter1 and the results are comprised in ,plates ,,xiv41 ,,xv41 and ,,xvi41 in which the spectra obtained are represented in black for white4 ,sidenote3 ,result of examination of the ,professor's propositions4 ,the result of the examination of ,professor ngstrm's principal propositions seems to be this3-- #ast4 ,two ,auroral spectra4 ,i agree in this1 but question whether the fainter lines may not possibly comprise more than one spectrum4 #bnd4 ,i agree also that the bright yellow-green line falls1 as ,professor ngstrm describes1 just behind the second line in the hydrocarbon yellow group 7see ,plate ,v4 fig4 #g74 ,and ,i find1 in common with the ,professor1 no well-marked or prominent line in the air-spectrum with which it accords4 #crd4 ,this may be conveniently divided into two parts1 viz43-- ,a4 ,the proposition that 8moisture in the region of the ,aurora must be regarded as nil40 ,sidenote3 ,moisture probably not nil in the ,aurora region4 ,reasons for this given4 ,aurora in vapour or mist4 ,frequently near to earth's surface4 ,here ,i see reason to differ1 since 7to quote a letter of ,mr4 ,procter's7 8the vapour-density of ,,oh is only #i against #ad for ,n and #af for ,o20 and again1 8electrical or heat-repulsion may carry water-dust up to enormous heights40 ,there are1 too1 ,i think1 circumstances connected with the ,aurora itself which make the assumption of moisture being nil in the ,auroral regions untenable4 ,the first of these is the fact that the white arc1 streamers1 and floating patches of light1 found in some ,auror1 have frequently the peculiarly dense and solid look of vapour-clouds--a circumstance with which ,i have been frequently struck4 ,mr4 ,procter and others have also remarked that the ,aurora is generally formed in a sort of 8mist or imperfect vapour40 ,the second1 that ,auror1 or portions of them1 are frequently near to the earth's surface4 ,instances of this are given in the section on the ,height of the ,aurora1 notably the experiences of ,sir ,w4 ,grove and ,mr4 ,w4 ,ladd4 ,sidenote3 ,coincidence of ,auroral lines with telluric solar lines4 ,on this point1 too1 note the peculiarities of the red line1 which 7and1 as ,i find1 the green line also7 are coincident with1 or very close to1 telluric bands or groups of lines in the solar spectrum usually attributed to moisture4 7,see ,plate ,,xiii4 fig4 #b47 ,sidenote3 ,continuous spectrum4 ,i think we may also claim the continuous spectrum in the ,aurora in further proof of water-vapour 7see ,plate ,,xv4 spectrum #g74 ,the continuous spectrum of the ,aurora is also1 to my observation1 more local and dense in the spectroscope than the glow generally seen between the lines or bands in gas-spectra4 ,sidenote3 ,violet-pole spectrum discussed4 ,most spectra have a general as well as special character4 ,b4 ,the question of the violet-pole spectrum4 ,here ,i make the remark that in comparing other spectra with that of the ,aurora1 it is1 ,i think1 too much the practice to trust to the coincidence 7more or less perfect7 of one or perhaps two lines out of many2 whereas we know by experience that most spectra have so well-marked a general as well as special character that1 when once seen1 they are recognized afterwards with the greatest ease and without measurements4 ,an experience and proof of this is found in a set of 8,photographed ,spectra0 which the ,autotype ,company have reproduced for me4 ,sidenote3 ,coincidence of one or two lines not sufficient to establish identity4 ,of course no two given spectra can be considered identical unless their principal lines coincide2 but1 on the other hand1 the coincidence of one or two lines out of many1 without other features1 cannot be satisfactorily or conclusively held to establish identity4 ,sidenote3 ngstrm's compared spectra4 ,in ,professor ,herschel's letter 7,phil4 ,mag4 ser4 #d1 vol4 xlix4 p4 #ga71 ,professor ngstrm's representation of the 8spectrum of the glow discharge round the negative pole of air-vacuum tubes0 is given1 in comparison with the ,aurora-lines and those of olefiant gas4 ,this illustration is here introduced4 ngstrm's representation of the ,spectrum of the glow discharge round the negative pole of ,air-vacuum tubes1 and its comparison with the ,spectrum of the ,aurora4 ,illustration3 ,wave-lengths1 in hundred-thousandths of a millimetre4 ,it is unfortunate that in this illustration and in ,professor ,herschel's paper the wave-lengths of the ,aurora-lines are not given in figures1 but must be roughly calculated from the scale4 ,professor ,herschel speaks of ngstrm's drawing as representing a normal spectrum1 and as derived from authentic sources1 such as ,vogel1 ,barker1 and others2 but beyond this we are not certain as to its origin4 ,in illustration of the difficulty of constructing any thing like a general typical ,aurora-spectrum ,i append a ,table of eight ,auroral spectra taken at hazard3-- ,sidenote3 ,table of compared ,aurora4 ,auroral lines and bands4 ---------------------------------------- --------------------------- ,observers4 ,red4 ,yellow4 ,green4,blue4 ,indigo4 ,violet4 ---------------------------------------- ------------------------ #dfid ,vogel1 ,april #i1 #ahga #fbigeefiecij #ebcc #eahi #ejjd -- to -- #dfbi ,barker1 ,nov4 #i1 #ahga #fbcjefbj -- -- #eagj #ejbj #dhbj -- -- #eccj #ejej #dicj #dgdj ,barker1 ,oct4 #ad1 #ahgcfcjjeeej -- to -- to to to #dcaj #ebjj #diij #dhej #dfgj ,a4 ,clarke1 junr41 ,oct4 #bd1 #ahgj #efij -- #ecbj -- -- #dhej -- #dcej ,backhouse1 #ahgc #fjfjeffj -- -- #eafe #ejae -- #dfbe #dcje ,backhouse1 ,feb4 #d1 #ahgd 99 #eegj -- -- #eahj #dihj #dhcj #dfdj #dcbj ,h4 ,r4 ,procter1 #ahgj 99 99 -- 99 -- -- -- 99 99 ,lord ,lindsay1 #ahgj -- 99 99 99 99 -- -- -- 99 ---------------------------------------- ------------------------ 99 ,mr4 ,procter's and ,lord ,lindsay's lines had no wave-lengths4 ,sidenote3 ngstrm's drawing discussed4 ,on examining ngstrm's diagram it certainly seems to me that1 upon the showing of the drawing itself1 the coincidences are not very exact4 ,all three of the violet-pole bands appear to be less refrangible than the ,aurora-lines with which they are compared-the middle one 7at #dg7 considerably so1 the one near ,e 7at about #ebcj7 appreciably so1 and the third 7at #dc7 slightly so4 ,sidenote3 ,diagram of ,vogel's ,aurora and violet-pole spectrum4 ,as it seemed desirable to adopt a specific ,aurora-spectrum for comparison1 and to show such comparison on a somewhat larger scale than ngstrm's drawing1 ,i prepared the diagram shown on ,plate ,,xi4 fig4 #a4 ,the upper spectrum is ,vogel's1 already described and figured on ,plate ,,xiii4 ,the lower spectrum is that of 8,air1 violet pole10 ,plate ,,xv4 spectrum #b1 graphically shown4 ,i can only find one absolute coincidence in the two compared spectra in this diagram4 ,it should1 too1 ,i think1 be borne in mind that there is a great difference in the character of the compared spectra1 whether as shown in ngstrm's drawing or mine--the bands of the violet-pole spectrum mostly degrading towards the violet1 while the lines or bands of the ,aurora in no way possess that character#ad4 ,sidenote3 ,dr4 ,vogel's violet-pole and ,aurora-lines4 ,to assist in the foregoing violet-pole comparison ,i add the following ,table derived from ,dr4 ,vogel's memoir3-- ,violet-pole lines4 ,aurora-lines4 ,w4,l4 ,w4,l4 #fajj1 broad1 moderately #eide1 bright stripe #fbig1 very bright stripe4 #edei1 broad1 moderately #eefi1 brightest line of spectrum4 #ebhi1 bright stripe #ecij1 extremely faint line4 #ebbd1 very bright line #ebcc1 moderately bright4 #eadg1 faint line #eahi1 moderately bright4 #ejjd1 bright line #ejjd1 very bright line4 #diab1 fainter than last4 #dhjh1 very faint line4 #ffid1 #dgjd1 very intense line4 #dffc1 band less brilliant in #dfdf1 very faint line4 #dfbi1 the middle4 #defi1 moderately bright4 #ddhf1 moderately bright4 #ddag1 quite faint line4 #dcdf1 moderately bright line4 #dbge1 very bright line4 ,on examination of these figures it will be seen that #ebbd and #ebcc are fairly close1 and that #ejjd is coincident4 ,beyond these there is little to identify the spectra4 ,sidenote3 ,conclusions arrived at adverse to the violet-pole theory4 ,as the general result of my observations and a comparison of the foregoing spectra and tables1 ,i see no reason for giving to the violet-pole glow any special or distinguished place in a comparison with the ,aurora1 and certainly not for assigning to it the nearly absolute monopoly of the spectrum4 ,it is true that the line in the violet-pole glow 7,plate ,,xv4 spectrum #b71 which1 by the way1 degrades towards the red1 is in close coincidence with one of the ,aurora-lines2 but how are the brighter bands and accounted for8 ,these1 as ,i have before pointed out1 alone survive when the tube is placed at a distance from the slit4 ,it is true they are thus reduced to shaded-off lines in lieu of bands2 but the difficulty still remains1 that they are conspicuous for their absence in the ,aurora-spectrum4 ,on the whole1 ,i cannot but conclude that ,professor ngstrm's theory fails4 ,at all events1 if the violet-pole glow-spectrum is to represent the ,aurora-spectrum1 it must be under conditions different from those by which it obtains in dry-air vacuum-tubes or flasks at ordinary temperature4 ,sidenote3 ,phosphorescence or fluorescence of the yellow-green line4 #dth4 ,i feel more in accord with ,professor ngstrm's memoir upon the subject of the phosphorescence or fluorescence of the bright yellow-green ,aurora-line4 ,sidenote3 ,external features of ,auror confirmatory of this4 ,i do not notice that the ,professor touches upon the external features of the ,aurora in respect of this question4 ,october #bj1 #ahgj4--;,i noted the grand ,auroral display of that evening1 including 8streamers of opaque-white phosphorescent cloud very different from the more common transparent ,auroral diverging streams of light40 ,february #d1 #ahgb4--;,a fine display4 ,the first signs were 7in dull daylight7 8a lurid tinge upon the clouds1 which suggested the reflection of a distant fire1 while1 scattered among these1 torn and broken masses of white vapour1 having a phosphorescent appearance1 reminded me of a similar appearance in ,october #ahgj40 7,other instances of this effect will be found in the section ,aurora and ,phosphorescence47 ,day ,auror1 too1 we might suppose could hardly be seen without the presence of some phosphorescent glow4 ,sidenote3 ,other confirmatory circumstances4 ,conclusion in favour of the theory4 ,having regard to the near proximity of the phosphoretted-hydrogen band to the bright ,aurora-line1 to the circumstance of this band brightening by reduction of temperature 7a phenomenon probably connected with ozone71 to the peculiar brightening of one line in the green in the 8,aurora0 and 8phosphorescent0 tubes 7the phosphorescent tubes probably containing ,o71 and to the observed circumstance that the electric discharge has a phosphorescent or fluorescent after-glow 7isolated1 ,i believe1 by ,faraday71 ,i feel there is strong evidence in favour of such an origin to the principal ,aurora-line1 if not to the red line as well4 ,sidenote3 ,invariability of gas-spectra questioned4 #eth4 ,professor ngstrm opens a wide door to discussion in his proposition of the invariability of gas-spectra1 and ,i do not now attempt to follow in detail this interesting part of the present subject4 ,suffice it to say1 that if the ,professor lays down this proposition in its strictest sense 7,i can hardly suppose he so meant it71 there is1 so far as ,i am aware1 no one spectrum that can at all claim comparison with the ,aurora-spectrum4 ,giving greater latitude to the ,professor's words1 ,i reply1 upon competent authority1 that lines vary in number and brilliancy with temperature1 and in breadth with pressure4 ,kirchhoff1 too1 in speaking of vapour-films as increasing the intensity of lines1 states 8it may happen that the spectrum appears to be totally changed when the mass of vapour is altered40 ,we may1 too1 now add magnetism as capable of effecting a change in certain spectra1 not only as to brilliancy1 but even as to position of lines4 7,chautard's ,researches1 #8,philosophical ,magazine1' #dth series1 vol4 #a4 p4 #gg1 and experiments detailed in ,chap4 ,,iii4 of this work47 ,,chapter ,,xiii4 ,,the ,,oxygen-,,spectrum ,,in ,,relation ,,to ,,the ,,aurora 7,,procter ,,and ,,schuster74 ,sidenote3 ,procter's oxygen-spectrum4 ,in a communication to #8,nature1' ,mr4 ,h4 ,r4 ,procter has pointed out an apparent coincidence in position of several of the ,auroral lines with those of a spectrum occasionally obtained from air at low pressure with a feeble discharge4 ,it is1 he says1 sometimes exhibited in lumire 7phosphorescent87 tubes1 and he believed it1 in part at least1 to be the spectrum described by ,wllner 7,philosophical ,magazine1 ,june #ahfi7 as a new spectrum of oxygen4 ,sidenote3 ,how obtained4 ,he had obtained it very vividly in pure electrolyzed oxygen with a feeble discharge1 but some perplexing observations made him doubtful of its origin4 ,plate ,,xi4 fig4 #d gives a representation of this spectrum as shown by ,mr4 ,procter1 except that my drawing is in black for white4 ,sidenote3 ,compared spectra described4 ,the upper spectrum is that above mentioned1 the centre one that of the ,aurora1 the lower one the lines of ,na and ,h for comparison4 ,the ,auroral yellow-green line1 in ,january #ahgj1 was found by ,mr4 ,procter coincident with a bright line or band in the tube 7with a spectroscope of a #fj bisulphide prism1 and magnifying-power about six74 ,the third and fifth lines in the ,aurora seemed also to correspond with tube-lines4 ,as to these ,mr4 ,procter says they were not bright enough to be compared with the same accuracy as the yellow-green line1 but that the positions could not be far wrong4 ,sidenote3 ,mr4 ,procter's subsequent views4 ,yellow-green line traced to some form of hydrocarbon4 ,mr4 ,procter subsequently 7#8,edinburgh ,encyclopdia1' art4 8,aurora07 considered he traced the yellow-green tube-line to some form of hydrocarbon4 ,on examination with instruments of greater dispersion1 it was found that1 though more refrangible than the first band of citron acetylene 7candle-flame71 it was less so than the ,aurora-line4 ,the tube-band1 too1 was shaded towards the violet1 which was not the case with the ,aurora-line4 ,the question as between hydrocarbon and oxygen ,i did not then consider as disposed of4 ,with the lumire tubes the question might be open1 but ,i did not see how it could be in the case of the electrolyzed oxygen-spectrum4 ,from a comparison of the tube-spectra1 ,i have shown that although the spectra of the carbon and oxygen tubes are proved to be1 photographically1 as a whole1 distinct1 they have1 as to position of some of the principal lines in the central part of the spectrum1 a very close resemblance4 ,sidenote3 ,probability that ,o may play a part in the ,aurora-spectrum4 ,that oxygen may in some form play a part in the ,aurora seems highly probable2 how far it is spectroscopically detected seems a different question4 ,sidenote3 ,difference between air-spark and tube-spectra4 ngstrm and ,herschel suggest its presence in the ,aurora in connexion with phosphorescence or fluorescence4 ,with a spark-discharge in air at ordinary pressure1 a mixed spectrum of bright lines of ,n and ,o is found2 while in the case of ,geissler vacuum-tubes 7representing a glow-discharge in a much more rarefied atmosphere7 the ,n lines appear mainly to usurp the spectrum4 ,sidenote3 ,h,o tube referred to4 ,it must1 however1 be borne in mind that a ,geissler tube1 as to temperature at least1 in no way represents the conditions of the ,aurora2 and when we remember the association of oxygen and ozone1 and the way in which the latter is affected by heat1 it may well be that temperature plays an important part in the matter4 ,in proof of this conduct of oxygen1 it may be cited that1 in the case of a ,h,o tube1 the ,h lines come out sharp and brilliant in the spectrum1 while what is seen of the ,o lines is comparatively weak1 misty1 and ill-defined4 ,vogel1 it will be remembered1 makes #eahi of the ,aurora coincident with an ,o line4 ,sidenote3 ,residual phosphorescence in ,geissler tubes4 ,garland tube4 ,professor ,herschel has pointed out1 and ,i have confirmed1 that the residual phosphorescence in ,geissler tubes1 after the spark has passed1 is probably associated with oxygen4 ,he also alludes to the fact that when one of the globes of a 8,garland0 tube was heated1 it did not shine after the spark had passed1 apparently because of the destruction of the ozone by heat4 ,some experiments with a tube of this description will be found detailed in ,part ,,iii4 ,oxygen was not1 ,i think1 the gas it was filled with4 ,sidenote3 ,dr4 ,schuster's tubes described4 ,subsequently to my examination and comparison of the ,o and ,,co spectra before detailed1 ,dr4 ,arthur ,schuster was good enough to send me three vacuum-tubes of his own preparation1 showing an oxygen-spectrum4 ,one1 with large disk-shaped brass electrodes1 was unfortunately broken in transit4 ,dr4 ,schuster informed me it showed the carbonic-oxide spectrum as well as that of oxygen4 ,the other two tubes had aluminium electrodes4 ,they were similar in shape to ordinary ,geissler tubes1 but had attached to each a supplemental bulb containing dry oxide of manganese4 ,illuminated by the larger coil1 one of these tubes 7which had a slight crack in the manganese bulb7 lighted up faintly2 the other was fairly bright1 and the glow had a somewhat reddish tint4 ,plate ,,xviii4 fig4 #ae represents as the upper spectrum ,vogel's ,aurora1 with ,w4,l4 numbers1 as the middle spectrum the capillary part of ,dr4 ,schuster's ,o tube1 and as the lower spectrum the negative 7violet7 pole of the same tube4 ,sidenote3 ,spectra described4 ,the tube-spectra were mapped out with the aid of the diaphragm micrometer before described4 ,sidenote3 ,capillary4 ,the capillary spectrum was mainly distinguished by four bright sharp lines--one in the red1 between the red ,aurora-line and ,d1 two in the green1 but considerably more refrangible than the yellow-green ,aurora-line1 while the fourth was found to be hydrogen ,f4 ,the other lines in the spectrum were considerably fainter1 and misty and band-like4 ,the red line1 though not brilliant1 was fairly bright and sharp4 ,the place of the less refrangible of the two bright bands in the violet-pole spectrum was occupied in the capillary spectrum by a faint glow only4 ,sidenote3 ,violet-pole4 ,the violet-pole spectrum was recognized by two very bright broad bands of light in the green1 each including within its limits one of the ,aurora-lines4 ,the bright red line in the capillary had a faint representative in the violet-pole spectrum1 as also had the two bright lines in the green4 ,other fainter lines appeared in the blue1 and three fairly bright ones towards the violet4 ,sidenote3 ,dr4 ,schuster's remarks on the spectra4 ,dr4 ,schuster remarks that one of these ,o bright bands is closely coincident with a band in the ,,co spectrum1 but that the ,,co band is bright towards one edge and fades off gradually thence1 while the ,o band is of pretty uniform strength throughout4 ,dr4 ,schuster finds the wave-lengths of the violet-pole ,o bands to be as follows3-- #ebjej #ebibe ,brightest part #ebee4 #eeebh #efbif ,brightest part #eehf4 ,sidenote3 ,his tubes free from impurity4 ,he also gives as weak bands #ehdj-eijj and #eifi-fjaj4 ,dr4 ,schuster comes to the conclusion that the green line of the ,aurora is not due to oxygen1 as1 under considerable dispersion and with good definition1 the oxygen-bands can be broken up into a series of lines1 when the brightest part is found to lie at #eehf1 which is too much towards the red to compare with the ,aurora-line4 ,he notices that the more refrangible of the ,o bands corresponds with a line sometimes seen in the ,aurora 7,vogel's #ebcc74 ,the same remark will1 however1 apply to this last as to the other coincidence1 viz41 that a broad band can hardly represent a line--at least1 the line can only be said to coincide in a loose and indefinite way4 ,it is evident that ,dr4 ,schuster's tubes were free from what must now be considered an impurity in those examined by me and by ,dr4 ,vogel1 and that ,mr4 ,procter's suspicions of carbon impurities in these1 and the ordinary oxygen-tubes1 are thereby quite confirmed4 ,sidenote3 ,experiments with an open ,geissler tube4 ,in some experiments which we made 7after receiving ,dr4 ,schuster's tubes7 with an open ,geissler tube1 so arranged as to connect with an air-pump and gas-receiver1 and thus from time to time to wash out the tube and vary its contents1 we found the same impure spectrum as in the case of the sealed ,o tubes2 and it seems to require a very large amount of precaution to avoid these impurities4 ,sidenote3 ,spectra of ,dr4 ,schuster's ,o tube examined4 ,dr4 ,schuster was kind enough to examine the spectra ,i mapped out1 and which are shown in ,plate ,,xviii4 fig4 #ae1 with the following results3--,the lines ,o1 ,o1 ,o are those he has referred to under that designation in his communications to #8,nature1' and undoubtedly belong to oxygen4 ,the bands ,a1 ,b1 and ,c are the bands characteristic of the negative pole4 ,he finds ,a divided into two parts by a dark space4 ,the spectrum of the negative pole1 under good exhaustion1 stretches into the capillary part2 hence ,b appears in the capillary as a faint band4 ,a similar thing happens with nitrogen4 ,i41 ,,ii41 ,,iii41 and possibly #h and #i1 he thinks1 are due to the spark-spectrum of oxygen1 obtained when the jar and a break are interposed1 the brighter lines of the line-spectrum being always present at the negative pole4 ,these last-mentioned lines ,i have already referred to1 as having been found by me in a tube showing phosphorescence after the spark has passed4 7,compare ,plate ,,xviii4 fig4 #ae1 ,o violet pole1 with ,plate ,,xv4 spectrum #e47 ,nos4 #a and #b1 he thinks1 are due to some foreign matter1 as they are not in all his tubes4 ,dr4 ,schuster often finds that a spectrum due to the aluminium electrodes is seen in tubes under great exhaustion2 and this he considers is the spectrum of aluminium oxide4 ,a drawing of this spectrum is found in ,watts's #8,index of ,spectra1' plate iii41 8,aluminium first ,spectrum40 ,to this1 he thinks1 are also due the bands1 or sets of lines in my aluminium-arc spectrum 7#8,photographed ,spectra1' plate ii471 and he believes lines #c1 #d1 #e1 #f1 and #g in the mapped-out spectra are due to it4 ,it would thus appear that the lines due to ,o are few in number1 and do not well compare with the ,aurora-spectrum4 ,,part ,,iii4 ,,magneto-,,electric ,,experiments ,,in ,,connexion ,,with ,,the ,,aurora4 ,,introduction4 ,sidenote3 ,object of experiments4 ,description of apparatus employed4 ,electro-magnet4 ,battery4 ,the set of experiments detailed in ,chapters ,,xiv4 to ,,xix4 was mainly conducted for the purpose of testing1 in connexion with the ,aurora1 the action of a magnet upon the electric glow in vacuo and on the spark at ordinary pressure4 ,it also includes some observations on the glow from the violet pole with and without the magnet1 and on the glow obtained from one wire only4 ,the apparatus employed was a ,ladd's electro-magnet1 with poles #aj inches high by #b inches across1 each pole being surrounded by a movable helix1 composed of two sets of stout copper wire wound together1 so that they could be used either in one length or as independent coils excited at the same time4 ,the latter form of arrangement was employed by us4 ,in most of the experiments conical armatures were employed for the purpose of bringing the action of the poles to bear upon the subjects examined4 ,a contact-maker was added to the magnet1 so that it could be put rapidly in or out of action without disturbing the wires4 ,the battery used to excite the magnet was of the form known as that of ,dr4 ,huggins1 and consisted of four vulcanite cells in a frame1 each holding seven pints of bichromate solution1 and containing two carbon and one zinc plate1 each #ac by #f inches4 ,sidenote3 ,small coils4 ,larger coil4 ,magnetic curves obtained4 ,a winch and pulley enabled the whole set of plates to be lowered into the liquid and withdrawn at pleasure1 and the large quantity of solution gave the battery a considerable amount of constancy4 ,we found it could be