244 AN ANALYsI8, &c. 
Something similar to this occurs in the evaporation of sea- 
water. It is, after a certain extent of evaporation, but while a 
large portion of liquor still remains, that the precipitation of 
sulphate of lime takes place ; that is, after the concentration is 
sufficient to favour the mutual action of the sulphate of soda, 
or sulphate of magnesia, and muriate of lime. After this, the 
quantity diminishes as the evaporation proceeds, till at last not 
a trace of it, or of sulphate of lime, remains in the bittern, 
which consists of muriate of soda, muriate of magnesia, and 
sulphate of magnesia alone. This curious fact has not been 
particularly noticed, though it is in consequence of it that mag- 
nesia is prepared from bittern on the large scale, perfectly 
pure. 
All these facts seem scarcely to admit of any explanation, 
but on the view that has been stated, and they afford a strong 
confirmation of it. 
XI. 
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