246 
THE GEOLOGIST. 
sand-running to modern clironometers, lever-watches, and to the 
delicate hijoux not larger than shillings, mamifactured at this day in 
the famous old city of Geneva. 
So it is in investigating any one subject of geological history. So 
mingled do we find it, so associated with other topics, as to be only 
unriddled or comprehended by very extensive and very different 
investigations. 
Look at that little rill issuing from the base of the chalk-downs, 
and trickling onwards to the green meadows. That rill has filtered 
through the chalk-rock, and few of us need a chemist to tell us 
that the crystal-looking water contains a large amount of chalky 
matter, for the e^ddence is plain in the incrustation of the bits of 
sticks and other objects in its rippling course ; but still we want the 
chemist's art to know that it is cai'bonic acid gas which enables the 
water to dissolve out that chalky matter from the solid hills, to hold 
it in solution, and that it is when the water liberates some portion 
of that gas into the atmosphere that the water becomes incapable of 
sustaining the whole of its chalky load and the encrusting sediment 
is deposited. 
So other waters and other springs issuing from other rocks, and 
in other countries, contain other materials iu solution according to 
the nature of the substance they permeate, as witness the natron- 
lakes of Egypt, the carbonate of soda springs of Carlsbad and Yichy, 
the siliceous waters of the geysers, and the ordinaiy calybeate and 
medicinal springs. 
Now for ages upon ages throughout all time since the diy land 
has peered above the sea has the percolation of water and the issuing 
of springs taken place ; from the hour when the first rain-drops fell 
unto the present have the dissolving and re-combining, the undoing 
and re-forming processes been going on. What has been taken from 
one place has been carried to another. Wliat has been taken from 
the land has been given to the sea. 
When we consider all the vast amount of clays mingled with the 
other strata in the earth's crust has been originally derived from the 
decomposition of the felspathic minerals of the old gneissic rocks, we 
perceive by comparison at once the importance of the part which the 
alkaline carbonates formed in the decomposition of the alkaliferous 
