INTRODUCTION 



It will be within tlie knowledge of most of those who take up 

 this book that it has long been much debated whether human 

 life can be sustained at great altitudes above the level of the 

 sea in such a manner as will permit of the accomplishment of 

 useful work/ 



The most opposite statements and opinions have been advanced 

 concerning this matter. The extremes range from saying that 

 fatal results may occur^ and have occurred, from some obscure 

 cause, at comparatively moderate elevations, down to that no 

 eifects whatever have been experienced at the greatest heights 

 which have been attained. Allegations of the latter class may be 

 set aside for the present, for the evidence is overwhelming that, 

 from 14,000 feet above the level of the sea and upwards, serious 

 inconveniences have occurred : that prostration (amounting in the 

 more extreme cases to incapacitation) has been experienced ; and 

 that, in some instances, perhaps, even death has resulted through 

 some cause which operates at great elevations. 



This evidence has come from all parts of the world, and has 

 accumulated during several centuries. It has been afforded, in- 

 dependently, by multitudes of persons of diverse conditions — by 

 cultured men of science down to illiterate peasants, the latter of 

 whom cannot have heard of experiences beyond' their own; and, 

 although the testimony often differs in detail, it agrees in the 



^ In saying this, it is not meant that there is any doubt as to the possibility 

 of tlie existence of life at great elevations, for aeronauts have several times shewn, 

 since the commencement of this century, that life may exist, for short periods, at 

 heights exceeding any as yet discovered upon the earth. 



