GEiOIvOGY OF LA SAIvLE COUNTY. 45 



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by cutting- them awa3% partly by piling- up against and 

 overtopping- them, and thus in time long- fing-ers of 

 g-littering- crystal streaked the country, and expanded 

 and crept on until they coalesced and covered all the 

 land for from 100 to 300 miles south of the St. Law- 

 rence and the great lakes, except an island in Wiscon- 

 sin, for there we find a tract which presents no traces 

 of g-lacial action. 



But the southern limits to which the ice extended 

 are not easily determined. When the temperature 

 rose, or for other reasons the ice beg-an to retreat, its 

 melting- must have gfiven rise to a g-reat flood, and it is 

 probable that to these we owe the g-reat beds of g-ravel 

 ever3^where found in this deposit. As the moraines 

 would be very irreg-ular„ and often several one behind 

 the other, and these connecting- one with another, 

 ponds or lakes would be formed, the waters of which 

 would be comparatively tranquil, and in these deposits 

 of clay would be laid down. The surface would be 

 left very uneven, diversified by long- low ridg-es, round- 

 ed-topped ridg-es, hills and roundish hollows to be 

 modified and chang-ed by various ag-encies, water and 

 time the chief, into the surface as we see it today. 



In central and eastern Deer Park Township w^e 

 have an almost ideal g-lacial surface, one for some rea- 

 son, but little chang-ed from what it was when the ice 

 vanished and the dry land appeared from beneath it. 

 The g-reat ridg-e, roug-hly paralleling- the Big- Vermil- 

 lion, and forming the highest land in Deer Park and 

 Farm Ridge Townships, and the great gravel beds of 

 South Ottawa are a part of the drift. 



Such, then, is the Ancient history of La Salle 

 county. First, the bed of the sea or ocean during the 

 Calciferous area; second, an area of shallow^ waters in 

 which vast beds of sand, the St. Peters, was depos- 



