174 Proceedings of Royal Society of Edinburgh. [sess. 
could not be removed in solution, and which I subsequently 
identified as silica. 
This then I consider is a clearly proved fact, that magnesia 
and silica are removed in solution from mineral magnesium silicates 
by the action of water containing sodium chloride. A considerable 
amount therefore of the magnesia present in the ocean, must, I 
believe, have been brought into a state of solution by the chemical 
action of the sea- water on the abundant magnesium silicate minerals 
of the earth’s crust. 
I have strengthened my belief in this matter also by experiment. 
A piece of pure steatite was permitted to remain completely im- 
mersed in water, brought from the North Sea, for several months. 
It was weighed before being placed in the liquid, and after being 
carefully dried, weighed after its removal. It was found to have 
decreased slightly in weight; its second weight was less than its 
first, not much it is true, but still decidedly less. 
( 1 ) W eight of pure steatite before being placed 
in sea-water, . . . . .12*421 grammes. 
(2) Weight of (1) after removal from the sea- 
water in which it had lain for several 
months, ...... 12*416 „ 
Difference, showing amount of magnesia and 
silica removed in solution by the sea- 
water, ...... 0*005 „ 
In an impure magnesium silicate decomposition by sea-water goes 
on of course more rapidly. 
It is, I consider, unnecessary to bring forward more evidence to 
prove that pure magnesium silicates are decomposed by sea-water ; 
but this question has yet to be answered, How were the magnesium 
and silica removed ? In what conditions ? What chemical changes 
took place ? I am daring enough to attempt to answer this 
question, and although I may be wrong, I am unable to find at 
present any other possible explanation than the one I now give. 
It seems to me that the magnesium combined with the chlorine of 
the common salt, and that the discarded sodium united with a por- 
tion of the silica freed from the magnesium, the other part of the 
