Kansas Academy of Science. 17 



hySchiapparelli aud Le Verrier, but it seems to leave the original difficulties, 

 with no diminution of their force. 



This theory seems to offer no satisfactory explanation of the mode by which 

 the material elements of the tail are seen first to follow the nucleus; then, 

 near perihelion, to be chiefly outside the orbit ; and finally, to be in advance 

 of the nucleus. Spectrum analysis has in a wonderful manner enabled 

 astronomers to penetrate long-hidden secrets ; and naturally, this agent has 

 been summoned to aid in the solution of this question. So far, however, the 

 ojiportunities to make this agent available in the examination of comets have 

 been limited. Donati was the first, in 1864, to study spectroscopically the 

 light of comets; and recently Secchi, Huggins, and others have given their 

 attention to the same object. No brilliant comet has in the meantime 

 appeared; and the results obtained, which chiefly pertain to the nucleus only, 

 though of importance, may be briefly stated. It seems then clearly estab- 

 lished by spectrum analysis, that the nucleus of a comet is self-luminous, and 

 that the luminous portion is a glowing gas — in some instances carbon being 

 present. It is also probable that the luminous nucleus may in a slight degree 

 reflect sunlight. Scarcely more than this has yet been determined by means 

 of the spectroscope ; but the appearance of any bright comet will be the occa- 

 sion of the most attentive observations, and we may hope then for a complete 

 solution of this interesting puzzle. 



In the meanwhile, waiting thus for the return of such a far-wandering 

 messenger, even now on the way laden with news, we can only indulge in 

 speculations; and I venture to offer some of these that point, it may be, toward 

 a solution — speculations that may subsequently be verified, or subsequently 

 proved to be fallacious. 



Allusion has already been made to the zodiacal light, wdiich indicates the 

 existence of a belt of luminous matter, or of matter that may become 

 luminous, extending far out from the sun. The motions of Encke's comet 

 indicate a resisting medium, and let us suppose this granted. In accordance 

 with this hypothesis, observation shows that for the same comet the display 

 of a brighter train occurs, with an increased velo.city and diminished distance 

 from the sun, the cumulative effects of which reach a maximum only after 

 perihelion passage. For different comets, so far as other conditions coincide, 

 the same principle is verified. 



We have seen, too, that comets and meteors appear in some instances to 

 have a common origin, and that meteors are composed chiefly of elements 

 well known, though it is probable that the more volatile elements become 

 entirely separated in passing through our atmosphere from the more solid 

 portion which actually reaches the surface of the earth. 



Let us sujipose, then, that we have merely a larger mass of meteoric matter, 

 possessing in its composition some elements capable of volatilization, moving 

 in such an orbit as any of the comets are observed to have; then, with the 

 exception of the tail, all the phenomena of a comet would naturally follow, 

 according to the different circumstances supposed. Entering the resisting 