used for two evenings' work1 of four hours each1 without any material dropping in power4 ,for obtaining the glow in the ,geissler and other small tubes1 a ,ruhmkorff coil1 giving a -inch spark1 excited by one plate of a -gallon bichromate 7bottle form71 was used4 ,for the glow in the larger tubes and the spark in air a larger coil1 giving a two-to three-inch spark1 and worked by two -gallon double-plate bichromates1 was employed4 ,notes were taken of the experiments1 and drawings of the effects at the time2 and these are reproduced almost literally in the text and ,plates comprised in this ,part4 ,to ascertain the direction and extent of the magnetic curves1 we covered large sheets of cardboard1 placed over the poles1 with iron filings2 excited the magnet so as to obtain the curves1 and then obtained permanent prints from the filings by spraying the cardboard with tannin solution4 ,the magnetic effects were thus found to extend to a radius of at least ten inches 7see diagram1 ,plate ,,xvii4 fig4 #a1 showing magnet-poles and curves on a scale74 ,sidenote3 ,chautard's investigations kept in view4 ,evidence obtained of change in colour1 form1 c4 of ,aurora4 ngstrm's flask-experiment tried4 ,in the vacuum-tube experiments we held ,mons4 ,j4 ,chautard's investigations 7on the action of magnets on rarefied gases in capillary tubes rendered luminous by the induced current1 ,phil4 ,mag4 #dth series1 vol4 #a4 p4 #gg7 in view4 ,we obtained in our experiments plenty of evidence of a change of colour and form in the discharge under the magnetic influence2 and both simple and compound spectra were found to be much varied by the exaltation or suppression of some parts of the spectrum1 so that apparently new lines sprang up2 but we failed to trace actual change of position or wave-length in any given line1 though we carefully looked for it4 ,a portion of our researches was directed to the subject of ngstrm's experiment of filling a dry flask with a violet glow1 analogous to that from the negative pole4 ,we entirely failed in obtaining the same result while two wires and an uninterrupted circuit were employed4 ,when1 however1 we attached a negative wire only 7the other wire being left free7 to an exhausted globular receiver1 we obtained an effect very similar to that referred to in ,prof4 ngstrm's memoir4 ,sidenote3 ,general results of experiments4 ,bulb effects noticed as a mode of analysis of gases4 ,the general result of the experiments was to prove1 assuming the ,aurora to be an electric discharge1 the great influence the magnetic forces may exercise on the colours1 form1 motions1 and probably the spectrum also of that phenomenon4 ,it is easy to conceive that the variation in number1 and intensity of the lines which has been remarked in ,auroral spectra may have its origin in such a cause4 ,the influence of the magnet on the capillary stream was mainly in colour and intensity2 but in the bulbs the effects were still more marked and striking1 and1 in a greater or less degree1 different in the case of each gas which we examined4 ,a careful and extended study of these effects1 conjointly with the changes in the spectrum1 might possibly form a new and valuable mode of analysis of compound gases4 ,this is well illustrated in the case of the iodine and sulphur tubes which we examined4 ,illustration3 ,plate ,,xvii4 ,,chapter ,,xiv4 ,,examination ,,of ,,geissler ,,tubes ,,under ,,action ,,of ,,the ,,magnet4 ,nitrogen-tubes4 ,sidenote3 ,nitrogen-tube ,no4 #a4 ,discharge described4 ,spectrum described4 ,capillary stream4 ,positive bulb4 ,violet-pole glow4 7#a7 ,a small ,geissler tube 7,no4 #a7 was lighted up by the small coil4 ,the capillary part showed a very bright1 slightly rosy-tinted stream4 ,negative bulb was filled with rosy-purple light1 the violet-pole glow being confined to the extent of the electrode4 ,positive bulb of the same rosy-purple colour1 but stream slightly contracted in volume4 ,glow throughout quiescent1 and no stratification in the tube4 ,a compound-prism spectroscope1 taking in the whole of the spectrum1 showed in the capillary stream1 from yellow to red1 a fairly bright wedge1 having a dark band in the centre1 and six bright columns1 with dark lines at intervals1 shading off on either side4 ,on the more refrangible side of the yellow1 the spectrum was composed of a set of bright bands and lines in the green1 blue1 and purple1 one line only 7in the green7 standing out very bright4 ,in the yellow and red no bright line stood out alone4 ,the positive bulb gave a fainter spectrum of the same character1 mainly confined to the centre1 the violet1 yellow1 and red not being well seen4 ,when the violet-pole glow was examined1 the general character of the spectrum was quite changed3 a brilliant broad band in the violet1 a bright narrower one in the blue1 and two bright lines in the green1 with intermediate fainter lines throughout1 were the main features4 ,the yellow and red part of the spectrum was also changed4 ,the yellow was fairly and evenly distinct up to the dark band2 then came a somewhat brighter orange band1 and after that the red1 but rather obscure and cut off4 ,no absolutely bright line could be traced in the red4 ,sidenote3 ,nitrogen-tube ,no4 #b4 ,glow described4 ,difference of spectra of capillary stream and violet-pole glow4 ,junction of the violet-pole glow and capillary stream4 7#b7 ,to compare the capillary stream and the violet-glow1 a second nitrogen-tube 7,no4 #b7 was used4 ,this tube was larger in bulk and bore than ,no4 #a4 ,the glow in the bulbs was considerably fainter and more salmon-coloured2 and there was much stratification in both1 extending to the capillary bore4 7,this stratification was considered due to ,h1 as the three principal lines of that gas came out very brightly in the spectrum47 ,the difference of the spectra of the capillary stream and of the violet-pole glow was extremely well marked--the former consisting of a set of bright lines and bands of fairly uniform intensity1 while the latter was split up into a few bright bands with fainter lines between4 ,the yellow and red of the violet-glow were very weak as compared with the same region of the capillary spectrum4 ,no bright line appeared in the red4 ,the tube being properly adjusted for the purpose1 the junction of the violet-pole glow and the capillary red-glow was easily observed4 ,the bright bands of the violet-pole were seen to run into the capillary line-spectrum1 and then1 gradually getting finer and more pointed1 to fade out4 ,sidenote3 ,tube ,no4 #a between the poles of the magnet4 ,change of colour in capillary stream4 8,tailing-over0 of capillary stream4 7#c7 ,the capillary part of tube ,no4 #a was arranged between the poles of ,ladd's electro-magnet1 the conical ends of the armatures almost touching the tube 7,plate ,,xvii4 fig4 #a74 ,with the magnet not excited1 the capillary stream was bright and of a slightly rosy-yellow tinge4 ,it varied a little in apparent diameter with the current4 ,as soon as the magnet was excited the capillary stream1 as also 7in a less degree7 that in the bulbs1 were seen to contract1 and to change from a rosy tint to a distinctly blue-violet4 ,the polished armatures1 acting as reflectors1 showed this change of tint in a most marked manner each time the magnet was excited4 ,at the same time the capillary stream was seen to run into the negative bulb1 as if overflowing1 and with an effect resembling the 8tailing-over0 of a gas-flame4 ,this effect took place each time the magnet was excited1 and was not found at the positive-bulb end4 ,sidenote3 ,spectrum examined4 ,occasionally1 when the magnet was excited1 flashes of light were discharged in the negative bulb from the capillary towards the violet-pole4 ,the spectrum was then carefully examined4 ,no change was seen in the actual position of any of the lines or bands when the tube was influenced by the magnet1 but those towards the violet end of the spectrum were conspicuously brightened4 ,sidenote3 ,negative bulb between poles of the magnet4 ,positive bulb within action of the magnet4 7#d7 ,the extremity of the negative bulb was now placed between the poles of the magnet4 ,a bright violet-coloured arc1 following the magnetic curve1 was at once formed1 as in the case of the large ,plcker tubes2 and at the same time a straight stream of not very bright light ran along the bulb4 ,the positive bulb was next placed within the action of the magnet2 and immediately a brilliant spiral of flickering light appeared in the bulb1 lighting it up1 and reminding one in shape of the spiral which water forms on being poured from a lipped jug 7see ,plate ,,xvii4 fig4 #i74 ,sidenote3 ,spiral formed4 ,this was repeated each time the magnet was excited4 ,the spiral1 though flickering in character1 was permanent in form1 and inclined to the side of the tube which was in contact with the ,n pole of the magnet4 ,oxygen-tubes4 ,sidenote3 ,o tube ,no4 #a2 spectrum described4 ,a tube 7,no4 #a7 was lighted up and examined with the spectroscope1 and found to give the spectrum shown on ,plate ,,xiv4 spectrum #c1 but with a strong set of ,h lines in addition4 ,sidenote3 ,o tube ,no4 #b2 spectrum described4 ,a second tube 7,no4 #b7 was then lighted up4 ,the spectrum was a bright one1 similar to the foregoing1 the principal ,h lines being present1 but not strong4 ,sidenote3 ,tube-glow described4 ,effect upon glow when magnet excited4 ,bulbs between poles of the magnet4 ,effect of magnet on spectrum4 ,the red region was indistinct1 and showed no prominently bright line4 ,the bulbs were mainly of a slightly blue-grey tint1 with a steady glow4 ,capillary stream quite pale white1 with a very slight tinge of red4 ,violet-glow small and confined to the electrode4 ,upon the magnet being excited1 the capillary stream became intensely brighter1 and the glow in both bulbs contracted into a single bright stream1 which curved towards the sides of the bulbs at right angles to the magnetic poles1 and changed from side to side with the current4 ,this effect was very marked1 and was more apparent in the positive than the negative pole4 ,a faint stratification was seen in both bulbs4 ,upon either bulb being placed between the armatures1 the glow left the electrode point and condensed into one bright stream1 running along the side of the tube and curving at each end 7,plate ,,xvii4 fig4 #aj74 ,no trace whatever of tendency to form a spiral was seen4 ,the spectrum with the magnet on was very conspicuously brightened up throughout4 ,a set of fluted bands with a bright line among them appeared in the red1 and several lines or bands appeared in the violet which could not be seen before4 ,the bright red line1 upon measurement1 proved to be the hydrogen-line ,c4 ,it thus seemed brighter in proportion than the ,f line1 although1 with the magnet off1 the latter was well seen1 while the ,c was not4 ,no actual change in position of the spectrum-lines could be detected4 ,it is to be noticed that the ,o tubes employed were those used by me in former experiments1 and had the bright lines now attributed to hydrocarbon impurity4 ,their bulb-effects differed1 however1 entirely from those of the ,,co tube4 7,compare figs4 #aj and #aa1 ,plate ,,xvii47 ,hydrogen-tubes4 ,sidenote3 ,h tube1 ,no4 #a2 glow described4 ,a small ,h ,geissler tube 7,no4 #a7 was selected1 and lighted up by the small coil4 ,the capillary was a bright white-pink stream1 with a tendency to redden at times4 ,the bulbs were both of a faint blue-grey tint1 with coarse lenticular stratification4 ,the violet-pole glow was pale and white as compared with that of ,n4 ,sidenote3 ,when the magnet was excited1 whole character of tube changed4 ,unexcited spectrum described4 ,effect when magnet was excited4 ,when the magnet was excited1 the whole character of the tube changed4 ,the capillary stream diminished in brightness and in apparent volume1 and changed to a deep amber-yellow4 ,the bulbs lost some of their light1 and their coarse stratification2 being1 in lieu1 filled with a vertical condensed stream of moderate light1 in which a fine stratification only was seen4 ,the stream in the positive bulb had a tendency to the spiral form4 ,the capillary1 each time the magnet was excited1 8tailed over0 into the negative bulb1 as in the case of ,n1 looking as if it were squeezed out of the capillary bore4 ,the unexcited spectrum was found to consist of the usual principal lines of ,h on a continuous glow1 with the intermediate bands and finer lines1 which are usually suspected to be due to impurity4 ,the sodium-line was also seen4 ,when the magnet was excited1 the spectrum grew much fainter--the continuous glow in the red and blue1 and the red and blue lines1 nearly disappearing1 and the line in the green alone shining out conspicuously4 ,no change of place in the lines could be noticed4 ,sidenote3 ,no4 #b ,h tube2 effects described4 ,a longer ,h tube 7,no4 #b7 was then tried1 with similar effects1 except that the diminution in brightness was not so conspicuous4 ,when the negative bulb of the tube ,no4 #a was placed between the poles of the magnet1 a stream of light was formed1 and the stratification became finer4 ,the same effect took place with the positive bulb1 with a tendency to the spiral form4 ,water-,gas 7,h,o7 tube4 ,sidenote3 ,water-gas 7,h,o7 tube2 effects produced described4 ,a faint purple glow was seen in each bulb1 the tube not lighting-up brightly4 ,the capillary showed a slightly rosy-tinted1 grey stream of brighter light4 ,with the magnet on1 the glow in the bulbs was condensed into a single bright stream4 ,the capillary brightened up1 and assumed a yellow tint--this effect being principally confined to that portion which was between the conical ends of the armatures1 and gradually diminishing as the distance increased from these4 ,without the magnet1 the principal ,h lines showed brightly in the spectrum1 the ,o lines being misty and indistinct4 ,with the magnet on1 the ,o lines and spectrum generally brightened up4 ,ammonia-tube4 ,sidenote3 ,ammonia-tube2 lighting-up described4 ,spectrum described4 ,this tube was difficult to light up4 ,hardly any light was seen in the bulbs1 except a very faint purple glow at the electrodes4 ,in the capillary part a fairly bright stream of purple-white light appeared4 ,the spectrum was a faintly shown one of ,n and ,h4 ,the effect of the magnet was to reduce the brightness of the glow in the capillary1 but with little marked action on the bulbs1 except to condense the faint glow into a slightly bright stream running along the side of the tube4 ,on a subsequent examination the tube and spectrum both brightened up under the influence of the magnet4 ,the ,n lines1 which were faint without the magnet1 shone out under its influence distinctly--the red and yellow parts of the spectrum specially showing this effect4 ,the ,h lines also brightened up1 but hardly so much in proportion as the ,n4 ,carbonic-,acid tube4 ,sidenote3 ,tube marked ,c ,a2 lighting-up described4 ,a ,geissler tube marked ,c ,a was examined4 ,capillary stream a brilliant bluish white2 bulbs grey-blue1 with a slight tint of green2 slight stratification in positive bulb2 stream diffuse1 not quite filling the bulbs1 and changing in volume as the coil-break was touched2 glow round the violet-pole considerable1 but markedly white in tint1 rather than violet2 stratification strong in capillary4 ,with magnet excited1 the capillary stream diminished in volume1 but greatly increased in brightness4 ,it 8tailed over0 into the negative bulb1 and the stream through both bulbs curved towards the sides4 ,a slight pattering noise was heard in the tube4 ,in the positive bulb bright1 imperfectly formed1 saddle-shaped rings of light1 with a tendency to spiral formation1 were seen1 somewhat similar to the effects in the ,plcker tube after described 7see ,plate ,,xvii4 fig4 #aa74 ,sidenote3 ,effects when magnet was excited4 ,the whole spectrum1 under influence of the magnet1 became much brightened up4 ,faint bands in the red came out bright1 as also did some in the violet4 ,the violet-glow was examined 7without the magnet71 and the light was found condensed into four prominent shaded bands1 one red1 one yellow-green1 one green1 and one blue1 with fainter bands seen between4 ,chlorine-tubes4 ,sidenote3 ,chlorine-tube ,no4 #a lighted-up4 ,action of magnet upon the tube and spectrum4 ,a chlorine-tube 7,no4 #a7 was lighted-up with the small-coil4 ,capillary stream of a pale green tint4 ,bulbs with very little glow in them2 spectrum pale1 and not very distinct4 ,under action of the magnet this tube brightened up throughout1 and the glow became more condensed1 and ran to the sides of the tube4 ,the spectrum also brightened1 the faint lines becoming stronger1 but the general character was preserved4 ,sidenote3 ,chlorine-tube ,no4 #b lighted-up4 ,effect on glow when magnet was put on4 ,a second chlorine-tube 7,no4 #b7 was then tried4 ,both bulbs were completely filled with a dense white 7very slightly rosy-tinted7 opaque light1 and capillary the same1 but brighter4 ,a very slight violet tinge was seen at the negative pole4 ,when the magnet was put on1 both bulbs were at once filled with flickering bright streams of light1 running towards the side of the tube1 according to the direction of the current4 ,the capillary stream at the same time changed from white to an intense bright green4 ,the spectrum without the magnet consisted of sets of lines1 with two well-marked absorption-spaces between1 all seen somewhat faintly1 as if through a mist4 ,sidenote3 ,changes in spectrum when magnet was excited4 ,when the magnet was put on1 the marked character of the absorption spaces was lost4 ,the sets of lines in the yellow-green and green started up intensely bright1 while those in the blue only slightly brightened4 ,the misty appearance was altogether lost1 and the bright lines all shone up upon a perfectly dark background1 with a strikingly metallic look2 we could not1 however1 trace change of position or actually new lines4 ,it seemed as if lines which had been faint in the yellow-green and green region suddenly increased in intensity1 the other parts of the spectrum not being similarly influenced4 ,they quite flashed up when sudden contact was made with the magnet commutator4 ,iodine-tubes4 ,sidenote3 ,iodine-tube ,no4 #a4 ,this tube 7,no4 #a7 had been used for photographic purposes1 and the bulbs were partly obscured by a white deposit4 ,sidenote3 ,lighting-up described4 ,effect of touching one wire with the finger4 ,on lighting it up1 both bulbs were filled with a violet-grey diffused light1 with much coarse well-marked lenticular stratification4 ,this stratification was mainly lost on changing the direction of the current1 but made its reappearance when one conducting-wire was touched with a finger4 ,this effect was still more marked when one finger of each hand was applied to the wire4 ,the capillary stream was of a pale lemon-yellow4 ,on putting on the magnet the light in the whole tube was nearly extinguished1 a faint thin stream of condensed light running through the centre of the tube alone remaining4 ,sidenote3 ,effect of the magnet4 ,on placing the bulbs between the magnet-poles1 effects were produced similar to those in the case of the tube1 after described 7p4 #add1 and marked ,si ,fl71 but in a less marked degree4 ,sidenote3 ,tube again tested4 ,the iodine-tube was subsequently again tested1 and it lighted-up better than on the last occasion1 showing nearly the same effects in bulbs and capillary1 the former having somewhat of a rosy tint and the latter an amber4 ,sidenote3 ,magnet effects4 ,the spectrum described4 ,change when magnet was excited4 ,on exciting the magnet1 the capillary part of the tube changed from amber to a decided light green4 ,the spectrum1 without the magnet1 gave one very bright line1 and several less bright ones near1 in the blue-green4 ,the rest of the spectrum1 with the exception of the absorption-spaces1 was misty and continuous1 with lines showing faintly through4 ,the red and yellow portions of the spectrum were quite bright4 ,when the magnet was excited1 the spectrum entirely changed4 ,the red and yellow portions of the spectrum1 and the misty continuous light1 all quite disappeared2 while a set of sharp lines on the yellow-green and green flashed up bright and clear1 and stood out alone upon a dark background1 in which the absorption-spaces were lost4 ,the effect was very strongly marked1 and gave a totally different character to the appearance of the spectrum4 ,the change seemed to arise from the suppression of one part of the spectrum1 and the increase in intensity of the lines in the other part4 ,sidenote3 ,no change in line-position4 ,the principal lines could not be traced to change in actual position4 ,this tube differing somewhat from a second one we examined 7,no4 #b7 in tint of glow and spectrum1 it suggested itself to us that there might be a partial mixture of ,n or ,h 7or both7 with the iodine vapour1 giving rise to some of the brighter parts of the spectrum which were extinguished under the action of the magnet4 ,sidenote3 ,comparison of iodine-tubes ,no4 #a and ,no4 #b4 ,comparison of the spectra4 ,we therefore compared these two tubes1 viz4 the old one 7,no4 #a7 and the new one 7,no4 #b71 and also their spectra1 by means of a comparison-prism on the slit of the spectroscope4 ,to the eye1 the tubes differed much in appearance4 ,no4 #a had a distinct transparent rosy tint throughout1 with considerable coarse flickering stratification2 and this contrasted strongly with the dense whitish light of tube ,no4 #b1 which showed neither movement nor stratification4 ,the spectra were also found different in general look4 ,that of tube ,no4 #a was strongly tinged in the red and yellow1 and showed a bright continuous spectrum1 crossed by many sharp lines1 with little trace of absorption-spaces4 ,the spectrum of ,no4 #b was much whiter in tint1 showed very little of the red and yellow1 and the absorption-spaces were very dark4 ,a few bright lines1 mainly in the yellow-green and green1 were faintly seen4 ,sidenote3 ,the two tubes examined in detail4 ,no4 #b4 ,the two tubes were then examined separately in detail4 ,no4 #b1 excited by the magnet1 showed curious effects4 ,the glow was rendered weak and intermittent1 and the rosy tint almost disappeared4 ,the capillary changed to a decided green colour1 and the positive electrode was surrounded by a yellow glow4 ,the changes in the spectrum were no less decided4 ,without the magnet1 the spectrum was found to be a bright continuous one of ,h 7with a full set of principal and intermediate lines7 and ,n--the ,n spectrum being rather faint and misty1 with very slight1 if any1 traces of the iodine-spectrum4 ,on the magnet being excited1 the spectrum changed as if by magic2 the ,h and ,n spectra disappeared 7except hydrogen ,f1 which still faintly remained71 and the iodine lines1 mostly in the yellow-green and green1 shone out wonderfully sharp and bright on quite a dark ground4 ,no4 #a1 upon examination1 showed between the magnet-poles only the same changes as on last occasion4 ,the spectrum seemed to be one of iodine1 with the addition of slight traces of the ,h spectrum4 ,sidenote3 ,effects discussed4 ,on excitation of the magnet1 the misty continuous part of the spectrum nearly disappeared1 and the bright lines shone up sharply upon the dark background as before4 ,the effects in the case of both tubes were strongly marked4 ,the impression as to tube ,no4 #b was that1 without the magnet1 the slight iodine-spectrum was overpowered and masked by the ,n and ,h spectra2 while under the influence of the magnet the ,n and ,h spectra were almost altogether suppressed1 the iodine-spectrum being at the same time intensified4 ,the disappearance of the continuous spectrum under the action of the magnet in ,no4 #a 7with the supposition it was mainly ,h7 would be accounted for in the same way4 ,bromine-tubes4 ,sidenote3 ,bromine-tube ,no4 #a4 ,lighting-up described4 ,effect of the magnet4 ,bromine-tube ,no4 #b4 ,effect of magnet4 ,this tube 7,no4 #a7 had been previously worked for photographic purposes4 ,excited by the small coil1 the whole tube was filled with a faint flickering light4 ,the positive bulb contained a faint purple glow1 with a yellow-green tinge at the electrode1 a curious flickering stream of light flashing from the electrode to the side of the tube4 ,the negative pole showed