PEELIMINARY DISCOURSE. 



PRIMARY causes are unknown to us; but are subject to simple 

 and constant laws, which may be discovered by observation, the 

 study of them being the object of natural philosophy. 



Heat, like gravity, penetrates every substance of the universe, 

 its rays occupy all parts of space. The object of our work is to 

 set forth the mathematical laws which this element obeys. The 

 theory of heat will hereafter form one of the most important 

 branches of general physics. 



The knowledge of rational mechanics, which the most ancient 

 nations had been able to acquire, has not come down to us, and 

 the history of this science, if we except the first theorems in 

 harmony, is not traced up beyond the discoveries of Archimedes. 

 This great geometer explained the mathematical principles of 

 the equilibrium of solids and fluids. About eighteen centuries 

 elapsed before Galileo, the originator of dynamical theories, dis 

 covered the laws of motion of heavy bodies. Within this new 

 science Newton comprised the whole system of the universe. The 

 successors of these philosophers have extended these theories, and 

 given them an admirable perfection: they have taught us that 

 the most diverse phenomena are subject to a small number of 

 fundamental laws which are reproduced in all the acts of nature. 

 It is recognised that the same principles regulate all the move 

 ments of the stars, their form, the inequalities of their courses, 

 the equilibrium and the oscillations of the seas, the harmonic 

 vibrations of air and sonorous bodies, the transmission of light, 

 capillary actions, the undulations of fluids, in fine the most com 

 plex effects of all the natural forces, and thus has the thought 



F. H. 1 



