264 



THE GEOLOGY OF MINNESOTA. 



[Springs. 



but an earlier more extensive fresh water lake for the production of the 

 upland loam. 



Fossil remains in the alluvium. At Minnesota City the remains of a 

 mastodon were taken out of the alluvium, and logs and "sea mud" are 

 found in deep wells at Dresbach, within the Mississippi valley, but at the 

 mouths of ravines descending from the uplands. 



Springs. Of the numerous copious springs in the county which issue 

 from the base of the bluffs, almost invariably at the level of one of the shaly 

 members of the St. Croix sandstone, it is only necessary to allude specifi- 

 cally to that of Mr. F. C. Bryan, which has acquired a local repute for medi- 

 cinal qualities. This is located near the centre of section 15, Rollingstone. 

 The water of this spring has been analyzed by Dr. W. A. Noyes for the 

 geological survey, and has been found to contain the following mineral in- 

 gredients. The sample here reported also contained sulpuretted hydrogen 

 gas. A second sample received later, gave no reaction for sulphuretted 

 hydrogen. 



Analysis of water from F. C. Bryan's spring, near Minnesota City, obtained in October, 1882. 

 Composition of residue from evaporation. 



Iodine and bromine, absent; phosphates, traces; borates, absent; hardness, 11.5 degrees. 



The water rises in a peat bog on the slope from the foot of the terrace 

 on which the village of Stockton is situated. This terrace rises fifty feet 

 above the spring, and contains white limy concretions and a bed of red clay 

 at the level of eighteen feet above the spring, visible at another place, which 

 probably runs through the terrace. Beneath the peat bog is a sloping bed 

 of blue clay, the result, presumably, of the denudation and redeposit from 

 the high rock bluffs that enclose the valley, of the shales of the St. Croix. 



