Yet, after all, I hardly think the lake was formed in this way, and suspect that it may have been dry for ages after it emerged from the primeval waves, and Snowdonia was a palm-fringed island in a tropic sea. Let us look the place over more fully.
You see the lake is nearly circular; on the side where we stand the pebbly beach is not six feet above the water, and slopes away steeply into the valley behind us, while before us it shelves gradually into the lake; forty yards out, as you know, there is not ten feet water; and then a steep bank, the edge whereof we and the big trout know well, sinks suddenly to unknown depths. On the opposite side, that flat-topped wall of rock towers up shoreless into the sky, seven hundred feet perpendicular; the deepest water of all we know is at its very foot. Right and left, two shoulders of down slope into the lake. Now turn round and look down the gorge. Remark that this pebble bank on which we stand reaches some fifty yards downward: you see the loose stones peeping out everywhere. We may fairly suppose that we stand on a dam of loose stones, a hundred feet deep.
But why loose stones? - and if so, what matter? and what wonder?
There are rocks cropping out everywhere down the hill-side.
Because if you will take up one of these stones and crack it across, you will see that it is not of the same stuff as those said rocks. Step into the next field and see. That rock is the common Snowdon slate, which we see everywhere. The two shoulders of down, right and left, are slate, too; you can see that at a glance. But the stones of the pebble bank are a close-grained, yellow-spotted rock. They are Syenite; and (you may believe me or not, as you will) they were once upon a time in the condition of a hasty pudding heated to some 800 degrees of Fahrenheit, and in that condition shoved their way up somewhere or other through these slates. But where? whence on earth did these Syenite pebbles come?
Let us walk round to the cliff on the opposite side and see. It is worth while; for even if my guess be wrong, there is good spinning with a brass minnow round the angles of the rocks.
Now see. Between the cliff-foot and the sloping down is a crack, ending in a gully; the nearer side is of slate, and the further side, the cliff itself, is - why, the whole cliff is composed of the very same stone as the pebble ridge.
Now, my good friend, how did these pebbles get three hundred yards across the lake? Hundreds of tons, some of them three feet long:
who carried them across? The old Cymry were not likely to amuse themselves by making such a breakwater up here in No-man's-land, two thousand feet above the sea: but somebody or something must have carried them; for stones do not fly, nor swim either.
Shot out of a volcano? As you seem determined to have a prodigy, it may as well be a sufficiently huge one.
Well - these stones lie altogether; and a volcano would have hardly made so compact a shot, not being in the habit of using Eley's wire cartridges. Our next hope of a solution lies in John Jones, who carried up the coracle. Hail him, and ask him what is on the top of that cliff . . . So, "Plainshe and pogshe, and another Llyn."Very good. Now, does it not strike you that this whole cliff has a remarkably smooth and plastered look, like a hare's run up an earthbank? And do you not see that it is polished thus only over the lake? that as soon as the cliff abuts on the downs right and left, it forms pinnacles, caves, broken angular boulders? Syenite usually does so in our damp climate, from the "weathering" effect of frost and rain: why has it not done so over the lake? On that part something (giants perhaps) has been scrambling up or down on a very large scale, and so rubbed off every corner which was inclined to come away, till the solid core of the rock was bared. And may not those mysterious giants have had a hand in carrying the stones across the lake? . . . Really, I am not altogether jesting. Think a while what agent could possibly have produced either one or both of these effects?
There is but one; and that, if you have been an Alpine traveller -much more if you have been a Chamois hunter - you have seen many a time (whether you knew it or not) at the very same work.
Ice? Yes; ice; Hrymir the frost-giant, and no one else. And if you will look at the facts, you will see how ice may have done it.
Our friend John Jones's report of plains and bogs and a lake above makes it quite possible that in the "Ice age" (Glacial Epoch, as the big-word-mongers call it) there was above that cliff a great neve, or snowfield, such as you have seen often in the Alps at the head of each glacier. Over the face of this cliff a glacier has crawled down from that neve, polishing the face of the rock in its descent: but the snow, having no large and deep outlet, has not slid down in a sufficient stream to reach the vale below, and form a glacier of the first order; and has therefore stopped short on the other side of the lake, as a glacier of the second order, which ends in an ice-cliff hanging high up on the mountain side, and kept from further progress by daily melting. If you have ever gone up the Mer de Glace to the Tacul, you saw a magnificent specimen of this sort on your right hand, just opposite the Tacul, in the Glacier de Trelaporte, which comes down from the Aiguille de Charmoz.
This explains our pebble-ridge. The stones which the glacier rubbed off the cliff beneath it it carried forward, slowly but surely, till they saw the light again in the face of the ice-cliff, and dropped out of it under the melting of the summer sun, to form a huge dam across the ravine; till, the "Ice age" past, a more genial climate succeeded, and neve and glacier melted away: but the "moraine" of stones did not, and remains to this day, as the dam which keeps up the waters of the lake.
