198 PROCESS OF G A SSIFI CATION. 



having subjected both to the same examination, 

 he did not find the former 1-30 better than the 

 latter. He also took the air from the upper gal- 

 lery of St. Paul's cupola, which is 313 feet from 

 the base, and that of the stone gallery, which is 

 202 feet below the other, and comparing these 

 with the air of the adjoining street, he was not 

 able to detect any sensible difference between 

 them. 



Although the correspondence which exists 

 between their various parts, tends to show, that 

 there is a considerable degree of uniformity in 

 the constituent materials of the atmosphere; 

 they, nevertheless, prove the imperfect condi- 

 tion of chemical analysis also, and how inade- 

 quate are the means which are employed, to 

 the attainment of the end. In the analysis 

 which is presented to us, neither the matter of 

 light, nor of fire, of color, nor of odor, are de*- 

 tected, or noticed,- but which are, nevertheless, 

 obvious and sensible to our organs of sense ; 

 the striking and astonishing effects which are 

 produced on the lungs, during the process of 

 respiration from the air of different situations, 

 prove, in a manner, the most decisive, that, 

 notwithstanding the supposed accuracy of 

 chemical analysis, an extreme degree of differ- 

 ence does exist in the constituent materials of 

 which the atmosphere, of different places, is 

 composed. 



