Origin of Rock-Salt. 
BY GEORGE W. SHRUBSOLE, F.G.8. 
Abstract of Paper read November 28rd, 1876. 
TE\ELE notion that salt was of igneous or volcanic origin has 
long since been exploded, and I propose to give some of 
the reasons that may be adduced in support of the theory that 
rock-salt has been derived from the evaporation of water. 
If we take a quantity of sea-water—say from the Mediter- 
rancan—we find that it contains the following ingredients :-— 
Carbonic Acid Chloride of Sodium 
Oxide of Iron Sulphate of Magnesia 
Carbonate of Lime Bromide of Sodium 
Sulphate of Lime ee Chloride of Potassium 
These constituents of sea-water may vary somewhat in their 
relative proportions, from local circumstances, but they will be 
found invariably present in sea-water, whether from the Atlantic 
or the Pacific Ocean, or even the Arctic seas. 
Now, if rock-salt be due to the evaporation of sea-water, we 
ought to find with the rock-salt some traces of the several bodies 
above-mentioned. 
This is what we actually do find in every salt mine in which 
there are facilities for exploration ; there occur thin bands of 
limestone, thick layers of sulphate of lime, immeuse masses of 
chloride of sodium, and last, though not the least in importance, 
c 
