Page:A book of the west; being an introduction to Devon and Cornwall.djvu/91

Rh Now the rain that falls on the chalk downs infiltrates and, reaching the sand and unable to sink through the clay, breaks out in land springs.

But where the chalk cliffs start sheer out of the sea, there the springs ooze into the sea itself, and, dissolving the texture of the sandy bed, resolve it into a quicksand, liable at the time of great floods to be washed out from under the superincumbent chalk. Should this take place, there is no help for it, but down the chalk bed must go. If you were lying on a bed, and the mattress under your feather bed were pulled away, you would descend, sinking to a depth equivalent to the thickness of the subtracted mattress. That is plain enough.

Now all along the coast to the east of Lyme Regis there is an undercliff—evident tokens of a subsidence of this description which has taken place at some time. When this undercliff has been eaten up by the sea, and a fresh face of crag exposed, then again there will occur a displacement, a pulling out of the mattress, and down will go the chalk above with all the houses and fields upon it. But the sea has not as yet done more than nibble at this undercliff.

It was not quite so to the west of Lyme. There sheer cliffs of glistening white rose above the pebbly shore, so abruptly and with such slight undulations, that several miles ensued before it was possible for those on the height to descend to the beach. Naturally, where the rain-water percolated through the chalk it formed no valleys with streams.

Thus the cliffs stood—for no one knows how long—till the end of December, 1839.