308 A SHORT HISTORY OF SCIENCE 



flame, very much like that enlarged flame with which a candle burns 

 in nitrous oxide, exposed to iron or liver of sulphur ; but as I had got 

 nothing like this remarkable appearance from any kind of air besides 

 this particular modification of vitreous air, and I knew no vitreous acid 

 was used in the preparation of mercurius calcinatus, I was utterly at 

 a loss to account for it. ... 



The flame of the candle, besides being larger, burned with more 

 splendor and heat than in that species of nitrous air; and a piece 

 of red-hot wood sparkled in it, exactly like paper dipped in a solution 

 of nitre, and it consumed very fast ; an experiment that I had never 

 thought of trying with dephlogisticated nitrous air. 



... I had so little suspicion of the air from the mercurius cal- 

 cinatus, etc., being wholesome, that I had not even thought of apply- 

 ing it to the test of nitrous air; but thinking (as my reader must 

 imagine I frequently must have done) on the candle burning in it 

 after long agitation in water, it occurred to me at last to make the 

 experiment ; and, putting one measure of nitrous air to two measures 

 of this air, I found not only that it was diminished, but that it was 

 diminished quite as much as common air, and that the redness of the 

 mixture was likewise equal to a similar mixture of nitrous and com- 

 mon air. . . . The next day I was more surprised than ever I had 

 been before with finding that, after the above-mentioned mixture of 

 nitrous air and the air from mercurius calcinatus had stood all night, 

 ... a candle burned in it, even better than in common air. 



At almost the same time (1775) Scheele, a Swedish chemist, 

 independently discovered the same gas. "Scheele remained a 

 poor apothecary all his life, yet was really one of the first chemists 

 of Europe." His name for oxygen was "empyreal air." 



But if Black and Cavendish and Priestley and Scheele and 

 others laid the foundations of modern chemistry, it was the yet 

 more famous Lavoisier, who, building upon the results of his 

 predecessors, began the erection of the present lofty superstruc- 

 ture. Lavoisier soon dismissed forever the long-standing, mysti- 

 cal theory of phlogiston through his unremitting use of the balance, 

 for the introduction and use of which in analysis he has been 

 rightly called " the founder of quantitative chemistry." By 

 means of the balance he proved that when metals are burnt in 



