The diagram on Plate 1 confirms these views in perhaps as striking a fashion as could be imagined. The beds of coal are evidently continuous from the northern to the southern part of the field. Each layer of carbonaceous matter has been widely and generally diffused throughout the water on the bottom of which it was ultimately deposited. How it came there, whether it was altogether of extraneous origin and transported from a greater or less distance, or whether it was the result of the death and decomposition of vegetables that grew in the water and were rooted in its bed, or whether some of them grew and some of them were transported thither, or how else the carbonaceous matter came there, is a part of the subjection which I offer no opinion. I wish merely to say as the result of an experience of a good many years, confirmed by the particular instance under examination, that it appears to me that the phenomena of the lamination and stratification of beds of coal, and their interstratification and association with other stratified rocks, are explicable solely by the relation of the specific gravity of their materials to the action of moving water, and the consequent diffusion of those materials through the mass of that water.
We know that at all events the materials of the clays and sandstones were transported into that water at intervals, and it appears that in the case of the South Staffordshire coal-field, the principal and most abundant source of these materials lay to the north of the coal-field, and that these materials which were largely and frequently deposited on the north, sometimes failed to reach the more southern part of the area, while the coals were diffused equally, or at least more equally, over the whole area.
If, for instance, we were to examine the constitution of the Bottom coal, commencing on the north and following it to the south, we should learn the following facts respecting,—
First of all about the latitude of the Rising Sun at the Brown Hills, a great number of layers of carbonaceous matter were deposited until eventually enough was accumulated to form a thickness of 5 feet of coal. In whatever way this took place we cannot conceive it to have been otherwise than a long process. No one perhaps has yet formed an adequate conception of the vast length of time and great growth of vegetable life, either on the spot or in the neighbourhood, required for the formation of 5 feet of coal over an area of many square miles. There was then a gradual and successive deposition of several hundred layers of fine black mud forming more than 3 feet of dark shale. This bed is only 2} feet thick at Pelsall, a mile or two farther south, but in one place becomes 9 feet thick in consequence either of some change in the currents or of some undulation in the bottom, or some other arrestation of the suspended materials. Farther south this bed is not mentioned at all, either because it does not exist at all or because it is too thin to notice. Near the Rising Sun we find over it another series of coal layers forming the Roof coal, which in one pit is a 10-inch and in another a 13-inch coal. At Pelsall, where the
