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.
There is my explanation. If you can find a better, do: but remember always that it must include an answer to—“How did the stones get across the lake?”
Now, reader, we have had no abstruse science here, no long words, not even a microscope or a book: and yet we, as two plain sportsmen, have gone back, or been led back by fact and common sense, into the most awful and sublime depths, into an epos of the destruction and re-creation of a former world.