the destruction by the sea of the forest lands on the northern and
western sides of the island, and in the separation of tracts of
considerable magnitude from the mainland. Geologists are agreed in
assigning to this event the date of March, 709, when great inundations
occurred in the Bay of Avranches on the French coast; they are not
equally unanimous as to the cause, but science now rejects the theory of
a raising of the sea-level and that of a general subsidence of the
island. The most reasonable explanation appears to be that the
overpowering force of a tidal wave suddenly swept away barriers whose
resistance had been for ages surely though imperceptibly diminishing,
and that the districts thus left unprotected proved to be below the
sea-level--owing, as regards the forests, to gradual subsidence easily
explicable in the case of undrained, swampy soil; and, as regards the
rocks, to the fact that the newly exposed surface consisted of
accumulations of already disintegrated deposits.

It is unquestionable that before the inroad of the sea the inlet in the
south-west of the island known as Rocquaine Bay was enclosed by two
arms, the northern of which terminated in the point of Lihou; on which
still stand the ruins of an old priory, while the southern ended in the
Hanois rocks, on which a lighthouse has been erected. Lihou is at
present an island, accessible only at low water by a narrow causeway;
the Hanois is entirely cut off from the shore, but it is a noteworthy
fact that the signs of old cart-ruts are visible at spring tides, and
that an iron hook was recently discovered attached to a submerged rock
which had apparently served as a gatepost; besides these proofs of the
existence of roads now lying under the waves, it is said that an old
order for the repair of Hanois roads is still extant. That Vazon and the
Braye du Valle were the sites of forests is indisputable, though the
former is now a sandy bay into which the Atlantic flows without