But where did the sandstone come from? You may say, it "grew" of itself in our sands and gravels; but it certainly did not "grow" on the top of a bare chalk down. The Druids must have brought the stones thither, then, from neighbouring gravel-pits. They brought them, no doubt: but not from gravel-pits. The stones are found loose on the downs on the top of the bare chalk, in places where they plainly have not been put by man. For instance, near Marlborough is a long valley in the chalk, which, for perhaps half a mile, is full of huge blocks of this sandstone, lying about on the turf. The "gray wethers" the shepherds call them. One look at them would show you that no man's hand had put them there. They look like a river of stone, if I may so speak; as if some mighty flood had rolled them along down the valley, and there left them behind as it sunk. Now, whence did they come? Many answers have been given to that question. It was supposed by many learned men that they had been brought from the sandstone mountains of Wales, like the rolled pebbles of which I spoke just now. But the answer to that was, that these great stones are not rolled: they are all squarish, more or less; their edges are often sharp and fresh, instead of being polished almost into balls, as they would have been in rolling two hundred miles along a sea- bottom, before such a tremendous current as would have been needed to carry them. Then rose a very clever guess. They must have been carried by icebergs, as much silt and stones (we know) has been carried, and have dropped, like them, to the bottom, when the icebergs melted. There is great reason in that; but we have cause now to be certain that they did not come from Wales. That they are not pieces of a rock older than the chalk, but much younger; that they were very probably formed close to where they now lie. Now--how do we know that? If you are not tired with all this close reasoning, I will tell you.--If you are, say so: but as I said at first, I want to show you what steady and sharp head-work this same geology requires, even in the nearest gravel-pit. Well, then. I do not think our gravel-pit will tell us what we want: but I know one which will.