66 Mr. H. H. Howorth on 



state his case as much as possible in his own words before I 

 proceed to criticize it. 



After expressing his agreement with those astronomers 

 who cannot connect a glacial period with any change in the 

 relations of the earth and sun, Dr. Croll goes on to say : — 

 " The important fact, however, was overlooked that although 

 the glacial epoch would not result directly from an increase 

 of eccentricity, it might nevertheless do so indirectly. 

 Although an increase of eccentricity could have no direct 

 tendency to lower the temperature and cover our country 

 with ice, yet it might bring into operation physical agents 

 which would produce this effect." He then goes on to say 

 that such a change in the eccentricity "would bring into 

 operation a host of physical agencies, the combined effect 

 of which would be to lower to a great extent the tempera- 

 ture of the hemisphere whose winters occur in aphelion, and 

 to raise to nearly as great an extent the temperature of the 

 opposite hemisphere, whose winters occur of course in peri- 

 helion." " By far the most important of all these physical 

 agencies, and the one which mainly brought about the 

 Glacial epoch," he continues, " is the Deflection of ocean 

 currents." — Climate and Time, 15. 



In his essays on Climate and Cosmology, he formulates 

 more in detail what he conceives to be the ultimate 

 result of these agencies. "When," he says, "the eccentricity 

 of the earth's orbit is at a high value, and the northern 

 winter solstice is in perihelion, agencies are brought into 

 operation which make the south-east trade winds stronger 

 than the north-east, and compel them to blow over upon the 

 northern hemisphere as far probably as the tropic of 

 Cancer. The result is that all the great equatorial currents 

 of the ocean are impelled into the northern hemisphere, 

 which thus, in consequence of the immense accumulation of 

 warm water, has its temperature raised, and snow and ice 

 to a great extent must then disappear from the arctic 



