RECEDING OF THE ICE. 177 



melting process became more and more rapid, larger masses 

 of water were produced and larger freshets, larger inundations 

 were produced, and the loose materials which were minute 

 enough to be carried by the current were moved forward, or 

 southward. And in the Southern States we find that we have 

 loose materials similar to those at the North, but which have 

 lost their glacial imprint, and are scattered in the way in which 

 floods would scatter them, where the materials are sorted, as it 

 were, according to weight, as they would be sorted in a current. 

 You find in the lower part of the valley of the Mississippi such 

 accumulations. You find them in the estuaries of all our 

 rivers, and you find that all our great streams have terraces 

 upon their sides which are never reached in the heaviest fresh- 

 ets in our days. The climatic conditions of our continent are 

 such that at no time do our rivers swell to the height of their 

 highest terraces. Whence did the water come in those days ? 

 It must have come from some source. It certainly was not the 

 consequence of atmospheric condensation, since for ages the 

 condensations of the atmosphere have never reached that level. 

 But they may have been the result of the rapid melting of the 

 northern glaciers. When, for instance, the sheet of ice which 

 once extended to the Gulf of Mexico had melted away to the 

 latitude of Washington, you see at once that the Mississippi 

 valley would be flooded by an amount of water far greater than 

 that which flows through it now, and thus the terraces upon its 

 sides which form the bank at Natchez might then have been 

 accumulated. When that sheet of ice had melted to the lati- 

 tude of the White Mountains, then the Connecticut Valley would 

 be swelled to the height of its highest terraces, while it could 

 not be flooded, under its present conditions, to that height. 

 When that ice melted further away to its Arctic limits at the 

 present time, the equilibrium which prevails now was estab- 

 lished, and from that time forward we had no other modifying 

 influences operating upon these loose materials than those of 

 the regular atmospheric agencies, as meteorology makes them 

 known to us now. So that you see that all these various and 

 complicated facts, which find no explanation in the idea of cur- 

 rents or freshets, are explained in a natural connection ; and 

 that adds great weight, in my estimation, to the theory which 



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