Thomas Stevenson, Esq., on Harbour Screw-Cramps. 43 
remained quite secure for the last thirty years. At the con- 
struction of Pulteneytown harbour it is recorded, that in 1827 
damage was done to the extent of £5000 in the course of two 
tides, though it seems now quite secure, after a lapse of nearly 
twenty years. At Ardglass harbour, which, I understand, 
cost about £20,000, a breach of 20 feet in extent was, from 
want of funds neglected, and the whole of the structure which 
was above low water was either utterly demolished, or greatly 
shaken, and has never been repaired. In 1844, I was 
informed that some of the stones at Dysart pier required, 
from decay, to be replaced by others, and a hole about four 
feet square had been made for the purpose, when a gale un- 
fortunately came on, and completely carried away the whole 
of the outer part of the pier, extending to about thirty yards, 
with the exception of a fragment of the quay-wall, where 
-many longitudinal and vertical fenders or stretchers of wood 
had been attached. On visiting the ruins about a week after 
the accident, I was surprised to find that this part of the 
quay-wall, though wholly deprived of backing, should have so 
successfully resisted the action of the sea, owing to the sup- 
port which it received from the fenders. On making inquiries 
at an eye-witness of the scene, I was told that the sea-wall 
and hearting were very speedily scattered before the destroy- 
ing element, and also ¢hat part of the quay-wall which had 
not been protected, or so securely protected by fenders. On 
the other hand, wherever the wall was strongly bound by 
fenders, the sea encroached very slowly; and that part which 
was most exposed to injury from vessels rounding their course 
into the harbour, and which was, in consequence, more 
strongly and closely bound with horizontal and vertical fen- 
ders, resisted successfully the force of the waves. 
From the foregoing statement of facts, which shew us the al- 
most total dependence of one stone on another, and the havoe 
which may ensue from even a single stone near the bottom of 
the structure being left insecure, we may readily see the ad- 
vantage which is to be derived from connecting them to- 
gether by iron bars and wooden fenders, or wrapping them 
round with chains, &e.; and hence, in many lighthouses and 
harbour works, great expense is incurred in joggling thestones, 
