89 



It may be said that we find all these salts in sea water ; true, 

 but the proportion is vastly different; in the solid precipitate 

 from sea water there are 75 parts chloride of sodium, 9 chloride 

 magnesium, 3 chloride potassium, 5 sulphate of magnesia, and 

 only 4 sulphate of lime : while in the Bath waters there are 80 

 parts sulphate of lime to 12 chloride of sodium, and 14 chloride 

 of magnesium, with the addition of Sulphate of Soda, which i» 

 absent in sea water. 



Whence, then, come these salts'? The sulphate of lime is 

 generally found in the New Eed Marls, i.e , above the Coal 

 measures. It is found in a fibrous form, with sulphate of strontia, 

 at Aust Passage, on the Severn ; the chloride of sodium is also 

 found generally in England in the same formation, though not 

 exclusively ; the chloride of magnesium does not exist naturally 

 as such in the form of a rock, but carbonate of magnesia is 

 plentiful in the form of Magnesian Limestone and Conglomerates, 

 such as are found on Durdham Downs. It appears that water, 

 such as rain water, impregnated with carbonic acid gas, dissolves 

 carbonate of magnesia, forming bi-carbonate of magnesia, as is 

 shown by a new process for obtaining carbonate of soda from 

 salt. This, brought into contact with chloride of sodium, decom- 

 poses it, and chloride of magnesium and bi-carbonate of soda are 

 the result. Thus, the presence of the chloride of magnesium 

 would appear to be a consequent of carbonate of magnesium, 

 which is only found in the rocks of the Poikilitic system. 



This view is confirmed by the fact that analysis shows that 

 carbonate of soda exists in these waters, in the proportion to the 

 chloride of magnesium of their respective chemical equivalents, 

 viz., to 7'142 chloride of magnesium, 5-760 carbonate of soda; 

 this is noteworthy. 



Thus, then, we find that these four principal salts are derived 

 from rocks that belong to the formation lying above the Carboni- 

 ferous rocks. 



It is evident that as the Bath springs rise above the surface of 



