160 
was the experience of Eroce Spinelli, Sivel 
and Tissandier, who, on August 15, 1875, 
reached an altitude of 7,000 m. (23,750 ft.) 
with an atmospheric pressure of only 300 
mm. in two hours. They followed Paul 
Bert’s advice and inhaled oxygenated air, 
as a result of which their strength immedi- 
ately revived. 
After a longer sojourn in regions of high 
altitude the symptoms of mountain-sick- 
ness pass away, as respiration is gradually 
regulated to suit the conditions of the 
rarefied atmosphere. The change which 
this necessitates is easily explained. In 
order to breathe deeply it is necessary to 
expand the lungs more slowly, and this is 
only accomplished by means of continuous 
unconscious practice which strengthens the 
respiratory muscles. The members of 
Alpine clubs who make high ascents keep 
in practice by repeating their excursions 
frequently. Hence they are far less sub- 
ject to mountain-sickness than those who 
have had no previous training. 
The wonderful feats of Paul Guessfeldt, 
which are described in the German Rund- 
schau of 1892, are a good illustration of the 
benefits to be derived from such a training. 
He breathed and moved without any in- 
convenience at an altitude of about 5,500 
meters, where the atmospheric pressure is 
equal to only one-half of the ordinary pres- 
sure. In ascending Mt. Aconcagua, in 
Chile, he had no difficulty in breathing until 
after the altitude of 6,000 meters had been 
reached, and even then he was finally able 
to ascend to the summit, which has an ele- 
vation of nearly 7,000 meters, or 23,910 ft., 
an altitude at which aeronauts are com- 
pelled to have recourse to their supply of 
oxygenated air. 
A distinguishing characteristic of the air 
of high altitudes as compared with that of 
lower regions is its freedom from moisture. 
The atmosphere is so dry on the plateaus 
of the Andes in Peru and Bolivia, where 
SCIENCE. 
[N. S. Von. VI. No. 135. 
the altitude ranges from 3,600 to 3,900 
meters, that the flesh of butchered cattle 
can be dried in the open air. The two ex- 
plorers, D’Orbigny and Wedell, both re- 
port that the sheep which are killed there 
are split open and salted, after which they 
are hung up in the open air, and are dried 
in four or six days. 
The ocean is the chief source of the mois- 
ture contained in the atmosphere; conse- 
quently the interior of the continents is 
drier than the coast regions, and in the 
same way the moisture decreases as we rise 
above sea level. The lower stratum of 
air up toabout 2,000 meters (6,500 ft.) 
contains one-half of the whole amount of 
aqueous vapor in the atmosphere, and here 
the cloud-formations are densest and most 
frequent, while above this altitude the sky 
is much clearer. 
It is a well-known fact that extreme dry- 
ness of the atmosphere stimulates the nery- 
ous system, making one feel brighter and 
more inclined for both physical and mental 
activity. The inhabitants of very dry re- 
gions, according to the reports of explorers, 
are free from any tendency to obesity. 
In trying to escape from the hot air of 
the cities in the summer we look for a 
place which is situated higher above sea 
level, because we know it to be cooler. In 
the torrid zone, resorts with an elevation of 
from 2,000 to 3,000 m. are popular. In 
spite of being nearer to the sun, the air is 
cooler, as the sun’s rays have practically no 
effect upon it. The air allows the rays to 
pass through it freely, but receives its 
warmth from the dark heat rays which are 
reflected from the earth after the sun has 
warmed it. The lower strata of air are, 
therefore, always warmer than the upper. 
But the plateaus of the highlands are cooler 
too, as well as the summits and crests, for 
their rarefied atmosphere is incapable of 
absorbing as much of the heat reflected by 
the earth as the denser atmosphere of the 
