SUPPLEMENTARY REPORT ON METEOROLOGY. 17 
in space, and in the adjacent atmospheric strata. Proceeding, 
however, to the mechanical conditions of equilibrium*, he infers 
that the temperature of the exterior part of the atmosphere 
must be prodigiously low, in order that it may have a definite 
termination, which condition of non-elasticity he calls liquefac- 
tion}, a term, the impropriety of which will sufficiently appear 
from the observations of M. de la Rive cited below. It is quite 
certain that an elastic atmosphere may be considered as rigor- 
ously limited, even wholly irrespective of the diminution of elas- 
ticity due to cold, and this without necessarily inferring an as- 
sent to the molecular constitution, from which Dr. Wollaston 
deduced the limitation as a necessary inference§. Hence, any 
hypothesis of extreme cold required to produce mechanical equi- 
librium in the higher parts of the atmosphere is devoid of sup- 
port. As to the actual extent of the finite atmosphere, this is 
a question on which experiments both direct and indirect leave 
us much in the dark; nor can the optical phenomena of twilight 
be cited with much confidence in such a case, the reflective power 
of rarefied air being a datum on which we want direct evi- 
dence ||. 
111. The effect of the atmosphere upon the temperature of the 
globe, as treated of by M. Poisson, is twofold; namely, /irst, 
the modification of solar heat, which after combination with the 
air both radiates, and communicates heat by contact, to the earth; 
if the sun were extinguished, this heat would also vanish, al- 
* Théorie, p. 459. ’ 
+ Théorie, p. 459, and Supplément, note D. p. 60; Traite de Mécanique, 
ii. 612. 
+ “ Nous ne pouvons admettre que cet état du fluide soit analogue a l’état 
liquide, du moins si nous attachons au mot liquide le sens physique dans lequel 
on l’entend communément, et par lequel on désigne, par exemple, l'état au- 
quel une basse température et une forte compression aménent la plupart des 
fluides élastiques. Si M. Poisson n’entend par liquide que cet état des fluides 
dans lequel la force élastique est disparu, ce n’est plus alors qu'une définition 
mathématique qui est bonne tant qu’on ne cherche pas a se representer l'état 
physique du fluide. Toutefois observons que ce n’est pas ainsi qu’on définit 
les liquides; parceque 1’état liquide suppose non seulement |’absence de force 
élastique, mais de plus une attraction moléculaire plus ou moins grande entre 
les particules du fluide, attraction qu’il nous est impossible d’admettre ici.” — 
Bib. Univ., Nov. 1835. 
 § Phil. Trans., 1822, p. 89. Abstracts, ii. 160. M. Biot appears to give the 
credit of this remark to M. Poisson; Comptes Rendus, vi. 395. 
|| See on this subject M. Biot’s Memoirs; Comptes Rendus, viii. 91 ; ix. 174; 
Lambert’sW orks; Lubbock on Heatand Vapours, 1840; also Poisson, Supplément 
Gla Théorie de la Chaleur, note D, where the author investigates the equilibrium 
of the atmosphere under certain conditions, but ends with these words: “il ne 
s’agit dans cette note, que d’un simple exemple de calcul, et vraisemblablement, 
les hypothéses que nous avons faites pour le faciliter ne sont pas conformes a la 
nature.” 
