Mr. Talbot on the Repulsive Power of Heat. 189 
also be devoted to the publication of the monthly results (ac- 
cording to a fixed tabular form) of observations taken in va- 
rious parts, not only of this kingdom, but of the whole world, 
if possible. I am, Gentlemen, yours obediently, 
JosEPH ATKINSON, 
Carlisle, Dec. 1, 1835. Sec. of the Carlisle Lit. and Phil. Soc. 
XXXVI. On the repulsive Power of Heat. By H.¥.Tarzor, 
Esq.) F.L.S.* 
Experiment 1.—On the Vaporization of Sulphur. 
W HEN a minute portion of sulphur is warmed between 
two plates of glass, it sublimes, and forms gray nebulous 
patches, which are very curious microscopic objects. Each 
cluster consists of thousands of transparent globules, exactly 
imitating in miniature the nebulz which we see figured in 
treatises on astronomy}. By observing those particles which 
are larger than the others, we find their figure not to be 
spherical, but plano-convex, with the flat side to the glass. 
Being very transparent, each of them acts the part of a little 
lens, and forms in its focus the image of a distant light, which 
can be perceived even in the smaller globules until it vanishes 
from minuteness. If they are examined again after a certain 
number of hours, the smaller globules are generally found to 
retain their transparency, while the larger ones are become 
opake, in consequence of some internal change in the arrange- 
ment of their molecules. I find that Mitscherlich and others 
have noticed this property in sulphur of undergoing a sponta- 
neous change}. There is a circumstance attending this expe- 
riment which deserves particular attention. Although the 
sulphur has been sublimed by heating it over a Jamp between 
two plates of glass almost in contact with one another, yet the 
globules are found adhering to the upper glass only; and as 
their number amounts generally to many thousands, it is evi- 
dent that the preference which they thus exhibit to the upper 
glass must have some strong determining cause. 
The reason of it is, no doubt, that the upper glass is a little 
cooler than the lower one; and by this means we see that the 
vapour of sulphur is very powerfully repelled§ by heated 
* Communicated by the Author. 
+ And owing, perhaps, their mutual disposition to the same general 
laws of attraction as the Nebula ?—Eprr. 
¢ See Phil. Mag. and Annals, N.S., vol. iii. p. 144, 152, for correlative 
facts.—Epit. 
This is a very beautiful instance in corroboration and extension of 
Prof. Powell’s experiment described in the Phil. Trans. 1834, part ii. 
p- 485.—Epit. 
