VARIATIONS IJY CLIMATE. 8ii 



to that of such geographical conditions as the distribution of 

 land and sea, and of mountains and lowlands. 



The idea that glaciation was dependent on extreme cold has 

 been rejected by other students. J. de Charpentier recognized the 

 conditions as inconsistent. Lecoq, of Clermont, '*' affirmed a cor- 

 relation between a great solar heat, provoking a powerful evapo- 

 ration, and the formation of glaciers." Tyndall has shown that 

 the ice of the Alps " derives its origin from the heat of the sun," 

 and that if that were diminished their source of supply would 

 be cut off. The thoughts of some other writers, as Le Blanc, 

 Forbes, and Charles Martins, have been turned to showing that 

 the depression of temperature, if there was any, need not have 

 been great. 



Another group of writers, whose views have been summarized 

 by M. Millot,* of Nancy, hold that warmer climates than now pre- 

 vail were more favorable to glaciation, and gave character to the 

 Glacial period ; and that the present conditions of limited glaciation 

 are the result of the sun's cooling, whereby the supply of evapo- 

 rated moisture has fallen off. They claim that their theory fur- 

 nishes the simplest explanation of the presence of warmth-lov- 

 ing plants and animals along with evidences of ice-action. The 

 hot and the glaciated region were so close to one another that the 

 mixture easily took place. 



Prof. G. F. Becker, of the United States Geological Survey, has 

 also expressed the opinion (Popular Science Monthly, February, 

 1884) that the Glacial period was one of higher mean temperature 

 at the sea-level than the present ; that while the formation of gla- 

 ciers may have been affected by all contemporaneous changes, 

 including secular revolutions, it is not necessary to have recourse 

 to such causes ; the question is chiefly one of differences between 

 the temperatures at the sea-level and those at the level where the 

 glacier was formed. 



M. Blytt, studying the distribution of the Scandinavian fauna, 

 has found it subject to considerable local variations at short dis- 

 tance, which have relation to differences in conditions of exposure 

 and the character of the soil. He concludes that no great changes, 

 but only small variations in the extremes of temperature and 

 rainfall, are required to explain these departures. Such variations 

 may be produced, for his country, by fluctuations in the direction, 

 force, and temperature of ocean currents and winds that need in 

 no case be great ; but he believes that these variations are coinci- 

 dent with periodical changes of climate corresponding with secu- 

 lar incidents. 



The considerable effects of exposure on local climates are 



* Popular Science Monthly, August, 1885. 



