PERMIAN GLACIATION 579 



as we have already seen, would tend toward glaeiation. One would be a 

 pronounced increase of snowfall on the mountains and the other the 

 general lowering of the temperature because of the great amount of heat 

 carried upward by the storms. Conditions would apparently resemble 

 those which would prevail in New Zealand if the temperature should 

 become somewhat lower than now and the snowy precipitation on the 

 mountahis should increase. At the present time the glaciers of New Zea- 

 land descend almost to sealevel. For instance, the Aorangi glaciers push 

 their way down into the forests as low as 400 feet above the sea. With an 

 increase in snowfall and a slight lowering of temperature, these glaciers 

 would descend still lower. They would coalesce with one another and 

 might spread out over a considerable area of land at approximately sea- 

 level. In order to get such conditions during the Permian era, the only 

 requirements seem to be that the phenomena which now prevail at times 

 of maximum sun-spots should become even more intensified than we have 

 assumed to be the case in Pleistocene times. 



THE EFFECT OF PRECIPITATION ON TEMPERATURE 



At this point it is necessary to consider two points which may be raised 

 as objections to the cyclonic hypothesis. One of these is the liberation 

 of latent heat by reason of increased precipitation, which might cause the 

 temperature to be raised instead of lowered in the subtropical storm 

 belts. The other is the blanketing effect of an atmosphere full of moisture 

 and clouds. The effect of the first can easily be determined. The heat re- 

 quired for the evaporation of a given amount of water is exactly equal to 

 the heat liberated by the condensation of the vapor thus produced. If 

 the circulation of the air in subtropical latitudes were much more rapid 

 in Permian times than at present, a constant supply of unsaturated air 

 would be brought to the equatorial areas of chief evaporation. This air 

 would take up moisture and in so doing would lose heat. It would then 

 be carried upward, partly in equatorial regions and still more in the sub- 

 tropical storm belt. At an altitude of a few thousand feet condensation 

 would take place and the latent heat would be liberated. This would 

 warm the air, and the amount of warming would be essentially the same 

 as the amount of cooling which took place when the moisture was first 

 evaporated. The effect on the earth's surface, however, would be to pro- 

 duce cooling, for the heat would be taken away from the air at low levels 

 and would be released at the high level of the clouds. Moreover, when 

 air is warmed by the condensation of moisture and the formation of 

 clouds, it of course expands, and hence tends to rise more rapidly than 

 before. Therefore its heat is carried to levels above those of the clouds, 



