Page:The South Staffordshire Coalfield - Joseph Beete Jukes - 1859.djvu/222

204 mere phenomenon of the Flying reed, and embrace that of the expansion of the whole Coal-measure series to the north, and the splitting up and separation of the coals in that direction. I must confess the idea of those coals being formed only at or above the surface of the water, while all the beds between the coals were deposited below the surface of the water, becomes one that I find it impossible to entertain. It will scarcely be worth while to go into an elaborate argument on this part of the subject, since I think an inspection of the diagram on Plate 1, p. 25, will be of itself sufficient.

It has been formerly pointed out from facts observed in this district, which are in perfect harmony with the well-known facts elsewhere, that single beds of stratified rocks have generally an area greater, and a thickness less, in proportion to the fineness of the materials of which they are composed. When the- materials are coarse they are usually heaped together co as to form a thick bed in one place, which gets rapidly thinner in different directions, and often soon ends altogether. When several beds of the same kind of substance rest on each other, so as to form a group or set of beds, the above statement is almost equally true. When, on the other hand, the materials of which a single bed, or any set of beds, is composed are of very fine grain, those materials are generally equally diffused over a very wide area, changes in thickness are rare and occur very gradually, and the bed or set of beds where it comes to an end does so very gradually, and sometimes almost insensibly. When beds of coarse material are interstratified with beds of fine, the changes that take place in the grouping of the beds is often the result, solely or chiefly, of the changes in the coarser members, their sudden terminations, or their sudden thickenings and thinnings; the apparent changes in the thickness of the finer beds is due to single continuous beds or single continuous layers or laminæ being either separated by the partial interposition, or brought together by the partial absence, of the coarser over certain spaces. Now, it is clear that this law of the area of beds and laminæ being greater and their thickness less, in proportion to their fineness of grain, means nothing else than that the materials were spread over a larger space in consequence of their comparatively light specific gravity, or at least of their being more easily and therefore more widely transported by water, and being more generally diffused through it before finally coming to rest at the bottom. It was pointed out before too, that beds of coal so far from forming any exception to this general rule, are its most marked example at the one extreme, while coarse sandstones and conglomerates form the most striking example at the other.

In no Coal-measures that I ever examined in any part of the world, either in the British Islands. Newfoundland, or Australia could I ever detect anything but the most perfect conformity and blending between beds of coal and the stratified aqueous rocks in which they lay, the whole apparently forming one series of deposits produced by one agent acting in one way.