HELMHOLTZ IN BERLIN 



About 1798 Count Rumford performed his famous 

 experiments on the boring of cannon, and he observed 

 that the heat produced was much greater than that 

 of boiling water. The older theorists held that heat 

 was a substance, but Rumford 's work went far to 

 prove that it was not matter. The proof was 

 conclusively given by Humphry Davy, who ob- 

 tained sufficient heat to melt ice by rubbing 

 two pieces of ice together. In 1812 Davy wrote: 

 { The immediate cause of the phenomena of heat, 

 then, is motion, and the laws of its communication 

 are precisely the same as the laws of the communi- 

 cation of motion.' Professor Tait remarks in this 

 connection : * If Davy had with this statement 

 taken into account the second interpretation of 

 Newton's third law, the dynamical theory of heat 

 would have been his.' 



It is said that Montgolfier entertained the idea of 

 the equivalence of heat and mechanical work, and his 

 nephew Seguin performed experiments with a steam 

 engine, in which he endeavoured to ascertain whether 

 the same quantity of heat reached the condenser as 

 had left the boiler. Had he succeeded in showing 

 that less heat reaches the condenser than had left 

 the boiler, he would have found that the heat 

 apparently lost was in proportion to the mechanical 

 work performed by the engine. 



The notion of the correlation of the physical forces 

 was slowly shaping itself. Mrs Somerville's book on 

 47 



