1879.] Various Altitudes on the Island and Peak of Teneriffe. 511 



Before collecting the air expired, the boards were worked at the 

 rate of forty-five steps per minute for a short time, in order to bring 

 the body thoroughly under the conditions of the experiment. 



The 68*4 litre bag connected with the water gauge was held by the 

 hand in the proper position, and at the same time as the first expira- 

 tion into the bag was commenced a preconcerted signal caused the 

 assistant to start the time-piece. A little practice made it quite easy 

 to step in time with the beats of the metronome, counting the number 

 of expirations. As soon as the water gauge showed a pressure of one 

 inch, the watch was stopped and the number of expirations imme- 

 diately recorded. 



The experiment was then completed as usual. 



Six experiments were made by each of us at the different stations, 

 and the results are entered in the following table : — (See p. 512.) 



On considering in this table the amount of carbonic acid exhaled, it 

 will be observed to vary but little at the different stations for both 

 myself and the guide respectively. In my case the amount expired 

 at 10,700 feet and seaside is nearly the same, while there is a 

 moderate increase at Gruajara, the intermediate station. In the case 

 of the guide the amount expired at the two highest stations is much 

 alike, and there is a moderate decrease at the lower station. 



The proportion between the mean carbonic acid expired sitting 

 and on the rocking-boards for each of us respectively at the various 

 stations were : — 



For myself. For the guide. 



Alta Yista 1 to 2 '05 1 to 2 23 



Guajara 1 „ 2 35 ...... 1 „ 2 -35 



Puerto 1 „ 2 'Ob' 1 „ 1 78 



Mean 1 „ 2 15 1 „ 2 12 



Consequently, the proportion of C0 2 is a little higher for both of us 

 at the intermediate station, while the total mean in each case is as 

 near as possible identical, and may be safely considered as the same. 

 These figures show, moreover, that while engaged with the regulated 

 work on the tread-board, we each of us expired nearly twice as much 

 carbonic acid as in the sitting posture, 



The mean volume of air expired per minute, reduced, is for myself 

 considerably smaller at the highest station than at the two others ; 

 while in the case of the guide we observe a slight falling off in the 

 volume of air expired at the middle station. 



If the relation between the volume of air and weight of carbonic 

 acid expired for each of us at all the stations be calculated, it will be 

 found that for myself 1 grm. of carbonic acid (expired on the tread- 



2 p 2 



