SOURCE OP ST. Peter's river. 309 



earthy ; it effervesces strongly in nitric acid ; its colour is a 

 light yellow. The thickness of this bed is about ten feet. 

 Below this another stratum of limestone is found, which im- 

 beds small black pebbles of quartz, and assumes, therefore, 

 in a slight degree, the characters of a pudding stone or 

 conglomerate. Its grain is more crystalline than that of 

 the preceding stratum. It i3 filled with small cavities, pro- 

 bably the result of a contraction during the consolidation 

 of the mass. Its colour varies from a bluish to a yellowish- 

 gray. This stratum is about seven feet thick. It rises but 

 four feet above the level of the water, and the only rock 

 visible under it, is another variety of limestone which dif- 

 fers from the preceding, inasmuch as its grain is much 

 finer and its texture more earthy. It is only visible for 

 four feet; the bed of the river appears to be excavated, 

 near the fort, in this stratum of limestone. Neither of 

 these limestone formations under the sandstone contain any 

 traces of organic remains. If we consider the three infe- 

 rior beds of limestone, as being modifications of the same 

 formation, as we doubtless ought to do, then we shall find 

 this bluff to be composed of three different formations ; a 

 superior one of limestone, with abundant impressions of 

 shells in one of its beds: an intermediate one of sandstone; 

 and an inferior calcareous formation, without any organic 

 remains. The latter certainly bears some resemblance to 

 the limestone found on the Wassemon, though we are un- 

 willing to pronounce upon their identity. 



The river runs upon a bed of sandy alluvion, resulting 

 from the destruction of the bluffs, but in many places the 

 rock is laid bare. These observations upon the geology of 

 the blufi" upon which the fort is erected, correspond with 

 those made at the Falls of St. Anthony, with this excep- 

 tion, that at the latter place our observations are limited 



