528 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



circulating stream and is the length of time required for one cycle. 

 If other conditions are the same then increases with the length 

 of the path, but q is independent of it. The longer the length of path 

 the less reat must be expended in maintaining an equal difference 

 of pressure in the two vertical columns. 



(9.) COMPARISON OF THE PRECEDING SYSTEM WITH NATURE 



The preceding- scheme was formerly a favorite one when it was 

 assumed that the anticyclones of winter are cold ; but it has become 

 obsolete since Hann has shown that this is only true for the lowest 

 calm layer and that on the other hand the higher strata of air in 

 anticyclones are very warm. 



In an area of high pressure the columns of air not only have a 

 temperature that is high for the season, but also one that is higher 

 than anywhere m the surrounding region of lower pressure. In 

 the lower portion the air flows steadily away in the direction 

 of the gradient: while the anticyclone as a whole remains stationary 

 and often for a week or more. We therefore must necessarily 

 assume that in the upper layer there is an inflow [toward the 

 anticylone]. 



Under this assumption the upper inflow can only take place 

 against the gradient. The differences of pressure do not disappear 

 with elevation, but become relatively larger in the upper level 

 provided the whole column in the area of high pressure is warmer 

 than the surrounding air. If we assume a circulation to exist 

 under these conditions then we cannot assume any heat to be con- 

 verted into work. The pressural forces do the work below the 

 lower layer, but for the inflow in the upper layer work must be 

 expended, and more than we gain in the lower layer. Hence this 

 system or cycle cannot be considered as in any manner similar to 

 that hitherto considered but must maintain itself by drawing 

 directly from a store of kinetic energy that feeds the upper inflow. 

 Like all other movements on the earth, this kinetic energy can only 

 have its ultimate source in heat : but in order to get an idea of the 

 whole process we must consider the conditions prevailing over a 

 very much larger region and for that purpose must devise some 

 scheme that shall include the conversion of heat into work. 2 



3 Compare Ekholm, Met. Zeit. 1S91, p. 366. 



