INTRODUCTION.
It will be within the 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.[1]
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 effects 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 eases to incapacitation) has been experienced; and that, in a few 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, independently, 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 the 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.
