DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20132#0517
THE DIFFERENT VARIETIES OF HABITATION. 483
to a height of 19,286 ft.,1 this being the extreme elevation attained at that period.
Some years afterwards (Dec. 16, 1831) Boussingault reached, on the same peak, a height
of 19,695 ft.2
The effect of height is chiefly perceptible in the decrease of temperature and
barometric pressure. The temperature, on such days at least as must be selected for
reaching extreme heights, differs not considerably for the chains of High Asia, if com-
pared with the Alps, the difference of latitude nearly compensating for the inequality
of height. But the decrease of pressure is in direct proportion to the absolute height.3
There are certainly other modifications of the atmosphere connected with height, such
as moisture, chemical composition, electricity, &c.; but these varying within limits so
narrow as to necessitate the application of instruments for their detection and de-
finition, do not affect the human frame in any unusual degree.
Although, from optical phenomena, 70 or 80 English miles have been approxi-
matively assigned as the extreme upper limit of the atmosphere, the decrease of
density is so much greater in the lower strata that, even at an elevation of
22,200 ft. (so trivial a proportion of the entire assumed distance), we observed a
barometric pressure of 13-364 inches, so that nearly 3/sths of the weight of the atmosphere
lay below the point reached by us at the time. At the height of about 18,600 or
18,800 ft., the atmospheric pressure is Va of that at the level of the sea.
It is evident that there must be a limit beyond which the degree of rarefaction
is incompatible with the conditions of human existence; but it will ever remain
extremely difficult, if not altogether impossible, to determine the line of demarcation
with an}- approach to scientific precision. There are many and variable elements to
be taken into account. Among others, the general state of health of the individual
observer, his power of resistance, and of adaptation to new conditions, the time spent
at these unusual heights, and the more or less favourable progress of inurement to
the effects of diminished atmospheric pressure, are all conditions of great moment in
affecting every particular result.
1 "Kleinere Schriften," p. 151. The height of 19,286 ft. is the definitive value deduced by Humboldt after a careful
re-calculation. The height he had formerly obtained was 19,388 ft. See his "Essai sur la geographie des plantes."
Paris, 1807, p. 145.
2 Ibid. p. 157.
3 The variation of pressure, as dependent upon the region of the globe, is not important enough to deserve
more than a passing recognition, when considering such unusually low readings of the barometer.
61*
to a height of 19,286 ft.,1 this being the extreme elevation attained at that period.
Some years afterwards (Dec. 16, 1831) Boussingault reached, on the same peak, a height
of 19,695 ft.2
The effect of height is chiefly perceptible in the decrease of temperature and
barometric pressure. The temperature, on such days at least as must be selected for
reaching extreme heights, differs not considerably for the chains of High Asia, if com-
pared with the Alps, the difference of latitude nearly compensating for the inequality
of height. But the decrease of pressure is in direct proportion to the absolute height.3
There are certainly other modifications of the atmosphere connected with height, such
as moisture, chemical composition, electricity, &c.; but these varying within limits so
narrow as to necessitate the application of instruments for their detection and de-
finition, do not affect the human frame in any unusual degree.
Although, from optical phenomena, 70 or 80 English miles have been approxi-
matively assigned as the extreme upper limit of the atmosphere, the decrease of
density is so much greater in the lower strata that, even at an elevation of
22,200 ft. (so trivial a proportion of the entire assumed distance), we observed a
barometric pressure of 13-364 inches, so that nearly 3/sths of the weight of the atmosphere
lay below the point reached by us at the time. At the height of about 18,600 or
18,800 ft., the atmospheric pressure is Va of that at the level of the sea.
It is evident that there must be a limit beyond which the degree of rarefaction
is incompatible with the conditions of human existence; but it will ever remain
extremely difficult, if not altogether impossible, to determine the line of demarcation
with an}- approach to scientific precision. There are many and variable elements to
be taken into account. Among others, the general state of health of the individual
observer, his power of resistance, and of adaptation to new conditions, the time spent
at these unusual heights, and the more or less favourable progress of inurement to
the effects of diminished atmospheric pressure, are all conditions of great moment in
affecting every particular result.
1 "Kleinere Schriften," p. 151. The height of 19,286 ft. is the definitive value deduced by Humboldt after a careful
re-calculation. The height he had formerly obtained was 19,388 ft. See his "Essai sur la geographie des plantes."
Paris, 1807, p. 145.
2 Ibid. p. 157.
3 The variation of pressure, as dependent upon the region of the globe, is not important enough to deserve
more than a passing recognition, when considering such unusually low readings of the barometer.
61*