1881.] On the Influence of Altitude upon Respiration. 419 



their capacity lias been determined with the greatest care by means 

 of a gas-holder or bell-jar, having a scale of cubic feet divided into 

 hundredths and tested as to correctness. I must beg to take this 

 opportunity of returning my best thanks to Mr. Henry Sporne, Inspector 

 of Gras Meters for the city of London, for his kindness in determining 

 in my presence the capacity of the bag used in these experiments, by 

 means of one of his beautifully graduated gas-holders, made for testing 

 the delivery of gas meters. The capacity of others of my experi- 

 mental bags was ascertained by the same means. 



The bulk of air held by the bag employed in all the experiments 

 referred to in the present communication was determined as follows : — 

 The gas-holder having been filled with air, and the pressure of the in- 

 strument regulated to one inch of water, it was placed in communication 

 with the bag laying flat and quite empty on a table. This bag was 

 also connected through one of its necks and india-rubber tubing with 

 another water-gauge. All these connexions being perfectly air-tight, 

 the height of the air-holder was read off, and the air admitted into the 

 bag from the holder. After some minutes the bag became fully dis- 

 tended, and the water began rising in the gauge connected directly 

 with it. As soon as a pressure of one inch in the bag was attained^ 

 the delivery from the air-holder was read off ; it had by that time all 

 but done falling, moving downward very slowly, to the extent of a 

 delivery of about one-hundredth of a cubic foot and then stopped ; if 

 the bag was then handled, one or two more hundredths of a cubic 

 foot might be given out from the holder. One experiment gave a 

 delivery of from 4 to 7*18 on the index = 3"18 cubic feet, read off as 

 soon as the water in the gauge connected with the bag showed a 

 pressure of one inch ; on waiting two or three minutes, 3*19 cubic feet 

 were read off ; and, after handling the bag, the volume of air delivered 

 into it rose to 3'22 cubic feet. In another experiment the reading on 

 the holder was made to commence at 6, and when the bag was full it 

 had fallen to 9*19, giving a bulk of 319 cubic feet of air delivered into 

 the bag; after handling the bag, the air given out rose to 3*22 cubic feet. 

 I have therefore taken 3'20 cubic feet, or 90*6 litres, as the correct 

 estimation of the air contained in the bag under the pressure of one 

 inch of water. In this last experiment the temperature of the air in 

 the bag was ascertained to be the same as that of the room, and, 

 moreover, the holder had been filled with air for some hours previously, 

 so that it is very unlikely that its temperature should have been 

 different from that of the external atmosphere ; the temperature of the 

 water in the gas-holder was a trifle below that of the room. 



I proposed this last summer to make the Col du Geant (altitude 

 11,030 feet) my highest experimental station, as this spot was easy to 

 reach with the necessary instruments, and a small wooden hut had 

 been lately erected at the summit of the pass, where we could make 



