I9IS.] IN AIR CIRCULATION OF THE GLOBE. 225 



uplands of northeastern Siberia, the smaller masses of inland-ice 

 within the Arctic region, and in fact any area where heat radiation 

 is large, contribute in lesser measure to draw down the upper air 

 currents and reverse their direction. It is the unhindered radiation 

 of desert areas which is responsible for the anticyclonic conditions 

 over them in the winter season. Abnormally high insolation in 

 the summer season may, however, overbalance this effect and pro- 

 duce cyclonic effects. The moisture locked up in the ice needles 

 of the cirri and related cloud forms above those areas of ocean 

 where evaporation is large, is thus returned to the earth and espe- 

 cially within the glacial anticyclones. Of this moisture a portion 

 is added to the glacier mass, but at the present time a much larger 

 portion is blown off the glacier surface into the sea and so returned 

 to its source in the waters of the ocean. 



University of Michigan, 

 Ann Arbor, 



March 12, 1915. 



