498 Rev.W.V.Harcourt on Lord Brougham's statements 



weight disappears, analysis is impossible. So he left the com- 

 position of the atmosphere to be demonstrated by those who 

 believed, with Mayow, that elastic fluids cannot penetrate 

 glass, and who took the pains to weigh both the air and the 

 substances by which it was diminished ; whilst he went on pur- 

 suing the phantom of his imaginative genius to the examina- 

 tion of imponderable essences and the great discovery of the 

 chemical forces of light, and of the distinctions between the 

 heat of contact, and the heat of radiation*. 



But what shall we say to the improvements of Priestley on 

 the principles of Mayow ? Priestley — who many months after 

 he is said by you, and others, to have discovered oxygen gas, 

 tells us himself, that he " had no doubt it had all the proper- 

 ties of genuine common air." On the 1st of August 1774, 

 Priestley with a burning-glass, following the method of Boyle, 

 collected this gas and observed " that a candle burnt in it with 

 a remarkably vigorous flame, but did not give sufficient atten- 

 tion to the circumstance at that time — that the flame of the 

 candle, besides being larger, burnt with more splendour and 

 heat, than in nitrous air exposed to iron or liver of sulphur." In 

 the October following, " I. mentioned," he says, " my surprise 

 at the air I had got, to M. Lavoisier, but at the same time had 

 no suspicion that it was wholesome, so far was I from know- 

 ing what it was that I had really found, and taking for granted 

 that it was nothing more than such kind of air as I had brought 

 nitrous air to be by the processes above-mentioned." He 

 mentioned it also to all his philosophical acquaintance at Paris 

 and elsewhere, " having no idea at that time to what these 

 remarkable facts would lead." On the 1 9th of November 

 however, having agitated it in water, he " found that a candle 

 still burned in it as well as in common air," though after " the 

 same degree of agitation phlogisticated nitrous air would cer- 

 tainly have extinguished a candle." " In this ignorance," he 

 adds, " of its real nature I continued from this time to the 

 1st of March following." " But in the course of this month 

 I not only ascertained the nature of this kind of air, though 

 very gradually ; but was led by it, as I then thought, to the 

 complete discovery of the constitution of the air we breathe. 

 Till this 1st of March 1775, I had so little suspicion of its 

 being wholesome, that I had not even thought of applying to 

 it the test of nitrous air;" " but 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 dimi- 

 nished, but that it was diminished quite as much as common 

 air, and that the redness of the mixture was likewise equal to 



* Scheele's Experiments on Air and Fire. 



