HENRI VICTOR REGNAULT. 457 



8. On the Elastic Forces of the Vapor of Water at Different Tem- 

 peratures. 



9. On the Latent Heat of Aqueous Vapor at Saturation under Dif- 

 ferent Pressures. 



10. On the Specific Heat of Water at Different Temperatures. 



11. On the Specific Heat of Elastic Fluids. 



1 2. On the Elastic Forces of Vapors. 



13. On the Latent Heats of Vapors under Different Pressures. 

 For every one of these investigations, an original method was 



pursued, and original apparatus was devised. The numerical results 

 obtained form the basis of the modern science of thermics, and are 

 quoted upon almost every page of works on the higher generalization 

 known as thermo-dynamics. The memoirs cited above are by no 

 means, however, the only contributions which Regnault made to his 

 favorite branch of physics. A great number of minor papers contain 

 important additions to our knowledge of physical data, or to our instru- 

 mental means of research. From time to time, he resumed and added 

 to the work of his earlier years, taking up single and special points 

 for investigation. In 1847, Regnault published a work on chemistry 

 in four volumes, written with remarkable clearness, and containing 

 many physico-chemical methods which are still in use ; as, for ex- 

 ample, a very elegant exposition of the theory and use of two of his 

 own forms of the air-thermometer. This work was translated into 

 several languages, and passed through several editions. In 1854, he 

 became director of the porcelain manufactory at Sevres. During the 

 war with Germany in 1870, Regnault lost his son Henri, an artist 

 of extraordinary promise ; and, after the final treaty of peace, he 

 returned to his laboratory to find that the results of an elaborate inves- 

 tigation on the heat of expansion of gases had been completely 

 destroyed during the German occupation of the town. 



Regnault possessed in a remarkable degree the talent for devising 

 apparatus and methods for the determination of physical constants. 

 It is safe to say that with him began a new era in experimental 

 physics. His mathematical powers were at least respectable, yet he 

 seems never to have employed the modern mathematical processes for 

 the treatment of his numerical results. He never devised experiments 

 which, like sounding-lines, reached the depths of the unknown. Experi- 

 ment was not with him, as with Faraday, an instrument of discovery, 

 but only a most refined and beautiful instrument of observation. He 

 never theorized, he drew no deductions from his own work, but he 

 laid at the feet of the great architects of science grand and shapely 



