relative to the Earth's Surface. 31 
be infinite. Hence at the poles and at some distance from 
them, on the hypothesis of no resistances from the earth’s sur- 
face, the atmosphere cannot exist. Between the parallels of 
85° and the equator D;¢ is less and also cos 6, and consequently 
the pressure from the equator and the depression there are com- 
paratively small, It was shown in the Mathematical Monthly 
in the case of a fluid surrounding the earth five miles 
high, the fluid would recede from the poles about 28° and be 
depressed at the equator about 4000 feet. This, however, is 
upon the hypothesis that the upward expansion of the atmos- 
phere arising from a greater temperature is insensible. 
10. The preceding results, it must be remembered, are all 
upon the hypothesis that the atmosphere is not resisted in its mo- 
tions by the friction of the earth’s surface. Although these re- 
sults are much modified by the resistance of the earth’s surface, 
yet they will be of great advantage in explaining its general mo- 
tions; for as there can be no resistance until there is motion, the 
atmosphere must have a tendency to assume, in some measure, 
the same motions and figure as in the case of no resistances. 
Hence, towards the poles the general motions of the atmosphere 
must be towards the east, and in the torrid zone towards the west ; 
but as these motions, in consequence of the resistances, are small 
in comparison with those in the case of no resistances, instead of . 
the atmosphere’s receding entirely from the poles, there must be 