pretty much the same effect as the positive4 ,the capillary stream expanded at the opening into the positive bulb1 but ran in a condensed stream into the negative bulb4 ,in colour it was of a rather bright lilac4 ,upon putting the magnet on1 the light-glow in the tube was at once and permanently extinguished1 the coil still working as if the current passed4 ,the same effect happened repeatedly2 but now and then the tube lighted-up for a second1 showing spiral arrangement in the bulb4 ,we tried another bromine-tube 7,no4 #b73 it lighted-up easily2 both bulbs were filled with a purple stream of light2 capillary stream bright grey4 ,the glass of the tube was strongly fluorescent and of a yellow tinge4 ,when the magnet was excited the stream of light was somewhat condensed in the bulbs1 and flew to the side of the tube2 while the capillary stream at the same time brightened4 ,the spectrum without the magnet was fairly bright2 it increased in brightness under the influence of the magnet1 and additional lines appeared2 but we considered them to be only faint existing ones brightened up4 ,no change in the position of the principal lines was traced4 ,silicic-,fluoride tubes4 ,sidenote3 ,si ,fl tube4 ,lighting-up described4 ,effect of magnet4 7#a7 ,a tube marked ,si ,fl had been worked for photographic purposes2 it lighted-up easily4 ,both bulbs were filled with a brown-pink diffused light1 inclined to condense into a stream in the positive bulb4 ,the violet glow was very bright1 and nearly filled the space round the electrode4 ,the capillary stream was of a bright violet tint4 ,the effect of the magnet was to decrease the intensity of the light throughout the whole tube4 ,in the positive bulb the stream broke up into a number of vibrating streamlets1 with little bright threads of light intermixed1 which flew towards the side of the tube at right angles to the magnetic poles4 ,there was an inclination to spiral arrangement in the streamlets4 ,this stream changed from side to side of the tube coincidently with change in the magnetic poles4 ,at the negative pole the violet glow formed an arc in the direction of the magnetic curves1 while a spiral of fainter 7positive87 light was formed in the upper part of the bulb4 ,a slight ringing sound was heard in the tube4 ,sidenote3 ,comparison of ,si ,f and ,si ,fl tubes4 7#b7 ,we compared two tubes 7,si ,f and the one marked ,si ,fl74 ,the ,si ,fl tube in general effect1 and in its spectrum1 when lighted-up1 resembled ,si ,f4 ,we compared the one tube under the influence of the magnet with the other not so1 by means of a comparison-prism on the slit4 ,as the spectroscope and second tube were necessarily removed some distance from the magnet1 the spectrum of the tube between the poles was not bright4 ,we could not trace a change of position in any of the principal lines4 ,the tube between the poles was brightened up when the magnet was in action#ae4 ,sulphuric-,acid 7,,so7 tubes4 ,sidenote3 ,,so tube ,no4 #a2 lighting-up described4 ,effect of the magnet4 ,changes in the spectrum4 7#a7 ,excited by the small coil1 both bulbs of this tube 7,no4 #a7 lighted-up brightly1 with a misty light-blue tinted stream of opaque light1 a yellow glow appearing at the negative pole4 ,the capillary stream partook of the same blue tint1 but was whiter and brighter4 ,under the magnet's influence1 the glow in the bulbs flew to the side of the tube in flickering streams of light1 the capillary at the same time changing to a distinctly green tint4 ,the spectrum without the magnet consisted of four fairly bright bands of light in the yellow1 green1 blue1 and violet1 connected by a faint misty continuous spectrum 7,o or possibly the hydrocarbon spectrum found in ,o tubes by way of impurity74 ,when the magnet was excited1 this spectrum entirely disappeared2 and a set of bright metallic-looking lines upon a dark background 7line-spectrum of ,s7 took its place4 ,this effect was produced whenever the magnet was excited1 and we tried it several times1 to make sure of the complete change4 ,after a time1 when the magnet1 battery1 and the coil-power were all weaker1 with the magnet on1 we obtained a compound of both spectra1 the bright lines being seen upon the continuous spectrum in which the bands appeared4 ,when the magnet was taken off1 the bright lines disappeared1 and the ,o spectrum alone remained4 ,sidenote3 ,,so tube ,no4 #b examined4 7#b7 ,we also tried another ,,so tube 7,no4 #b7 which had been worked for photographic purposes1 and was suspected of a carbon impurity4 ,without the magnet1 the spectrum was very like that of the first tube2 but when the magnet was excited1 the spectrum only brightened1 and no bright metallic-looking lines appeared4 ,sulphur-tube4 ,sidenote3 ,sulphur-tube4 ,lighting-up 7without heating7 described4 7#a7 ,a small bent vacuum-tube containing some solid sulphur1 excited by the smaller coil1 and without being heated1 gave a narrow stream of bright blue-green light running straightly through it4 ,with the magnet on1 this stream was deflected in the bulbs1 and the capillary changed from a blue-green to a distinct rosy tint4 ,sidenote3 ,effect of magnet4 ,changes in the spectrum4 ,without the magnet1 the spectrum consisted of four bright bands1 with a continuous spectrum between1 resembling that of ,,so tube ,no4 #a4 ,with the magnet on1 the spectrum brightened1 especially in the yellow and red1 which were dull before2 and a set of lines appeared upon it 7a line or band in the yellow especially showing7 which were not seen before4 ,the lines were distinct1 but not very bright4 ,the action on the capillary was noticed to be strongest just between the conical points of the armatures2 and1 in accordance with this1 the central part of the spectrum-band in the red and yellow showed an increased brightness4 ,sidenote3 ,effects when one of the bulbs of the tube was heated4 ,changes in the spectrum under influence of magnet4 7#b7 ,one of the bulbs of the tube was then gradually heated with a small gas-flame4 ,the single stream in the heated bulb became somewhat deflected and broken up into a number of smaller streams2 and these1 when placed under the magnetic influence1 had small spark-like threads of light running among them4 ,the capillary1 as the tube was heated1 and the sulphur rose in it1 changed somewhat in tint1 and1 under the magnetic influence1 became of yellow-rose hue4 ,as the heat was applied to the bulb the bands of sulphur gradually appeared in the field of the spectroscope1 until at last the band-spectrum of sulphur entirely took the place of the spectrum seen in the cool tube4 ,the magnet being excited1 the spectrum changed at once1 a set of bright sharp lines 7line-spectrum of ,s7 appearing upon a faint and dull image of the band-spectrum4 ,this effect was constantly repeated upon the magnet being excited4 ,the magnet being taken off1 the band-spectrum alone was to be seen4 ,,chapter ,,xv4 ,,effect ,,of ,,magnet ,,on ,a ,,capillary ,,glass ,,tube4 ,sidenote3 ,capillary portion of a ,geissler tube tested in three ways4 ,the capillary portion of a ,geissler tube was cut away from the bulbs1 cleaned1 and connected by a small vulcanite tube with the gas-pipe in the room conveying coal-gas at ordinary pressure4 ,the flame was small and oval in shape1 #h millims4 high1 by #d millims4 wide1 and burnt quite steadily4 7,plate ,,xvii4 fig4 #ac47 ,sidenote3 ,no effect on flame4 7#a7 ,the capillary tube was placed between the poles of the excited magnet1 almost1 but not quite1 touching them2 no effect at all was produced on the flame4 7#b7 ,the tube was placed so that the conical ends of the armatures were allowed to compress the centre of it between them2 still no effect was produced on the flame4 7#c7 ,the tube was placed so that the straight sides of the armatures compressed it between them2 still no effect took place on the flame4 ,sidenote3 ,flame between poles of magnet4 7#d7 ,the flame itself was placed between the poles of the magnet4 ,it was slightly drawn towards one pole with an inclination to form the magnetic curve4 ,sidenote3 ,quill glass tubing tested4 ,no effect on the flame4 7#e7 ,a piece of quill glass tubing was selected1 #e millims4 in diameter and #a millim4 thick1 and drawn out to a point1 the end of which was snapped off and the tubing connected as before4 ,the flame was #bj millims4 high1 and #e millims4 across1 and somewhat lambent4 ,on being placed 7#a7 between the conical ends and 7#b7 between the flat ends of the armatures1 no effect could be seen on the flame4 ,sidenote3 ,effect on taper and spirit-lamp flames4 7#f7 ,a small taper-flame was placed between the poles of the magnet3 no effect was produced1 except that the flame gave a slight 8jump0 each time the magnet was excited4 ,a spirit-lamp flame was tried with a similar result4 ,action of ,magnet on a bar of heavy glass4 ,sidenote3 ,heavy glass bar and mounting described4 ,a piece of heavy yellow-tinted glass was selected1 being a bar #aj centimetres in length1 and #h millimetres square4 ,this was mounted in a frame with a ,nicol prism at one end1 and a double-image prism 7next the eye7 at the other4 ,sidenote3 ,placed along poles of magnet4 ,effect of magnet on candle-images4 7#a7 ,the glass bar and mounting were placed upon and along the poles of the magnet 7in the direction of the magnetic curves71 and the double-image prism and ,nicol were so adjusted that two images of a candle were seen--the one below bright and normal1 the one above1 by rotation of the prism1 as nearly as possible extinguished 7,plate ,,xvii4 fig4 #d74 ,on exciting the magnet the faint image at once conspicuously brightened1 at the same time assuming a slightly green tinge4 ,to get full effect of brightening1 it seemed necessary to have good pressure-contact between the battery-wires and the binding-screws4 ,sidenote3 ,effect on using a tourmaline as analyzer4 7#b7 ,using a tourmaline as analyzer in lieu of the double-image prism1 the candle-flame was seen alternately brightened and darkened1 as the tourmaline was rotated2 and when the image was obscured by rotation1 excitation of the magnet caused it to brighten strongly4 ,this effect was accompanied by the apparent removal of a dusky red patch or spot1 which occupied the centre of the field when the flame was obscured4 ,sidenote3 ,bar placed at right angles to the poles3 no effect produced4 7#c7 ,the bar of glass and double-image prism being placed between the conical ends of the armatures1 but at right angles to1 instead of along1 the poles1 upon excitation of the magnet no effect at all was produced4 7#d7 ,the bar and prism being placed in the same position between the flat ends of the armatures1 no effect at all was produced4 ,sidenote3 ,slight effect on second experiment4 7#d;a7 ,experiment ,no4 #d was repeated4 ,it was thought that on excitation of the magnet the secondary image slightly brightened2 but there was a doubt about it1 and the effect 7if any7 was slight4 ,sidenote3 ,effects produced when a biquartz was introduced4 7#e7 ,the apparatus was now changed for one of the following arrangement3--#a1 a rotating ,nicol prism next the eye2 #b1 the glass bar2 #c1 a biquartz with the halves horizontal2 #d1 another ,nicol prism4 ,the neutral-passage tint of the biquartz was found to be rather green 7from mixture with the yellow of the glass74 ,sidenote3 ,change in colour of the halves4 7i47 ,placed along the poles of the magnet and the magnet excited1 a change of tint was seen in both halves of the biquartz1 the slightly purple-reddish tint of the upper half passing into a full purple4 ,effect not so marked as with the double-image prism4 7ii47 ,placed across flat ends of the armatures 7as in experiment ,no4 #d7 no effect was seen4 ,,chapter ,,xvi4 ,,effect ,,of ,,magnet ,,on ,,wide ,,air 7,,aurora7 ,,tube4 ,sidenote3 ,wide air-tube described4 ,a large1 wide air-tube was tried2 it was #ad inches long by #a inch in diameter1 of the same bore throughout1 and with straight platinum electrodes4 ,sidenote3 ,magnet effect when tube placed vertically between conical armatures4 7#a7 ,to excite it the larger coil was used4 ,the tube was filled with bright1 steady1 rosy light1 and beautiful stratification1 which1 as it flickered1 seemed to incline to a continuous spiral 7,plate ,x4 fig4 #h74 ,this stratification was very close and fine1 and extended nearly throughout the tube4 ,on excitation of the magnet 7the tube having been placed vertically between the conical armatures71 the glow was condensed into a bright solid line or stream of light at the point which lay directly between the poles4 ,this line or stream expanded into an elongated funnel-shape as it retreated from this centre towards the extremities of the tube1 the stratification showing itself more distinctly as the glow of light became less dense 7,plate ,,xviii4 fig4 #c74 ,the stream of light was driven away at right angles to the poles1 and changed from side to side of the tube with the direction of the current4 ,with the small coil this tube showed only a flickering stream of light1 with very slight indications of stratification4 ,sidenote3 ,effect when tube placed horizontally between the armatures4 7#b7 ,the tube was placed horizontally between the conical ends of the armatures4 ,the condensed stratified stream of light flew upwards and downwards 7according to direction of current7 instead of to the respective sides of the tube4 ,sidenote3 ,tube placed along the poles of the magnet4 7#c7 ,the tube was placed along the poles of the magnet4 ,in the interval between these the stream was driven upwards1 but at either end sideways1 right or left according to whether the pole was ,n4 or ,s4 7,plate ,,xviii4 fig4 #d74 ,the result gave a complete spiral of stratified condensed light within the tube4 ,note on ,stratification4 ,sidenote3 ,stratification in small tubes arranged in series4 ,the current from the large coil was sent through a set of five small ,french vacuum-tubes1 of equal calibre1 containing salts of strontium and calcium1 and showing phosphorescent effects4 ,these tubes were arranged in single series2 and1 from the colour of the glow-discharge1 were presumed to contain rarefied air in contact with the salts4 ,a strong coarse stratification was seen in the central 7,no4 #c7 tube4 ,tubes ,nos4 #b and #d also showed stratification1 but in a less degree2 while the outside tubes1 ,nos4 #a and #e1 showed no stratification at all4 ,the current was steady1 and these effects did not fluctuate4 ,effect of ,magnet on ,plcker 7,air-7 ,tube4 ,sidenote3 ,plcker air-tube4 ,lighting-up described4 ,effect of magnet on the positive-pole stream4 7#a7 ,a ,plcker air-tube was selected of the form shown on ,plate ,v4 fig4 #a1 and was excited by the small coil4 ,the ring was used for the positive pole1 the straight electrode for the negative4 ,when lighted up1 the tube glowed with a perfectly steady and quiescent light4 ,the negative electrode was surrounded by the usual bright violet glow1 extending itself and being gradually lost at a short distance from the wire1 while the ring let fall a faint1 tubular1 salmon-coloured1 diffused stream of light1 which met the violet glow as it approached the negative pole4 ,the tube was then placed vertically between the poles of the electro-magnet1 the armatures being almost in contact with the sides of the tube around the negative pole4 ,on excitation of the magnet1 an instantaneous change took place4 ,the stream of light from the positive pole contracted itself1 so that it became of a long funnel-shape 7the ring forming the mouth of the funnel71 while it tapered almost to a point where it met the violet glow4 ,sidenote3 ,effect on negative violet glow4 ,the stream also became very brilliant 7the sides of the tube being left proportionately free from light71 and crossing it were a set of bands1 or stri1 having a waving or vibratory motion4 ,the whole of the negative violet glow was simultaneously gathered into a brilliant narrow arc1 which stretched across between the poles of the magnet4 ,these effects are shown on ,plate ,v4 fig4 #a4 ,the edges of the arc were remarkably sharp and well defined1 and with no surrounding aura or shading off4 ,sidenote3 ,arc of light followed the magnetic curves4 ,by moving the tube between the armatures it was seen that the arc of light followed the magnetic curves4 ,if the tube was moved upwards1 the arc curved towards the zenith1 if downwards1 contrariwise2 and a middle position could be selected1 in which the edges of the arc were nearly parallel4 ,moving the tube a short distance from the pole had the effect of rendering the arc more diffuse1 but not of otherwise altering its character4 ,sidenote3 ,direction of the current changed4 ,effects on glow described4 7#b7 ,the direction of the current in the tube was then changed2 and1 without the magnet1 the ring electrode was surrounded by a diffused violet glow2 while the straight wire gave forth a faint salmon-coloured stream of light1 spreading up to the ring4 ,sidenote3 ,magnet effects described4 ,on negative pole4 ,rings from positive pole described4 ,effects on rings of making and breaking contact with magnet4 ,shape of rings described4 ,on excitation by the magnet 7the positive pole being now placed between the armatures71 the violet glow of the negative pole contracted into a compact mass round the ring electrode4 ,at the same time from the positive pole sprang a set of bright saddle-shaped rings1 which increased in size as they advanced2 and spreading upwards with a rapid but smooth motion towards the negative pole1 closely approached to1 but never actually came in contact with1 the violet glow4 ,the positive end of the tube was otherwise but slightly lighted1 and the sudden appearance of this brilliant stream of rings of light was very striking4 ,a single bright ray was also seen running from the positive wire1 in a somewhat transverse course1 along one side of the tube4 ,when wire-contact with the magnet ceased1 so that it was not excited1 the rings ran back in succession to the positive pole and disappeared1 and by making and breaking contact they were caused to advance and retire at will4 ,they were accompanied by a waving or vibratory motion1 and were evidently of the same character as the smaller stri or bands mentioned as seen when the ring formed the positive pole4 ,the general appearance was that of a hollow cone of light 7the base towards the negative pole71 composed of brilliant rings with dark spaces between1 which appeared and expanded under the magnetic influence1 and contracted and disappeared on its removal4 ,the rings did not appear to be flat disks1 but were somewhat curved or saddle-shaped4 ,they reminded one much of the diatom ,campylodiscus spiralis2 that is to say1 they were apparently flat if looked at from above1 but like a figure of #h when viewed sideways1 the peak of the saddle forming a kind of brilliant point or apex4 ,all this is difficult to describe2 but an illustration from a sketch made of the tube is given on ,plate ,,xvii4 fig4 #b4 ,sidenote3 ,negative pole placed vertically on the magnet4 7#c7 ,the negative pole 7straight electrode7 was then placed vertically on one of the poles of the electro-magnet4 ,on excitation1 the violet glow was contracted into a small upright brush or column of bright light1 with a slight inclination to curvature4 ,sidenote3 ,tube laid horizontally across poles of magnet4 7#d7 ,the same ,plcker tube was laid horizontally across the poles of the electro-magnet 7without armatures71 the respective electrodes being above each pole4 ,sidenote3 ,effects produced4 ,from the negative 7straight electrode7 pole sprang a dense and compact arc of violet light1 in the direction of the magnetic curves1 which terminated at the upper circumference of the tube1 but which1 if prolonged1 would have followed the curves to the opposite pole4 ,the stream from the positive pole was very considerably brightened1 as in the other experiments1 but did not appear in the form of rings or waves4 ,it assumed that of a bright steady continuous glow1 which formed round the tube a not perfectly continuous1 but distinct and well-marked1 spiral4 ,this form of discharge seems connected with the peculiar contour of the rings mentioned in experiment #b4 ,one might1 indeed1 conjecture the spiral-shaped glow to be a ring of light extended or drawn out towards the negative pole4 ,sidenote3 ,effects like those obtained by ,gassiot4 ,experiment ,no4 #b seems in result very like that of ,gassiot's with his grand battery and the ,royal ,institution magnet1 the effects 7though of course upon a smaller scale7 being similar to those obtained by him4 ,effect of ,magnet on ,plcker ,tube 7,tin ,chloride74 ,sidenote3 ,plcker tube 7tin chloride74 ,lighting-up described4 ,a large ,plcker tube was examined1 which had a bulb attached at each end1 communicating with the central portion by a narrow neck or constriction4 ,on connexion with the small coil1 a narrow stream of pale diffused cobalt-blue light ran along the whole tube1 from point to point of the electrodes1 the positive wire at the same time glowing with an aura of amber-yellow light4 7,see ,plate ,,xvii4 fig4 #c1 where the narrow stream of light is shown by dotted lines47 ,at the two necks or constrictions the stream of light was perceptibly brightened4 ,sidenote3 ,effects of magnet upon the stream4 ,when the magnet was connected1 the stream in the positive bulb was not much changed1 but only slightly bent4 ,in the central partition of the tube and in the negative bulb1 the stream of light was broken and split into a number of smaller streams1 and at the same time bent or forced against the sides of the tube4 7,see ,plate ,,xvii4 fig4 #c47 ,sidenote3 ,peculiar noise within the tube4 ,in the central partition1 the blue streamlets were accompanied by a number of spark-like threads of golden light1 which shone out among them as the whole vibrated against the side of the tube2 at the same time a peculiar pattering1 as of a miniature hail-storm within the tube1 made it ring with a slightly metallic tinkle4 ,the direction of the bending or deflection of the stream was at right angles to the axis of the poles of the magnet1 and changed from side to side of the tube as the direction of the current from the coil was varied4 ,sidenote3 ,spectrum described4 ,without magnet4 ,with the magnet excited4 ,in the positive bulb the stream1 instead of joining the point of the electrode1 left this and ran along one side of the whole length of the wire4 7,see effect1 ,plate ,,xvii4 fig4 #c47 ,the spectroscope was applied to the neck of one of the bulbs where the stream was bright4 ,without the magnet a faint continuous spectrum1 mainly of the blue and green1 with very slight traces of the yellow and red1 was seen4 ,upon this1 five or six faint but sharp and metallic-looking lines were seen4 ,on the magnet being excited1 the continuous spectrum was not changed2 but the sharp lines shone out brighter and clearer1 one in the blue being especially conspicuous4 ,these lines were measured with a micrometer2 and their places being compared with ,lecoq de ,boisbaudran's 8,spectres lumineux10 they were easily recognized to be those of tin4 ,on each excitation of the magnet the same brightening of the lines took place4 ,effect of ,magnet on ,tin-,chloride ,geissler ,tube4 ,sidenote3 ,geissler tube1 ,sn ,cl1 examined4 ,glow described4 ,effect of the magnet4 ,we then examined a ,geissler tube1 marked ,sn ,cl4 ,when first excited by the small coil1 the spark passed freely4 ,the glow in the bulbs was of a diffused1 light purple tint2 the positive electrode had a bright yellow glow around it4 ,the capillary stream was of a sharp green-yellow1 at times brightening up to a metallic-looking green4 ,when the magnet was first employed1 the tube distinctly and permanently brightened up throughout4 ,sidenote3 ,spiral formed in positive bulb4 ,glow in tube extinguished4 ,the negative bulb was not much changed in appearance2 but in the positive bulb a curious permanent and steady cloud-like spiral1 of a purple colour1 made its appearance1 and lasted while the tube was under the magnetic influence4 7,see ,plate ,,xvii4 fig4 #ab47 ,after a short time the tube seemed to lose a great deal of its conducting-power1 and to light up in a feeble and intermittent manner1 brightening only when the coil was made to work its best4 ,while in this condition1 the magnet 7which had been previously