178 PROGRESS OF SCIENCE. 



of inflammable air, we have hydrogen (water-producer) ; 

 instead of fire-air, we have oxygen (acid-producer), and so 

 forth. It was Lavoisier, too, who discovered the fixed air 

 of Black, or the air-acid of Bergmann, to be an acid made 

 up of 72 parts of oxygen and 28 parts of carbon, for which 

 reason he called it carbonic acid. 



As a physicist, Lavoisier formulated the principle of 

 equilibrium between the effect of heat on the one hand, and 

 that of universal gravitation on the other heat tending to 

 dilate or separate matter, gravitation tending to keep it to- 

 gether and enunciated the hypothesis that HEAT rs MOTION 

 in his " Principles of Heat." He also invented, with Laplace, 

 the ice CALORIMETER. 



1743 1817. Klaproth was the first to publish all the 

 numerical and analytical details of scientific investigations ; 

 discovered the elements CERIUM, URANIUM, ZIRCONIUM, and 

 analysed many minerals little known until then. 



1748 1822. Berthollet ascertained nitrogen to be one 

 of the essentials to the composition of animal substances; 

 his investigations into the combination of carbon and hydro- 

 gen received an application in gas light ; the art of dyeing is 

 much indebted to him ; discovered the LAWS which govern 

 THE MIXTURE OF GASES. 



1762 1807. Richter discovered (1792) THE LAW which 

 rules the proportions of chemical elements : " Elements in 

 compound bodies are mixed in fixed and definite propor- 

 tions" a corollary of Lavoisier's law of fixity; but not 

 until Dalton was the significance and truth of this law 

 recognised, although Proust (17541826), Wenzel (1777),. 

 and Higgins had intimated its importance. Richter's pro- 

 cess of investigation largely accelerated the progress of 

 electricity. 



1763 1829. Vauquelin discovered CHROMIUM AND- 

 GLUCINUM ; made the first accurate analysis of beryls and 

 emeralds. 



1766 1828. Wollaston discovered PALLADIUM AND- 

 RHODIUM ; found the process of rendering platinum malle- 

 able ; invented a sliding scale of chemical equivalents; was 

 one of the most skilful analysts of his time. Wollaston did, 

 besides, good service to biology. While in Madeira he 



