Here, again, we may anticipate future remarks. It may be thought—by some it has been roundly asserted—that these _fossils were placed in their present situations by the deluge_. Without entering into the theological question, as to the universality or partiality of the Noachian flood, although, as we shall hereafter see, there is but one opinion on that subject held by our best geologists, namely, that the deluge recorded in the Bible was simply the subsidence or submerging of so much of the earth, _and no more_, as was then inhabited by man, and that so partial and so limited was its character, and so brief its duration, compared with those vast geological epochs we have been considering, that there are no traces in nature of that event at all, _i.e._ that we have no one single fossil that can be referred to that event,—without, we repeat, entering upon the investigation of this subject, which will be done in a subsequent part of this volume, we would merely remark, in reply to this absurd notion, that the Wealden is evidently an _alluvial_, and not a _diluvial_ formation; and as these terms are so frequently used as if they were synonymous, we shall venture upon our old habit of explanation. An _alluvial_ deposit is formed by the _ordinary_, but a _diluvial_ deposit by the _extraordinary_ action of water. Thus all the straths and carses of Scotland, and our English dales or dells, (may not the remote etymology be _delta_?) are all of alluvial formation; while, as owing their origin to diluvial, or the violent action of water, we are to ascribe the heaps of rubbish, gravel, sand and boulders, that are found in firm compact together. Thus, if we take a basin of water holding a quantity of earthy matter in solution, and place it on a quiet table, and allow the earthy matter gradually to subside, that which is found at the bottom of the basin is an _alluvial_ formation, deposited by the quiet and ordinary action of water. But when, as sometimes here in Royston, a sudden and heavy rain occurs, when for a while “the windows of heaven” seem opened, and the surrounding hills pour down their rushing streams through the town, filling, as unfortunately they do on such occasions, the cellars of our neighbours in the bottom of the town, with sticks, stones, flint, gravel, bits of chalk, paper, bones, cloth, and a variety of intermingled sundries too numerous to mention, and all huddled together in wild confusion, then is formed in such ill-fated cellars a _diluvial_ deposit, occasioned by the extraordinary action of water.