478 Scientific Intelligence. 
Seah short with reference to the interval nece in 
astm case, and the smaller the amount ‘of matter the shorter this 
time would be. The smaller comets, which often have the appear- 
ance of Pephiertnal masses of vapor, are examples of bodies of sucha 
nature. Prof. Zéllner thinks there is no improbability of the 
existence of such fluid masses in space, > aaa of water or of 
liquid hydro-carbons,* and the spectra of some of the nebule and 
smaller comets confirm the idea very str saiglvt 
The peculiarities already mentioned are readily Bt cron a 
reference to the general properties of fluid su 
comets, el offer others which are the result of other esses, 
name ely, t thei el fl and the formation of a train, with a 
special relation’ “of the tatieny in its position and aitwction: % the 
sun. 
As to the origin of the former of these phenomena, the question 
arises, under what circumstances can a vaporous or gaseous mass 
be babeAistnlsistg ? and only two causes are ring through the 
operation of which this can happen. These are, first, elevation of 
temperature, as by combustion, and second, hassle rahi 
The former of these causes the author sets aside, on account of its 
insufficiency and the theoretical difficulties and contradietiall 
which it involves. The second, therefore, must be assumed to. 
u 
from it, we h 
account both for the self- iffuminosity of the comets and the forma- 
tion of their trains. It is sh wn, moreover, by numerous experl- 
ments, that the Seeamestee of electricity by similar processes 
within the limits of our experience is a well established fact. 
of these substances, and in this manner the resemblance and rel 
tial coincidence of the fear Se cometic spectra with those o 
* See note, p. a. 
