130 Notices of Memoirs — Ice Age and Antarctic Research. 



explored by him. Sir Ernest Shackleton said: "Some time in the 

 future these lands will be of use to humanity." ^ 



This impressive and conclusive evidence is corroborated by the 

 greater and still more impressive evidences of the comparatively 

 recent uncovering of temperate land areas,^ and the progressive 

 retreat of the snow-line to higher elevations in temperate and 

 tropical latitudes and towards the poles at sea-level, being far greater 

 in Arctic than in Antarctic regions. We are therefore confronted 

 with the conclusions — 



1. That the disappearance of the Ice Age is an active present 

 process and must be accounted for by activities and energies now at 

 work, and that the use of assumptions and hypotheses is not 

 permissible. 



2. That the rates and lines of retreat are and have been determined 

 by exposure to solar energy and the temperatures established 

 thereby ; and by the difference in the specific heat of the land and 

 water hemispheres. 



3. That the lines of the disappearance of ice are not conformable 

 with those of its deposition, and mark a distinctly different exposure 

 and climatic control from that which prevailed prior to the 

 culmination of the Ice Age. 



4. This retreat also marks a rise in mean surface temperature 

 along these new lines, manifestly due to recently inaugurated 

 exposure to solar radiation and also the inauguration of the trapping 

 of heat derived from such exposure ; which process is cumulative 

 and has a maximum not yet reached. 



The researches under the direction of Captain Scott and Sir Ernest 

 Shackleton have therefore very rigidly conditioned any inquiry as to 

 the causes of glacial accumulation and retreat. These conditions 

 are correctivk and directive — corrective, in that they have entirely 

 removed any doubts as to the alternate glaciation of the poles under 

 the alternate occurrence of aphelion and perihelion polar winters by 

 the precession of the equinoxes, as advanced by Croll ; directive, in 

 that they have imposed an appeal to energies now active as causes of 

 retreat, and divested the problem of resorts to the fascinating but 

 dangerous uses of suppositions and hypotheses. 



They have, moreover, pointed out with unerring accuracy the 

 vital conclusion that the same energies which have but recently 

 converted the glacial lake beds of Canada into the most productive 

 grain fields of the world will in time convert the tundras of to-day 

 into the grain fields of to-morrow. ^ - 



^ Address to the Commonwealth Club, San Francisco, Calif., November 7, 

 1916. 



- Slight fluctuations in the retreat of the small residual glaciers in temperate 

 latitudes are noted in the reports of the Commission on Glaciers of the 

 International Geological Congress by Professor Harry Fielding Eeid. But 

 the great measures of the progressiveness of glacial retreat are in the past 

 disappearance of the Pleistocene ice-fields of temperate latitudes and the 

 present retreat in the Antarctic and Arctic regions. 



' See also Compte Rendu du Xleme Congres Geologique International, 

 Stockholm, 1910, p. 1102. 



