238 Historical 



It is natural for one to breathe more air in a rarefied atmosphere, 

 in order to bring the same quantity of oxygen to the blood, since in a 

 given volume of air there is less weight of it than on the plain. If 

 there are many mountain climbers who have not noticed this phe- 

 nomenon, that is because the diminished atmospheric pressure is a great 

 help in the expansion of the thoracic cavity, and thereby makes 

 respiration easier. 



Father Hue 71 is not a skeptic, far from it. His well-known 

 credulity even robs his accounts of much authority. Nothing is so 

 strange as this simplicity which very lightly borrows the language 

 and the aid of science. In fact, he adopts absolutely the idea of 

 poisonous emanations or vapors; but, more daring than his prede- 

 cessors, he even specifies the nature of them, and considers that they 

 are formed of carbonic acid: 



The mountain Bourhan-Bota has this very strange peculiarity, 

 that the harmful gas exists only on the part that faces east and north; 

 on the other side, the air is pure and quite respirable; it seems that 

 these poisonous vapors are nothing but carbonic acid gas. The people 

 attached to the embassy told us that when it was windy, the vapors 

 were hardly noticeable, but that they were very dangerous when the 

 weather was calm and serene. Since carbonic acid gas is known to 

 be heavier than atmospheric air, it must condense on the surface of 

 the ground and remain there until a great agitation of the air sets it 

 in motion, scatters it through the atmosphere, and neutralizes its 

 effects. When we crossed Bourhan-Bota, the weather was quite calm. 

 We noticed that when we were lying down on the ground, we breathed 

 with much more difficulty; if, on the contrary, we mounted our horses, 

 the influence of the gas was hardly felt. Because of the presence of 

 carbonic acid, it was very difficult to light a fire, the argals burned 

 without flame, shedding much smoke. However, it is impossible for 

 us to tell how this gas was formed and whence it came .... 



A terrible quantity of snow fell during the night; those who, on 

 the day before, had not dared to keep on, joined us in the course of 

 the morning; they told us that they had finished the ascent of the 

 mountain with ease because the snow had dispelled the vapors. 

 (P. 265.) 



These regions, so rarely explored, were crossed in 1873 by Cap- 

 tain Przevalski. 72 He rejects absolutely the explanation which we 

 have just reported: 



The great elevation of northern Thibet causes marked difficulty 

 in breathing, especially if one walks quickly; then come vertigo, 

 trembling in the legs, and even vomiting. The fuel of the country 

 (argal) is hard to burn because of the rarefaction of the air and 

 the rarity of the oxygen. 



The missionary Hue explains the same phenomena, which he 

 observed on the mountain of Burchan-buda, by emanations of carbonic 