disconnected7 was excited1 and at once what moderate glow was still shining in the tube was totally extinguished4 ,at first it was thought some accident might have happened to the conducting-coil wires2 but repeated trials satisfied us that the effect was due to the magnetic influence alone4 ,efforts were made1 by looking to the coil and battery1 to brighten up the tube as at first1 but they quite failed2 and it was evident some change had taken place in its conducting qualities4 ,this tube was accidentally broken1 so that we had no opportunity to renew the experiments4 ,sidenote3 ,another tin-chloride tube tried4 ,glow described4 ,we subsequently tried another tin-chloride tube1 purchased of ,mr4 ,browning4 ,this lighted up like the former tube1 but brighter4 ,there was an amber glow at the junction of the negative bulb which adjoined the capillary part4 ,this was lost on putting on the magnet4 ,at the same time a perceptible pattering ringing noise was heard in the tube1 and metallic-looking threads of light ran through the bulbs4 ,sidenote3 ,spectrum described4 ,without the magnet1 the spectrum was a continuous faint misty one1 with bright lines of tin occasionally flashing up4 ,with the magnet1 the tin lines at once shone out bright1 strong1 and clear upon a black background1 the change in effect being very marked4 ,,chapter ,,xvii4 ,,effect ,,of ,,magnet ,,on ,,bulbed ,,phosphorescent ,,tube4 ,sidenote3 ,large phosphorescent bulbed tube4 ,lighting-up described4 ,spectrum described4 ,glow when discharge stopped1 described4 ,mr4 ,john ,browning kindly lent me a large phosphorescent tube with five bulbs1 said to be filled with anhydrous sulphurous-acid gas 7,,so74 7,see ,plate ,,xviii4 fig4 #a47 ,this tube lighted up beautifully with the large coil4 ,the connecting tubular parts of it were filled with a bright1 beaded1 transparent1 rosy light2 while the bulbs glowed with a more opaque blue-tinted effect4 ,the spectrum of the tubular part was found to agree exactly with the principal bright band seen in a ,,so ,geissler tube4 ,the spectrum of the bulb-glow was a faint green-blue continuous one1 with bright bands or lines faintly flashing up at times4 ,when the discharge was stopped1 the tube still glowed with a moderately bright1 opaque1 grey-green light4 ,this glow gradually faded out1 always commencing with the bulb forming the negative or violet pole1 and so dying out1 bulb by bulb1 towards the positive pole4 ,the negative-pole bulb at times was1 on suddenly stopping the current1 hardly lighted at all1 the other bulbs being luminous4 ,sidenote3 ,comparison with ,,so ,geissler tube4 7#a7 ,we compared the large tube with a ,,so ,geissler tube1 by means of a comparison-prism on the slit1 with the result before detailed4 ,the ,geissler tube1 however1 showed no after-glow4 ,sidenote3 ,effects in bulbs on lighting-up the tube described4 ,effects of reversal of the current4 ,after-glow restored by passing of current4 7#b7 ,we lighted up the ,browning tube with the large coil4 ,the negative bulb was always the least filled with the blue opaque vapour1 and the other bulbs increased in vapour-density in the order they approached towards the positive bulb4 ,when the current was reversed1 so that the negative and positive glow changed places1 the negative bulb still remained transparent1 although the positive opaque glow had 7presumably7 been thrown into it4 ,when the after-glow had quite disappeared in the bulbs1 it was again strongly restored1 by the passing of the current for a few seconds only through the tube4 ,sidenote3 ,effect of reversal of current on positive-pole glow4 7#c7 ,the tube was well excited1 and the four bulbs 7other than the negative one71 upon stopping the current1 glowed strongly4 ,the current was then sent through reversed1 so as to throw the negative glow for a few seconds into the positive bulb4 ,the after-glow in the positive bulb was at once extinguished4 ,on once more reversing the current1 it was only restored after a certain amount of continuance of the positive stream4 ,illustration3 ,plate ,,xviii4 ,sidenote3 ,effect of change of current on the three central bulbs4 ,the time during which the negative glow was thrown into the positive bulb did not appear sufficient to have heated it4 ,after rapidly changing the direction of the current several times and then stopping it1 the three central bulbs alone had an after-glow1 the two extreme ones having none1 being both equally transparent4 ,sidenote3 ,effect of heat on the bulbs4 ,effect of cooling by ether-spray4 7#d7 ,a moderate heat from a spirit-lamp was applied to the centre bulb 7a7 while the current was on2 and also 7b7 when this was stopped1 and the bulb glowed4 ,in the first case the bulb was found to get more transparent2 and in the second case the after-glow disappeared in a proportionately shorter time in the heated bulb than in the others4 ,to test the result of cooling the bulbs1 the negative-pole bulb and also the central one were each subjected to the action of ether-spray1 and also of ether and water-spray mixed4 ,this was done1 7a7 when the current was passing1 and 7b7 when it was stopped and the glow only was in the bulb4 ,the bulbs were cooled until a marked cold effect to the touch was produced4 ,we did not notice any difference in the behaviour of the bulbs so treated as compared with the others1 either when the current was passing or in the case of the after-glow4 ,sidenote3 ,negative-pole bulb between the armatures of magnet4 ,effects on negative and positive glow4 7#e7 ,we placed the negative-pole bulb between the conical points of the armatures1 and excited the magnet4 ,the negative glow contracted itself into a condensed violet-tinted crescent1 in accord with the magnetic curves4 ,the positive glow of the same bulb lost its beaded 7stratified7 character1 and was condensed into a bright stream of light1 which latter protruded from the small inner tube and formed a spreading spiral set of cloud-rings within the bulb 7see ,plate ,,xviii4 fig4 #b74 ,the action of the magnet seemed to be exercised in subduing the stratification1 condensing the glow into a bright stream of light1 and forcing the latter to 8tail over0 at each extremity of the tubular joints into the bulbs--this effect extending even so far as the second bulb4 ,when the positive bulb was placed between the poles of the magnet1 the glow was simply condensed into a bright stratified stream1 which flew to either side of the bulb4 ,sidenote3 ,effect of magnet on glow in bulb ,no4 #d4 7#f7 a4 ,bulb ,no4 #d 7see ,plate ,,xviii4 fig4 #a7 was placed between the poles of the excited magnet1 and the current was passed and then stopped4 ,the glow in that bulb faded away out of its order1 and earlier than in ordinary cases 7nearly as soon as ,no4 #b74 ,sidenote3 ,other bulbs tested in similar manner4 b4 ,the same and other bulbs were tested in a similar manner4 ,in all cases the bulb influenced by the magnet1 when the current was stopped1 was found perceptibly fainter in after-glow4 ,sidenote3 ,effect of magnet upon the after-glow itself4 c4 ,the tube was arranged with one of the bulbs between the poles of the unexcited magnet2 the current was passed and stopped1 and the after-glow obtained4 ,the magnet being then quickly excited1 the after-glow in the bulb1 under its influence1 faded out2 and the bulb became transparent1 perceptibly sooner than under ordinary circumstances4 ,we tried this several times1 with the same result in each case4 ,sidenote3 ,mr4 ,thompson's experiments on action of magnets upon liquid rings4 ,note4--,in relation to these experiments1 it may be mentioned that ,mr4 ,s4 ,p4 ,thompson1 of ,bristol1 is reported to have studied the action of magnetism upon rings of coloured liquid projected through water1 and to have observed their retardation and partial destruction in passing through a powerful magnetic field4 ,sidenote3 ,mr4 ,ladd's explanation of some of the phenomena observed4 ,mr4 ,ladd has suggested to me that some of the phenomena produced indicate a driving of the gas in the direction from the negative to the positive pole--a theory which is supported by the action of the magnet on the bulbs1 if this be considered a repulsive one as regards the gas influenced4 ,effect of ,magnet on small ,phosphorescent 7powder7 ,tubes4 ,sidenote3 ,tubes containing phosphorescent powders described4 ,we examined six vacuum-tubes containing phosphorescent powders1 which1 upon exposure to sunlight and removal to the dark1 or after passing of the electric current over them1 continued to glow in the tubes after the exciting cause had ceased4 ,they were of thin glass1 and of equal calibre throughout4 ,one was #f inches long and inch in diameter1 and had no label2 the other five were #g inches long and inch in diameter1 and were labelled respectively3-- ,strontium vert1 0 jaune1 ,calcium violet1 0 orange1 0 vert-bleutre4 ,sidenote3 ,lighting-up of the tubes described4 ,effect of magnet on -diameter tube4 ,spectrum without magnet4 ,the powders in tubes of this description are said to contain either sulphide of strontium1 or calcium1 or sulphate of quinine4 ,the first-mentioned tube shone with a white and bright light1 and probably contained the latter substance4 ,the general effect of the current on the tubes was similar in all cases4 ,under a sufficiently strong current1 they lighted up with a brilliant1 slightly green-white glow2 in which1 however1 by looking sideways1 it was possible to detect a delicate rosy tint4 ,any colours beyond these in the tubes seemed to depend on the powders enclosed in them4 ,when the current was stopped1 the powders alone glowed in accordance with the colours mentioned on the labels1 the rarefied gas or air in the tubes not giving any after-glow1 as in the case of the sulphurous-acid tube4 ,when the -diameter tube was excited by the small coil1 the effect of the magnet was to entirely suppress and extinguish the glow4 ,when this and the other tubes were worked with the larger coil1 the spectrum1 without the magnet1 was bright and continuous1 either showing no lines or else very faint traces of them1 and1 extending through the whole range of colours was brightest in and about the green4 ,sidenote3 ,magnet effect on glow4 ,same on spectrum4 ,with the magnet excited1 a bright line of pink light was condensed against the upper side of the tube2 while the glow in the tube generally became very decidedly fainter1 except at the electrodes1 which still preserved a certain amount of brilliancy4 ,the spectrum also was much changed4 ,the bright continuous glow became much fainter1 and many sharp and fairly bright lines were seen upon it4 ,these lines were1 as to character1 not easy to recognize4 ,hydrogen 7,f7 was1 however1 plainly distinguished2 and other lines1 which we considered to be ,n1 were common to all the tubes4 ,some lines were also remarked as being1 without the magnet1 not so constant4 ,sidenote3 ,tubes examined and compared for spectra4 ,calcium orange and calcium violet1 compared for spectra1 were identical2 the two strontium tubes hardly so1 but with strontium vert a bright continuous spectrum mainly hid the lines4 ,strontium jaune and calcium orange were not alike2 strontium vert and calcium violet differed4 ,calcium orange and calcium vert-bleutre were considered alike2 but the comparison was not easy1 as the calcium vert was bright1 and the lines were only seen faintly upon the continuous spectrum4 ,in order not to shift the powders1 the tubes were laid horizontally1 and two spectra simultaneously examined across the tubes4 ,lighting-up ,tubes with ,one ,wire only 7,marquis of ,salisbury's ,observations74 ,sidenote3 ,one wire only connected with an electrode4 ,the vacuum-tubes employed were examined in the usual way1 but one wire only was connected with an electrode4 ,the other wire was attached to the end of a glass rod1 and circuit was from time to time completed while the tube was before the spectroscope4 ,the large coil was used4 ,in all cases1 with the one wire1 the glow was very faint as compared with that of the closed circuit4 ,sidenote3 ,ether vapour4 7#a7 ,ether ,vapour4--,with both wires1 in company with the usual bright bands of the carbon spectrum1 shading-off towards the violet1 the ,h lines were very sharp and brilliant4 ,with the one wire only1 the carbon bands were left faintly shining1 with both sides nebulous alike1 and with no shading-off towards the violet4 7,we were not quite sure whether this was not the effect of the reduction of the light47 ,the ,h lines1 though originally stronger than the carbon bands1 quite disappeared from the spectrum4 ,sidenote3 ,coal-gas4 7#b7 ,coal-gas4--,the same effects were produced2 but we thought we could detect very faint traces of the ,h lines4 ,sidenote3 ,nitrogen4 7#c7 ,nitrogen4--,the ,n lines1 as well as those of ,h 7also seen in the tube71 were much fainter with one wire1 but the ,h lines more so in proportion4 ,sidenote3 ,hydrogen4 7#d7 ,hydrogen4--,only a marked reduction in brilliancy of the whole spectrum4 ,sidenote3 ,oxygen1 ,n and ,h4 7#e7 ,oxygen4--,an impure tube1 showing ,o 7some of the lines hydrocarbon871 ,n1 and ,h spectra simultaneously4 ,with one wire the ,o lines still remained fairly bright1 the ,n and ,h being only faintly seen4 ,sidenote3 ,water-gas4 7#f7 ,water-gas4--,same effect4 ,sidenote3 ,turpentine vapour4 7#g7 ,turpentine ,vapour4--,same effect as ether1 but the ,h lines could be faintly seen4 ,,chapter ,,xviii4 ,,action ,,of ,,the ,,magnet ,,on ,,the ,,electric ,,spark4 ,sidenote3 ,apparatus employed4 ,the magnet was excited with two plates of the large battery1 and the larger coil with the other two plates1 the action in both cases being strong4 #a4 ,a spark from the coil was passed between two platinum wire electrodes1 about three centimetres apart4 ,sidenote3 ,spark and aura described4 ,it consisted centrally of a thin stream of bluish-white light1 vividly bright1 around which was seen a narrow1 uniform1 diffuse1 yellow-tinted aura1 which accompanied the spark in all its movements4 ,the spark always struck across from the extreme points of the electrodes 7see ,plate ,,xvii4 fig4 #e74 ,sidenote3 ,effect of magnet upon the aura4 #b4 ,on being placed between the conical poles of the excited magnet the bright thread of the spark did not change2 but instead of the inconsiderable yellow-tinted aura which accompanied the unmagnetized spark1 there now struck out1 at right angles to the magnet-poles1 a thin rosy-tinted half-disk of aura-like flame4 ,this extended aura ran considerably along each electrode1 though the spark proper still struck from the points4 ,sidenote3 ,extended aura described4 ,the aura was somewhat larger in extent upon one electrode than on the other4 ,in the first case1 it sprang from a considerable number of minute illuminated points2 on the other electrode1 these illuminated points were fewer in number1 and the flame was more purple in tint4 ,reversing the current these effects were reversed4 ,the aura was uniformly thin and disk-like1 and the curved edge remarkably true in shape 7see ,plate ,,xvii4 fig4 #f74 ,the lateral direction of the aura was changed when the current was reversed4 ,sidenote3 ,aura not proportionate to length of spark4 #c4 ,the aura was found not proportionate to the length of the spark4 ,when the electrodes were approached1 so as to very much shorten the spark1 the aura still sprang out to a distance and extent quite out of proportion to the length of the spark4 ,even when the electrodes were approached so close that the spark was very short indeed1 still1 under the magnetic influence1 a very considerable aura made its appearance4 ,sidenote3 ,effect of working coil-break upon the aura4 #d4 ,upon working the coil-break1 it was found that in proportion as the contact screw was drawn apart from the break1 so the aura gradually diminished in extent1 until at last1 by continuing to increase the distance between the screw and the break1 a point was reached when thin bright sparks1 without any aura1 passed4 ,upon the screw being worked up closer1 thicker sparks passed1 and the aura again made its appearance4 ,as the aura diminished in size it gradually changed in tint from yellowish rose-pink to purple4 ,sidenote3 ,spark taken in glass bulb4 #e4 ,the spark was taken in a glass bulb1 the tube in which it was blown being open at both ends1 with the same effect as in the open air4 #f4 ,a plate of glass was laid on the poles of the magnet1 and the spark was passed along the poles 7in the same direction as the heavy glass was laid in the ,faraday experiment74 ,no aura was formed4 ,the points were then moved round1 so as to carry the spark at right angles to the poles1 and the aura was formed as before4 ,sidenote3 ,aura could be blown away from the spark4 #g4 ,the aura1 it was found1 could be blown away at right angles to the spark4 ,when strongly urged1 it assumed the shape of a flickering tongued curtain of flame1 flying away in the contrary direction to that from which the current of air proceeded1 and again returning to its original shape as the impulse was removed4 ,the spark proper was not influenced 7see ,plate ,,xvii4 fig4 #h74 ,sidenote3 ,effect of withdrawing spark from central position between the poles4 #h4 ,as the spark was withdrawn from its central position between the poles of the magnet1 the convex edge of the aura became gradually less perfect1 and assumed a ragged and broken-up appearance1 the inequality at times amounting almost to jets or flickering sprays of light4 ,the spark was also slightly curved away from the electrodes 7see ,plate ,,xvii4 fig4 #g74 ,sidenote3 ,magnet had no effect upon condensed spark4 #i4 ,a condenser of four coated plates was introduced into the circuit1 causing a sharp brilliant blue-white spark1 apparently divided into streams and with no aura4 ,the magnet had no effect whatever upon this form of spark4 ,,chapter ,,xix4 ,,the ,,discharge ,,in ,,vacuo ,,in ,,larger ,,vessels1 ,,and ,,magnetic ,,effects ,,thereon4 ,a ,tate's air-pump was used1 and the spark from the larger coil4 ,the exhaustion could not be carried very far4 ,sidenote3 ,globular receiver described4 ,discharge described4 7#a7 ,a globular receiver was used1 having brass caps for exhaustion1 and platinum wires passing through the opposite sides for electrodes 7see ,plate ,,xviii4 fig4 #f74 ,with partial exhaustion1 from the positive electrode proceeded long1 sharp1 bright1 rosy sparks1 striking in zigzags across the receiver4 ,from the negative terminal sprang a larger number of bluer and more diffuse streams of light1 like spiders' webs2 and these were enveloped1 for a short distance from the terminal1 in a slight misty aura4 ,both sets played round the sides of the glass as well as across4 ,sidenote3 ,bell-shaped receiver described4 ,discharge described4 7#b7 ,a bell-shaped receiver1 with terminals inserted at the sides and one also at the top1 was next used 7see ,plate ,,xviii4 fig4 #i74 ,when the side terminals were employed1 the effect was much the same as in the last case4 ,when the top terminal was used for one wire 7the other wire being connected with the pump-plate7 a single stream of bright rosy light ran from the upper terminal to the plate4 ,first striking the central part of the plate1 the stream then glided towards one of the lateral terminals1 and so to the edge of the receiver4 ,after partly discharging itself by contact with the terminal1 the stream as rapidly retreated to the centre of the plate again--this effect being from time to time repeated while the current was passing4 ,the current being reversed1 a number of bright1 but weaker and more diffused1 streams of light had the appearance of shooting from the upper electrode1 and of striking upon the plate below2 with a tendency to fly off from where they struck1 in a similar manner to the single stream before described4 ,where each stream touched the plate a brilliant point of light appeared1 and a strong pattering noise was heard in the receiver4 ,sidenote3 ,bell-shaped receiver without electrodes4 ,induction discharge described4 7#c7 ,another bell-shaped receiver of similar shape was used4 ,this had no electrodes forming a direct communication with the interior2 but1 in lieu of these1 two wafers of thin sheet brass were cemented1 one inside and one outside the glass1 opposite to one another4 ,on connexion being made with the outside wafer1 the effects produced by induction were similar to1 and very nearly as strong as1 those in the cases where direct communication with the interior of the receiver was made4 ,sidenote3 ,long large tube exhausted and illuminated4 ,spiral form of discharge4 7#d7 ,a large tube1 #bd inches long and #b inches in diameter1 with ball and point electrodes respectively1 was exhausted1 and the current passed through it4 ,the effects were similar in most respects to those produced in the globular and bell receivers1 but the streams of light assumed a distinctly spiral form in their passage 7see ,plate ,,xviii4 fig4 #e74 ,this tube when placed between the poles of the magnet showed no effect1 except a slight condensation of the streams of light towards the sides of the glass4 ,sidenote3 ,globular receiver again used4 7#e7 ,the globular receiver first described was again used 7the ,tate pump having been cleaned and working easier74 ,sidenote3 ,phosphorescent after-glow succeeding the spark4 7a7 ,when exhaustion was as good as it could be got1 the spark struck across in a single1 slightly expanded1 stream of rosy light1 having a tendency to curve upwards 7see ,plate ,,xviii4 fig4 #f74 ,the electrodes had but little glow round them1 only just enough to distinguish the poles apart4 ,when the flow of the stream was interrupted by breaking contact with one terminal1 so that sparks passed in succession1 we thought we detected a faint blue phosphorescent after-glow succeeding each spark4 ,sidenote3 ,positive wire only attached4 7b7 ,the positive wire only was attached to one electrode1 the negative being unconnected4 ,a set of faint whity-blue cobweb-looking streams of light spread from the electrode all over the receiver1 having a vibratory motion4 ,the spaces between these were dark1 and there was no aura--the effect being similar1 but not quite so bright and pronounced1 as when both wires were attached 7see ,plate ,,xviii4 fig4 #g74 ,sidenote3 ,negative wire only attached4 7c7 ,the negative wire only was attached4 ,the cobweb streams were absent1 or only shot out very occasionally4 ,the main effect was a straight nebulous stream of violet light1 which commenced at the electrode and spread out in a fan-shape towards the lower brass cap of the receiver2 while1 at the same time1 an aura or glow of similar light1 but fainter in quality1 spread from the electrode over at least one half of the receiver4 ,this aura would no doubt have filled a small flask 7see ,plate ,,xviii4 fig4 #h74 ,sidenote3 ,effect of gradual exhaustion on the discharge4 7d7 ,when exhaustion was first commenced1 both electrodes of the receiver 7both wires being connected7 threw out spider-web-like streams1 as in ,experiment #a1 pale blue from the one pole and somewhat rosy from the other4 ,as the exhaustion progressed the pale-blue streams disappeared1 while the rosy flickering ones diminished in quantity and extent until ultimately a single rosy stream of light crossed the receiver as in ,experiment #e;a4 ,upon admitting the air1 these effects took place in an inverse order--the single stream being gradually broken up1 and the spider-webs taking its place4 ,sidenote3 ,globular receiver placed on poles of the magnet4 ,magnet effect4 7e7 ,the exhausted globular receiver was placed upon the poles of the excited magnet1 with the stream at right angles to them4 ,looking across the ,s4 pole of the magnet1 the negative electrode was on the left hand1 and the positive on the right4 ,the effect of the magnet on the stream was apparently to split it up into several2 but this appearance must have been due to vibration only1 as a revolving mirror showed the stream as single4 ,when the current was reversed1 the stream which1 without the magnet1 was somewhat flickering and vibrating1 slightly straightened at the positive pole1 and the whole stream became steadier4 ,sidenote3 ,single wires attached4 7f7 ,single wires were successively attached to the negative and positive poles1 and the cobweb streamers and glow before described obtained4 ,the magnet was found to have