THE OBLIQUITY OF THE ECLIPTIC. 107 



sive view of the glacial epoch and all its attendant phenomena than is 

 usually found in any one or many of the text-books, or papers, reports, 

 and lectures, upon the subject. Of all the geological changes and revo- 

 lutions in the earth, out of which has been evolved the present world of 

 animal and plant life, the glacial epoch is certainly the most unique, 

 and full of interest to the scientific observer. What caused the glacial 

 cold has been the constant inquiry, but never answered, ever since it 

 was first proposed some forty or fifty years ago. Why should corals 

 live in security in Spitzbergen, and the red-woods of California and the 

 cypress-trees of the southern United States flourish in the north of 

 Greenland as late as tertiary times, where now are the almost constant 

 rigors of an Arctic winter? What caused the recession of the glaciers, 

 and why may we not have a recurrence of them ? What influence, if 

 any, did the polar ice- caps exert upon the ocean-level and ocean- 

 currents'? Were the ice-caps equal in magnitude; and if not, what 

 effects, if any, followed such inequality, from the attraction of the sun 

 and moon upon the mass of the earth, thus abnormally distributed? 

 These questions and kindred ones must be considered before we are 

 prepared to comprehend the full significance and consequence of the 

 glacial epoch. 



" It seems incredible that a great ice-cap, several thousand feet 

 thick, should accumulate, and remain throughout the summer, in the 

 temperate zones, if the ecliptic were as oblique in those times as now. 

 The sun on the 21st of June would be nearly perpendicular to the 

 southern limit of the glacier, and would certainly exert a powerful 

 influence in preventing its formation or accumulation south of the 

 northern limits of Minnesota. On the other hand, bower, if we place 

 the sun continuously perpendicular at the equator, the temperate zone 

 would be characterized by continual spring weather similar to that 

 occurring in A pril at the present time. In such case we may readily 

 conclude that the precipitations of snow might be greater than that 

 melted by the slanting rays of the vernal sun, and hence might continue 

 to increase, and form a glacier of ice. 



"It appears that the polar ice-caps in glacial times extended as far 

 as the 30th parallel of latitude from either pole ; in some places the 

 north glacier in the United States extended as far south as the 39th 

 and even to the 38th parallel ; and in South America Professor Agassiz 

 found evidences of glacial action as far north as the 37th parallel. Mr. 

 D. Forbes informed Mr. Darwin that he had seen ice-worn rocks and 

 scratched stones at about 12,000 feet height, between 13° and 30° south 

 latitude. There seems also some evidence of glacial action in the south- 

 east corner of Australia. In northern Asia, owing to the great extent 

 of land surface, it may be reasonably inferred that the southern limit of 

 the glacier was much beyond that in the United States. The mountain 

 ranges in both hemispheres doubtless were covered with a much greater 

 accumulation of snow and ice than they are at present, extending at 

 that time to within the tropics, and perhaps to the equator. But from 

 the whole record, we may safely assume 40° as the average limit of 

 each, the southern being the more widely extended of the two. There 

 are many evidences that these ice-sheets were not confined to the land, 

 but that they crossed gulfs, seas, and even oceans. Professor H. Carvill 



