1 88 T. C. CHAM BERLIN 



nous life developed into rather ample chains of dependent life, some 

 of the chains being based on land plants, and some on sea plants, 

 the former rising to the grades of hares, ptarmigan, reindeer, and 

 the foxes and other animals that prey on these, while the latter 

 rise into the much more complex and ample chains of sea Hfe, ran- 

 ging up to walruses, whales and Eskimos. These are pretty well 

 scattered around the Circle but on the west side of Greenland in a 

 land-gitt region there are two limited areas of exceptional mildness 

 of climate and remarkable abundance of life, constituting veri- 

 table climatic oases in the frigid desert of the north. These have a 

 very significant story to tell which will be taken up in a later article. 

 Let us inquire whether theoretical considerations tally with the 

 array of facts brought out by the foregoing comparisons. 



THEORETICAL CONSIDERATIONS 



To secure brevity, these may be put in the form of affirmative 

 propositions. 



I. Water surfaces reflect more insolation than land surfaces. — The 

 surface of water is normally smooth and close-grained, so that it has 

 much the effect of a polished surface and is highly reflective. In the 

 high latitudes the angle of incidence of the solar rays is always low 

 and for the larger part very low, and this gives a high percentage of 

 total reflection from the water surfaces. The surface of the land, 

 on the other hand, is rough and granular, so that it is highly absorp- 

 tive; it closely approaches the theoretical "black body." The 

 vegetal clothing of the land is also rather highly absorptive, due to 

 a selective adaptation to meet the absorptive requirements of 

 vegetal life. The combined effect is to render the land surface much 

 more highly absorbant of solar rays than the sea surface. 

 . 2. Water surfaces lose more heat hy evaporation than land surfaces. 

 — The annual evaporation from sea surfaces is greater than that 

 from the land surface, even though it is a few degrees lower in mean 

 temperature. As a result less of the heat absorbed by the land 

 takes the latent form and ceases thereby to have a heating effect. 

 These differences are qualified, however, both pro and con, by the 

 formation of surfaces of ice and snow on both land and sea. These 

 surfaces are highly reflective and only slightly evaporative. 



