various Altitudes, in connexion with the act of Ascending. 335 



due to the necessity of slackening my speed of ascent in order to 

 record my observations. 



At about 1565 metres above the level of the sea, the thermo- 

 meter in my mouthy and while I was ascending, showed 36 0, 5, 

 but rose to 37° during the next few minutes. In another expe- 

 riment at the same place, although under different circumstances, 

 the thermometer after five minutes' exposure was up to 35°*3, 

 rising immediately after to 36°, and five minutes later to 36°*3, 

 although I had not stopped walking up hill. At a height of 

 2060 metres, near "Pierre Pointue," while ascending, the tem- 

 perature under my tongue, after five minutes' exposure, was 

 35°*5, rising during the subsequent few minutes' climbing to 

 36°-8. At the " Pierre a l'echelle," near the glacier " Des Bos- 

 sons," while ascending and after an exposure of six minutes, 

 the temperature first observed was 36° # 5, and five minutes later 

 36 0, 8, although I had not stopped. 



Result IV. — Finally, the sickness many people suffer from at 

 great altitudes appears to be attended with a remarkable fall in 

 the temperature of the body, 



I suffered from this affection, for a short time, at the Pavilion 

 du Mont Frety, on awaking early in the morning. Immediately 

 after an attack of retching, my stomach being then quite empty, 

 I took the temperature under my tongue : the reading of the 

 thermometer was steady at 35°; and the mercury rose slowly 

 during the following few minutes to 36°, during which time I 

 recovered my health perfectly. On arriving at the summit 

 of Mont Blanc the same kind of sickness returned. I then 

 attempted to ascertain my temperature, but while so doing had 

 the misfortune to break my thermometer. Professor Lortet 

 of Lyons, with whom I had the pleasure of making the ascent, 

 then kindly lent me a maximum-thermometer, which he read 

 after its bulb had been under my tongue for a short time ; 

 the instrument then showed a much lower temperature than I 

 had ever yet observed ; but the time of exposure was, I feel cer- 

 tain, too short for an accurate observation ; still, after a similar 

 exposure while in health, I believe the mercury would have 

 risen higher. I can hardly think that in perfect health, and 

 with no great degree of muscular exhaustion, the heat of the 

 body at rest is much lower at the top of Mont Blanc than in 

 the plain — and this for the reason that on the highest point of 

 the " Bosse du Dromadaire," at an altitude of 4672 metres, and 

 consequently only 138 metres below the very summit of Mont 

 Blanc, my temperature when sitting down was 37°*1, which is cer- 

 tainly not below the normal temperature of man in the plain. 

 I then felt in no way indisposed, and not at all tired. 



