July 23, 1874] 



NATURE 



!27 



but regions of greatest possible' number of collisions asso- 

 ciated with greatest luminosity. 



It would be a comfort if the comet, to partly untie a 

 hard knot for us, would di\-ide itself as Biela's did. Then, 

 I think, the whirl idea would be considerably strengthened. 

 I could not help contemplating the possibility of this when 

 the meaning of the "ears" first forced itself upon my 

 attention. 



The spectroscopic observations which I attempted, 

 after the telescopic scrutiny, brought into strong relief the 

 littleness of the planet on which we dwell, for a seven 

 hours' rail journey from London had sufficed to bring me 

 to a latitude in which the twilight at midnight was strong 

 enough to show the middle part of the spectrum of the 

 sky, while to the naked eye the tail of the comet was not 

 so long as I saw it in London a week ago. 



I had already in observations in my own observatory, 

 with my 61 in. refractor (an instrument smaller than one 

 of Mr. Newall's four finders !) obtained indications that 

 the blue rays were singularly deficient in the continuous 

 spectrum of the nucleus of the comet, and in a com- 

 munication to Nature I had suggested that this fact 

 would appear to indicate a low temperature. 



This conclusion has been strengthened by Sunday 

 night's observations, and it was the chief point to which 

 I directed my attention. The reasoning on which such a 

 conclusion is based is very simple. If a poker be heated, 

 the hotter it gets the more do the more refrangible— /.<■. 

 the blue — rays make their appearance if its spectrum be 

 examined. The red colour of a merely red-hot poker and 

 the yellow colour of a candle-flame are due, the former 

 to an entire, the latter to a partial, absence of the blue 

 rays. The colour, both of the nucleus and of the head 

 of the comet, as observed in the telescope, was a distinct 

 orange yellow, and this, of course, lends confirmation to 

 the view expressed above. 



The fan also gave a continuous spectrum but little in- 

 ferior in brilliancy to that of the nucleus itself ; while 

 over these, and even the dark space behind the nucleus, 

 were to be seen the spectrum of bands which indicates 

 the presence of a rare vapour of some kind, while the 

 continuous spectrum of the nucleus and fan, less precise 

 in its indications, may be referred either to the presence 

 of denser vapour, or even of solid particles. 



I found that the mixture of contmuous band spectrum 

 in different parts was very unequal, and further that the 

 continuous spectrum changed its character and position. 

 Over some regions it was limited almost to the region 

 between the less refrangible bands. 



It is more than possible, I think, that the cometary 

 spectrum, therefore, is not so simple as it has been sup- 

 posed to be, and that the evidence in favour of mixed 

 vapours is not to be neglected. This, fortunately, is a 

 question on which I think much light can be thrown by 

 laboratory experiments. 



J. Norman Lockyer 

 Mr. Newall's Observatory, Ferndene, Gateshead 

 P.S. — (By Telegraph.) — Wednesday^ night. — Sunday's 

 observations are confirmed. The cometary nucleus is 

 now throwing off an ear-like fan. Ten minutes' exposure 

 of a photographic plate gave no impression of the comet, 

 while two minutes' gave results for the faintest of seven 

 stars in the Great Bear. 



THE FORMS OF COMETS* 



1. 

 A FEW years ago astronomers studied comets almost 

 '-'*- solely to determine their movements. So little 

 advance had been made in the study of the figures of 

 these bodies, that M. Arago believed himself jus- 

 tified in stating in his " Astronomic populaire : " — " ' I 



* A lecture by M. Faye delivered at the "Soirees Scientiftques de la 

 Sorbonne." Translated from La Revue ScieHti/tque. 



don't know' will slill be the leply we have to make to 

 questions asked concerning the tails of comets." If I 

 venture to take as the principal subject of this lecture the 

 researches which I have undertaken during recent years 

 in this difficult subject, I hope to disarm criticism before- 

 hand by at once declaring that the results contrast singu- 

 larly, by their imperfection, with the degree of power and 

 of certainty we admire in the other more ancient branches 

 of astronomy. 



The reason of this contrast is veiy simple. While plane- 

 tary astronomy received the precious heritage of the science 

 of the Greeks and the treasury of observations bequeathed 

 by the highest antiquity, cometary astronomy finds in 

 the archives of history observations travestied by su- 

 perstitious terror. One of the strongest prejudices of 

 previous centuries was that which attributed to the stars 

 a rnysterious influence on our destinies. And comets, by 

 their unforeseen appearance in the midst of the familiar 

 constellations, their monstrous heads, their gigantic tails, 

 were calculated to inspire a sort of apprehension which 

 judicial astrology, that long infirmity of the human mind, 

 did not fail to interpret as menacing presages ; and as 

 catastrophes have not been wanting in every period of 

 our history, the singular sophism, /(U/ Jioc, ergo propter 

 hoc, so natural to our poor logic, helped to confirm ten or 

 twelve times in a century this miserable superstition. 



Did a comet appear in the heavens, morning or even- 

 ing, the astrologer had to be consulted. He did not go 

 to work without rules ; he had a complete classifica- 

 tion of strange forms under which these heavenly bodies 

 already had been observed, and to each form was attached a 

 particular signification. Pliny has preserved this nomen- 

 clature for us : Hevelius, the \e.z.xYie.Apcitsioiiiiaire of Louis 

 XIV., faithfully reproduced it in the middle of the 17th cen- 

 tury, in the fantastic figuresof his Comctographia. And, cer- 

 tainly, everything was taken in the most literal manner : 

 in a comet with a crooked, or straight, or multiple tail 

 they traced, such is the power of imagination, a gigantic 

 sabre, a lance, or a fiery bolt, a burning torch or a dragon 

 hurling upon an entire country the plague, rebellion or 

 famine. Figs, i and 2 are indications of this idea taken 

 from the " Theatricum cometicum " of Lubienitzki. The 

 first comet, in the form of a blazing torch, indicates very 

 clearly by the direction of its tail the flames which will 

 consume the neighbouring town ; the second, a veritable 

 dragon, whose tortuous folds the artist has reproduced, 

 threatens France and Ireland from the seven points of its 

 tongue of fire. 



These specimens will suffice ; there is no use in pro- 

 ducing similar statements and similar pictures ; at the 

 most we can barely find here and there in the theories 

 which were then formed some traces of the truth. 



Astrology thus stifled real observation until the begin- 

 ning of the seventeenth century. This may now appear 

 strange to us, but there is no doubt of it. The astronomers 

 of those times, so near in time to ourselves, and already so 

 boldwiththeuniversal;i7/(?/,f.f(r;/i"t'ofthe human mind, were 

 almost all to some extent astrologers. Kepler himself, 

 one of the glorious fathers of modern astronomy, was 

 obliged by the duties of his office as Imperial Astronomer 

 both to draw the horoscope of the war of the Pope against 

 Venice, and to give to his powerful but too-straitened 

 patron, the Emperor Rodolph II., an opinion on the 

 comet of 1607, which appeared to be menacing Hungary 

 Besides, Rodolph counted much then upon his alchemist 

 to find the gold necessary to pay his army ; while his 

 general, the Duke of Friedland, the celebrated Wallen- 

 stein, never failed to consult the heavens, always by the 

 help of Kepler, who has preserved for us his horo- 

 scope. 



But already, from the time of Tycho Brahd, astro- 

 nomy had commenced to place a hesitating foot in the 

 domain of comets, from which she was soon to drive 

 astrology. Until then men had lived, upon the faith of 