no decided effect on either of these4 ,sidenote3 ,plcker tube placed between poles of magnet with negative wire only attached4 7#f7 ,the ,plcker air-tube 7,plate ,,xvii4 fig4 #b7 was placed between the poles of the magnet1 and the negative wire only was connected with the straight electrode4 ,a pale violet glow was seen round this electrode1 and another1 but rather fainter1 glow of a similar description at the ring electrode1 the intermediate space being filled with a salmon-coloured light4 ,this violet glow was condensed into an arc by the action of the magnet4 ,reversing the current1 the violet glow still remained at each electrode1 and that between the poles of the magnet was still influenced into an arc4 ,sidenote3 ,geissler tube substituted1 with similar results4 7#g7 ,an air ,geissler tube was substituted for the ,plcker tube1 with very much the same result4 ,whichever wire was attached1 a violet glow appeared at the connected electrode1 and a fainter one of the same character at the other2 and the magnet influenced both4 ,the connecting salmon-coloured glow was faint4 ,sidenote3 ,globular receiver treated with phosphoric anhydride4 7#h;a7 ,the globular receiver had some phosphoric anhydride shaken into it2 and it was then exhausted4 ,the cobweb streamers and violet glow each appeared according to which wire was connected4 ,there was no marked difference between the receiver with the anhydride and without2 except that in the former case the streamers and glow were reduced in extent and strength1 and were comparatively faint4 ,sidenote3 ,discharge in water-vapour described4 7b7 ,the anhydride having been washed out1 first with plain and afterwards with distilled water1 some drops of the latter were allowed to remain in the receiver4 ,on exhaustion a vapour-cloud was formed1 and the discharge passed 7both terminals being connected with the coil7 through this4 ,the rosy stream of light was formed as usual1 but was more flickering and unsteady4 ,as the exhaustion was lessened1 the rosy stream disappeared1 and the cobweb streams began to fill the receiver4 ,these were1 however1 not so bright and sharp as in a dry receiver1 but were faint and broad2 while some diffused and nebulous streams of light1 running 7slightly bent7 from pole to pole1 and from to of an inch broad1 were intermixed with them4 ,when one wire only was connected1 the glow and streamers from the electrode were very faint4 ,sidenote3 ,large bell-receiver and plate described4 ,receiver exhausted and stream of light formed4 7#i7 ,a large bell-shaped receiver1 #aa #h inches1 was next used4 ,it was open at the bottom1 which was ground as usual2 and had a small opening at the top1 also carrying a ground edge4 ,a solid brass plate was prepared1 ground only round the edge 7in order to take the receiver71 and in the centre of this brass plate were inserted two disks of soft iron1 corresponding in position and size with the poles of the ,ladd electro-magnet 7see ,plate ,,xviii4 fig4 #aa74 ,when this plate was placed on the magnet1 the poles and disks were in contact2 and the disks became ,n4 and ,s4 poles within the receiver4 ,a small brass plate carrying a tap and exhaust-tube1 and a binding-screw for attaching an electrode within1 closed the receiver at top4 ,the receiver and plate being placed on the magnet-poles1 the former was exhausted until the discharge became a rosy slightly-diffused stream of light2 with a small unilluminated space between it and the negative pole1 where the usual violet glow appeared round the wire4 ,this stream of light was used for the experiments after detailed4 ,in some cases the conical armatures were placed within the receiver1 in others the disks alone were used as the magnetic poles4 ,sidenote3 ,effect on same when magnet excited4 7a7 ,with the apparatus arranged as shown on ,plate ,,xviii4 fig4 #aj1 and the magnet excited1 a violet glow appeared round the end of the wire which was negative4 ,a small unilluminated space then intervening1 the stream ran in a curve between the wire and the armature1 which latter was positive4 ,the stream was not steady and had a tendency to rotate2 but as this was better observed with the disks only1 it is described further on4 ,sidenote3 ,experiments with the conical armature removed4 ,vibrating stream4 7b7 ,the conical armature within the receiver was removed1 and the stream allowed to connect with the centre of the pump-plate4 ,when the magnet was excited1 the stream was violently projected at right angles to the poles1 with a vibrating movement to either side according to the direction of the current4 ,when the wire was positive the movement was towards the left1 with a slight inclination towards the ,n4 pole4 ,when the wire was negative the movement was to the right1 but in a rather strong curve towards the ,n4 pole4 ,the vibrating motion was very distinct1 and gave the appearance of six or seven streams running off at regular intervals 7see ,plate ,,xviii4 fig4 #ab74 ,sidenote3 ,rotating wire over ,s4 pole4 7c7 ,the wire was next placed over the centre of the disk forming the ,s4 pole4 ,with the wire negative and the pole positive1 rotation of the stream was decidedly1 but not very strongly1 from right to left from the centre of the plate 7as the hands of a watch74 ,with the wire positive and the pole negative1 rotation was strongly left to right1 with a disposition to spiral twist in the stream 7see ,plate ,,xviii4 fig4 #ac74 ,sidenote3 ,same over ,n4 pole4 7d7 ,the wire was placed over the disk forming the ,n4 pole4 ,with the wire negative and the pole positive1 rotation of the stream was left to right4 ,with the wire positive and the pole negative1 rotation was right to left 7see ,plate ,,xviii4 fig4 #ad74 ,sidenote3 ,stream thrown across the receiver above the magnet-poles4 7e7 ,the stream was thrown across the receiver from the lateral binding-screws above1 and at right angles to1 the disks1 and afterwards in the opposite direction1 i4 e4 along them4 ,in neither case was there any marked change when the magnet was excited4 7f7 ,the conical armatures were placed with the pointed ends upon the disks in the receiver1 and the stream thrown above and along them4 ,it diverged--one part running straight across between the electrodes1 whilst another stream and some cobwebs ran from each electrode to its nearest pole4 ,the streams and cobwebs flickered a good deal4 ,there was no marked change when the magnet was excited4 ,some of ,baron ,reichenbach's ,magnetic ,researches tested4 ,sidenote3 ,baron ,reichenbach's researches4 ,in #ahdf ,dr4 ,w4 ,gregory published an abstract of ,baron ,reichenbach's #8,researches on ,magnetism and on certain allied subjects1 including a supposed new ,imponderable4' ,sidenote3 ,auror considered to be magnetic lights4 ,flames seen by 8sensitive0 persons4 ,from a paragraph in this work1 it would seem that the ,baron considered his observations as tending to an explanation of the ,aurora ,borealis2 and1 since it was generally admitted that these phenomena occur within our atmosphere1 that there appeared a great probability of ,auror being visible magnetic lights4 ,the ,baron1 in the original work1 fully describes the ,aurora ,borealis2 and concludes it must be similar in its nature to the flames of light seen streaming from the magnet-poles by ,mdlle4 ,reichel and other sensitive patients of the ,baron's4 ,it is unfortunate that these flames were only seen by certain 8sensitive0 persons4 ,the drawings given of them1 too1 show no analogy to the magnetic curves4 ,sidenote3 ,magnet tested for such flames4 ,having the opportunity of a powerful magnet in that used during our tube-experiments1 we made an attempt to detect the ,baron's magnetic flames1 on or around the poles of our magnet1 in a perfectly dark room4 ,arrangements were made to silently connect and disconnect the battery with the magnet1 without the knowledge of any one except the operator4 ,the experiment proved a complete failure2 no flames or discharges of light of any kind were to be seen4 ,the observers were five in number1 two gentlemen and three ladies1 but not one of the party proved 8sensitive40 ,sidenote3 ,mr4 ,brooks's experiments on action of the magnet on a sensitive photographic plate4 ,some experiments made by ,mr4 ,w4 ,brooks1 and detailed in a paper read by him before the ,south ,london ,photographic ,society1 seem to corroborate 7to a certain extent7 the statements made by the ,baron in regard to the influence of the magnet on a sensitive photographic plate4 ,remembering1 however1 how it has been demonstrated that light may be 8bottled up0 as an actinic source for a considerable period of time1 it seems a question whether the images obtained were not due to some such source rather than to any magnetic aura4 ,,summary ,,of ,,the ,,foregoing ,,experiments ,,and ,,their ,,results4 ,sidenote3 ,summary of the experiments4 ,chapter ,,xiv4 ,action of magnet on glow and spectrum of ,geissler gas vacuum-tubes demonstrated4 ,chapter ,,xv4 ,action of magnet on glass capillary tube negatived4 ,faraday's experiment with heavy-glass bar repeated4 ,chapter ,,xvi4 ,action of magnet on glow in wide air-tube demonstrated4 ,note on stratification4 ,in ,plcker tube1 action of magnet on negative pole 7arc formed7 and positive pole 7,gassiot's rings produced7 demonstrated4 ,effects of magnet upon glow and spectrum of tin-chloride vacuum-tubes demonstrated4 ,chapter ,,xvii4 ,effect of magnet upon after-glow in a bulbed phosphorescent tube demonstrated4 ,effect of magnet upon glow in small phosphorescent 7powder7 tubes examined4 ,marquis of ,salisbury's experiments 7lighting-up with one wire only7 tested1 and confirmatory results arrived at4 ,chapter ,,xviii4 ,action of magnet on aura of electric spark demonstrated4 ,chapter ,,xix4 ,effects of magnet on discharges in vacuo in larger vessels demonstrated4 ngstrm's flask experiment tested2 same results not obtained unless one wire only was connected4 ,experiments demonstrating the action of a magnet on an electric stream1 viz4 vibration between1 and rotation round1 poles4 ,baron ,reichenbach's magnetic flames tested without result4 ,,chapter ,,xx4 ,,some ,,concluding ,,remarks4 ,it is usual1 in concluding a work on a special subject1 to sum up its contents1 and to examine the general results arrived at4 ,this1 however1 it is not easy to do in the present case4 ,the contents of our volume comprise a short history of the ,aurora1 its qualities and spectrum2 and a statement has been given of the several conclusions at which various observers have arrived as to its character and causes4 ,in the present state of our knowledge of the subject1 to add an opinion to these might seem to savour of presumption2 and the questions involved may perhaps be better treated as still sub judice1 and as requiring further and fuller evidence before arriving at a verdict4 ,the following observations must therefore be taken rather as further notes and memoranda1 than as conclusions4 ,apart from the spectroscopic questions involved1 the oldest and most received theory of the ,aurora--that of its being some form of electric discharge in the more rarefied regions of the atmosphere1--seems to hold its own3 and if1 as is probable1 some form of phosphorescence is involved in the discharge1 ,m4 ,lecoq de ,boisbaudran's observations on the brightening of the red line under the influence of cold1 and the falling of the yellow-green line within a band of phosphoretted hydrogen1 come into play2 and a connexion1 though slight and imperfect1 may be in this respect traced between the discharge and its spectrum4 ,the experiments detailed in ,part ,,ii4 seem to have an important bearing1 as showing the very marked effect of the magnet on the rarefied glow1 as well as on the spark in air at ordinary pressure4 ,the well-defined arc formed by the aura of the spark1 the flickering jets which replace the even edge of the arc when partially withdrawn from the magnetic influence1 and the streamers formed when the aura is blown away from the spark 7,plate ,,xvii4 figs4 #f1 #g1 and #h71 are certainly highly suggestive of frequent forms of ,auroral discharge2 and1 but for trial and failure1 might lead one to expect results from a comparison of the line air-spectrum with that of the ,aurora4 ,the experiments with a wire attached to one electrode only1 show how the glow may be affected and varied in colour and character when the discharge is interrupted and incomplete4 ,differences in electric tension may also considerably vary the character of the discharge4 ,the influence of the magnet in exciting and brightening the glow and spectrum of one gas1 while it depresses and extinguishes the glow and spectrum of another gas in the same tube1 suggests an explanation of the observed variation in intensity1 and difference in number1 of the ,aurora-lines4 ,intensity of lines depending on temperature1 and this again on resistance1 and it appearing that resistance is influenced by the magnetic action1 the same effects of brightening or depressing of the spectrum are probably produced in the ,aurora1 as in the vacuum-tubes placed between the magnet-poles4 ,in the ,marquis of ,salisbury's observations1 paraffin-vapour gave ,c and ,h lines when connected with both poles of the battery1 but ,c lines only when connected with one pole2 and in that case the lines were equally sharp on both sides4 ,these observations 7repeated in our experiments7 may afford an explanation why the hydrogen-lines are not seen in the ,aurora-spectrum2 although there can be hardly any doubt that the phenomenon usually takes place in air more or less moist4 ,professor ngstrm's researches on the violet-pole glow are not entirely corroborated by our experiments2 and it seems doubtful whether his results in the exhausted flask were not obtained from the negative pole only4 ,one great difficulty in the comparison of the ,aurora-spectrum with the violet pole of air-tubes and some other spectra 7including oxygen71 arises from the presence in the latter of broad bands2 and it is difficult to understand how these bands can be aptly compared with the definite1 though faint1 lines observed by ,dr4 ,vogel and others in the ,aurora-spectrum4 ,it must1 too1 be borne in mind that the conditions under which we may consider the ,aurora to obtain1 are such as can be only very imperfectly imitated in the laboratory4 ,auror also no doubt differ in density and thickness of layer2 and ,kirchhoff's observation must be remembered3--8,that if thickness of a film of vapour be increased1 the lines are increased in intensity1 the bright lines more slowly than the fainter2 and it may happen that the spectrum appears to be totally changed when the mass of the vapour is altered40 ,were it possible to test with the spectroscope a cloud or film of gaseous vapour corresponding in some degree in density and thickness with an ,auroral discharge1 we might perhaps get nearer the truth4 ,mr4 ,procter also remarks 7as we proved in our magnet experiments73--8,that frequently very small traces appropriate to themselves the whole of electrical discharges at low pressures1 and completely mask the spectra of any other gases present40 ,the oxygen-spectrum1 with its possible variation by the conversion of that gas into the allotropic condition termed ozone1 seemed at first to afford a prospect of close relation to the ,aurora-spectrum2 which1 however1 disappeared on closer examination4 ,if nitrogen could be modified in some such way as oxygen is converted into ozone1 it might perhaps afford another opportunity for investigation2 but we have no evidence at present of such a change4 ,the spectrum of nitrogen is usually found singularly distinct and persistent2 and1 except as varied from band to line by intensity of the discharge1 not liable to alteration#af4 ,colours of lines are functions of wave-length1 subject1 however1 to the observation that in a weak spectrum the colours lose their intensity4 ,the red line in the ,aurora has sometimes been found brighter than the green4 ,it has been suggested that the red and green may be independent spectra2 but the variations of tint observed in the capillary of hydrogen and other tubes according to resistance of the current1 demonstrate that the varying colours of the ,aurora may be connected with the lighting-up of particular parts of the spectrum1 and do not necessarily indicate that different gases and spectra are excited4 ,absorption may also play an important part in the nature of the ,aurora-spectrum 7,zllner's theory that the lines are really spaces between absorption bands74 ,most gases will give a continuous spectrum under certain circumstances1 even at a low pressure4 ,the question of cosmic dust is inviting1 but the facts collated hardly warrant at present its probable connexion with the ,aurora4 ,if ,auror were composed of incandescent glowing meteors1 it would be reasonable to expect to find in the spectrum the lines of iron1 a metal constituting so prominently the composition of meteorites4 ,no connexion between the iron and the ,aurora-spectra is1 however1 proved2 though it may be suspected4 ,the iron-spectrum1 as remarked elsewhere1 contains so many lines that some may1 as a mere accidental circumstance1 closely agree with the ,aurora-lines4 ,the iron-lines are1 it may be remarked1 as a rule1 sharper and finer than the ,auroral lines1 though it is possible that these characteristics might vary if the spectrum were obtained in a rarefied medium4 ,tubes with iron terminals are said to evolve a compound gas of ,h and ,fe4 ,i have not had an opportunity to verify this4 ,it may be added that the comparative faintness of the more refrangible lines of the ,aurora-spectrum suggests a feeble resistance to the exciting current1 and a low temperature inconsistent with a meteoric theory2 and this is not contradicted by the brightness of the red and green lines1 if these are due to a phosphorescent origin4 ,expansion of a line is recognized to be dependent on pressure1 and consequently the breadth of the green or red lines might indicate the height of the ,aurora2 while their brightness or otherwise might also give some idea as to its density4 ,no observations in this direction have1 as far as ,i am aware1 been recorded4 ,as the general result of spectrum work on the ,aurora up to the present time1 we seem to have quite failed in finding any spectrum which1 as to position1 intensity1 and general character of lines1 well coincides with that of the ,aurora4 ,indeed1 we may say we do not find any spectrum so nearly allied to portions even of the ,aurora-spectrum1 as to lead us to conclude that we have discovered the true nature of one spectrum of the ,aurora 7supposing it to comprise1 as some consider1 two or more74 ,the whole subject may be characterized as still a scientific mystery--which1 however1 we may hope some future observers1 armed with spectroscopes of large aperture and low dispersion1 but with sufficient means of measurement of line positions1 and possibly aided by photography1 may help to solve4 ,the singular absence of ,auror has1 for some time past1 given no opportunity in that direction4 ,may some of my readers be more fortunate in obtaining opportunities of viewing the glorious sky-fires1 and assist to unravel so interesting a paradox6 ,,appendices4 ,,appendix ,a4 ,,references ,,to ,,some ,,works ,,and ,,essays ,,on ,,the ,,aurora4 7,most of these are cited in the #8,edinburgh ,encyclopdia' and the #8,encyclopdia ,britannica4'7 ,musschenbroek1 ,instit4 ,phys4 c4 #da4 #8,trai4 ,phys4 et ,hist4 de l',aurore ,borale1' par ,m4 de ,mairan4 ,paris1 #aged4 ,beccaria1 #8,dell',elettricismo ,artif4 e ,nat4' p4 #bba4 ,smith's #8,optics1' p4 #fi4 ,d',alembert's #8,opuscules ,mathmatiques1' vol4 vi4 p4 #ccd4 #8,philosophical ,transactions' as under3-- ,vol4 ,pages #agaf #djf #agag #ehd1 #ehf #agai #ajii1 #aaja1 #aajd1 #aajg #agbj #ba #agba #ahj1 #ahf #agbc #cjj #agbd #age #agbf #abh1 #acb1 #aej #agbg #bde1 #cja #agbh #dec #agbi #acg #agcj #bgi #agca #ec-ee #agcd #bdc1 #bia #agcf #bda #agdj #cfh #agda #gdd1 #hci1 #hdj1 #hdc #agej #cai1 #cde1 #cdf1 #dii #agea #ci1 #abf #ageb #afi #agec #he #agfb #dgd1 #dgi #agfd #cbf1 #ccb #agfg #ajh #agfi #hf1 #cjg #aggj #ecb #aggd #abh #agha #bbh #agij #cb1 #dg1 #aja #8,miscell4 ,berolinens4' #agaj1 vol4 i4 p4 #aca4 #8,comment4 ,petrop4' tom4 i4 p4 #cea1 tom4 iv4 p4 #aba4 #8,acta ,petrop4' #aghj1 vol4 iv4 p4 #a4 #8,mem4 ,acad4 ,paris1' #agdg1 pp4 #cfc1 #dbc2 #agca2 #agea4 #8,mem4 ,acad4 ,berl4' #agaj1 vol4 i4 p4 #aca2 #agdg1 p4 #aag4 ,schwed4 #8,abhandlungen1' #ageb1 p4 #afi2 #agec1 p4 #he2 #agfd1 pp4 #bjj1 #bea4 ,bergman1 #8,opusc4' vol4 v4 p4 #bgb4 #8,americ4 ,trans4' vol4 i4 p4 #djd4 #8,mm4 de ,mathmat4 et ,phys4' tom4 viii4 p4 #ahj4 ,rozier1 vol4 xiii4 p4 #dji2 vol4 xv4 p4 #abh2 vol4 xxxiii4 p4 #aec4 ,franklin's ,works1 vol4 ii4 ,weidler1 #8,de ,aurora ,boreale4' #dto4 ,nocetus1 #8,de ,iride et ,aurora ,boreale1 cum ,notis ,boscovisch4' ,rome1 #agdg4 ,chiminello1 #8,mem4 ,soc4 ,ital4' vol4 vii4 p4 #aec4 ,gilbert's #8,journal1' vol4 xv4 p4 #bjf2 and 7particularly7 ,dr4 ,t4 ,young's #8,nat4 ,phil4' vol4 i4 pp4 #fhg1 #gaf1 and vol4 ii4 p4 #dhh4 ,wiedeburg1 #8,ueber die ,nordlichter4' ,jena1 #agga4 ,hpsch1 #8,untersuchung des ,nordlichts4' ,cologne1 #aggh4 ,van ,swinden1 #8,recueil de ,mmoires4' ,hague1 #aghd4 ,wilke1 #8,von den neuesten ,erklrungen des ,nordlichts1' ,schwed4 ,mus4 ,wismar1 #aghc4 ,dalton's #8,meteor4 ,observ4' #agic1 pp4 #ed1 #aec4 ,loomis1 #8,sill4 ,journal1' #bnd series1 xxxii4 p4 #cbd2 xxxiv4 p4 #cd4 ,the same1 #crd series1 v4 p4 #bde2 ,b4 ,v4 ,marsh1 #crd series1 xxxi4 p4 #caa4 ,oettingen and ,vogel1 ,pogg4 ,ann4 cxlvi4 pp4 #bhd1 #efi4 ,galle and ,sirks1 ibid4 cxlvi4 p4 #acc2 cxlix4 p4 #aab4 ,silbermann1 #8,comptes ,rendus1' lxviii4 pp4 #ajdi1 #aabj1 #aadj1 #aafd4 ,prof4 ,fritz1 8,geog4 ,distrib410 ,petermann's ,mitth41 ,oct4 #ahgd4 ,zehfuss1 #8,physikalische ,theorie4' ,adelman1 ,frankfort4 #8,nature1' iii4 pp4 #f1 #g1 #bh1 #ajd1 #abf1 #cdf1 #cdh1 #eaj2 iv4 pp4 #bji1 #bac1 #cde1 #dig1 #eje2 x4 #baa 7ngstrm74 #8,edinburgh ,astronomical ,observations1' vol4 xiv4 #ahgj-ahgg4 #8,english ,mechanic1' ,no4 #dfa 7,january #bc1 #ahgd71 pp4 #dde-ddg2 and ,no4 #dfb1 pp4 #dge1 #dgf4 ,,appendix ,b4 ,,extracts ,,from ,,the ,,manual ,,and ,,instructions ,,for ,,the 7,,english7 ,,arctic ,,expedition1 #ahge4 ,note on ,auroral ,observations4 ,by ,prof4 ,,stokes1 ,sec4 ,r4,s4 ,the frequency of the ,aurora in ,arctic regions affords peculiar facilities for the study of the general features of the phenomenon1 as in case the observer thinks he has perceived any law he will probably soon1 and repeatedly1 have opportunities of confronting it with observation4 ,the following points are worthy of attention3-- ,streamers4--,it is well known that1 at least as a rule1 the streamers are parallel to the dipping-needle1 as is inferred from the observation that they form arcs of great circles passing through the magnetic zenith4 ,it has been stated1 however1 that they have sometimes been seen curved4 ,should any thing of this kind be noticed1 the observer ought to note the circumstances most carefully4 ,he should notice particularly whether it is one and the same streamer that is curved1 or whether the curvature is apparent only1 and arises from the circumstance that a number of short1 straight streamers start from bases so arranged that the luminosity as a whole presents the form of a curved band4 ,have the streamers any lateral motion8 and if so1 is it from right to left or left to right1 or sometimes one and sometimes the other1 according to the quarter of the heavens in which the streamer is seen1 or other circumstances8 ,again1 if there be lateral motion1 is it that the individual streamers move sideways1 or that fresh streamers arise to one side of the former1 or partly the one and partly the other8 ,do streamers1 or does some portion of a system of streamers1 appear to have any uniform relation to clouds1 as if they sprang from them8 ,can stars be seen immediately under the base of streamers8 ,do streamers appear to have any definite relation to mountains8 ,are they ever seen between the observer and a mountain1 so as to appear to be projected on it8 ,this or any other indication of a low origin ought to be most carefully described4 ,when streamers form a corona1 the character of it should be described4 ,auroral ,arches4--,are arches always perpendicular to the magnetic meridian8 ,if incomplete1 do they grow