Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/437

 372 the new-born lake of thick turbid water, is first seen covering river and field, wood and crops, homestead, bridge, and church, rushing over its obstructing dam, and sweeping it away, perhaps rolling over it, the bodies of drowned cattle, or even of men, with all sorts of floating wreck; is nothing more, than may occur any day in a similar locality, without any earthquake, nor anything more enduring in its effects, or more capable of permanently changing the face of the country than the accidents of the first great flood in the river.

The only case in which the lake, can possibly become a permanent one, is when two conditions unite, both rare and improbable—

1st. The dam must, by accident, precipitate itself so, as to be absolutely water-tight from the first moment, for otherwise its final destruction is only a question of time.

2nd. The ordinary and extraordinary discharge of the river, must owing to accidental configuration of surface, of the country at either one or both sides of the river course, abreast of the dam, find a new and permanent channel of overflow for the ponded waters, at the level of the permanent surface of the new-made lake, so that all water shall be diverted permanently from falling over the face of the dam.

With both these conditions, it is just possible, though still highly improbable, that the suddenly-formed dam may stand long enough, to get finally consolidated, and become a permanent water-tight construction of Nature's hand.

Such possibly may have been the case with the lakes said to have been formed in Calabria and elsewhere, (but not noticed by or known to the describers); it is, however, much more probable that were examination now made at the sites in Calabria where those lakes are stated to have