Febeuaey 14, 1919] 



SCIENCE 



161 



clone, a subject that still requires further in- 

 vestigation, one of its chief features is deep 

 winds from liigher latitudes in its eastern por- 

 tions. These winds, because of the rotation 

 of the earth, necessarily lose more or less of 

 such west-to-east velocity as they previously 



surface up to near the base of the stratosphere. 

 This increase of pressure in turn forces the 

 loaded air to descend, wanning on the way 

 according to the adiabatic gradient of 1° C. 

 per 103 meters (if free from clouds) and 

 thereby raising the temperature at all levels 



-6(r -55- -50' -45- -40- .-35- -30' -25- -20- -IS" -lO" -5' Or 5" lO' 15' 

 TEMPERATURE 



Fig. 3. Relation of winter temperatures to baro metric pressure. 



may have had. They lag in the midst of the 

 general circulation. Hence the prevailing 

 westerlies flow over them as over a mountain 

 barrier. But by this overflow the westerlies 

 produce at least three different effects : (a) 

 They load the atmosphere over which they 

 pass, and thus increase the pressure from the 



through which it passes, (ft) They bodily lift 

 tlie stratosphere whose pressure tliereupon 

 tends to decrease at every level in proportion 

 to the initial pressure at that level — a result 

 that would produce dynamically an equal drop 

 in temperature throughout the stratosphere, 

 (c) By their own dynamical cooling, and at 



