YW 20 -Hypothetical restoration of the relative positions of areas of hgh and low 



""' ' barometric pressure, and of the prevalent direction of tJieivinds m the 



Northern Hemisphere, during the maocimum glaciatwn of North America. 



SUMMED. 



ReglofiB supposed to T:ave been glaciated. -■»► Erevalent storm-.tracJcs. ^'Prevalent winds. 



