1881.] On the Influence of Altitude upon Respiration. 425 



mean temperature and corresponding mean weight of carbonic acid 

 expired will be as follows : — 



so that rather less carbonic acid was expired at the lower temperatures. 

 Consequently, not only the total mean carbonic acid expired at the Col 

 was found to be lower than the total mean either at Courmayeur or 

 at Yvoire, but moreover during our stay on the Col the coldest weather 

 was attended with the least formation of carbonic acid for both of us, 

 which is quite in opposition to what might have been expected. This 

 circumstance, however, is easily accounted for. After spending two or 

 three days at Courmayeur were the sun was very hot, the thermometer 

 (sheltered from the sun under or inside a bush) rising to 80°, we 

 started for the summit of the Col without having in any way prepared 

 our functions to the sudden change of climate to which they were 

 going to be subjected. We were indeed fresh from the plains in the 

 hottest time of the year, and it was as taking a leap from the middle 

 of summer into the midst of winter. We left Courmayeur one after- 

 noon, and slept at the inn about 3,000 feet higher ; next morning an 

 early start brought us in good time to the hut at the summit of the 

 Col, in the midst of snow slopes and glaciers. The floor of the hut 

 was found covered in a great measure with ice and snow, which had to 

 be removed with axes, while the small stove in one corner was nearly 

 buried in snow, and so imbedded in ice that it took us some time before 

 we could get it free. People who cross this pass, one of the most 

 beautiful in the Alps, spend an hour at the hut and often less ; few 

 travellers sleep in it, but this was to be our home for at least three 

 days. The wind was cold and cutting, and a thick greatcoat proved 

 quite insufficient. M. David had taken with him a coat lined with fur, 

 but even that was not equal to keeping up a comfortable warmth. The 

 air was very dry ; on the 19th July at 10 a.m. the readings of the dry 

 and wet bulb thermometers were 42° and 33°, giving, a relative humidity 

 of 44 per cent. (Glaisher's tables), so that the atmosphere possessed a 

 great capacity for moisture, and therefore an increased power of cooling 

 down the body. The experiments were to be made out of the welcome 

 sun's rays, and, with this object in view, I had brought up a wooden 

 shed which had already done useful work on an expedition to the 

 Peak of TenerifEe ; this shed or roof was erected on four poles, kept 

 in their places by tent ropes and pegs. It may be readily understood 

 that sitting under the shed with the back resting against a rock and 

 facing the beautiful glacier which descends directly from the Col, was 



grm. 



For M. David. . 



For myself .... 



2 h 2 



