22 LEADING AMERICAN MEN OF SCIENCE 



placed in his birthplace, Woburn, Mass., bearing an inscription 

 by President Eliot of Harvard. 



Rumford found the Bavarian army most deficient in the two 

 arms in which he was especially interested, cavalry and artillery, 

 and he set himself to remedy the former by establishing a veteri- 

 nary school and introducing improved breeds of horses; and to 

 develope the artillery service he built a foundry at Munich where 

 guns were constructed according to his designs, based upon care- 

 ful experimentation. He adopted the method of casting both brass 

 and iron cannon solid and boring them afterwards, and it was while 

 superintending this operation that he made the observations 

 which led to his greatest discoveries, that heat is not a material 

 substance but a mode of motion, and that there is a definite 

 quantitative relation between mechanical work and heat. The 

 "Inquiry Concerning the Source of the Heat which is Generated 

 by Friction" is one of the shortest of his scientific papers, but it 

 would be hard to match it in all scientific literature for originality 

 of conception, importance of matter, completeness of experimen- 

 tal demonstration and clearness of expression. Tyndall quotes 

 it in his Heat as a Mode of Motion with the remark: "Rumford 

 in this memoir annihilates the material theory of heat. Nothing 

 more powerful on the subject has since been written." 



The dominant theory of the time was that heat was a fluid sub- 

 stance, which was called caloric, held in the pores of bodies and 

 squeezed out like water from a sponge, when they were hammered 

 or rubbed. Rumford was led to question this by observing the 

 large amount of heat continuously generated by friction in the 

 boring of his cannon. If, he reasoned, heat is a substance that 

 has been squeezed out of the metal, then the powder produced by 

 the boring must have less heat in it than the original solid metal, 

 and therefore would require more heat to raise it to a given tem- 

 perature. Accordingly, he tested the specific heat of a piece of 

 the gun-metal and an equal weight of the borings with his calo- 

 rimeter, and found that equal amounts of heat raised them to the 

 same temperature. This experiment was not absolutely conclu- 

 sive, for it still could be argued that, although their thermal ca- 



