278 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
himself went up some hundreds of feet. Two years later the French 
scientist Charles reached a height of 13,000 feet with a hydrogen 
balloon. 
ALTITUDE PRESSURE GRAPH 
PRESSURE CABIN | 
OR SUIT 
ESSENTIAL 
TOTAL PRESSURE 
QWALS ND LEV! 
OXYGEN PRESSURE 
\ V4 ATMOSPHERE 
ADDITIONAL 
L ie =44' OXYGEN 
ESSENTIAL 
ALTITUDE IN THOUSANDS OF FEET 
ADDITIONAL OXYGEN 
ECESSARY IF FLIGHT 
OXYGEN 
NECESSARY 
20 400 ; 
ATMOSPHERIC PRESSURE IN mm.Hg. 
Ficure 4.—Relationship between altitude and atmospheric pressure. (I. C. A. N. 
seale.) 
Figure 5 shows the upward progress of man’s exploration of the 
air. 
It is necessary to emphasize the difference between rapid ascent 
from ground level, as in an airplane, and slow ascent in climbing 
