208 THE CHEMISTRY OF CREATION. 



again weighed. By this means the amount of 

 oxygen in the whole quantity of air that had 

 passed through was accurately ascertained, as 

 by uniting with the copper it gave additional 

 weight to the apparatus, consequently all that 

 was necessary to ascertain the precise quantity 

 of oxygen in the flask of air was to find out 

 how much the copper had increased in weight ; 

 all the grains of increase represented grains of 

 oxygen. 



The result of a large number of experiments, 

 although occasionally some striking variations 

 were noticed,* gave an average which exhibits 

 the composition of ths air in the following pro- 

 portions : 



One hundred parts of air consist of, by weight 

 Oxygen ..... 231-lOth 

 Nitrogen ....'. 76'9-lOths 



100- 



This question was therefore at length satis- 

 factorily decided. But it had often been much 

 disputed by philosophers whether air was uni- 

 versally of a similar composition. Is it the 

 same in the loftiest regions as it is on the level 

 ground, on Mount Blanc, or Chimborazo, as on 

 the sea-shore? The late Dr. Dalton held the 



* According to analyses made by M. Lewy, it appears pro- 

 bable that the quantity of oxygen varies slightly in different 

 seasons of the year, lover sea and over land. 



