264 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
the warmth of summer. Both conditions are probably effective in 
increasing the temperature difference. The most important deduc- 
tion to be made from the results is that the mountains are not cold 
because the upper air is cooled by convection, but they are cooled by 
their radiation to space. 
The mean values of the gradients up to 15 kilometers, found from 
registering balloon ascents at ten European stations and for St. Louis, 
Mo., are given in the table: 
Gradient. Gradient. 
Height. > Height. = 
Europe. | St. Louis. Europe. | St. Louis. 
Km Km 
0-1 3.6 Soll 8-0 6.8 7.4 
1-2 4.3 583 9-10 5.0 6.7 
2-3 5.2 4.7 10-11 3.0 5.5 
3-4 5.8 5.2 11-12 0.7 2.9 
4-5 6.3 5.9 12-13 —0.8 1.4 
5-6 6.8 GRY 13-14 0.0 0.6 
6-7 Ub? 7.8 14-15 —0.1 —0.9 
7-8 7.4 8.7 
The maximum value occurs in the layer 7 to 8 kilometers, and its 
magnitude indicates that the effect of radiation is to leave practically 
unchanged the natural gradient in air in vertical motion. Gold 
showed that in the upper layers absorption exceeded radiation and 
in the lower layers radiation exceeded absorption, and both processes 
would diminish the temperature gradient. At an intermediate stage 
absorption and radiation must balance, and the results indicate that 
this is the case at a height of 7 to 8 kilometers. The temperature at 
different heights up to 15 kilometers shows practically no variation 
for the ten European stations, except in the case of Pavlovsk, where 
the temperature is uniformly lower up to 10 kilometers and higher 
above 10 kilometers than at the other stations. The difference of 
temperature between Strassburg and Pavlovsk, taken to represent 
latitude 50° and latitude 60°, respectively, is sufficient to produce a 
gradient of pressure at a height of 10 kilometers which would corre- 
spond to a steady west wind of about 24 m. p. s. (54 miles per hour). 
The difference between Strassburg and St. Louis (representing lati- 
tude 39°) would at the same height correspond to a steady west wind 
of 15 m. p. s. in intermediate latitudes. The observations are not 
sufficiently extensive to warrant much stress being laid on the absolute 
values of these velocities, but it is of interest to note that the approxi- 
mate ratio of the west winds in latitudes 45°, 55°, deduced from Ober- 
beck’s solution by a purely theoretical treatment of the problem of 
the general circulation, is 16/21 for the upper strata, a result in toler- 
able agreement with the ratio of 15/24 deduced from the temperature 
observations. 
