192 



At a former meeting of this Society, I described the chemical 

 changes, through which the sulphate of soda found on the tribu- 

 taries of the Missouri River, becomes converted into bicarbonate 

 of soda, after its solution mixes with the waters of the Mississippi, 

 which are charged with organic matter in a state of change. 

 The fact of principal importance in connection with what is to 

 follow is, the flow of so large a body of water containing in solu- 

 tion bicarbonate of soda, into the ocean, which contains dissolved 

 several lime and magnesian salts. 



As this might be considered an unusual occurrence, favored 

 by certain local causes, the object of the present paper is to 

 point out other instances, where, from similar changes, the water 

 flowing below the surface, and constituting the drainage of the 

 country, is largely composed of a solution of the bicarbonate of 

 soda. 



The subterranean waters of the peninsula of Boston, have at 

 the depth of about 14,0 feet, a remarkable uniformity of compo- 

 sition, and the flow towards the shore line is abundant. Like the 

 water of the lower Mississippi, they are turbid, holding in sus- 

 pension finely divided carbonate of lime and iron, and hydrate 

 of silicic acid ; affording, when greatly heated, a precipitation 

 of hydrated carbonate of lime, due to the instantaneous decom- 

 position of sulphate of lime, by a solution of bicarbonate of soda 

 present. The latter salt is in these cases always in excess; so 

 that the whole mass of the drainage, at about the same level, has 

 a marked alkalinity, and belongs to the class of alkaline waters. 



Numerous observations have shown that this water is covered 

 by a compact marl-earth, which has so large a proportion of clay 

 that it effectually divides the upper drainage from the lower, or 

 alkaline water, which, from its depth below the surface, can 

 enter the harbor water only at some distance from the shore. 

 When attempts have been made by continuous pumping for 

 many days, to exhaust the supply, or overcome the flow of the 

 water at one point, the wells or borings at contiguous points have 

 shown a reduction of volume in the water; but a reflux of the 

 ocean water through the same channels has been effected only 

 where, after several days, a very large volume of water had been 

 pumped from one opening. This fact establishes our knowl- 

 edge of a continuous flow of alkaline water towards the sea 



