262 
Notices of European Science. 
[Aug. 
ence in causing disease— the second is a history of the diseases-and part three 
inV^hP t0 t ' he t ^ eatment / ound most efficacious. An Appendix is annexed, shew- 
ing the various degrees of visceral disease in forty-seven cases. 
VII . — Notices of European Science. 
On the Limits of Vaporisation — By M. Farraday, Esq. 
There is a paper in the first number of the new Journal of the Royal Institution 
on tins subject, which bearing, as it does on a very interesting theory, our readers 
will, we doubt not, be glad to see noticed. We allude to the explanation which has 
been offered of the origin of the Aerolites, in which, it is a necessary assurap- 
10n ,. ia a ^ ie in gredients of those singular bodies are vaporisable, more or less, 
at ordinary temperatures. This opinion had been acquiesced in pretty generally, 
w e e ie\ e, and extended even to all matter. Sir H. Davy and Mr. Dalton are 
mentioned by Mr. Farraday, as two of the most eminent supporters of it; their 
opinion bemg that evaporation never ceased entirely, but was in action, however 
lmims ed, even at the lowest temperatures, and from the most apparently fixed 
An evident corollary from this dogma would be that the earth’s atmosphere 
would have no limit, and consequently that there could be no such thing as free 
space. ut fiom the regularity of the planetary periods recognised by Astrono- 
mers the latter opinion must have been, to say the least, doubtful ; and from the 
o owing considerations, first brought forward by Dr. Woollaston, the contrary 
fixed' ° n was no ^ onI y rendered probable, but the actual limits of our atmosphere 
Atmospheric air, like every other portion of matter, gravitates towards our earth, 
an w on t in consequence condense into a fluid, were it not for the antagonist 
princip e o e asticity, which occasions it to diffuse itself in every direction into 
e ,. ma y cons * d ® r then the actual condition of our atmosphere as the 
t i u i° ie ad | ustni ent ot these two forces; and we see from the phenomena, 
elasticity greatly exceeds that of gravity, at the surface of the 
t t o' " f S 'V ^ 1S affected by two circumstances pressure and temperature , or in 
otber words, the more condensed or pressed air is, the more it tends to diffuse itself 
• a ' 0 every direction. Also the higher the temperature of air, the greater 
power of diffusing itself. But as we recede from the earth’s surface, the pressure 
the temperature continually lessens ; so much so, that at a height of 
ce y miles the elasticity is already diminished to one-half. But in this 
* \ 6 P ower pt" gravity, which tends to oppose the unlimited diffusion of the 
£° s . u ?, 8ta “. c j:> IS scarcely lessened in an appreciable degree. It is obvious 
tnen that the difference between these antagonist forces is less at that height than 
l u r Proceeding higher, we find the elasticity becoming rapidly less, 
whfle the force of gravity ,s still nearly the same, so that at last we shall reach 
^^r!. a » 0 w W ,er ^ th L CSe forCeS are in e( l ui librium, and where a particle of air shall 
driven In th * S r** e eartI ! *’•. attraction of gravity, quite as much as it is 
limiJ l“ t h f? her direction by the force of elasticity. Here then, there will be a 
or orennSlL US1 ° n ’ i°.\ ts e , va P 0ratl0n > and all beyond that will be either a vacuum 
at al C IirrLt^T^ Uld , 0t gr6& ^ ? laKtic force. Dr. Woollaston fixed this point 
diminished a) Lt ° e mi . es , ’ a height at which the force of gravity would onlybe 
= i^T; fortieth Pf - whiJe the elastic spring” of the air would be 
P Tht c y otir 5 n^t) ? L n - e_hVe 1 thoUSandth P art of what it is at the surface, 
matter and it wJe ti U * w C ea , r and convincing, was naturally extended to all 
substanee and m lou ^ 1 that there was a limit to the vaporisation of every 
bodvth-tt » i it n s c quen y that in a temperature sufficiently low there was no 
off va non r (Lr ti C C °S?\ (C1 u Cd llxed an d totally deprived of the power of giving 
before all,. 1 i ^ Stl11 thls conclusion was not at variance with the theory 
miS,^ 5 , ° r h ° U !: h T St ,° f the ^gredients of these singular bodies 
it was nr t i 1 Glet P, er se as ilxcd 111 the ordinary temperatures of our atmosphere, 
produce effect the presence of aqueous vapour in the air might 
much more -v' n fif 0 re, " ;u bed in the distillation of certain essential oils, how 
and it “as Z K' y t ";, va ‘’ ou r the addition of a little water in the still, 
other sStanco. 8 A S , 0me , thl ?F 0i f i be sam e kind might happen with regard to 
- • ccoidtngly Mr. Farraday undertook a series of eapentnunl 5 
