PROGRESS IN PHYSICS. 317 



afterwards entered the service of the Elector of Bavaria, by whom he 

 \va,s made a count of the Holy Roman Empire. In 1799 he returned 

 to London and founded the "Royal Institution," which was destined 

 during- the next hundred years to surpass all other foundations in the 

 richness and importance of its contributions to physical science". It 

 was while at Munich that Rumford made his famous experiments in 

 the nature of heat, to which he had been led by observing the great 

 amount of heat generated in the boring of cannon. Finding that he 

 was able to make a considerable quantity of water actually boil by the 

 heat generated by a blunt boring tool, he concluded that the supply of 

 heat from such a source was practically inexhaustible and that it could 

 be generated continuously if only the motion of the tool under friction 

 was kept up. He declared that anything which could thus be produced 

 without limitation by an insulated body or system of bodies could not 

 possibly be a material substance, and that under the circumstances of 

 the experiment the only thing that was or could be thus contiiuiously 

 communicated was motion. 



Count Rumford's conclusions were not accepted for a long time. 

 Davy, the brilliant professor and eloquent lecturer at the newly estab- 

 lished Royal Institution, espoused the mechanical theory of heat, and 

 made the striking experiment of melting two pieces of ice by rubbing 

 them together remote from anj^ source of heat. His contemporary. 

 Thomas Young, who overturned Newton's corpuscular theory of light 

 and showed that it was a wave phenomenon, also advocated Rumford's 

 notion of the nature of heat; but even among physicists of high rank 

 it had made little headway as late as the middle of the nineteenth cen- 

 tury. In the eighth edition of the Encyclopedia Britannica, published 

 in 1856, the immediate predecessor of the current issue, heat is defined 

 as a ''material agent of a peculiar nature, highly attenuated." And 

 this in spite of the fact that previous to that date the mechanical theory 

 had l)een completely proved by the labors of Mayer, Joule, Helmholtz, 

 and William Thomson (Lord Kelvin). By these men a solid founda- 

 tion for the theory had been found in a great physical law of such 

 importance that it is justly considered to be the most far-reaching gen- 

 eralization in natural philosophy since the time of Newton. Some 

 account of this law and its discovery will be given later in this paper. 



Among the most important of the century's contributions to our 

 knowledge of heat must be included the work of Fourier, as embodied 

 in his Theorie Analytique de la Chaleur, published in 1822. Joseph 

 Fourier was born in 1768 and died in 1830. He belonged to that 

 splendid group of philosophers of which the French nation may always 

 be proud, whose work constitutes a large part of the luster of intel- 

 lectual France during her most brilliant period, the later years of the 

 eighteenth and the earlier years of the nineteenth century. His con- 

 temporaries included such men as Laplace, Arago, Lagrange, Fresnel, 

 SM 1900 23 



