ix] Doctrines of Respiration. 237 



acute and careful observer, skilful experimenter, but strange 

 being, obtained nitric acid from the atmosphere by electric 

 sparking, that the connection between nitre and the chief 

 constituent of the atmosphere became known. It was this 

 connection which led the French chemist Chaptal to suggest 

 for the atmospheric constituent the name nitrogen ; but it was 

 Lavoisier who first clearly defined its characters, and he always 

 preferred to call it by a name which indicated its inability to 

 sustain life, azotic gas or azote. 



We have said that Black rediscovered under the title of 

 fixed air the carbonic dioxide which van Helmont had dis- 

 covered as gas sylvestre. We may similarly say that Priestley 

 and Lavoisier rediscovered the gas which Mayow had made 

 known by the name of igneo-aereal salt or spirit. 



I need not here dwell at any length on the life of Joseph 

 Priestley. Born in 1733 at Fieldhead near Leeds, in Yorkshire, 

 educated to be a minister in the Unitarian Church, at first a 

 somewhat " stickit " minister in Suffolk and in Cheshire, after- 

 wards holding a more congenial post as tutor in the academy 

 at Warrington, for some time literary companion to Lord 

 Shelburne, his most active life was spent as minister first at 

 Leeds, then at Birmingham. Man of letters as well as man of 

 science, prolific theologian and ardent politician, his views did 

 not commend themselves to the people, or shall I rather say to 

 the populace ; as is well known he had to flee from Birmingham, 

 and after hiding somewhile in London passed over to America 

 and took up his abode at Northumberland in Pennsylvania, 

 where in 1804 he died. 



Priestley's first work on respiration consisted in attempts to 

 restore, to render once more respirable, air which had been 

 vitiated, rendered irrespirable by being breathed. After several 

 failures he at last succeeded by means of vegetation. He says : 



" I have been so happy as by accident to have hit upon a 



" method of restoring air which has been injured by the burning 



" of candles, and to have discovered at least one of the restora- 



" tives which nature employs for this purpose. It is vegetation. 



* * * * ' * # * 



" One might have imagined that, since common air is 



