106 COLE: EROSION OF THE YORKSHIRE COAST. 
the bottom of a cliff, the cliffs would become beetling; but they 
seldom, if ever, are so. most all cliffs have a decided slope back- 
wards, from the bottom upwards. Hence sub-aerial denudation must 
more than counter-balance the destruction wrought by the sea. 
The main work of the sa consists in breaking up and removing 
masses which have fallen from above. It also has a tendency to 
form caves, the roofs and pillars of which subsequently fall in, by 
three separate processes, viz., by the weight of water hurled against 
the rocks ; by the battering of stones, shingle, and sand contained in 
the waves; and by the force of compressed air driven into the 
interstices of the joints. But the agency of wind, rain, frost, and 
percolating water on the upper surface of the cliff causes it to retreat 
at a more rapid rate than the sea can undermine it, and so — 
the before-mentioned slope. 
On August 24th, 1890, an extensive landslip took place on the 
north cheek of the Castle Hill, Scarborough. From all accounts 
thousands of tons of rock were precipitated into the sea. In a 
description of the catastrophe published in the ‘Scarborough Gazette,’ 
August 28th, 1890 (with which we have been favoured by the Editor) 
occurs the passage: ‘We understand it is questionable whether the 
slip is to be attributed to the action of the sea, or to the natural 
character of the cliff throughout its extent. Probably both causes 
have been in operation.” Asa matter of fact the sea had nothing to 
do with it; but the natural character of the cliff had a great deal. 
The lowest portion of the cliff consists of massive boulders of hard 
Kellaways Sandstone, which present an almost impervious barrier to the 
attacks of the waves ; but the upper portion, consisting of Calcareous 
Grit and Oolitic Limestones, rests on a yielding base of Oxford Clay. 
Three inches of rain fell in the first three weeks of August, and this, 
percolating through the joints and fissures in the super-incumbent 
limestone, moistened the surface of the clay and rendered it insufficient 
to support the weight of rock above, already somewhat loosened and 
ready for disintegration by the repeated discharges of cannon on the 
Castle Hill plateau ; consequently down it came, and more is ready 
to follow. A similar phenomenon occurred on August 6th, 1857, 
and from similar causes. 
s the writer in the ‘Gazette’ suggests ‘the desirability of a sea- 
wall at the base, to prevent further disruptions as much as possible,’ 
it is only fair,to the promoters of the proposed drive to say, whilst 
exonerating the sea, that the danger from the cliff will be as great 
as ever. 
The fall of the cliff at Scarborough in 1857 gave rise to a ‘cloud 
of yellow smoke.’ The Rev. B. Irvin, Vicar of Saltburn, describes a 
Naturalist, 
