REPORT ON METEOROLOGY. 
203 
One of the most universally admired investigations of a phy¬ 
sical law by which science has been recently benefited, is that 
of MM. Dulong and Petit into the law of cooling, published 
in the Journal de VEcole Polytechnique, and in the Annales de 
Cliimie ; one to which, from its universally acknowledged beauty 
and importance, we need do no more than allude. The radia¬ 
tion of heat, which has been so powerfully illustrated, and whose 
general laws are so well determined by these experiments, forms 
one of the most important elements of the science of Meteoro¬ 
logy. Baron Fourier has recently deduced from theory the 
law of radiation experimentally proved by Professor Leslie,— 
that the calorific rays decrease proportionally to the sines of the 
angles they make with the radiating surface ; and he has drawn 
some interesting conclusions* * * § . The same author, considering 
our globe as a radiating body placed in indefinite space, and as 
having reached a condition of temperature sensibly invariable, 
has deduced the temperature of planetary space to be —50° 
cent.f Swanberg, arguing from the observed decrement of heat 
in the atmosphere, has arrived at almost the same result J. 
Considering heat as the power by which liquids are converted 
into vapour, the science of Hygrometry has received of late 
years important additions, not merely from several researches 
upon the theory of vapour, but from the elaborate experiments, 
undertaken with praiseworthy zeal under the superintendance 
of the French Academy of Sciences, upon the force of vapour 
at different temperatures §. Mr. Faraday, on the other hand, 
has pointed out the existence of a limit to vaporization ||. 
I have thought it necessary briefly to point out the prodigious 
obligations under which Meteorology lies to the science of 
Heat, because the truly philosophical procedure of arriving at 
the great truths of the former seems to be too much overlooked. 
The results just enumerated have every one been attained by 
constant and assiduous labour, some by a course of most arduous 
experiment, others by the application of the most refined 
mathematical analysis. Till we have the laws of heat more com¬ 
pletely unravelled than at present,—till the most important yet 
profoundly difficult problem of its relation to a gaseous atmo¬ 
sphere of varying density shall have been adequately solved,— 
Meteorology will stand upon an uncertain basis, and will abound 
* Memoires de VInstitut, tom. v. f Annales de Chimie , xxvii. 
X Bibliotheque Universelle, xliii. 367 ; and Edinburgh Journal of Science, 
N.S. iii. 13. 
§ Annales de Chimie, xliii. 74. The Commission was composed of MM. De 
Prony, Arago, Ampere, Girard, and Dulong. 
|| Philosophical Transactions ; and Journal of the Royal Institution. 
