consisting of lias about one hundred feet
in height, gradually fell away at the rate of one yard a year, from 1800
to 1829.[431]

[Illustration: Fig. 36.

Landslip, near Axmouth, Dec. 1839. (Rev. W. D. Conybeare.)

A. Tract of Downs still remaining at their original level.
B. New ravine.
C, D. Sunk and fractured strip united to A, before the convulsion.
D, E. Bendon undercliff as before, but more fissured, and thrust
forward about fifty feet, towards the sea.
F. Pyramidal crag, sunk from seventy to twenty feet in height.
G. New reef upheaved from the sea.

]

An extraordinary landslip occurred on the 24th of December, 1839, on the
coast between Lyme Regis and Axmouth, which has been described by the
Rev. W. D. Conybeare, to whose kindness I am indebted for the
accompanying section, fig. 36. The tract of downs ranging there along
the coast is capped by chalk (_h_), which rests on sandstone,
alternating with chert (_i_), beneath which is more than 100 feet of
loose sand (_k_), with concretions at the bottom, and belonging like _i_
to the green-sand formation; the whole of the above masses, _h_, _i_,
_k_, reposing on retentive beds of clay (_l_), belonging to the lias,
which shelves towards the sea. Numerous springs issuing from the loose
sand (_k_), have gradually removed portions of it, and thus undermined
the superstratum, so as to have caused subsidences at former times, and
to have produced a line of undercliff between D and E. In 1839 an
excessively wet season had saturated all the rocks with moisture, so as
to increase the weight of the incumbent mass, from which the support had
already been withdrawn by the action of springs. Thus the superstrata
were precipitated into hollows prepared for them, and the adjacent
masses of partially undermined rock, to which the movement was
communicated, were made to slide down on a slippery basis of watery sand
towards the sea. These causes gave rise to a convulsion, which began on
the morning of the 24th of December, with a crashing noise; and, on the
evening of the same day, fissures were seen opening in the ground, and
the walls of tenements rending and sinking, until a deep chasm or
ravine, B, was formed, extending nearly three-quarters of a mile in
length, with a depth of from 100 to 150 feet, and a breadth exceeding
240 feet. At the bottom of this deep gulf lie fragments of the original
surface thrown together in the wildest confusion. In con