WoeiTcof — CrolVs Hypotheses of Geological Climates. 173 



The greater part of the snow which lies on the ground m 

 Northeast Siberia falls in autumn, when the air contains vapor 

 of water enough to allow of a great precipitation ; the snow- 

 fall of winter contributes very little. Now what would a 

 further lowering of the temperature of winter produce ? A 

 further diminution of the quantity of the falling snow. It 

 would thus even be melted sooner in the warmer, summer 

 months. The cold of winter in the interior of large continents, 

 of high latitudes, especially that of Asia, has a very important 

 indirect result : the high pressure and the resulting cold and 

 dry winds of winter, especially toward the south and east of 

 the region of high pressure. These winds, the cold, dry win- 

 ter monsoon winds of Eastern Asia are unfavorable to snow- 

 fall ; so that in the interior of Transbaikalia with a mean 

 winter temperature of —13° F. and below, there is generally 

 too little snow for sleighing, and if the quantity of snow falling 

 near the mouth of the Amoor is larger, it falls almost entirely 

 in October and November, that is, at the beginning of the cold 

 season, and in the few days with east winds, which bring warmer 

 and moister air from the seas, not yet frozen in these months. 

 A lower winter temperature and an earlier beginning of the 

 cold in the interior of Asia would increase the pressure toward 

 the north and the interior of the continent, and thus give a 

 greater impetus, strength and duration to the dry northwest 

 winds, which is thus less favorable to snowfall and an accumu- 

 lation of snow. 



In summer the winds in Eastern Asia are southeast, and 

 carry clouds and rain far inland. Owing to the high tempera- 

 ture of the continent and of the surrounding seas, rain and not 

 snow, falls on great heights, such as that of 15,000 feet in the 

 mountains of Kansu in Western China (37° N.) Thus the 

 heavy rains of summer are not favorable to an accumulation of 

 snow, but on the contrary assist in melting the small quantity 

 which may remain on the ground. 



During a high excentricity and winter in aphelion the tem- 

 perature must be higher in summer and this would cause a 

 lower pressure on the plateaus in the interior of Asia. This 

 would increase the difference of pressure between the ocean 

 and the interior of the continent and give a greater impetus to 

 the moist winds and bring larger quantities of rain at least 

 where the air is ascending. Such conditions would then favor 

 the melting of snow at a greater height than now. At present, 

 in Northern Thibet, for example, permanent snow is found at 

 17,000 feet ; then it would disappear perhaps even from a 

 height of 20,000 feet. 



The climatic conditions of Asia show us, so to say, the nor- 

 mal reactions between continent and ocean. Everywhere there 