laterally8 and if so1 in what manner1 and towards which side8 ,do they always move from north 7magnetic7 to south8 and if so1 is it by a southerly motion of the individual streamers1 or by new streamers springing up to the south of the old ones8 ,what 7by estimation1 or by reference to known stars7 may be the breadth of the arch in different positions in its progress8 ,do arches appear to be nothing but congeries of streamers1 or to have an independent existence8 ,what relations1 if any1 have they to clouds8 and if related1 to what kind of clouds are they related8 ,pulsations4--,do pulsations travel in any invariable direction8 ,what time do they take to get from one part of the heavens to another8 ,are they running sheets of continuous light1 or fixed patches which become luminous1 or more luminous1 in rapid succession8 and if patches1 do these appear to be foreshortened streamers8 ,are the same patches luminous in successive pulsations8 ,sounds 7874--,as some have suspected the ,aurora to be accompanied by sound1 the observer's attention should be directed to this question when an ,aurora is seen during a calm4 ,if sound be suspected1 the observer should endeavour1 by changing his position1 brushing off spicules of ice from the neighbourhood of the ears1 his whiskers1 c41 to ascertain whether it can be referred to the action of such wind as there is on some part of his dress or person4 ,if it should clearly appear that it is not referable to the wind1 then the circumstance of its occurrence1 its character1 its relation 7if any7 to bursts of light1 should be most carefully noted4 ,these questions are prepared merely to lead the observer to direct his attention to various features of the phenomenon4 ,answers are not demanded1 except in such cases as definite answers can be given2 and the observer should keep his attention alive to observe and regard any other features which may appear to be of interest4 ,it is desirable that drawings should be made of remarkable displays4 ,observations with ,sir ,william ,thomson's electrometer would be very interesting in connexion with the ,aurora1 especially a comparison of the readings before1 during1 and after a passage of the ,aurora across the zenith4 ,spectroscopic ,observations4 ,by ,prof4 ,g4 ,g4 ,,stokes1 ,sec4 ,r4,s4 ,spectrum of the ,aurora4 ,the spectrum of the ,aurora contains a well-known conspicuous bright line in the yellowish green1 which has been accurately observed4 ,there are also other bright lines of greater refrangibility1 the determination of the positions of which is more difficult on account of their faintness1 and there are also one or more lines in the red1 in red auroras4 ,advantage should be taken of an unusually bright display to determine the positions of the fainter lines4 ,that of the brightest lines1 though well known1 should be measured at the same time to control the observations4 ,the character of the lines 7i4 e4 whether they are strictly lines1 showing images of the apparent breadth of the slit1 or narrow bands1 sharply defined or shaded-off7 should also be stated4 ,sometimes a faint gleam of light is seen at night in the sky1 the origin of which 7supposed from the presence of clouds7 is doubtful4 ,a spectroscope of the roughest description may in such cases be usefully employed to determine whether the light is auroral or not1 as in the former case the auroral origin is detected by the chief bright line4 ,the observer may thus be led to be on the look-out for a display which otherwise might have been missed4 ,it has been said1 however1 that the auroral light does not in all cases exhibit bright lines1 but sometimes1 at least in the eastern and western arch of the ,aurora1 shows a continuous spectrum4 ,this statement should be confronted with observation1 special care being taken that the auroral light be not confounded with light which1 though seen in the same direction1 is of a different origin1 such1 for example1 as light from a bank of haze illuminated by the moon4 ,sir ,edward ,sabine once observed an auroral arch to one side 7say north7 of the ship1 which was in darkness4 ,presently the arch could no longer be seen1 but there was a general diffuse light1 so that a man at the mast-head could be seen4 ,later still1 the ship was again in darkness1 and an auroral arch was seen to the south4 ,should any thing of the kind be observed1 the whole of the circumstances ought to be carefully noted1 and the spectroscope applied to the diffuse light4 ,polarization of ,light4 ,by ,w4 ,,spottiswoode1 ,m4,a41 ,,ll4,d41 ,treas4 ,r4,s4 ,it has been suggested that the ,aurora1 inasmuch as it presents a structural character1 may afford traces of polarization4 ,having reference to the fact that the stri of the electric discharge in vacuum-tubes present no such feature1 the probability of the suggestion may be doubted4 ,but it will still be worth while to put the question to an experimental test4 ,if traces of polarization be detected1 it must not at once be concluded that the light of the ,aurora is polarized2 for the ,aurora may be seen on the background of a sky illuminated by the moon1 or by the sun1 if not too far below the horizon1 and the light from either of these sources is1 in general1 more or less polarized2 therefore1 if the light of the ,aurora is suspected to be polarized1 the polariscope should be directed to an adjacent portion of clear sky1 free from ,aurora1 but illuminated by the moon or sun as nearly as possible similar1 and similarly situated to the former portion2 and the observer must then judge whether the polarization first observed be merely due to the illumination of the sky4 ,the presence of polarization is to be determined3-- 7#a7 ,with a ,nicol's prism1 by observing the light through it by turning the prism round on its axis1 and by examining whether the light appears brightest in some positions and least bright in others4 ,if such be the case1 the positions will be found to be at right angles to one another4 ,the direction of 8the plane of polarization0 will be determined by that of the ,nicol at either of these critical positions4 ,the plane of polarization of the light transmitted by a ,nicol1 is parallel to the longer diagonal of the face2 and1 accordingly1 the plane of polarization1 or partial polarization1 of the observed light is parallel to the longer diameter of the ,nicol when the transmitted light is at its greatest intensity1 or to the shorter when it is at its least4 7#b7 ,the observation with a double-image prism is similar to that with a ,nicol4 ,this instrument1 as its name implies1 gives the images which would be seen through the ,nicol in two rectangular positions1 both at once1 so that they can be directly compared2 and when in observing polarized light the instrument is turned so that one image is at a maximum1 the other is simultaneously at a minimum4 ,both these methods of observation1 7#a7 and 7#b71 are especially suitable for faint light2 because in such a case the eye is better able to appreciate differences of intensity than differences of colour4 7#c7 ,the observation with a biquartz differs from 7#a7 only by holding a biquartz 7a right-handed and a left-handed quartz cemented side by side7 at a convenient distance beyond the ,nicol1 and by observing whether colour is or is not produced4 ,if the ,nicol be so turned that the two parts of the biquartz give the same colour 7choose the neutral tint1 teint de passage1 rather than the yellow71 we can detect a change in the position of the plane of polarization by a change in colour1 one half verging towards red1 the other towards blue4 ,this observation is obviously applicable to a change in the plane1 either at different parts of the phenomenon at the same time1 or at the same parts at different times4 7#d7 ,we may use a ,savart's polariscope1 which shows a series of coloured bands in the field of view4 ,for two positions at right angles to one another corresponding to the two critical positions of a ,nicol1 these bands are most strongly developed2 for two positions midway between the former the bands vanish4 ,in the instruments here furnished1 the plane of polarization of the observed light will be parallel to the bands when the central one is light1 perpendicular to them when the central band is dark4 ,instructions in the use of the ,spectroscopes supplied to the ,arctic ,expedition4 ,by ,j4 ,,norman ,,lockyer1 ,f4,r4,s4 ,spectroscopic ,work4 ,scales prepared on ,mr4 ,capron's plan1 together with forms for recording positions1 also accompany the instrument4 ,a4 ,in using these1 carefully insert the principal solar lines in their places on the forms1 as taken from a fine slit1 and keep copies of this scale for use4 ,if the slit opens only on one side1 note on scale in which direction the lines widen out1 whether towards red or violet4 ,also fill up some of these forms with gas and other spectra1 as taken at leisure with the same instrument and scale4 ,when observing1 close the slit 7after first wide opening it7 as much as light will permit1 and then with pen or pencil record the lines as seen upon the micrometer-scale on the corresponding part of the form1 and note at once relative intensities with ,greek letters1 1 1 c4 7or numbers74 ,reduce at leisure line-places on scale to wave-lengths1 and note as to each line the probable limits of instrumental error4 ,b4 ,in case the auroral spectrum is so faint that the needle-point or micrometer-scale is invisible1 half of the field of view may be covered with tinfoil1 with a perfectly straight smooth edge running along the diameter of the field1 in perfect focus1 and parallel to the lines of the spectra4 ,the reading-screw being set to #aj1 the bending-screw should then be adjusted so that the green line of the ,aurora is just eclipsed behind the blackened edge of the tinfoil4 ,a similar eclipse of other lines will give their positions4 ,in this instrument the reference-prism is brought into action by turning the slipping piece to which is fixed the two terminals4 ,care should be taken that the prism itself is adjusted before commencing observations1 as it may be shaken out of position on the voyage4 ,the tubes provided for the reference-spectra may be either fastened to the terminals or arranged in some other manner4 ,the air-spectrum may also be used as a reference-spectrum4 ,to get this1 two wires should be screwed into the insulators1 their ends being at such a distance apart and in such a position that the spectrum is well seen4 ,general ,observations regarding the ,spectrum of the ,aurora#ag4 ,c4 ,note appearance1 colour1 c4 of arc1 streamers1 corona1 and patches of light4 ,get compass positions of principal features1 and note any change of magnetic intensity4 ,if corona forms1 take its position and apparent height4 ,look out for phosphorescence of ,aurora and adjacent clouds4 ,listen for reported sounds4 ,note any peculiarity of cloud scenery1 prior to or pending the ,aurora4 ,sketch principal features of the display1 and indicate on this sketch the parts spectroscopically examined4 ,examine line in red specially in reference to its assumed connexion with telluric lines 7little a group71 and note as to its brightening in sympathy with any of the other lines4 ,examine line in yellow-green 7ngstrm's7 as to brightness1 width1 and sharpness 7or nebulosity7 at the edges4 ,notice as to a peculiar flickering in this line sometimes seen2 note also whether this line is brighter 7or the reverse7 with a fall of temperature4 ,note ozone papers at the time of ,aurora4 ,note whether the ,auror can by their spectra be classed into distinct types or forms1 and examine for different spectra as under3-- 4 ,the auroral glow1 pure and simple4 4 ,the white arc4 4 ,the streamers and corona4 4 ,any phosphorescent or other patches of light1 or light cloud in or near the ,auror4 ,d4 ,the information collected together in the #8,manual' should be carefully consulted1 and the line of observations suggested by ngstrm's later work followed out4 ,to do this1 not only record the positions of any features you may observe in the spectrum1 but endeavour to determine1 if any1 and if so which1 of the features vary together4 ,compare1 for instance1 the two spectra of nitrogen in the ,geissler tube supplied1 by observing first the narrow and then the wider parts of the tube4 ,it will be seen that the difference in colour and spectrum results simply from an addition to the spectrum in the shape of a series of channelled spaces in the more refrangible end in the case of the spectrum of the narrow portion4 ,try to determine whether the difference between red and green ,auroras may arise from such a cause as this1 and which class has the simpler spectrum4 ,see whether indications of great auroral activity are associated with the widening or increased brilliancy of any of the auroral lines4 ,remember that if auroral displays are due to gaseous particles thrown into vibration of electric disturbance1 increased electric tension may either 7#a7 dissociate those particles and thus give rise to a new spectrum1 the one previously observed becoming dimmer2 or 7#b7 throw the particles into more intense vibration without dissociation1 and thus give rise to new lines1 those previously observed becoming brighter4 ,careful records of auroral phenomena from both ships may enable the height of some1 observed from both1 to be determined4 ,it will be very important that those the heights of which are determined by such means should be carefully observed by the spectroscope1 in order to observe whether certain characteristics of the spectrum can be associated with the height of the ,aurora4 ,,appendix ,c4 ,,extracts ,,from ,,parliamentary ,,blue ,,book1 ,,containing ,,the 8,,results ,,derived ,,from ,,the ,,arctic ,,expedition #ahge-gf40 7,eyre and ,spottiswoode1 #ahgh47 ,auroras observed #ahge-ahgf1 at ,floebery ,beach and ,discovery ,bay4 ,by ,lieutenant ,a4 ,c4 ,,parr1 ,r4,n4 ,though the auroral glow was often present1 and served in some degree to lighten the darkness of the sky during the long winter1 when the moon was absent1 the actual appearances of the ,aurora itself were few1 and the nimbus worthy of any particular remark extremely small4 ,those which were stationary assumed the form of low arches1 with streamers flashing up to them from the horizon1 and usually to the eastward4 ,but the more common form was for an arch to appear low down in some part of the sky where the glow was brightest2 at first it was very faint and narrow1 but as it rose gradually in the heavens it would increase both in size and intensity1 till on arriving near the zenith1 with its ends extending nearly to the horizon1 it would be about the breadth of three or four rainbows1 and its colour that of white fleecy clouds lit up by the rays of the full moon4 ,on reaching this point1 however1 its course was nearly run2 for after appearing to remain stationary1 as little white gaps would suddenly rend the arch asunder1 the portions thus detached seemed to roll together and concentrate all their brightness in the smaller space1 and then gradually fade away and become extinct4 ,sometimes a very pale green would show itself in the more luminous patches1 and once or twice there was a slight suspicion of red2 but never was the whole sky illuminated by streams running in all directions1 and forming coron1 while these colours varied every moment4 ,when instead of the arch rising up from the horizon a streamer appeared1 its origin was in the north4 ,from the northern horizon it would stretch out towards the zenith1 passing nearly overhead1 and reaching to within a few degrees of the land to the south4 ,in appearance they would be the same as the arches1 but sometimes a second would grow out of the first1 and on one occasion three were visible at the same time4 ,they had lateral motion either from east to west1 or west to east1 but there was no flashing to brighten them1 and they gradually faded away4 ,the time at which ,auroras usually occurred was between #i ,p4,m4 and midnight1 the last display being on ,february #aith1 commencing at #aa ,p4,m4 ,it was a beautifully clear night1 without mist or haze of any description1 and small stars visible close down to the horizon4 ,at the above-named hour two arches made their appearance1 and remained stationary2 the lower one was the brighter1 being of a pale green colour1 its centre bearing ,e4,s4,e4 7true71 and having an altitude of about #e1 with a breadth of about twice that of a rainbow4 ,the second arch was concentric with the first1 and about #g above it1 but rather broader and fainter4 ,these arches maintained their altitude1 the upper one at about the same intensity1 but that of the lower one varied considerably4 ,it would gradually lighten up1 then send flashes to the upper one1 then break up and fade away2 before1 however1 it had quite disappeared1 flashes would come up to it from the horizon which seemed to endue it with new life1 for the arch would be reformed1 brighten up1 and the same performance would be again repeated4 ,this occurred three or four times in the course of three quarters of an hour2 but the flashes from the horizon never extended beyond the lower arch1 and those from the lower never went beyond the upper4 ,during this display the citron-line was obtained very clearly with the spectroscope1 but no other lines were visible4 ,on six or seven occasions ,auroras were visible at the same time on board both the #8,alert' and #8,discovery2' but the absence of characteristic features makes it impossible to determine whether they were the same display1 or merely two distinct ones which happened to occur at the same time4 ,but as by far the larger number of those recorded in the one ship were not visible at the other1 it was certainly only under exceptional conditions that they could be simultaneously observed at both stations1 if1 indeed1 they ever were4 ,auroras seemed to appear indifferently both when there was wind and when it was calm1 with either a high or low barometer1 and seemed quite unconnected with the temperature1 although on an occasion the thermometer was observed to fall #c during the display1 and to rise #b almost immediately afterwards4 ,but it was never seen illuminating the edges of clouds1 as we saw it on the passage home1 nor playing about the outline of the land1 and never was there the slightest suspicion of sound being produced by it4 ,the opportunities for observing the spectrum of the ,aurora in this position have been most unsatisfactory1 as the displays were small in number and deficient in brilliancy4 ,the form they generally assumed was to rise like an arch from a portion of the horizon where there was a luminous glow1 at first very faint1 but gradually increasing in brilliancy till near the zenith1 where it would remain stationary for a short time and then break up and disappear4 ,sometimes they would rise up as streamers1 but only occasionally was more than one visible at a time1 and they lasted for such a short time1 that even if they had been bright it would have been very difficult to make satisfactory observations4 ,very few showed any signs of colour1 and those only the slightest tinge4 ,nearly all that were observed gave the citron-line with the small pocket spectroscope with more or less distinctness1 though no signs of any other lines were ever seen2 but on only two occasions was it bright enough to get the line with ,nury's spectroscope1 and then only for such a short time that a satisfactory measure could not be obtained4 99 99 99 99 99 ,then follows a descriptive list of the ,auror seen1 from which ,i have selected three of the finest1 viz4 ,january #bnd1 ,february #adth1 and ,february #aith1 #ahgf4 ,january #bnd1 #ahgf4 ,lieut4 ,parr4 ,floeberg ,beach4--#i ,p4,m4 ,streams of ,aurora4 ,stars shining brightly4 ,register4 ,discovery ,bay4--#i ,p4,m4 ,observed an ,aurora like a pale band of light in the form of an arch whose centre was on the true meridian and #ae from the zenith4 ,it shortly afterwards broke up into feathered edges1 their direction being a little to the eastward of the zenith4 ,the arch grew fainter1 and shifted to the eastward of the meridian four points2 the left extremity of the arch faded away1 and the right assumed the shape of the folds of a curtain doubled over4 ,the weather was clear and calm4 ,the display lasted upwards of #cj minutes4 ,a spectroscope1 one of ,browning's #h-;in4 direct-vision1 was directed towards the ,aurora1 but the light was not sufficient to give any spectrum4 ,the temperature was -#ci4 ,barometer #bief inches4 ,no wind4 ,clouds stratus #b4 ,eight meteors were observed during the time the ,aurora was visible4 ,february #adth4 ,register4 ,discovery ,bay4--,at #b ,a4,m4 a faint ,aurora passing across the heavens from ,s4,e4 to ,s4,w4 was observed1 like an arch of a pale colour4 ,it lasted only a short time1 and was very indistinct4 ,temperature -#dg4 ,barometer #cjdd inches4 ,no wind or clouds4 ,lieut4 ,aldrich4 ,floeberg ,beach4--#b ,a4,m4 ,a faint ,aurora towards the ,s4,w4 ,weather calm4 ,cumulus-stratus clouds #c4 ,temperature -#df4 #h ,p4,m4 ,faint flashes of ,aurora in the ,e4 and ,s4,w4 ,lieut4 ,aldrich and ,lieut4 ,parr4 ,floeberg ,beach4--#aa4ej ,p4,m4 ,a moderately bright arch of ,aurora extended from due ,n4 to about ,s4,s4,w41 where it terminated close down to the horizon in a crook turned to the eastward4 ,in a few moments a streamer flashed from the end of the crook parallel to the first and right across the heavens1 its edges being quite sharp and parallel to each other4 ,a third streamer shot up a minute afterwards1 but did not extend more than #hj upwards4 ,the streamers were visible for a very short time1 the first remaining longest4 ,the second-named arch gradually faded away till within a few degrees of the ,s4,s4,w4 horizon1 and 7still being a continuation of the crook7 bent round to the eastward1 and towards the horizon1 going on to what was left of the stump of the third arc4 ,a lateral motion to the eastward now began1 the whole body gradually turning round until it disappeared about due south4 ,stars were visible through it at its brightest1 but not very distinctly4 ,this is the most intense and variegated ,aurora we have experienced1 but scarcely any colours were to be seen4 ,temperature -#ea4 ,barometer #cjdc inches1 stationary4 ,calm weather4 ,clouds cumulus #a4 ,preceded and followed by calm weather4 ,meteorological ,register4 ,discovery ,bay4--#i4ae ,p4,m4 ,an ,aurora was observed to the southward1 spreading out like a fan in separate ways4 ,it was faint4 ,a few cirro-stratus clouds were visible1 apparently between the observer and the ,aurora4 ,it lasted about #dj minutes1 and then gradually faded away4 ,temperature -#dg4 ,barometer #cjea inches1 stationary4 ,no wind4 ,clouds cirro-stratus #d4 ,february #aith4 ,meteorological ,report4 ,discovery ,bay4--#i4de ,p4,m4 ,an ,aurora like a fluted arch1 with rays flashing towards the ,pole1 was observed spanning the hills from the south to the east4 ,the direction of the lines of light from all parts of the arch was towards the zenith4 ,above the arch a pale band of colour appeared1 like a secondary arch above the other4 ,it appeared very much as if it was caused by the reflected light of the ,aurora4 ,the ,aurora was bright for a few seconds1 and then gradually died away4 ,it lasted altogether about #cj minutes4 ,the centre of the arch bore ,s4,e41 having an altitude of about #cj4 ,the secondary arch was about #ae above the former4 ,both arches were of a pale light colour1 the upper one very faint4 ,temperature -#cd4 ,barometer #bihg inches1 rising rapidly4 ,weather calm4 ,misty4 ,no clouds4 ,lieut4 ,parr4 ,floeberg ,beach4--,an ,aurora appeared shortly after #aa ,p4,m41 consisting of bright arch1 whose centre bore about ,e4,s4,e41 and had an altitude of about #e1 with a second broader and fainter arch about #g above the first4 ,these arches maintained their altitudes1 the upper one at about the same intensity1 but that of the lower one varied considerably4 ,it would gradually brighten up1 then send streamers up to the second1 then break up into light patches1 and gradually fade away4 ,this happened three or four times during the #dj minutes that the display lasted4 ,at times streamers would come up from the horizon to the lower arch1 for it was a splendidly clear night1 and seemed to brighten it up1 but none of them extended beyond it4 ,neither did the streamers from the