42 Biographical Memoir of Count Rumford. 



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, precise- 

 ly what it had given out during the first. The other instrument 

 serves to disclose the slightest 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 colored 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 trans- 

 mission of heat, and also pointed out to him numerous methods of 

 retarding or acceleratng, heating or cooling at will. 



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

 ence to illumination, ought to interest us more particularly, because 

 he had made them after he had fixed his residence at Paris, and ta- 

 ken an active part in all our occupations. He considered them as 

 his contributions in quality of a member of the Institute. 



Such are the principal scientific labors of Count Rumford, but 

 they are far from being the only services which he rendered to sci- 

 ence. He knew that, in discoveries, as in philanthropy, the work of 

 an individual is transitory and limited, and, in the latter, as in the for- 

 mer, he strove to establish durable institutions. Thus he founded 

 two prizes, which were to be annually assigned by the Royal Society 

 of London, and the Philosophical Society of Philadelphia,* to the 

 author of the most important experiments on heat and light ; an en- 

 dowment by which, in evincing his zeal for natural philosophy, he 

 also testified his respect for his native and for his adopted country, 

 and proved, that, by having served the one, he had not quarrelled 

 with the other. 



He was the principal founder of the Royal Institution of London, 

 one of the best contrived establishments for hastening the progress 

 of science and its application to the arts. In a country where every 

 individual prides himself on encouraging whatever can be of service 

 to the community, the mere distribufion of his Prospectus brought him 

 considerable funds, and his activity would soon have led to its execu- 

 tion. The prospectus itself was already a sort of description, for he 



* Tho Americin) Acaclcinv of Ail? and Science? of Boston — E'L 



