336 Analysis cf Scientific Books. 
more especially, the construction of an artificial atmosphere, of greater 
efficacy than any that has hitherto been recommended. 
It is to be feared, however, that such knowledge might not lead to 
results as valuable as might at first be imagined. Jt would not seem 
that air highly charged with aqueous vapour, if unaccompanied with 
excessive heat or cold, or noxious exhalations, is remarkably inju- 
rious to human health. In the marshy districts not only in this 
country, but universally, consumptions are comparatively rare, and 
considerable benefit has been derived from sending phthisical indi- 
viduals from dry and lofty districts, into others where the atmo- 
sphere has been more charged with humidity. Pisa is chiefly on 
this account one of the most genial climes in the south of Italy for 
consumptive subjects, although in cther respects extremely un- 
healthy, owing to the malaria exhaled by the surrounding marshy 
districts. Were accurate registers, however, taken of the compara- 
tive barometric, thermometric, and hydrometric variations, and the 
corresponding states of public health or disease correctly registered, 
as might be readily done in some of the large valetudinarian esta- 
blishments of this country; considerable advantage would inevitably 
follow, if not in a therapeutical at all events in an hygienic point of 
view. Unfortunately, meteorology has heretofore been but little 
studied as a science, and although many of its parts have been ably 
elucidated by several existing philosophers, amongst whom the 
author of the volume before us stands especially conspicuous, yet 
it must be considered to be still in its infancy. - 
The three first sections of this scientific production are occupied 
by an elaborate disquisition on the constitution of the atmosphere, of 
which it is impossible for us to give more than a recapitulation of 
the principal conclusions to which the author has arrived, after a 
patient investigation of the researches of the most eminent philoso- 
phers, conjoined with the results of his own observations. 
The grand conclusions are as follows:—There are two distinct 
atmospheres, mechanically mixed, surrounding the earth, whose 
relations to heat are different, and whose states of equilibrium, con- 
sidering them as enveloping a sphere of unequal temperature, are 
incompatible with each other. The first is a permanently elastic 
fluid, expansible in an arithmetical progression by equal increments 
of heat, decreasing in density and temperature according to fixed 
ratios, as it recedes from the surface, and the equipoise of which 
under such circumstances, would be maintained by a regular system 
of antagonist currents. The second is an elastic fluid, condensable 
by cold with an evolution of caloric, increasing in force in geometrical 
progression with equal augmentations of temperature : permeating the 
former and moving in its interstices, as a spring of water flows 
through a sand-rock. When in a state of motion, this intestine 
filtration is retarded by the znertia of the gascous medium, but in a 
state of rest the particles press only upon those of their own kind. 
. 
