Agassis at Penikcse. 



69 



Now let us go over the globe to our imagination 

 and see to what the facts load us. A snow-storm in 

 Siberia sufficient to bury these animals so that they 

 would remain frozen to this day could not have 

 been limited to Siberia and North America. The 

 laws of the distribution of moisture are such that 

 when largo masses of snow accumulate in the north 

 the inlluence will be felt in the south, so that the 

 stinw would be simultaneous over both hemispheres. 

 A great cosmic-il Winter set in over the globe which 

 extinguished life to an extent not yet determined. 

 This statement has not the value of a barometric 

 observation, but still has & value, and is not a wild 

 assumption based upon no premises. 



Within the north portion of our hemisphere th 

 glacier passage is well marked, decreasing toward 

 the tropics. The glacier also covered to a small 

 extent --^tropical regions, and produced slight 

 changes. When the copper was left uncovered by 

 the ice, then all to the south of Lake Superior had 

 disappeared, but still covered all the land to the 

 north. During this glacial Winter the annual 

 snow-fall must have been much iess in the tropical 

 regions than in the north, just as it is at the present 

 time. Now, can we determine how much or how 

 little snow there was anywhere? We concluded 

 that there were 50,000 feet over the tropics. 

 That does not imply that there were 

 10,000 feet over the tropics. How much, 

 then ? This it is desirable to ascertain, 

 so as to be able to lay down the isothermal lines for 

 that period. When Cuttyhunk and the other 

 islands of the Elizabeth group were the terminal 

 moraine of the glacier, our climate was like Baffin's 

 Bay. Fifteen degrees further south, or about the 

 latitude of South Carolina, the climate of New-En- 

 gland must have prevailed, and at the hight of K N 

 glacial period a climate similar to the present cli- 

 mate of Labrador must have prevailed at the mouth 

 of the Amazon. As soon as the ice began to wane 

 the tropics became free from ice, and the southern 

 limit of the glacier gradually retreated to the north, 

 so that a better condition of things prevailed in low 

 latitudes, while the north end of the continent was 

 still under the ice. 



Europe, as compared to America, is a mountainous 

 country ; they are a distinguishing character. The 

 European glaciers, in past as well as present 

 time, were limited by valleys more or less narrow, 

 and the glaciers all had the usual lateral and termi- 

 nal moraines \vhich are now a prominent feature of 

 those valleys. But in America we have no such nar- 

 row valleys except over narrow areas. Over the 

 broad expanse of tlio prairies and plains there are no 

 lateral moraines, the trlacier being continental in its 

 extent, tuns rendering lateral moraines out of the 

 question. 



The North American glacier was uninterrupted 

 from the Arctic Ocean to Alabama. The general 

 tendency of the ice sheet over the States bordering 

 on the Atlantic Ocean was to move N. W. to S. E. 

 All the small but marked irregularities are to be 

 accounted for by local glaciers or local obstacles in 

 the way of the continental glacier. Almost all the 

 bowlders in North America are rounded, but those 

 of Europe are mostly angular. This proves that in 

 our North American glacier we had no lateral or ter- 

 minal moraines, and that our glacier was conti- 

 nental in extent. We could only have had lateral 

 or medial moraines in North America, where the 

 mountains reached above the immensely thick sheet 

 of ice. There are few or no large bowlders south 

 of the line from Washington west. And 

 here must have been the end of the 

 glacier for a long time. Another line of 

 terminal moraines extends along the southern shore 

 of Maine and through the White Mountains. A third 

 line is along the north shore of Lake Superior. The 

 glacier must have been then over the Southern 

 States. There may have been terraces forming in 

 the valleys of the south before the ice began to melt 

 in the north. The borders of the ice no doubt pro- 

 tected the land from the erosioa of the sea. But 

 when the glacier began to wane, the bowlders 

 dropped by the glacier would be worked over by 

 the sea, and the surf would roll up a wall of water- 

 worn pebbles, which would be mixed with the 

 material brought down by the ice. The warm water 

 of the ocean would also eat into and hollow out the 

 front of the glacier. 



THE FORMATION OF GLACIERS. 



Whenever a glacier in motion meets an obstacle 

 which it cannot remove, the glacier breaks, forming 

 crevasses. Inequalities in the sides and bottom of the 

 valley in which a glacier moves are the chief causes 

 of breaks and crevasses. The round, vertical, deep 

 holes found in glaciers are formed where a stream of 

 water produced by the surface-melting of the ice 

 pours into a crevasse, thus forming a cascade which 

 bores out the ice to a great depth. 



When the cataract has penetrated through the 

 glacier it will form pot-holes in the rocky bed below. 

 These glacial pot-holes are now found in places far 

 removed from living glaciers, perched upon moun- 

 tain sides or high ridges, where no ordinary river op 

 torrent competent to produce them could hava 

 flowed. Anterior to the glacial hypothesis no reason- 

 able explanation could be given of the production 

 of these ancient pot-holes. No one has done so much 

 in tracing to their origin erratic bowlders as Prof, 

 Andrew Guyot. 



At the foot of the glacier of the Aar are 30 ter 

 mmal moraines, denoting halting-places iu the 

 retreat of the glacier. 



