OF SEA-WATER. 223 



the evaporation be decomposed by the muriate of magnesia, 

 and converted into the sulphate of magnesia ; and hence, in 

 the subsequent solvent action of the alcohol, by which it is ob- 

 tained, it must be re-formed. And, on the other hand, if sul- 

 phate of magnesia is the primary ingredient, and is obtained as 

 such by the evaporation, it remains to be explained, how it is 

 converted in the subsequent solution by the alcohol into sul- 

 phate of soda. The whole question, therefore, resolves itself 

 into the nature of the action of the alcohol, producing sul- 

 phate of soda ; and of this I perceive no other solution than 

 that which I have now to illustrate. 



The fact, however it is to be explained, or to be reconciled 

 with the doctrine of chemical attraction giving rise to combi- 

 nations or decompositions according to the strength with 

 which it is exerted, seems to be established by an induction 

 too strict and extensive to admit of doubt, that these results 

 are often determined by the force of cohesion, in such a man- 

 ner, that in principles acting on each other, those on which 

 this force operates most powerfully, in relation to the fluid 

 which is the medium of action, are combined together. So 

 much is this the case, that, as Berthollet has justly remark- 

 ed, we may, from a knowledge of the solubility of the com- 

 pounds which substances form, predict what combinations 

 will be established when they act on each other ; those always 

 combining which form the least soluble compounds. So far 

 the influence of this has been illustrated by this able chemist. 

 But it appears to me to admit of farther extension, so as to af- 

 ford a solution of the present question. 



If the force of cohesion can so far modify chemical attrac- 

 tion, as to establish among compound salts dissolved in any 

 medium, those combinations whence the least soluble com- 

 pounds are formed, we are entitled, I conceive, to conclude, 



that 



