THE PLEISTOCENE CLISERES AND COSERES. 369 



character of the advances and retreats of the ice and the number of them 

 demands a cause which shows a similarly pulsatory nature. These require- 

 ments seem to be met only by the grand sun-spot cycles, in connection with 

 their control of storm-belts and hence of rainfall and temperature. Hunt- 

 ington (1914: 567), whose views are chiefly followed here, states that he — 



"Fully accepts the idea that both deformation of the earth's crust and 

 changes in the amount of carbonic acid in the atmosphere have been and will 

 continue to be among the chief causes of cUmatic changes whose length is 

 measured in hundreds of thousands or millions of years. They do not seem, 

 however, to have been anything like so effective in producing changes meas- 

 ured in hundreds, or thousands, or even tens of thousands of years. 



"If we have reasoned correctly in our exclusion of other hypotheses, the 

 only one which seems to be competent to explain Glacial epochs and the minor 

 cycles shown by the Californiu trees is the solar hypothesis. In its caloric 

 form, it does not seem to stand the test, for present changes of climate do not 

 agree with changes in solar temperature. The cyclonic form of the hypothesis 

 seems to be free from such objections. We have already seen that there is a 

 striking agreement between the changes of solar spots and variations in storms 

 and winds. We have also seen that there is no inherent reason why the 

 activity of the sun's surface, especially in its magnetic or electrical conditions, 

 may not have varied greatly and rapidly during past eras. It is now incmn- 

 bent upon us to test the matter in one more way. We must see what would 

 happen if the present solar changes and the terrestrial phenomena were to be 

 greatly intensified." 



In applying the cyclonic hypothesis to the cycles of the glacial period, 

 Huntington's assumption is that the sun-spots and associated terrestrial 

 phenomena became more intense than at present. In their waning they did 

 not reach as low an ebb as at present, and in their waxing they became decidedly 

 more intense than to-day. The total number of storms, or rather the total 

 storminess, would be greater in times of many sim-spots than in times of few. 

 Then, according to the assiunption, the degree of storminess during a glacial 

 period would be several times as great as now. Moreover, if these conditions 

 increased in the proportion assumed, two main storm-belts would appear, in 

 Europe as well as in America. In the latter, a boreal belt of great severity 

 would he in southern Canada or a little farther north. The less severe subtrop- 

 ical belt might reach as far south as latitude 25° or 30°. Between the two 

 would lie a region of comparatively few storms. In Europe, during times of 

 many sun-spots, a belt of increased storminess extends from Scotland up into 

 Scandinavia, down into Germany and eastward. In England is found a belt of 

 deficiency which extends eastward into northern France and down the Danube 

 into Austria and into the Crimea. If the European conditions became intensi- 

 fied, there would presumably be a stormy area in the northwest and north, an 

 area of deficiency in the west and center, and again an area of excess in the 

 southeast. As to temperature, this appears to diminish in the tropics with 

 high sun-spot frequency, and, according to Huntington's assumption, would 

 be lowered still more. In the storm-belts the temperature would also be 

 somewhat lower than at present, while polar temperatures might remain much 

 the same as they are now. 



"Having indicated the conditions that would prevail according to our 

 assumption, let us now set the mechanism in motion. In America, and to a 



