REPORT ON METEOROLOGY. 
201 
vestigating many of its laws, it is surprising how very imperfect 
are the notions entertained by mankind at large, and even by 
the scientific world, as to the importance of the part which it 
assumes in the oeconomy of nature. To attempt to study 
Meteorology without it, is like trying to read a cipher without 
previously mastering the key. The laws, so far as they are 
known to us, by which it is regulated, though generally simple 
in their enunciation, rise, when pursued into their consequences, 
to highly complicated deductions, and soon (as is the case 
with every science rising above the limits of first generali¬ 
zations of facts, and empirical laws,) require all the resources 
of mathematical analysis to eliminate general laws and to re¬ 
descend to the prediction of phenomena*. The propagation of 
heat in solid bodies, which forms the first problem in the theory 
of heat to be solved, and one of the greatest importance in the 
consideration of the globe as a heated mass in the course of cool¬ 
ing, has occupied the attention of some of the first philosophers 
of France. At an early period in this century M. Biot pointed 
out the expression for the condition of a solid bar with regard 
to temperature, receiving a constant supply of heat at one end, 
and parting with it towards the other by conduction and radia¬ 
tion, which gave rise to a partial differential equation, which 
has since undergone repeated discussionf. Laplace took up 
the question, and removed some analytical difficulties in which 
it was involved. He was succeeded by Fourier and Poisson, who 
gave greater generality to the solution, and extended it to bodies 
of various figures J. Fourier, in his great work the Theorie 
Analytique de la Chaleur , has extended his profound inquiries 
to a vast number of problems in the propagation of heat, most 
important to our present subject, and which, in special relation 
to the temperature of the mass of the earth, will shortly be 
noticed more particularly. 
A variety of points connected with the relation of many sub¬ 
stances to heat have of late years been determined, though 
there is yet much to be done in this important field. The con¬ 
stants which regulate the passage of heat through various 
bodies, and which have been termed by Fourier “external con- 
ducibility,” or penetrability, and “ internal conducibility/’ or 
permeability §, have been determined for several bodies, but a 
* “ L’etude approfondie de la Nature est la source la plus feconde des decou- 
vertes mathematiques.”—Fourier, Theorie de la Chaleur , Disc. Prel. xiii. This 
beautiful discourse gives some fine views on the application of mathematical 
reasoning to physical questions. 
f Traite de Physique, iv. 669. Fourier, Theorie, chap. i. sect. v. 
+ Memoires de VInstitut: Journal de V Ecole Polytechnique : Connaissance 
des Terns, fyc, § Theorie Analytique, Art. 30, 37. 
