280 GEOLOGY. 



great changes in the disposition of its loose materials. 

 The third epoch was the Terrace period. Now there 

 was gradual elevation of the land till it reached its pres- 

 ent level, the waters all the time acting upon the mate- 

 rials laid down in the Champlain epoch, especially in the 

 rivers. This action made terracdt skirting rivers, lakes, 

 bays, etc., which fact has given the epoch its name. It 

 is a transition epoch, for it is separated by no well-de- 

 fined line from the succeeding age, the age of Man. 



The same division can be made essentially in Europe. 

 I will speak of each epoch separately. 



391. Glacial Epoch. In this epoch, the summer heat, 

 which prevailed over the now temperate regions during 

 the Tertiary age, was succeeded by arctic cold. The cap 

 of ice which now covers each pole extended then far to- 

 ward the equator. In this country, all New England, 

 New York, and other parts in the same latitudes were 

 covered by it. In Europe, those parts that have now 

 glaciers far up in the valleys of their mountains were 

 then covered with them as Greenland is now. Ice reign- 

 ed then all over Great Britain. The change in tempera- 

 ture was a gradual one, produced, as it is supposed, by 

 the elevation of all the land in a body at the north to 

 a much higher level than it has at the present time. 

 The glaciers of that period moved down in the valleys 

 as the glaciers of the present time do. One moved down 

 the valley of the Connecticut, another down the valley 

 of the Hudson, etc. They produced results similar to 

 those which are produced by glaciers at the present day, 

 described in 190. Many of them were thicker and lar- 

 ger than present glaciers, and produced, therefore, larger 

 results. There were then, as now, icebergs wherever 

 the glaciers reached to water instead of terminating on 

 land. 



392. Drift. As a consequence of the action of glaciers 

 and icebergs in the Glacial period, there is scattered over 

 all the northern parts of America, Europe, and Asia what 



