242 AN ANALYSIS 
of muriate of lime, but in all of them with sulphate of lime 
considerable quantities of sulphate of magnesia. In the latter, 
therefore, the muriate of lime had been converted entirely into 
sulphate of lime from the excess of sulphate of magnesia ; in 
the former, from the deficiency of the sulphate, a portion of 
the muriate of lime had remained undecomposed. 
A result somewhat similar, and which affords a very direct 
application of the same principles, is stated by Mr Horner, in 
his analysis of the salt-brine at Droitwich, compared with that 
of Cheshire *. The latter contains a little muriate of lime ; 
the former contains none. But, then, that of Droitwich con- 
tains sulphate of soda and sulphate of lime ; there is every pro- 
bability, therefore, that its muriate of lime has been converted 
into sulphate of lime by the sulphate of soda, which is in ex- 
cess; while in the Cheshire brine, as there is no sulphate of 
soda in excess, that is, none after the evaporation, a portion of 
muriate of lime remains. 
There is a singular fact stated by Dr Henry with regard to 
what is called fishery salt, prepared from salt brine, which 
seems to admit of explanation only on these views. He found 
the proportion of sulphate of lime mixed with it to be less, as it 
was collected at a later period of the evaporation ; that drawn 
from the boiler, after two hours application of the heat, con- 
tained in 100 parts 16 of sulphate of lime ; that, after 4 hours, 
contained only 11; and that, after 6 hours, only 33. Now if 
the water of this brine held sulphate of lime in solution, the 
sulphate would begin to be deposited when the quantity of 
water was diminished to that extent that it was unable to re- 
tain the whole dissolved ; and, in the progress of the evapora- 
tion, would continue to be deposited proportional to this, 
' to 
* Geological Transactions, vol. it. 
S > 
