24B On the Proportion of 



. 3.. Exploding hydrogen gas and air by elec- 

 tricity. 



4. Exposing the air to a Solution of green 

 sulphat or muriat of iron in water, strongly 

 impregnated with nitrous gas. 



5. Burning phosphorus in the air. 



In all these xases the oxygen enters, into 

 combination and loses its elasticity ; and if the 

 several processes be conducted skilfully, the 

 results are precisely the same from all. In all 

 parts of the earth and at every season of the 

 year, the bulk of any .given , quantity of at- 

 mospheric air appears to be reduced nearly 2\ 

 per cent, by abstracting its oxygen. This 

 fact, indeed, has not been generally admitted 

 till lately; some chemists having found, as 

 they apprehended, a great difference in the 

 quantity of oxygen in the air at different time^ 

 and places ; on some occasions 20 per cent, 

 and on others 30, and more of oxygen are said 

 to have been found. This I have no doubt 

 was owing to their not understanding the 

 nature of the operation and of the circumstances 

 influencing it. Indeed it is difficult to see, on 

 any hypothesis, how a disproportion of these 

 two elements should ever subsist in the at^ 

 mosphere. 



As th,e first of the processes above-mentioned 

 has been much discredited. by late authors, and 



