B 3 4 EIGHTEENTH CENTURY. FT. lit 



Properties of Nitrogen determined by Dr. Ruther- 

 ford in 1772. There now remains to be mentioned only 

 one of the four gases spoken of at page 225. namely, nitrogen. 

 This gas was first properly described by Dr. Rutherford in 

 1772, but there is very little to be said of it^except that it 

 has scarcely any of those properties which belong to the 

 other gases. It does not support life or flame like oxygen ; 

 it does not make lime-water cloudy as carbonic acid does, 

 nor does it burn like hydrogen. In fact, it is a dull sleepy 

 gas, which remains after oxygen has been taken out of 'the 

 air. 



Lavoisier lays the Foundation of Modern Chemistry, 

 1778. The determination of nitrogen completes the history 

 of the discovery of those gases which play the chief part 

 in combustion, respiration, and the maintenance of animal 

 and vegetable life. But you will have noticed that we 

 have not yet arrived at the new explanation of chemical 

 changes which was to take the place of 'phlogiston.' 

 The fact is that Bergmann, Cavendish, Scheele, and 

 Priestley, were all so cramped by the old theory, that 

 though they discovered the facts they could not make the 

 right use of them. Black had, indeed, proved that fixed 

 air would combine with lime (see p. 227), but he did not 

 work out any theory of combustion from this discovery. 

 The man who did this, and who laid the foundation of 

 modern chemistry, was the celebrated French chemist, 

 Lavoisier. 1 



1 This statement having been questioned by one of the reviewers of 

 the first edition of this book, it may be well to quote the words of Dr. 

 Crum- Brown, upon whose advocacy of Black's claims to precedence 

 the objection was founded. After stating how Black ' was the first to 

 point out the new path,' Dr. Brown continues, ' We would be ungrate- 

 ful if we undervalued the services of the French chemist. The facts 



