MANUAL WORK. 401 



burning hot the masses of iron they were 

 hammering and perforating then, and then 

 only, Seguin, senior, in France, and a doctor, 

 Mayer, in Germany, ventured to bring out the 

 mechanical theory of heat with all its con- 

 sequences : and yet the men of science ignored 

 the work of Seguin and almost drove Mayer 

 to madness by obstinately clinging to their 

 mysterious caloric fluid. Worse than that, 

 they described Joule's first determination of 

 the mechanical equivalent of heat as " un- 

 scientific." 



When thousands of engines had been illus- 

 trating for some time the impossibility of 

 utilising all the heat disengaged by a given 

 amount of burnt fuel, then came the second 

 law of Clausius. When all over the world 

 industry already was transforming motion into 

 heat, sound, light, and electricity, and each one 

 into each other, then only came Grove's theory 

 of the " correlation of physical forces " ; and 

 Grove's work had the same fate before the 

 Royal Society as Joule's. The publication of 

 his memoir was refused till the year 1856. 



It was not the theory of electricity which 

 gave us the telegraph. When the telegraph 

 was invented, all we knew about electricity was 

 but a few facts more or less badly arranged in 

 our books ; the theory of electricity is not 



