INTRODUCTION. ix 



It is, however, a certain fact that all individuals are not equally 

 affected by diminished pressure, and that instances have occurred 

 at such heights as 14-15,000 feet in which some persons have 

 suffered whilst others have escaped, though the latter have not 

 been exempt upon mounting to greater altitudes. But whilst this 

 must be admitted ; and also the probability that the effects of 

 fatigue have often been wrongly interpreted ; and, further, that 

 personal frailties are frequently manifested upon mountain ascents, 

 or at great elevations, there is a large residuum which cannot be 

 explained away ; and any one examining the matter can hardly 

 fail to arrive at the conclusion that mountain-sickness is a world- 

 wide reality. 



This subject, long since, appeared to me to be worthy of inves- 

 tigation for its own sake, more particularly for ascertaining the 

 heights at which effects begin to manifest themselves ; the symp- 

 toms ; and whether the effects are permanent. It seemed certain 

 that, sooner or later, every one must be affected by diminished 

 pressure, but the manner in which it would operate was uncertain, 

 and whether its effects would be felt permanently at any given, 

 elevation was unknown. Those who have been affected by mount- 

 ain-sickness have always desired to be rid of the infliction, and 

 have descended to lower levels at the earliest opportunity. Hence 

 it had not been ascertained whether cures might be effected on the 

 spot ; or, to put the matter in another way, whether one can be- 

 come habituated to low pressures. The remarks which have fallen 

 from those who are most entitled to attention have not been of an 

 encouraging nature, and it may be inferred from their general tenor 

 that as the cause is constant and permanent so will the effects be 

 constant and permanent. 



De Saussure, after finding himself through weakness, and diffi- 

 culty in breathing, unable to make during a four and a half hours' 

 stay on the summit of Mont Blanc the experiments which he had 

 repeatedly performed in jess than three hours at the level of the 



h 



