Life of Count Rumford. 617 



the scientific occupations of the Count after he had 

 taken up his residence in France. His various lamps 

 became as popular as were his fireplaces and soups. 

 His curious experiments and information on agreeable 

 harmonies and contrasts in colors proved equally in- 

 structive for helping ladies about their ribbons and 

 apparel, and for decorators and furnishers of household 

 apartments. 



I now translate the words of the Eloge : 



" He has constructed two singularly ingenious instruments of 

 his own contrivance. One is a new calorimeter for measuring 

 the amount of heat produced by the combustion of any body. 

 It is a receptacle containing a given quantity of water, through 

 which passes, by a serpentine tube, the product of the combus- 

 tion ; and the heat that is generated is transmitted through the 

 water, which, being raised by a fixed number of degrees, serves 

 as the basis of the calculations. The manner in which the 

 exterior heat is prevented from affecting the experiment is very 

 simple and very ingenious : he begins the operation at a certain 

 number of degrees below this outside heat, and terminates it 

 at the same number of degrees above it. The external air takes 

 back* during the second half of the experiment exactly what it 

 gave up during the first. The other instrument serves for 

 noting the most trifling differences in the temperature of bodies, 

 or in the rapidity of its changes. It consists of two glass bulbs 

 filled with air, united by a tube, in the middle of which is a bell 

 of colored spirits of wine : the slightest increase of heat in one 

 of the bulbs drives the bell towards the other. This instrument, 

 which he called a thermoscope, was of especial service in mak- 

 ing known to him the varied and powerful influence of different 

 surfaces on the transmission of heat, and also for indicating a 

 variety of methods for retarding or hastening at will the pro- 

 cesses of heating and freezing. 



lt The last two classes of researches, and those which relate 

 to illumination, ought more especially to interest us [the mem- 

 bers of the Institute], because they were made after Rumford 