lower arch extend beyond the upper one4 ,it was slightly green in colour when brightest1 and the citron-line was well defined1 but no others were visible4 ,temperature -#df4 ,barometer #biie inches1 steady4 ,weather calm4 ,cumulus clouds #d4 ,misty4 ,,table of ,,dates when ,,auroras were observed by the ,,arctic ,,expedition1 #ahge-gf4 ---------------------------------------- ------------------------- ,h4,m4,s4 #8,alert1' ,h4,m4,s4 #8,discovery1' ,date4 ,floeberg ,beach4 ,discovery ,bay4 ---------------------------------------- ------------------------- #ahge1 ,october #be #aa4de ,p4,m4 ,faint4 ,cloudy4 0 0 #bf #aj ,p4,m4 ,very faint4 #aj ,p4,m4 0 0 #cj ,sky obscured4 ,faint4 ,ditto4 0 ,november #a ,ditto4 ,faint1 but well marked4 ,ditto4 0 0 #b #i to #aj ,p4,m4 ,arches and streamers4 ,a few clouds4 0 0 #ba ,ditto4 ,bright #i to #aj ,p4,m4 streamer4 and #aj to #aa ,p4,m4 0 0 #bb #b ,p4,m4 and #h ,p4,m4 ,slight1 red4 ,clear sky4 0 0 #be #i4cj ,a4,m4 ,character not recorded4 ,ditto4 0 0 #bf #aj ,a4,m4 ,stream of light4 ,a few clouds4 0 0 #bf ,cloudy to #aj ,p4,m41 bright afterwards4 #aj ,p4,m4 0 0 #bg ,midnight4 ,slight4 #aa4dj ,p4,m4 0 0 #bh #a ,a4,m4 ,bright streak4 ,clear sky4 0 0 #bi ,cloudy1 brighter at #aa ,a4,m4 ,faint glow4 #i4cj ,a4,m4 0 0 #cj ,a few clouds4 ,very faint4 #d4cj ,a4,m4 0 0 #cj #e ,p4,m41 #h ,p4,m41 and #aj ,p4,m4 ,flashes4 #e ,p4,m4 0 ,december #b ,evening4 ,streamers4 ,clear sky4 0 0 #c #a ,a4,m4 ,flashes4 ,ditto4 0 0 #c ,bright sky4 ,faint ,aurora4 #b4cj ,p4,m4 0 0 #af #aj ,p4,m4 ,slight2 showed citron-line4 #aa ,p4,m4 0 0 #ai #c ,p4,m4 to #e ,p4,m41 faint2 and #i to #aj ,p4,m41 ,very clear sky4 moderately bright arc4 0 0 #bb #aj ,p4,m4 ,slight4 ,ditto4 0 0 #bc #f ,p4,m4 ,ditto4 ,ditto4 0 0 #bd ,misty1 a few stars visible4 ,arch4 #i ,a4,m4 0 0 #bf ,very bright sky4 ,faint4 #f ,p4,m4 0 0 #bi ,ditto4 ,very faint4 #f4ae ,p4,m4 0 0 #ca #d ,p4,m4 ,same4 ,sky obscured4 #ahgf1 ,january #a #e ,p4,m4 and #aa ,p4,m4 ,slight4 ,a few clouds4 0 0 #b #i ,p4,m4 ,described and figured4 #i ,p4,m4 0 0 #ag ,very bright sky4 ,very faint streamers4 #i4be ,a4,m4 0 0 #ah #i4de ,p4,m4 and #aj4e ,p4,m4 ,character not recorded4 #aj4ae ,p4,m4 0 0 #ai ,very bright sky4 ,faint4 #i4de ,p4,m4 0 0 #bj #b ,a4,m4 ,slight4 #b4cj ,a4,m4 0 0 #bc #g4ee ,a4,m4 and #b ,p4,m4 ,slight4 #h4de ,p4,m4 0 0 #bd ,bright sky4 ,slight flash4 #b ,a4,m4 0 0 #bd #e ,p4,m4 and #aa4ae ,p4,m4 ,faint ,aurora4 ,very clear sky4 0 0 #bg #b ,a4,m4 to #c4de ,a4,m4 ,faint4 #a ,a4,m4 to #d ,a4,m4 0 0 #bg ,very bright sky4 ,faint double arch4 #h4cj ,p4,m4 0 0 #bh #f ,p4,m4 and #g to #i ,p4,m4 ,faint flashes4 #g4bj ,p4,m4 0 0 #cj #h ,p4,m4 ,streak4 #g4ej to #i ,p4,m4 0 0 #ca #h4cj ,a4,m4 and #g4cj ,p4,m4 ,very faint4 #h4be ,a4,m41 #e4cj ,p4,m4 0 ,february #c #aj ,p4,m4 ,slight flash4 ,very clear sky4 0 0 #aa ,sky obscured4 ,very faint4 #aa ,p4,m4 0 0 #ac #aa ,p4,m4 ,flashes4 ,clear sky4 0 0 #ad #b ,a4,m41 #i4ae to #aj ,p4,m4 ,described and figured4 #b ,a4,m4 and #aa4ej ,p4,m4 0 0 #ai #i4de ,p4,m4 #aa ,p4,m4 0 0 #bj #b ,a4,m4 ,very faint4 #b4cj ,a4,m4 0 0 #bb #b ,a4,m4 ,character not recorded4 ,very clear sky4 0 0 #bd ,bright sky4 ,very faint4 ,midnight4 0 0 #bf #aj ,p4,m4 and #aa ,p4,m4 ,faint flashes4 ,sky obscured4 ---------------------------------------- ------------------------- ,i have added to the above ,table the character of the ,aurora in each instance as taken from the fuller descriptions given4--,j4 ,r4 ,c4 ,auroras and ,magnetic ,disturbances4 ,the appearances of ,auroras and the synchronous movements of the declinometer-magnet were subjects of special observation during the stay of the #8,alert' and #8,discovery' at their winter-quarters4 ,the ,table on page #ahg gives the dates and hours when ,auroras were visible4 ,on all occasions they were observed to be faint1 with none of those brilliant manifestations which are described by our own officers as seen at ,point ,barrow1 and by the ,austro-,hungarian ,expedition at ,franz-,josef ,land1 where the magnetical instruments were so sensibly disturbed4 ,these phenomena were not observed either in the #8,alert' or the #8,discovery1' especially no connexion between magnetical disturbances and the appearances of ,auroras could be traced4 ,this is quite in accordance with the remarks of previous observers within the region comprehended between the meridians of #fj and #ij west1 and north of the parallel of #gc north4 ,for example3-- ,in the ,phil4 ,trans4 #ahbf1 ,part ,,iv4 p4 #gf1 ,capt4 ,parry and ,lieut4 ,foster remark1 in the discussion of their magnetical observations at ,port ,bowen3--8,as far1 however1 as our own observations extended1 we have reason to believe that on no occasion were the needles in the slightest degree affected by ,aurora1 meteors1 or any other perceptible atmospheric phenomenon40 ,again1 in the ,smithsonian ,contributions1 vol4 x41 #aheh1 ,mr4 ,a4 ,schott1 in his discussion of ,dr4 ,kane's observations at ,van ,rensselaer ,harbour1 in #ahed1 remarks--8,in conformity with the supposed periodicity of this phenomenon as recognized by ,professor ,olmstead1 no brilliant and complete ,auroras have been seen2 with an exception of very few1 they may all be placed in his fourth class1 to which the most simple forms of appearances have been referred40 ,the following statement is given in the same page as a footnote3--8,the processes have no apparent connexion with the magnetic dip1 and in no case did the needle of our unifilar indicate disturbance40 99 99 99 99 99 ,the following description of the ,aurora observed on #bast ,november1 #ahge1 is given by ,commander ,markham and ,lieut4 ,giffard1 in their abstract of observations at ,floeberg ,beach3-- 8,between #aj and #aa ,p4,m4 bright broad streamers of the ,aurora appeared #aj or #ae above the north horizon1 stretching through the zenith1 and terminating in an irregular curve about #be above the south horizon1 bearing ,s4,s4,w4 ,during the ,aurora's greatest brilliancy the magnet was observed during five minutes to be undisturbed40 ,note4--,i applied for a loan of the lithographic stones to enable me to give copies of the three diagrams of ,auror referred to in the ,arctic 8,results20 but the ,lords ,commissioners of ,h4,m4 ,treasury refused this1 except on the terms of my paying one third of the original cost of production of such diagrams4 ,i did not think it worth while to accept these conditions4 ,only one of the drawings has any special interest2 and this is a 8curtain0 ,aurora1 similar to that figured on ,plate ,,ii4 of this work4--,j4 ,r4 ,c4 ,,appendix ,d4 ,,the ,,aurora ,,and ,,ozone4 ,sidenote3 ,aurora and ozone4 ,dr4 ,allnatt's notes and conclusions deduced therefrom4 ,while ,part ,i4 was in the press1 ,dr4 ,allnatt1 formerly of ,frant1 and for many years the well-known meteorological contributor to #8,the ,times' newspaper1 kindly placed at my disposal his large series of notes4 ,upon an examination of these we came to the following conclusions3-- #a4 ,that ,auroral periods are also periods of comparative abundance of ozone4 #b4 ,that instances are by no means wanting in which an abnormal development of ozone appears to be coincident with the manifestation of an ,aurora4 ,sidenote3 ,year #ahgj remarkable for sun-spots1 auror1 and ozone4 ,in reference to the first point1 it is found1 as the result of an examination of ,dr4 ,allnatt's notes1 that particular years and months are notable at once for ,auror and for ozone in abundance4 #ahgj was one of these years1 and was specially recorded by ,dr4 ,allnatt1 in his #8,summary for the ,year1' as remarkable for sun-spots1 ,auror1 and ozone4 ,sidenote3 ,particulars of some of the monthly records4 ,the month of ,february in that year was marked by intense cold and brilliant ,auror4 ,atmospheric electricity was feeble1 but ozone was1 throughout the month1 well developed2 and there was no tangible period of antozone4 ,in the month of ,april of the same year1 eight days consecutively 7#aith to #bfth7 were marked for ozone #aj1 the maximum of ,dr4 ,allnatt's scale4 ,in ,may of the same year there were magnificent ,auror1 and atmospheric electricity was intense4 ,ozone was scanty2 but this was accounted for by the wind being generally ,e4,n4,e41 ozone being mostly developed with a ,w4 or ,s4,w4 wind1 and a moist state of the atmosphere4 ,in ,august #ahgj the unusually large number of #bb days were recorded for a maximum of ozone4 ,september #ahgj was hardly less remarkable1 with #ai days of maximum4 ,it was recorded that there were splendid ,auror during this month1 and the solar spots were very large4 ,october #ahgj had #bj days of maximum ozone1 and ,november had several fine ,auror and maxima of ozone noted4 ,in fact1 nearly every month in that year was referred to by ,dr4 ,allnatt for displays of ,aurora 7of both ,arctic and ,antarctic forms7 and for a development of ozone very considerably above the average4 ,sidenote3 ,year #ahga4 ,the year #ahga had more or less of the same character4 ,in the month of ,october of that year1 fine ,auror were prevalent1 and ozone was registered as at its maximum during #bb days4 ,there seems reason to conclude that if a systematic comparison of annual or other periods of ,aurora and ozone development were made1 it would result in disclosing a connexion 7probably an intimate one7 between the two phenomena4 ,sidenote3 ,instances showing a connexion between a specific ,aurora and an ozone maximum4 ,with reference to the second point1 the following 7among other7 instances may be quoted1 for the purpose of showing a connexion between a specific ,aurora and an ozone maximum4 ,the ,aurora of #bdth ,september1 #ahgj1 was splendid and universal1 being seen in ,europe1 ,asia1 ,africa1 ,america1 and ,australia4 ,ozone reached1 on the morning of the #bdth1 #h of the scale 7the scale running from #a to #aj71 and1 on the morning of the #beth1 #aj1 the maximum4 ,in ,october #ahgj there were grand displays on the #adth1 #bjth1 #bbnd1 #bdth1 and #beth1 and ozone was correspondingly abundant1 as is seen by the following ,table3-- ---------------------------------------- ------------------- ,date4 ,aurora4 ,ozone4 ---------------------------------------- ------------------- #ahgj1 ,october #adth4,aurora4 #h ,the display of the #bdth 0 0 #bjth4,aurora4 #aj was accompanied by 0 0 #bast4,none seen4 #e the formation of a 0 0 #bbnd4,aurora4 #aj corona1 and that of 0 0 #bcrd4,none seen4 #h the #beth was splendidly 0 0 #bdth4,aurora4 #aj seen in ,edinburgh4 0 0 #beth4,aurora4 #h ---------------------------------------- ------------------- ,the foregoing figures somewhat point to the conclusion that ozone quantity rises and falls coincidently with the ,aurora displays4 ,the following seems1 however1 a case still more strongly in point4 ---------------------------------------- ------------- ,date4 ,wind4 ,aurora4 ,ozone4 ---------------------------------------- ------------- #ahga1 ,january #beth4 ,e4,s4,e4 ,none seen4 #j 0 0 #bfth4 ,n4,n4,w4 ,none seen4 #b 0 0 #bgth4 ,e4,s4,e4 ,aurora at night in ,n4 and ,s4 horizons4 #aj 0 0 #bhth4 ,e4 ,none seen4 #h 0 0 #bith4 ,s4,e4 ,none seen4 #b ---------------------------------------- ------------- ,it is curious1 in examining the above ,table1 to note how the ozone rose1 notwithstanding an east wind1 from #j on the #beth1 and #b on the #bfth1 to #aj on the #bgth1 when the ,aurora appeared1 and #h on the #bhth1 when it might have lingered2 and how it again descended to #b on the #bith4 ,the case of the ,aurora of #fth of ,october1 #ahfi1 when a broad belt of ,aurora was in the north1 is also an illustrative one1 as will be seen by the following data3-- ------------------------------------- ,date4 ,wind4 ,ozone4,aurora4 ------------------------------------- #ahfi1 ,october #eth4,s4,s4,w4 #a -- 0 0 #fth4,s4,s4,e4 #e ,aurora4 0 0 #gth4,s4,s4,w4 #aj -- 0 0 #hth4 ,s4 #aj -- 0 0 #ith4 ,s4,e4 #e -- ------------------------------------- ,the ,aurora of the night of the #fth was here represented by the ozone-paper of the morning of the #gth with a maximum of #aj1 which lasted till the #hth4 ,it should be borne in mind1 in examining these ,tables1 that the ,aurora is of the night of the given date1 while the ozone-papers are taken and recorded in the morning of the date quoted4 ,sidenote3 ,other instances4 ,we will now take instances where the ozone has not reached its maximum2 but even in these cases a certain amount of rise and fall of the ozone development towards and from the ,aurora is traceable4 ---------------------------------------- ------------------ ,date4 ,wind4 ,ozone4 ,aurora4 ---------------------------------------- ------------------ #ahga1 ,april #hth ,s4,s4,e4 #e ,aurora on #ith1 but 0 0 #ith ,s4,s4,e4 #h wind ,e4 and unfavourable 0 0 #ajth ,s4,e4 #e to ozone4 ---------------------------------------- ------------------ #ahga1 ,november #ith ,n4 #e ,aurora on all three 0 0 #ajth ,n4,w4 #h nights4 0 0 #aath ,n4 #e ---------------------------------------- ------------------ #ahgb1 ,february #crd ,s4,w4 #d ,aurora on night of the 0 0 #dth ,s4,s4,w4 #e #dth represented by 0 0 #eth ,s4,w4 #h ozone-paper of morning 0 0 #fth ,s4,w4 #e of the #eth4 ---------------------------------------- ------------------ ,other cases are1 we are bound to say1 found1 in which ozone was either not remarkable for quantity1 or positively fell during the ,aurora1 as1 for instance1 this3-- ---------------------------------------- ------------------- ,date4 ,wind4,ozone4 ,aurora4 ---------------------------------------- ------------------- #ahgd1 ,march #afth ,w4,n4,w4 #f ,aurora on the #ahth represented 0 0 #agth ,s4,w4 #f by test-paper of 0 0 #ahth ,w4 #e the #aith with only two 0 0 #aith ,s4,s4,w4 #b degrees of discoloration4 ---------------------------------------- ------------------- ,it is1 however1 possible that such instances may be accounted for1 either by some reaction on the test-papers after they have been coloured1 or by some accidental antagonistic circumstance affecting the tests4 ,the following is a case well illustrating this3-- ---------------------------------------- ----------------------- ,date4 ,wind4,ozone4 ,aurora4 ---------------------------------------- ----------------------- #ahgd1 ,january #cast,n4,n4,w4 #f ,there was an ,aurora on 0 ,february #ast ,n4,w4 #h the night of the #bnd represented 0 0 #bnd ,n4,w4 #b by the ozone-paper 0 0 #crd,n4,n4,w4 #d 7#d only7 on the 0 0 #dth,e4,n4,e4 #h morning of the #crd4 ---------------------------------------- ----------------------- ,this instance would seem strongly opposed to the theory of a connexion between ,aurora and ozone but for the fact that on the #bnd1 when the ,aurora was seen at night1 and on other days in the same month1 ,dr4 ,allnatt has recorded a strong wave of antozone to have swept over the whole of ,england1 and blanched the ozone-papers1 however deep their coloration might have previously been4 ,indeed1 it is easy to understand that some antozonic influence may1 at times1 disturb the evidence of the test-papers1 even in so elevated and apparently pure an atmosphere as that of ,frant4 ,it may not be considered that the foregoing instances are enough to establish a case of ozone,aurora2 but there seems1 at least1 sufficient to base a requisition for further inquiry upon4 ,it would1 too1 be interesting to investigate whether ,auror and ozone development are respectively localized4 ,mr4 ,ingall's fine ,aurora1 seen at ,champion ,hill1 ,s4,e41 ,july #ahth1 #ahgd 7ant1 pp4 #bb and #bc71 was not observed at ,frant1 and the ozonoscopes there were described as blanched by antozone4 ,,appendix ,e4 ,,inquiries ,,into ,,the ,,spectrum ,,of ,,the ,,aurora4 ,,by ,h4 ,c4 ,,vogel4#ah ,the frequent appearance of the ,aurora in the past winter1 as well as this spring1 has given me opportunity to institute exact inquiries into the spectrum of the ,aurora4 ,it is known that the nature of ,auror is as yet but little explored4 ,it has been considered necessary to abandon the former view--that they are discharges of the electricity collected at the poles--because it has been hitherto found impossible to bring the chief lines of the ,aurora-spectrum into coincidence with the spectra of the atmospheric gases4 ,theoretical considerations1 based on the great alterations to which the spectrum of the same gas is subject under varying conditions of temperature and density1 have very recently led ,zllner to the opinion that probably the spectrum of the ,aurora does not coincide with any known spectrum of the atmospheric gases1 only because it is a spectrum of another form of our atmosphere hitherto incapable of artificial demonstration#ai4 ,the following article will show how far ,i have succeeded1 in conjunction with ,dr4 ,lohse1 in supporting this view by exact observations of the ,aurora-spectrum itself1 as well as by comparison with the spectra of the gases constituting the air4 ,the star-spectrum apparatus belonging to the #aa-;inch equatorial of the ,bothkamp ,observatory was used for these observations4 ,it consists of a set of prisms vision directe1 five prisms with refracting angle #ij1 slit1 collimator1 and observing telescope4 ,the lowest eyepiece 7magnifying four times7 of this telescope was employed4 ,the telescope is capable of being moved in such a way1 by the aid of a micrometer-screw1 that different portions of the spectrum can be brought into the centre of the field of vision4 ,as fractions of the rotation of this screw are marked1 the distances of the spectral lines can be readily found4 ,repeated measurements of #ajj lines of the solar spectrum have enabled me1 upon the basis of ngstrm's ,atlas 7#8,spectre normal de ,soleil'71 to express the indications of the screw directly in wave-lengths4 ,in place of the cross wires originally introduced into the focus of the observing telescope1 ,i have inserted a tiny polished steel cone1 the very fine point of which reaches to the centre of the field of vision4 ,the axis of this cone stands perpendicular to the length of the spectrum1 therefore parallel with the spectral lines1 and the setting of the point of the cone on the latter is accomplished with great sharpness4 ,if the spectrum is very faint1 or consists only of bright lines1 the cone is lighted by a small lamp4 ,for this purpose1 opposite to the point of the cone1 there is an opening in the telescope1 through which1 regulated by a blind1 light can be thrown on the point4 ,as the latter is polished1 a fine line of light thus appears1 which extends to the centre of the field of vision1 and the brilliancy of which can be altered by withdrawing the lamp to a greater distance or lowering the blind1 so that even the faintest lines of a spectrum can be brought with facility and certainty into coincidence with this line of light4 ,the head of the micrometer-screw is divided into #ajj parts1 and each part1 in the neighbourhood of the ,fraunhofer line ,f1 answers to about #jjjaf wave-length4 ,the probable error of position on one of the well-marked lines in the sun's spectrum amounts to about #jjjh of a turn of the screw with the lowest eyepiece of the telescope4 ,i have subjected the screw itself to a thorough examination with reference to such range1 as well as to periodical inequalities in the single worms of the screw1 but could discover no error exceeding #jja of a turn of the screw4 ,i have to mention1 further1 that after each observation in the position in which the instrument was used1 readings followed on the sodium-lines1 or on some of the hydrogen-lines1 in order to eliminate errors which might arise in the unavoidable disturbance of any particular part of the spectral apparatus4 #a4 ,observations of the ,aurora4 #ahgj1 ,oct4 #beth4--,a very bright ,aurora4 ,in the brightest parts1 besides a very bright line between ,d and ,e1 several other fainter lines were to be discerned1 situated further towards the blue end of the spectrum4 ,they appeared on a dimly-lighted ground1 and stretched out over the ,fraunhofer lines ,e and b to about midway between b and ,f4 ,towards the red end the spectrum was terminated by the bright line first mentioned4 ,no measurements could be taken1 as the apparatus had not yet undergone the above-mentioned alterations1 and even the brightest line of the spectrum did not diffuse sufficient light to be able to perceive the fine cross wires4 ,the red rays of the ,aurora were not examined4 #ahga1 ,feb4 #aath4--,towards ten o'clock appeared in the north-west a very bright light-bow of greenish colour as the edge of a dark segment4 ,even with a very narrow slit1 the line between ,d and ,e could be well recognized and measured4 ,the average of six readings gave #gaa turns1 equal to #eegb wave-length4 ,in a small spectroscope of low dispersion which is arranged on ,browning's plan1 a few more lines placed further towards the blue could be recognized 7as in ,october74 ,towards the red end of the spectrum no lines were observable4 ,the greatest development of the ,aurora was about midnight4 ,magnificent rays rose to about #fj elevation2 they had the same greenish colouring as the bow of light1 and the appearance of the spectrum also was exactly the same4 ,i again obtained two sets of measurements3 the average of six readings in the first set gave #gaj turns1 #eegb wave-length2 in another part of the heavens at the same time #gaj was the result of four readings4 ,on ,feb4 #ab1 towards eight o'clock1 the intensity of the ,aurora was already great enough to allow measurements of the brightest line4 ,the average of six readings gave #gji turns1 or #eegf wave-length4 ,dr4 ,lohse took observations later1 with the same apparatus1 and found from six readings #gab turns1 or #eefi wave-length4 ,yet the appearance of the spectrum in the spectroscope of low dispersion was essentially distinct from that of ,february #aath4 ,the green continuous spectrum was present2 it extended from the bright ,aurora-line to the lines b of the solar spectrum1 and was traversed by some bright lines4 ,between band b and ,f1 was another line standing alone1 out beyond ,f1 in the blue part of the spectrum1 a clear bright stripe2 and just before ,g a very faint broad band of light was perceived4 ,amongst the rays which1 later on1 shot upwards1 and were coloured red at their ends1 another very intense red line appeared in the spectrum between ,c and ,d1 yet placed nearer to ,c#bj4 ,april #ith4--,an exceedingly brilliant ,aurora1 of which the greater development took place in the early morning hours4 ,magnificent red sheaths rose up to the zenith4 ,the spectrum was like that observed on ,february #abth1 only much more intense1 so that the lines could be seen and measured with the larger spectral apparatus4 ,in the brightest part of the ,aurora was the dark segment2 the spectrum consisted of five lines in the green1 and a somewhat indistinct broad line or band in the blue4 ,the red rays1 on the other hand1 allowed us to recognize seven lines1 whilst the bright line again appeared in the red part of the spectrum4 ,i could not again perceive the faint stripe observed on ,february #abth1 in the vicinity of line ,g4 ,the mean measurements of four readings on an average1 for each line1 gave3-- ---------------------------------------- ----------------------------- ,turns ,prob- ,prob- of able ,wave- able screw4errors4length4errors4 ,remarks4 ---------------------------------------- ----------------------------- #dfb #jjcg #fbig #jjjad ,very bright stripe4 ,on #gab #i #eefi #b ,brightest line of the spectrum2 a becomes noticeably fainter at faintly appearance of the red line4 lighted #gib -- #ecij -- ,extremely faint line2 unreliable ground4 observation4 #hga #ba #ebcc #d ,moderately bright4 #hie #di #eahi #i ,this line is very bright when the red line appears at the same time1 otherwise equal in brilliancy with the preceding one4 #ajjf #bj #ejjd #c ,very bright line4 #abcc -- #dfid -- ,broad band of light1 somewhat less #abei #bb #dffc -- brilliant in the middle4 #abhh -- #dfbi #c ,very faint in those parts of the ,aurora in which the red line appears4 ---------------------------------------- ----------------------------- ,april #adth4--,faint ,aurora2 only the bright line in the green could be recognized in its spectrum4 ,the mean of two readings gave #gab turns1 or #eefi wave-length4 ,i append a table of the wave-lengths of the brightest line1 as exactly measured on four evenings3-- #ahga1 ,february #aa #eegc 0 #ab #eegc ,april #i #eefi 0 #ad #eefi ,therefore the average result 7if only half-weight is