Appendix F. EFFECTS OF DIMINISHED PRESSURE OF AIR. 413 



dew-point is on the average 5° G below the temperature ; none of the 

 English months are so wet as those of Sikkim, but none are so dry 

 as the Sikkim December sometimes is. 



On the weight of the atmosphere in Sikkim ; and its effects on the 



human frame. 



Of all the phenomena of climate, the weight of the atmosphere is 

 the most remarkable for its elusion of direct observation, when 

 unaided by instruments. At the level of the sea, a man of ordinary 

 bulk and stature is pressed upon by a superincumbent weight of 30,000 

 pounds or 13^ tons. An inch fall or rise in the barometer shows that this 

 load is lightened or increased, sometimes in a few hours, by nearly 1,000 

 pounds ; and no notice is taken of it, except by the meteorologist, or 

 by the speculative physician, seeking the subtle causes of epidemic 

 and endemic complaints. At Dorjiling (7,400 feet), this load is reduced 

 to less than 22,500 pounds, with no appreciable result whatever on 

 the frame, however suddenly it be transported to that elevation. And 

 the observation of my own habits convinced me that I took the 

 same amount of meat, drink, sleep, exercise and work, not only 

 without inconvenience, but without the slightest perception of my 

 altered circumstances. On ascending to 14,000 feet, owing to the 

 diminished supply of oxygen, exercise brings on vertigo and headache ; 

 ascending higher still, lassitude and tension across the forehead ensue, 

 with retching, and a sense of weight dragging down the stomach, 

 probably due to dilatation of the air contained in that organ. Such 

 are the all but invariable effects of high elevations ; varying with most 

 persons according to the suddenness and steepness of the ascent, the 

 amount and duration of exertion, and the length of time previously 

 passed at great heights. After having lived for some weeks at 15,300 

 feet, I have thence ascended several times to 18,500, and once above 

 19,000 feet, without any sensations but lassitude and quickness of 

 pulse ; * but in these instances it required great caution to avoid 

 painful symptoms. Residing at 15,300 feet, however, my functions 

 were wholly undisturbed ; nor could I detect any quickness of pulse 



* I have in a note to vol. ii. p. 160, stated that I never experienced in my own 

 person, nor saw in others, bleeding at the ears, nose, lips, or eyelids. 



