j;6 PROGRESS OF SCIENCE. 



CRYSTALLOGRAPHY, and made a chemical classification of 

 minerals a very valuable performance. 



1742 86. Scheele published a famous paper on Man- 

 ganese, showing the peculiar characters of this metal (1774) ; 

 found tartaric acid, barytes, fluor-spar and its acid, chlorine, 

 glycerine (the sweet principle of oils), sugar of milk, Prussian 

 acid (while studying Prussian blue) ; but his great discovery, 

 made in 1775 concurrently with Priestley and Lavoisier, was 

 that of OXYGEN which was to open a new era in chemistry : 

 so that Scheele should be remembered as one of the greatest 

 chemists of the XVIIIth century, although unfortunately for 

 science he was still imbued with phlogistic views. 



J 743 94- Lavoisier, the FOUNDER OF MODERN 

 CHEMISTRY, gave the death-blow to StahPs phlogistic 

 philosophy by his DISCOVERY OF OXYGEN (1778), the 

 mysterious character of which he unravelled after it had 

 puzzled generations of chemists. This discovery, made some 

 time after Priestley's and Scheele's, did not remain a fruitless 

 one in his hands ; for by it he thoroughly explained the 

 PHENOMENON OF COMBUSTION a fact of supreme im- 

 portance in chemistry. He showed that a rusty or heated 

 metal gains the exact weight which air loses by the process 

 thus demonstrating the process to be the reverse of that 

 imagined by Stahl, since air, instead of receiving something 

 additional by the burning of a substance, loses, on the con- 

 trary, a part of its constituents, namely, its fixed air (oxygen). 

 The law may be formulated thus : "All burning and breathing 

 and the change in metals are caused by a gas (oxygen} being 

 taken up out of air, and joined to other substances" Lavoisier 

 next showed oxygen to be the most abundant* and the most 

 useful of all substances in the economy of our earth ; and for 

 this reason he made this gas the basis of chemical nomen- 

 clature, giving to acids the termination of ic when they con- 

 tain much oxygen ; the termination of ous when they contain 

 less ; he designated bases by the name of oxides ; and affixed 

 ate or zte, according to the degree of oxygenation of the acid, 



* It constitutes more than one-half of the earth's crust, and is 

 present in water to the extent of eight-ninths of the total weight, and in 

 air to the extent of one-fifth of the bulk. 



