IX.] CHEMISTRY OF NATURAL WATERS. 123 



case the lime is separated as carbonate, the magnesia remaining 

 in solution ; while in the other, by the action of silicate of soda 

 (or of lime), the magnesia is removed and the lime remains. 

 Hence carbonate of lime and silicates of magnesia are found 

 abundantly in nature ; while carbonate of magnesia and sili- 

 cates of lime are produced only under local and exceptional 

 conditions. It is evident that the production from the waters 

 of the early seas of beds of sepiolite, talc, serpentine, and other 

 rocks in which a magnesian silicate abounds, must, in closed 

 basins, have given rise to waters in which chloride of calcium 

 would predominate. 



[ 42 of the original paper contains descriptions and anal- 

 yses of eight waters of Class II., the solid contents of which 

 vary from 9 to 20 parts in 1,000; they rarely contain sul- 

 phates. The three given below, which may be taken as exam- 

 ples, rise from the Trenton limestone of the Ottawa and St. 

 Lawrence valleys, the first being that known as the Intermittent 

 Spring of Caledonia.] 



[ 43 gives the description and analysis of eight waters of 

 Class III. which hold from less than 5 to more than 10 parts 



