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GEOLOGY. 223 



much, in mincralogical characters, that wliich has been 

 named cHff hmestonc by Dr. Locke in his Report on the 

 Geology of the State of Ohio, and which has been more 

 recently again described by Dr. Owen in his Report on the 

 Mineral Region of Illinois and of Iowa. Should the two 

 rocks be identical, No. 2 of the preceding section would then 

 be tlie equivalent of the Western blue limestone of these 

 geologists ; with the difference, that the two rocks are here 

 less developed than in the other localities observed by them. 



" 3. Soil, consisting of sand, gravel, and clay, mixed with 

 the disintegration of the limestone in place, and amidst 

 wliich there are erratic blocks scattered over tlie plains and 

 on the slopes on the hills, and which are traced to the sum- 

 mits of the Pilot Knob. 



*' As it is important, in geology, to determine the precise 

 limits of formations, I shall add a few words on this subject. 

 The geological formation of St. Peter's continues to show 

 itself in the river of the same name, and goes on thinning 

 out as far as Waraju Rivci (the riviere aux Liards of the 

 French), and there it disappears. Hence it passes to the 

 head-waters of Mankato River, crosses the southern part of 

 the Coteau des Prairies, and finally loses itself in the Mis- 

 souri, Sioux, and Iowa Rivers, as previously explained when 

 describing the extent of the cretaceous formation." 



Mr. Keating, tlie geologist of Long's second expedition, 

 gives tlie following description of a portion of country east 

 of the river : — 



" On the banks of this stream" (the Wassemon, one of the 

 upper branches of the Pectanon, as called by Long, or Peck- 

 tonica, as called by the Indians) " we observed the lime- 

 stone in place, forming cliffs of about filly feet in height. 

 The rock is in very distinct horizontal stratification ; its 

 structure is in many parts crystalline, or perhaps it may 



