161 



where the strata become crystalline, the mineral waters are no longer 

 met with. 



In this eastern region the saline waters issuing from the same 

 limestones as the springs just described, are generally more dilute 

 than those of the west, and although, like them, containing but very 

 little carbonic acid, deposit by boiling or evaporation large quantities 

 of earthy salts, chiefly carbonate of magnesia. Many of these waters 

 contain earthy chlorides, and are analogous to the Piillna spring, 

 while others, still strongly saline, are alkaline from the presence of 

 carbonate of soda. The solubility of the carbonate of magnesia in 

 these waters is explained by the observations of H. Rose, who has 

 shown that the partial precipitate produced in the cold, by carbonate 

 of soda in a solution of a neutral salt of magnesia, is redissolved by an 

 excess either of the magnesian salt or the alkaline carbonate, and is 

 only thrown down from these solutions by heat. Longchamp has 

 further remarked, that the precipitation by heat is rendered less com- 

 plete in proportion as the carbonate, sulphate or hydrochlorate of the 

 alkali is in excess, and that the precipitate at first formed under these 

 circumstances is redissolved on cooling. I have verified this last 

 observation in the case of these natural waters, from which the mag- 

 nesian carbonate is only separated, when they are evaporated to a 

 small volume. When thus evaporated, even at a very gentle heat, 

 these mineral waters yield large quantities of granular carbonate of 

 magnesia, often nearly pure. 



With these facts in view, it is very easy to trace a relation between 

 the saline waters, containing carbonate of magnesia, and another class 

 of springs in which the predominant element is carbonate of soda, 

 with small quantities of common salt, borax and earthy carbonates. 

 These waters, although wanting in the west, are very abundant in 

 eastern Canada, and rise from the same formations as the saline 

 springs, but are most abundant in the argillaceous strata immediately 

 overlying the lower limestones, which appear to be the source of the 

 salines. These alkaline waters probably owe their origin to the slow 

 decomposition of felspathic debris in presence of earthy carbonates. 

 By the mingling of these solutions of carbonate of soda with the 

 bitterns of the limestones, the carbonate of lime would be precipitated, 

 except so far as an excess of carbonic acid were present, while car- 



