BY ETHEL C. PlNKERTON. 



867 



estimations of the amount of oxygen in the air of the room. The 

 results of these analyses are given in Table i. 



Table i. 



The figures in this Table for the oxygen in tlie air of the room 

 have varied from 20-81 to 20*97%. These figures are all some- 

 what lower than 2096, but the clift'erences between the analyses 

 on different days do not exceed OIG parts in 20-89 parts of air, and 

 the duplicates do not vary by more than 009 parts in the same 

 quantity. In the first series of experiments, a plug of glass-wool 

 was placed in the brass tube, as proposed by Henderson, Chilling- 

 worth and Whitney(2)5 but this was omitted in a second series. 

 The omission of the plug of cotton-wool has made no dilference to 

 the ease with which the breath displaced the air in the brass tube. 

 It would appear that the expired air is driven into the tube at 

 such a rate, that the air already in the tube is displaced by the 

 advanchig wave of the entering air. 1 am indebted to Mr. F. W. 

 Carpenter for the suggestion, that tiie air respired into the brass 

 tube behaves like an "explosive wave," driving tlie contents of the 

 tube before it. 



HesuKs. — As it felt easier to breathe quickly into the empty 

 brass tube, and as the results of the analyses show the least change 

 along the tube, the results of the second series of experiments, in 

 which no glass-wool was placed in the brass tube, will be described 

 fu-st. The figures are given in Table ii. 



