Dr. Cr oil's Theory of Glacial and Warm Periods. 77 



seas towards the torrid zone. The trade winds, attracted 

 by the force of equatorial heat, blow incessantly in the 

 same direction, and always driving the waves before them, 

 thus accelerate the march of the oceanic current." (Reclus, 

 The Ocean, 60 and 61.) 



With this argument, except the part which brings the 

 intrusive water from the poles, I very largely agree, and it 

 seems to me that, if there were no winds at all, but evapo- 

 ration were to go on as it does now, it would inevitably cause 

 a certain circulation of water between the torrid and the 

 colder zones, and I cannot, therefore, attribute all this move- 

 ment to the wind as Dr. Croll seems disposed to do. This, 

 however, is a minor issue, and it seems clear that the winds 

 are, as Dr. Croll makes them, the really efficient factors in 

 creating ocean currents. 



So far I have no dispute with Dr. Croll. I would remark 

 that the discussion of these postulates, about which I raise 

 no question, forms a substantial part of Climate and Time,, 

 occupying at least 1 30 pages of it, and that his clear and 

 incisive criticism of Maury, Carpenter, and others, produces 

 an impression in casually reading the book that, in destroying 

 their arguments, he is establishing his main position, which 

 is not so, these polemics being really side issues, and filling 

 only a subsidiary part in the main argument. 



Having granted two of Dr. Croll's postulates, namely 

 that climate is largely dependent on the distribution of ocean 

 currents, and that these are chiefly dependent on the winds, 

 let us now come to closer quarters and see whether the 

 demands he makes upon the aerial currents are justifiable. 



Meteorology is a difficult inquiry, and full of pitfalls. 

 If we are to tread its quagmires with any confidence we 

 must do so in very elementary fashion. " If," says Mr. 

 Buchan, " atmospheric pressure were equal in all parts 

 of the earth, we should have the physical conditions of 

 a stagnant atmosphere. Such, however, is not the case. 



