44 DAVIS : FISH- REMAINS IN THE COAL-MEASURES. 
whose remains form the coal probably having grown on the 
site which it now occupies. We shall find, when the fossils 
are taken into consideration, that they also afford evidence 
largely tending to substantiate this theory. 
Beverting to the general section already given, it will be 
seen that the varying alternations of shale, sandstone, and 
coal are repeated, with modifications according to the longer 
or shorter periods during which the land was submerged or 
elevated above the water — the shales indicating the period of 
greatest submergence ; the sandstones being deposited above 
the shales, as we may naturally infer, near the shore, as the 
land was rising ; and the coals being aggregated from the 
shedding of the spores or decay of the plants, in the situation 
where they grew, when the land was quite above water. 
Whatever may have been the circumstances under which 
the Lower Coal Measures were formed, there can be little doubt 
that those higher in the series, of which we are now speaking, 
were accumulated in a large fresh-water lake, to which the 
sea may, during periods of more than usual depression, have 
had access. That marine conditions did prevail during the 
deposition of any part of the Middle Coal Measures in the 
West Riding, is, however, not a necessary supposition. This 
conclusion has been arrived at after a careful consideration of 
the general circumstances attending their deposition, but 
more especially, from the occurrence throughout the series of 
the fossil remains of fishes and mollusca of fresh-water types, 
and the number of impressions, most perfectly preserved, of 
the delicate fronds of ferns and other equally fragile plants. 
I do not intend to enter into any description of the deposition 
of the latter ; but it does appear incompatible with our 
ordinary ideas of the result which might be expected, to 
suppose that the vegetable remains found so frequently in the 
shales, could be carried by rivers into the sea, subjected to 
some extent to the action of the waves or tides, and still sink 
