COUNT RUMFORD. 171 



or lamp, without these shadows being coloured, the one 

 yellow, and the other blue." He obtained shadows 

 from a light coloured by means of interposed glasses, 

 and compared them with shadows obtained from Tin- 

 coloured light. The shadows were always coloured 

 when the lights differed from each other in whiteness, 

 and the colours of the shadows were always such as, 

 when added together, produced a pure white. The 

 real colour, in fact, evoked, or " called up," or sum- 

 moned an imaginary complementary colour. Goethe 

 probably derived the expression " gef orderte Farben," 

 which occurs so often in the " Farbenlehre," from the 

 terminology of Kumford. 



But the experiments and discussion on which the 

 fame of Rumford mainly rests are described in an essay 

 of twenty pages a vanishing quantity when compared 

 with the sum-total of his published work. A cannon 

 foundry had been built under his superintendence at 

 Munich, where the heat developed during the boring of 

 cannon powerfully attracted his attention. Upon this 

 heat he made numerous tentative experiments, which 

 are described in the essay. With the view of determin- 

 ing its exact quantity, he cut a cylinder from the muzzle 

 end of a gun not yet bored, partially hollowed out this 

 cylinder, and fitted into it a borer which resembled a 

 blunt chisel in shape. The borer being strongly pressed 

 against the bottom of the cylinder, it was caused to 

 rotate by horse-power. He surrounded his cylinder with 

 a wooden box, filling the box with water which embraced 

 the entire cylinder. Soon after the starting of the rota- 

 tion, the water felt warm to the hand. In an hour 

 it had risen to 107 in temperature. In two hours and 

 twenty minutes it had risen to 200, while in two hours 

 and thirty minutes it actually boiled. 

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