Theories and Experiments 223 



more and more, until the greater pressure is so much more than the 

 lower pressure as to be unendurable to the experimenter. At 18,480 

 feet, the barometer stands on the average, at 15 inches, so that we then 

 breathe an air only half as dense as that at sea level; who could be 

 surprised at the effects observed? (P. 323.) 



Captain Hodgson, 36 who in his turn reports the statements of 

 the natives, seems not far from believing them himself: 



The mountaineers, who know nothing of the rarefaction of the 

 air, attribute their weakness to the exhalations of harmful plants, and 

 I think that they are right, for a sort of unwholesome effluvium was 

 exhaled by them here as Well as on the heights below the snowy 

 peaks which I crossed last year on Setlej; although, on the highest 

 snow, the complaint was not of weakness, but of the impossibility of 

 walking for some time without stopping to breathe. (P. 111.) 



We shall see later, by the testimony of recent travellers, that 

 this idea of wind poisoned by plants is today quite popular in 

 Upper Asia. 



If now we return to our Alps, about this same time we find 

 Hipp. Cloquet 37 republishing the mechanical explanation: 



The pressure of the air, which weighs constantly upon us from 

 all sides . . . seems necessary to the maintenance of the equilibrium 

 between the living solids and the humors which circulate or float 

 within them; it counterbalances the elastic force of the fluids of our 

 bodies; and since this pressure is considerably diminished here, it is 

 not surprising that the equilibrium is ruptured. (P. 36.) 



Dr. Hamel, 38 when he undertook the fatal expedition on Mont 

 Blanc in 1820, had planned to make experiments there; one of his 

 plans gives evidence of a remarkable sagacity and shows very 

 definite and very scientific hypothetical views about the cause and 

 the effects of rarefied air: 



I had prepared a flask of lime water to see whether, at the sum- 

 mit, the expired air was laden with carbon in the same proportion as 

 in the regions where at every inspiration about one-third more oxygen 

 enters with the same volume of atmospheric air. I also planned to 

 extract, on the summit, the blood of some animal, to see by its color 

 whether it had been sufficiently decarbonated in the lungs. 



The account of the ascent of Mont Blanc carried out by Clis- 

 sold 3n in 1882 brings us to an explanation which had not appeared 

 up to that time, and which might serve as type for that physiology 

 of probabilities which has done such harm to science. 



In the first place, Clissold attributes the symptoms observed to 

 the smaller quantity of oxygen contained in the same volume of 

 air, which compels respiration to be deep and hasty. 



