38 The Tron Ores of Great Britain. | Jan., 
of coal and coally shale, that they have been associated in some way 
with the formation of the coal itself. As the coal deposits have 
been produced by a series of chemical changes in vegetable matter, 
spread over an immensity of time, so have the Iron-ore deposits, 
as we find them, been the result of sundry changes carried out upon 
the older rocks, those especially which belong to the Devonian or 
Old Red Sandstone period. The enormous deposits of Sandstones 
and Shales formed in our coal basins prove the gigantic nature 
of the denudations which have taken place, and which have pro- 
duced the sedimentary beds, as they are placed before us, striking 
records of the world’s mutations. From all that remains of those 
older rocks we know how highly ferruginous they were. The 
waters of the coal period swept around Old Red Sandstone 
rocks, and the plants from which our fossil fuel is derived 
grew upon the soil produced by the disintegration of these 
formations. 
Let us study for awhile the phenomena which, in all probability, 
took place. As we now find at the mouths of great rivers,—especially 
within the tropics,—vast masses of vegetable matter, undergoing a 
series of changes, in the process of decay, so must we suppose the 
condition of a swamp, of an estuary, a lake, or inland sea, to have 
been, when the vegetable matter of an ancient world was rotting, 
in its progress towards coal. The result of the change was the 
formation of immense quantities of carbonic acid, and this would 
be largely retained by the water holding vegetable extractive in 
solution. This water would rapidly dissolve any limestone with 
which it came in contact, and would change the peroxide of Iron in 
the rocks into a protoxide; which would be eventually dissolved, 
either as a carbonate of the protoxide of Iron, or in water holding 
an excess of carbonic acid, as a protoxide merely. LHxperiment 
shows this satisfactorily. Place recently precipitated peroxide of 
Tron in a shallow vessel with a large quantity of dead leaves and 
water ; expose this to the ordinary atmospheric changes; it will 
be found eventually, that the peroxide will be changed into a pro- 
toxide and dissolved. Under some conditions,—especially if the 
arrangement is made part of a voltaic circuit—crystals of carbonate 
of Iron will be the result ; and under others an accretion of amor- 
phous carbonate will form around small fragments of vegetable 
matter, producing indeed, in miniature, the clay-band Iron-stones 
of the coal measures. 
Now, if the water flows away from the influence of this mass of 
vegetable matter in its state of change, and if it be exposed in 
a thin sheet, to the action of the atmosphere, the Iron in solution 
will be rapidly oxidized and it will fall to the bottom of the vessel 
as peroxide of Iron. 
These results appear to teach us that the present conditions of 
