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order to form a soil one foot in depth, such as we find on 
the Lincolnshire wolds and Derbyshire hills, the carbonate 
of lime must be removed to a depth of fifty feet. Now, 
supposing each gallon of water to dissolve ten grains, then 
the 5,168,756 gallons which fall on an average on each acre 
of land in this country would dissolve about three tons. We 
must remember that out of the above quantity of water falling 
not more than one-third, probably, finds its way into the sea, 
and, consequently, on this supposition, not more than one ton 
could be carried away from each acre per annum. Now this 
is precisely the quantity which the agriculturists of some 
parts of Lincolnshire consider requisite to restore to the soil 
in the form of marl, and pretty nearly the amount which I 
have found, on examination, to disappear. Hence we may 
conclude that the formation of soils from limestone rocks 
must have required not merely a series of ages, but a 
geological epoch to accomplish. 
There is a beautiful instance of the decomposition of 
limestone exhibited to us in the mineral called rotten stone. 
This substance consists of the silicious and aluminous parts 
of the stone from which the carbonate has been removed, as 
above described. [A specimen in process of decomposition was 
here produced.] This decomposition had undoubtedly been 
produced in a sheltered position, or a substance of so friable 
a nature must soon have been reduced to ordinary soil by the 
action of rain or wind, as we find to be the case on the surface. 
In this manner is produced the carbonate of lime constantly 
dissolved from all our limestone beds and calcareous springs. 
When the water of such springs is exposed to the air, or 
made to run through mossy sedges, the carbonic acid gas 
escapes, giving rise to tufaceous deposits, or what is called 
petrified moss. When it drops from the roof of a cavern or 
runs down the side of a fissure, the gas also escapes, and we 
have beautiful stalactites and concretions which often add to 
