THE AGE OF ICE. 833 



THE AGE OF ICE.* 



By II. B. NORTON. 



ANCIENT moraines, striations denoting the action of vanished 

 glaciers, the lost rocks, clay -beds evidently of glacial origin 

 all these are evidences testifying that at some period not very remote, 

 as we count geological periods, the whole northern hemisphere down 

 to the southern limit of 40 was submerged and covered with vast 

 glaciers and ice-floes. There is not a living scientist of any eminence 

 who questions the truth of this assertion. 



When we come to study the cause of these phenomena, we find 

 many perplexing and contradictory theories in the field. A favorite 

 one is that of vertical elevation. But it seems impossible to admit 

 that the circle inclosed within the parallel of 40 some 7,000 miles 

 in diameter could have been elevated to such a height as to produce 

 this remarkable result. This would be a supposition hard to recon- 

 cile with the present proportion of land and water on the surface of the 

 globe and with the phenomena of terrestrial contraction and gravita- 

 tion. Moreover, it seems evident that an extensive submergence was 

 one of the features of the glacial age. The frozen archipelago called 

 Greenland is a fair picture of what northern America and Europe must 

 have been at that time ; and, of course, this precludes the idea of ele- 

 vation. 



If it were not true that submergence and a great lowering of tem- 

 perature occurred simultaneously, we might imagine that a sort of 

 undulation in the earth's crust, alternately raising and lowering each 

 portion of it, could have caused this result. However, there is no 

 evidence that such an undulatory motion has ever occurred, and we 

 can not conceive of any force likely to produce it. 



For the past fifty years, the relation of the inclination of the earth's 

 axis to the plane of the ecliptic and its varying angle with the line of 

 the apsides, has been the subject of careful study, from the impression 

 that herein was a key to the mystery. Astronomical and geological 

 works abound with hints and suggestions of this sort, but I have never 

 yet seen any satisfactory analysis of the question. St. Pierre, Adhe- 

 mar, and others have presented theories which seem strangely illogical 

 in many of their conclusions. I have been striving to analyze the 

 question, and will present a few of my conclusions. 



The orbit of the earth is an ellipse, of which the sun occupies one 

 of the foci. The major axis, or line of the apsides, is the longest 

 diameter of the ellipse, passing through its two foci and through the 

 points of perihelion and aphelion. This line is not fixed with respect 



* Abstract of a lecture delivered before the Kansas Academy of Science. 

 vol. xv. 53 



