314 J. G. Goodchild—Formation of Coal-seams. 
One can readily imagine to what different distances the leaf of an 
oak and one of some tender annual would travel if they started to- 
gether in the same current. And the difference thus exemplified 
was probably often as marked in the case of the vegetation forming 
coal. 
In consequence of this relative power of resistance to maceration, 
a further sorting out of the different vegetable bodies from each 
other must be in progress. Leaves of one kind subside within one 
zone, those of another kind within a second; spores, being resinous, 
must resist maceration longer, and therefore reach the sea-bottom 
at a zone more distant still; and so on, each kind tending to be 
sorted out into zones by themselves. 
With any disturbance of level the absolute position of any one of 
these zones must change; but their relative order must, if other 
conditions remain constant, be the same as before. With a slight 
upward movement, or with a shallowing of the water of the estuary, 
due to the seaward advance of banks of sediment, shore conditions 
advance seaward, and clay, or even coarser material, may be spread 
over the zone where under former conditions only vegetable matter 
was left. Such a process might continue until the whole of the 
depth between the sea-level and that of the old submarine peat had 
been silted up and converted into dry land. Soils might thus be 
formed, and lagoon vegetation start into existence, not far above the 
old submarine deposits of carbonaceous matter. With a slight 
depression thalassic conditions advance towards the former coast-line, 
and limestone might be built up where just before coal had been 
formed. In this case it is important to remember that the formation 
of the coal would still go on, only that the outer zone where this 
happens would be situated on the landward side of the limestone 
zone. ‘The two, however (the coal and the limestone), must be con- 
temporaneous, even though they are not deposited in exactly the 
same area. 
The amorphous parts of coal, and, indeed, much of its present 
character, owe their peculiarities to the fact that there is a constant 
reaction going on in sea-water between the sulphate of lime in 
solution and the bituminous matter carried down in suspension. 
The bituminous matter is acted upon by the sulphate of lime, and is 
thereby partly dissolved, and under particular conditions returns to 
the solid form; while the decomposing vegetable matter, in its 
turn, reacts upon the sulphate of lime, giving rise eventually to a 
precipitate of lime in the form of carbonate. Where the proportion 
of vegetable matter is in excess, beds of impure limestone result ; 
but where, as in the case of inland lakes, an unusually large per- 
centage of sulphate of lime is present, geological facts warrant us in 
concluding that the whole of the vegetable matter is dissolved. 
Hence the marked (and otherwise puzzling) absence of vegetable 
remains in Red Rocks of all kinds. Hence, also, the presence of 
bitumen in connection with saline lakes. JI am inclined to believe 
that the conversion of vegetable matter into coal is partly affected 
by the action of the sulphate of lime in sea-water. Where this sub- 
