226 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
the maximum, within the stratosphere, it remains constant. These 
curves show that the ceiling of the troposphere above the North 
Atlantic trade wind lies higher than 12 kilometers; in fact, it is 
found at an altitude of 16 kilometers. In the southern part of this 
country the corresponding altitude is 12.5 kilometers, in the northern 
11 kilometers, in middle Europe 10.5 kilometers, and over the part 
of the Arctic we have traversed it is only 8.5 kilometers. Our results 
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SCALE OF WIND-VELOCITY IN METERS PER SECOND 
AVERAGE WIND - VELOCITY AS A FUNCTION OF ALTITUDE 
1 — NORTH ATLANTIC TRADE-WIND REGION, LATITUDE 23° 
2 — MEAN EUROPE, LATITUDE 52° 
3 — ARCTIC SEA NORTH OF SIBERIA, LATITUDE 75° 
Fig, 3 
confirm the conclusion that the distance to the ceiling of the tropo- 
sphere decreases toward the pole. 
Direct observations of the temperature of the free air are available 
from the lowest part of the atmosphere and have been obtained by 
means of self-recording instruments lifted by kites. The instruments 
were tested in the laboratory of the Maud from time to time. The 
big kite reel for letting out and hauling in the kites was placed on 