allowed to the last observation1 because it only depends upon two readings7 gives for the wave-length of the brightest line #eegac1 with a probable error of #jjjib4 ,according to ngstrm#ba1 the wave-length of this line is #eefg2 according to ,winlock#bb1 on the other hand1 #eegj4 #b4 ,on the ,spectra of some ,gases in ,geissler's ,tubes1 as well as on the ,spectrum of the ,atmospheric ,air4 ,numerous experiments have been made in order to find out some admitted connexion between the spectrum of the ,aurora and the spectra of the principal gases composing the atmosphere4 ,i limit myself to noticing some of the often-repeated observations in ,plcker's tubes1 which contained oxygen1 hydrogen1 and nitrogen1 as well as the observations of the spectrum of the air under different conditions4 ,the experiments were made with a small inductive apparatus1 in which the length of the spark between platinum points in ordinary air was #ae millims4 at the most4 ,as ,zllner 7in the pamphlet mentioned7 comes to the conclusion1 that if the development of the light in the ,aurora1 according to the analogy of gases brought to glow in rarefied spaces1 is of an electric nature1 it must belong to very low temperature--in order to bring the gases enclosed in the tubes to glow at the lowest possible temperature1 ,i have always employed such weak currents that the gas was only just steadily alight4 ,the following observations have been repeated often and at various times4 ,the figures are averages of the indications of the micrometer-screw1 so that the uncertainty of the figures will1 in the rarest cases1 amount to no more than #jjae turn of the screw1 and must be reckoned somewhat more highly only in the case of completely faint misty lines4 ,the spectrum apparatus was that described above1 and the slit was nearly the same in every experiment1 and so narrow that the sodium-lines could be seen separated4 ,the measurements1 for the most part1 extend only to the ,fraunhofer line ,g1 as ,i feared lest1 through further turning the telescope by means of the micrometer-screw1 too great a pressure might be exercised on the worms of the latter4 ,i4 ,oxygen4 a4 ,in the narrow part of the ,plcker tube4 ---------------------------------------- ---------------------------- ,screw4,wave-length4 ,remarks4 ---------------------------------------- ---------------------------- #cig #fefb ,moderately bright4 #ejd #fadf ,very bright4 #fih #efjc ,very bright1 misty towards the violet4 #hai #eccb ,faint4 #hie #eahi ,moderately bright4 #ajig #dhgj 0 0 #aajb #dhfc ,faint4 #aabf #dhbi ,bright2 misty towards the red end of the spectrum4 #accj #dehc ,very faint4 #adje #dejf ,moderately bright4 #aeee #dcgb 0 0 ---------------------------------------- ---------------------------- b4 ,in the wide part of the ,plcker tube4 ------------------------------------ ,screw4,wave-length4 ,remarks4 ------------------------------------ #fih #efjc ,very faint4 #hie #eahi ,very bright4 #aabf #dhbi ,moderately bright4 ------------------------------------ ,the lines near #cig and #aajb belong to hydrogen4 ,probably traces of aqueous vapour were present in the tube1 which were decomposed by the galvanic current4 ,these two lines are not to be found in a lower temperature in the broad part of the tube4 ,it is striking that the red nitrogen-line near #ejd is also missing there4 ,in the narrow part of the tube the lines stand out in the green on a very dimly-lighted ground1 whilst in the wider part they appear on a perfectly dark ground4 ,,ii4 ,hydrogen4 a4 ,in the narrow part of the tube4 ---------------------------------------- ---------------------------- ,screw4,wave-length4 ,remarks4 ---------------------------------------- ---------------------------- #cih #feeh ,very bright4 #faf #ehac ,moderately bright1 on both sides very faint lines4 #gja #eeif ,moderately bright4 ,on a dimly lighted ground1 #gah #eeee ,moderately bright4 which becomes fainter towards #ggg #edbb ,faint4 the violet4 #hie #eahi ,moderately bright4 #ajjc #ejjh ,faint4 ,on a faint steadily bright #ajee #dibi ,moderately bright4 ground4 #aajd #dhfa ,very bright4 ,from #aae to #abi a bright #abhf #dfcb ,moderately bright4 ground1 which towards the violet becomes very bright4 #accb #deha ,very faint4 #adje #dejf 0 ,on a dull ground4 #aeij #dcdb ,very bright4 ---------------------------------------- ---------------------------- b4 ,in the broad part of the tube4 ------------------------------------- ,screw4,wave-length4 ,remarks4 ------------------------------------- #ecj #fjfc ,faint4 #gjj #eeih ,bright4 #hif #eahg ,very bright4 #aabh #dhbh 0 #adjd #dejg ,moderately bright4 ------------------------------------- ,the lines appeared on a perfectly dark ground4 ,the tube shows in the narrow part the hydrogen-spectrum of the first order2 the lines in the green do not coincide with the lines of the nitrogen1 though some lines belonging to nitrogen are found4 ,here1 too1 most probably small particles of aqueous vapour have been enclosed in the tube and are decomposed4 ,very striking is the spectrum in the broad part of the tube2 nothing is to be seen of the bright shining lines ,h #cih1 ,h #aajd1 ,h #aeij2 on the other hand1 four very bright lines and one quite faint one are in the red end of the spectrum1 which appear1 in opposition to the spectrum of the narrow part1 not on a partially lighted1 but on an entirely dark ground4 ,the appearance is very striking if we bring the tube in front of the slit2 and so1 by degrees1 at first the light in the narrow part1 then the light at the connecting-point of the narrow and wide parts1 and1 finally1 the light in the latter fall upon the slit4 ,at the connecting-point of the wide ends of the tube the three well-known hydrogen-lines decrease in intensity1 the continuous ground of some parts of the spectrum disappears1 and a new line appears near #aabh1 which has about the same brilliancy as ,h4 ,a comparison with the spectrum of oxygen shows the bright lines which are in the spectrum in the wide end of the tube as belonging to that element4 ,the heat evolved by the current appears insufficient to bring the hydrogen to glow1 whilst by it the oxygen1 which is of a more rarefied character1 becomes incandescent4 ,an alteration of the direction of the current has no influence on the appearance4 ,,iii4 ,nitrogen4 a4 ,in the narrow part of the tube4 ---------------------------------------- ---------------------------- ,screw4,wave-length4 ,remarks4 ---------------------------------------- ---------------------------- #chd #ffbj ,several faint1 broad1 close lines1 increasing in #dhe #fbac brilliancy as they approach the violet end4 #ecj #fjfc ,broad bright lines1 #eea #fjjj so close together #efi #eidh that the intervening spaces appear #ehg #ehif like fine dark lines4 ,this part of #fjd #ehdf the spectrum is very bright1 but #fbj #ehjb not uniform1 being brighter towards #fdc #egda the violet end4 #fif #efjg ,group of faint but at the same time #gac #eefg very broad lines4 ,the #gbh #eecb last is the brightest4 #gee #edgj ,the dark intervening spaces are somewhat broader1 #ggd #edbh the bright lines somewhat more intense than #gib #echi in the preceding group1 and all of almost equal #hji #ecec brilliancy4 #hcb #ecjf #hej #ebgb ,very faint fine lines4 #hfi #ebcg #ija #eagh ,very bright broad misty line4 #ifg #ejff ,very bright line4 #ajbe #dige 0 0 #ajff #diac 0 0 ,the bright lines #aajc #dhfb ,very faint line4 are sharply #aada #dhaa ,bright line4 defined towards #abaa #dgba 0 0 the red end of #abeg #dfff ,faint line4 the spectrum1 #abeg #dfdd ,bright1 broad1 misty line4 fading away towards #acdb #degj ,very bright line4 the other end of #adbd #ddhg 0 0 the spectrum4 #aejb #ddag ,bright line4 #aeff #dcfc ,bright lines4 ,bright lines sharply defined #aegb #dceg 0 towards red end1 indistinct #aehg #dcde ,bright line4 towards other end of #afgb #dbgc 0 spectrum4 ---------------------------------------- ---------------------------- ,here follow several lines4 b4 ,in the wide part of the tube4 ---------------------------------------- --------- ,screw4,wave-length4 ,remarks4 ---------------------------------------- --------- #fbj #ehjb ,faint1 indistinct1 broad line4 #ggb #edcc ,dull stripe4 #hbj #eccj ,faint line4 #hid #eaia ,very faint line4 #ijc #eage ,broad band of light4 #iij #ejbi ,dull band of light4 #ajfh #diaa ,moderately bright line4 #aadb #dhji ,faint line4 #abei #dffc ,bright line4 #acdc #defi 0 #adjg #dejd ,moderately bright line4 #adbe #ddhf ,very bright line4 #aehe #dcdg 0 0 #afgf #dbgc ,moderately bright line4 ---------------------------------------- --------- c4 ,at the aura of the negative pole4 ---------------------------------------- --------------------------- ,screw4,wave-length4 ,remarks4 ---------------------------------------- --------------------------- #eah #fajj ,broad1 moderately bright stripe1 indistinct #egj #eide at the edges4 #gfj #eaei ,broad1 moderately bright stripe4 #hda #ebhi #hgf #ebbd ,very bright line1 somewhat indistinct towards the violet4 #iai #eadg ,faint line4 #ajjj #ejjd ,bright line1 indistinct towards the red4 #ajfg #diab ,somewhat fainter than the last1 indistinct towards the red4 #aadc #dhjh ,very faint line4 #abbe #dgjd ,very intense1 broad1 indistinct towards the violet4 #abgc #dfdf ,very faint line4 #acdc #defi ,moderately bright1 indistinct towards the violet4 #adbe #ddhf ,like the last4 #aejc #ddag ,quite a faint line4 #aehf #dcdf ,moderately bright line4 #afgf #dbge ,very bright line4 ---------------------------------------- --------------------------- ,here follow several other lines4 ,the observations in the different parts of the tube show plainly the dependence of the spectrum on the temperature4 ,the aura of the negative pole gives the line near #ajjg so characteristic of the air-spectrum4 ,this is the same line which is met with in the spectra of most of the nebul4 ,the very striking groups of lines in the red and yellow in the spectrum of the narrow part of the tube disappear entirely in the wide part4 ,if we compare the spectra with those above quoted1 of oxygen and hydrogen1 we find line ,h very faint in the spectrum of the narrow part of the tube near #aajc2 on the other hand1 oxygen-lines appear in the broad part near #hbj1 #hid1 and #adjg4 ,thence ,i would conjecture that the tube was not filled with pure nitrogen1 the appearance of which is precise1 but with dry rarefied air1 since ,wllner's researches have proved that dry air yields the same spectrum as nitrogen gas4 ,perhaps the air in the tube examined by me had not been thoroughly dried1 and thus the appearance of some lines of the elements before named is to be explained4 ,i must further mention that the electrodes of the tubes consisted of aluminium2 yet a comparison of the spectra observed and the aluminium spectrum has shown no connexion between them4 ,,iv4 ,atmospheric ,air4 ---------------------------------------- ------------------------- ,screw4 ,wave-length4 ,remarks4 ---------------------------------------- ------------------------- #ehh #ehib ,very bright double line 7,na74 #ffg #efhj ,very bright line4 #gbj #eeej ,faint line4 #ijj #eahj ,very bright line4 #igi #ejdg ,fine faint line4 #ajjc #ejjh ,very bright double line4 #ajjg #ejjb #aadc #dhjc ,faint confused line4 #abfi #dfea #abhd #dfcc ,faint line not sharply defined4 #acjd #dfab ,from #adfa #ddec ,confused band of light1 which ends with to #aehh #dddd a broad washy line4 ---------------------------------------- ------------------------- ,here follow several other lines4 ,rarefied air saturated with aqueous vapour4 ---------------------------------------- ---------------------------- ,screw4 ,wave-length4 ,remarks4 ---------------------------------------- ---------------------------- #cig #fefb ,moderately bright line4 7#ehh7 #ehib ,bright double line 7,na74 7#fbe7 #eghi ,bright line 7,h74 ,from #gjc #eeia ,broad dull band of light2 near #gjc a to #gee #edgj somewhat brighter line4 #gei #edfa ,bright line 7,h74 #hgb #ebca ,dull stripe4 #hif #eahg ,broad misty stripe4 ,on a dull steady ground4 #ajjg #ejjb ,faint line4 #aaje #dhei ,very bright line4 #abba #dgji ,moderately bright line4 ,on dimly lighted #abge #dfdd ,line fainter than the ground1 becoming preceding4 fainter towards #acbh #eehe ,very faint line 7,h74 the violet4 7#aega7 #dceh ,very bright line 7,h74 #aeij #dcda 0 0 ---------------------------------------- ---------------------------- ,here follow several more lines4 ,in the first observations1 the electric spark1 about #a centim4 in length1 was allowed to pass between platinum points in ordinary air4 ,the sodium-line near #ehh appeared continually4 ,the bright double line at #ajjc and #ajjg1 with a weaker current or longer spark1 was no longer to be recognized as a double line1 but appeared as a broad somewhat confused line1 of which the brightest part was near #ajje4 ,no lines belonging to the platinum spectrum appeared4 ,ordinary rarefied air1 under a pressure of #be to #cj millims41 and which was enclosed by mercury in a tube #h millims4 wide1 showed exactly the same lines as ,plcker's nitrogen-tube 7b71 except that some lines belonging to the spectrum of mercury also appeared4 ,this observation may be regarded as a confirmation of the conjecture above expressed as to the condition of ,plcker's tube ,,iii4 7nitrogen74 ,in the observations described under b1 the air saturated with aqueous vapour was under a pressure of #bb millims4 ,besides the sodium-lines1 lines of the mercury-spectrum appeared at #fbe1 #gei1 and #aega4 ,the spectrum of rarefied air under similar pressure was found to accord completely with the spectrum of the light in the broad part of ,plcker's tube4 ,,iii4 7,nitrogen b47--,a comparison of the spectrum of rarefied air saturated with aqueous vapour with the former shows the striking alterations in the spectrum which are brought about by the presence of the aqueous vapour4 #c4 ,comparison of the ,aurora-,spectrum with the ,spectra of ,atmospheric ,gases and of ,inorganic ,substances4 ,in the next place1 ,i turn to the comparison of the observed spectra of different gases and of the air with the spectrum of the ,aurora4 ,the first band of light in the red part of the ,aurora-spectrum most probably coincides with the first system of lines in the spectrum of nitrogen 7a74 ,probably only the bright part of this group of lines is perceptible1 on account of the extreme faintness of the ,aurora2 and as in nitrogen the increase of the brilliancy of the spectrum takes place towards the violet end1 the absence of the intermediate spectrum towards this direction would find its explanation4 ,the most intense line of the ,aurora-spectrum at #gab is to be also found in the spectrum of nitrogen 7a7--as a very faint line1 however4 ,that this line appears in the ,aurora by itself1 and with intensity relatively great1 need not appear strange1 considering the great alteration of the gas-spectra under different conditions of pressure and temperature4 ,the third line of the ,aurora-spectrum1 very vaguely defined on account of its great faintness1 coincides in the same way with a nitrogen-line4 ,the line at #hga is met with in the nitrogen-spectrum 7c71 as well as in the air-spectrum 7b74 ,the third line of the oxygen-spectrum at #hie1 which seems to appear under very different conditions1 is found again1 as the fifth line in the spectrum of the ,aurora4 ,moreover1 the sixth line in the ,aurora at #ajjf coincides very exactly with the known nitrogen-line appearing in the spectra of some of the nebul4 ,lastly1 as to the broad band of light in the ,aurora-spectrum from #abcc to #abhh1 several lines are found in this place in the spectrum of nitrogen as well as the air-spectrum 7a1 b72 so that here1 too1 a coincidence between the spectra may be regarded as probable4 ,the observations show with some certainty that at least one line at #ajjf of the ,aurora-spectrum coincides with the maximum brilliancy of the air-spectrum1 and that the other lines appear with great probability in the spectra of atmospheric gases4 ,in the very great difference of the gas-spectra under varying conditions of pressure and temperature1 it would indeed be difficult to succeed in producing artificially a spectrum which should resemble that of the ,aurora in all parts4 ,moreover1 it must be admitted1 under the hypothesis that the ,auror are electric discharges in rarefied air-strata1 that these strata1 qualified for the transmitting of electricity1 will have a very considerable thickness4 ,in this case the conditions of pressure on these air-strata are themselves so different that1 within certain limits1 each will yield its own peculiar spectrum2 but we shall see the sum of collective spectra1 so to speak1 spread out behind each other2 and therefore the impossibility of attaining a perfect agreement between the ,aurora-spectrum and the artificially exhibited spectra of mixed gases is evident4 ,a comparison of the ,aurora-spectrum with the spectra of inorganic substances may be easily worked out by the help of the above-quoted wave-lengths of the single lines of the former1 with due regard to probable errors1 and with the aid of ngstrm's ,atlas of the ,solar ,spectrum4 ,here the perfect harmony of the brightest ,aurora-line 7which was fixed with an exactitude of about one seventh of the separation of the sodium-lines7 with the lines of the iron-spectrum is especially striking4 ,the wave-lengths in the above-cited observations of the bright ,aurora-line vary between #eefi and #eegc1 whilst1 according to ngstrm1 two lines of the iron-spectrum are situated at #eefhe and #eegag4 ,iron-lines corresponding to the other ,aurora-lines1 within certain limits of accuracy1 are also to be found1 as will be seen from the following comparison3-- ---------------------------------------- ---------------- ,aurora-lines4 ,lines of the ,remarks4 iron-spectrum4 ---------------------------------------- ---------------- #fcjjh ,moderately bright4 #fbig #fbihe #ecifj #eciib ,mostly very faint4 #ecij #ecije #echhe #ebcdc ,very faint4 #ebcc #ebcba ,moderately bright4 #ebbij ,very faint4 #eaigi 0 #eaidj 0 #eahi #eaiaf ,moderately bright4 #eaijf 0 0 #eahea ,very faint4 #ejjfe #ejjeb #ejjd #ejjdi ,very faint4 #ejjcj #ejjbj ,from #dfid to #dfbi #c stronger and #d very faint iron-lines4 ---------------------------------------- ------------------ ,yet this agreement1 though remarkable1 can only be considered as complete proof of the presence of iron-vapour in the atmosphere when we shall have succeeded in showing by observation analogous modifications of the relative conditions of brilliancy in the iron-spectrum by alterations of temperature and density2 and in this way explain the appearance of relatively very faint iron-lines in the ,aurora-spectrum1 or1 on the other hand1 the absence of the most intense lines4 ,it will meanwhile remain far more in accordance with probability to regard the ,aurora-spectrum as a modification of the air-spectrum2 since we are already aware1 in the case of gases1 of the alteration of the spectra by conditions of temperature and pressure2 and an agreement1 at any rate1 quite as certain between the spectrum in question and the spectra of atmospheric gases has been proved above4 ,i am indebted to ,miss ,annie ,ludlam for a translation from the ,german of the above ,memoir4--,j4 ,r4 ,c4 ,,footnotes #a 1 a hollow4 #b 1 a cask4 #c 1 a chasm4 #d ,m4 ,lemstrm 7,swedish ,expedition1 #ahfh7 concludes that the corona of the ,aurora ,borealis is not entirely a phenomenon of perspective1 but that the rays have a true curvature1 that they are currents flowing in the same direction and attract each other4 ,there is also an account ant1 p4 #af of an ,aurora at ,melville ,island 7,parry's first voyage71 in which two arches were seen curving towards each other4 #e ,a brilliant display in ,december #ahgj1 on the east coast of ,sicily1 was followed by very violent storms1 with the overflow of the ,tiber and the flooding of ,rome4 #f ,some curious instances have been recently 7,january #ahgi7 given in the #8,times' of such electric phenomena1 comprising1 amongst others1 gas lighted by the finger in ,canada1 points of flame seen on the ironwork of ,teignmouth ,bridge1 and similar points seen on the alpenstocks and axes of a party making a mountain ascent in ,switzerland4 #g ,on the occasion of the ,aurora of ,september #bd1 #ahgj1 ,dr4 ,allnatt says1 8the air seemed literally alive with the unwonted phosphorescence40 #h ,see1 however1 ,dr4 ,schuster's article 8,on the ,spectra of ,lightning10 ,phil4 ,mag4 ,may #ahgi1 p4 #caf4 #i ,the proof from occulted stars merely goes to the fact that the moon possesses no atmosphere appreciable in that way4 ,it may still be a question whether there does not exist something of the kind1 lying low and close to the surface1 and possibly of a rarefied character1 which would scarcely make itself visible by its effects in occultations4 ,cloud-vapour might form in an atmosphere of inconsiderable density4 #aj ,this observation is not without a certain amount of confirmation by more recent ones1 in which certain lunar objects and regions have been suspected of mist or vapour4 ,mr4 ,birt 7#8,english ,mechanic1' vol4 xxviii4 no4 #gbe7 mentions two--the cloud-like appearance of the white patch west of ,picard1 and the interior of ,tycho1 which at one time always misty and ill-defined1 is now become perfectly distinct and sharply defined4 ,december #d1 #ahgh1 #d;h #dem4 ,i observed ,klein's crater as a dull dark spot1 larger than the true object2 and while definition was good and other objects were well defined1 8the floor of ,klein's object1 the oval spot near1 and also ,agrippa 7especially71 all had an odd misty look as if vapour were in or about them0 7#8,english ,mechanic1' vol4 xxviii4 no4 #gbg74 ,the mystery of different observers seeing and not seeing ,klein's object on the same night is hardly to be accounted for by the angle of illumination4 #aa ,some doubt has been cast on this observation1 on the ground that nothing unusual was seen1 and that the appearances were only those ordinarily presented by the moon at its then phase4 ,i simply give the account as it appears in the scientific journal in which it was published4 #ab ,the question of a connexion between the waxing and waning of the solar corona and the prevalence of sun-spots is now being mooted1 and may have an important bearing on the subject of the constitution of the corona4 ,it would seem that when the corona has been examined about the time of minimum of sun-spots1 it has proved fainter though more extended1 while the bright lines of the spectrum have been absent1 indicating a change or variance in the gaseous part of it at those periods4 #ac ,there seems to be some confusion as to the ,w4,l4 here given2 #eefg is usually accepted as ngstrm's line1 while ,prof4 ,smyth refers to it as #eegi4 ,the position1 too1 when examined with a spectroscope of greater dispersion1 is not exactly over the citron-line of acetylene1 both the above referred to lines lying somewhat more towards the violet end of the spectrum 7see ,plate ,v4 fig4 #g74 #ad ngstrm's drawing1 in giving this character to the two ,aurora-bands which are said to correspond with violet-pole bands about #dg and #dc1 is incorrect1 and calculated to mislead by giving the ,aurora-bands a feature corresponding to the violet-pole bands which they do not possess4 ,i am not aware of any ,aurora-line or band which is described as distinguished by degrading towards the violet4 #ae ,the tubes generally seem marked ,si ,fl instead of the ordinary notation ,si ,f4 ,si ,fl is probably1 in fact1 ,si ,f4 #af ,dr4 ,schuster has found that while the line-spectrum of lightning is attributable to ,n1 it has also a band-spectrum1 which he considers due to ,o and a slight trace of ,,co 7,phil4 ,mag4 #eth ser4 vol4 vii4 p4 #cba74 #ag ,in these observations some suggestions made by ,mr4 ,capron have been incorporated4 ,this was ,mr4 ,lockyer's note4 ,in point of fact1 the ,author was responsible for the verbatim paragraphs comprised between the letters ,a and ,b1 and ,c and ,d1 in the instructions as now reprinted4 #ah ,communicated by the author to the ,royal ,saxon ,academy of ,science1 #ahga4 #ai ,reports of the ,royal ,saxon ,academy of ,science1 ,oct4 #ca1 #ahga4 #bj ,this red line was first noticed by ,zllner4 #ba ,recherches sur le ,spectre ,solaire1 p4 #db4 #bb ,american ,journal of ,science1 lxviii4 #abc4