224 Biographical Memoir of Count Rumford. 



He moreover proved, better than any person, that heat has no 

 weight. A phial of spirit of wine, and another of water, re- 

 mained in equilibrium after the congelation of the latter, although 

 it had lost by this, caloric enough to raise the same weight of 

 gold to a white heat. 



He invented two singularly ingenious instruments. The one, 

 which is a new Calorimeter, serves to measure the quantity of 

 heat produced by the combustion of a body. It is a box filled 

 with a given quantity of water, through which the product of 

 the combustion is made to pass by a serpentine tube ; and 

 the heat of this product transmitted to the water, raises it a 

 determinate nimiber of degrees, which serves as a basis to the 

 calculations. The manner in which he prevents the external 

 heat from altering his experiment, is very simple and ingenious. 

 He commences the operation at some degrees below that heat, 

 and terminates it at as many degrees above it. The external 

 air resumes, during the second half, precisely what it had given 

 out during; the first. The other instrument serves to disclose 

 the shghtest differences in the temperature of bodies, or in the 

 facility of its transmission. It consists of two glass balls filled 

 with air, connected by a tube, in the middle of which is a bubble 

 of coloured spirit of wine. The smallest increase of heat in one 

 of the balls drives the bubble toward the other. This instru- 

 ment chiefly, which he named a Thermoscope, made known 

 to him the varied and powerful influence of different surfaces 

 over the transmission of heat, and also pointed out to him nu- 

 merous methods of retarding or accelerating, heating or cooling, 

 at will. 



These two last kinds of researches, and those which have re- 

 ference to illumination, ought to interest us more particularly, 

 because he had made them after he had fixed his residence at 

 Paris, and taken an active part in all our occupations. He con- 

 sidered them as his contributions in quahty of a member of the 

 Institute. 



Such are the principal scientific labours of Count Rumford, 

 but they are far from being the only services which he rendered 

 to science. He knew that, in discoveries, as in philanthropy, 

 the work of an individual is transitory and limited, and, in the 

 latter, as in the former, he strove to establish durable institu- 



