A Treatise On The Principles And Practice Of Harbour Engineering

PIERHEADS, QUAYS, AND LANDING-STAGES. 199 upon which the quay surface is prepared and laid. They also serve to present a uniform frontage against which vessels may be moored and warped without damage. As retaining walls, they possess characteristic features and discharge special functions which call for very detailed treatment ; and as the author has subjected them to a careful investigation elsewhere,1 it would be unwise to attempt any further, and necessarily restricted, allusion to them here. Landing ’ Slipways. —In situations where the water does not maintain a fairly uniform level, it becomes necessary to provide sloping ways, or slip- ways, leading from the surface of the quay down to the lowest water level. These slipways are even desirable under any circumstances, and especially for the purpose of affording access to small craft of shallow draught and rowing- boats, and to facilitate the withdrawal of the latter from the water. Slipways range from about 5 to 15 or 20 feet in width, with an inclination not greater than 1 in 5. They should have a covering of concrete or be paved with large heavy stones, having a flat upper surface and presenting as few joints as possible to the pick-like action of the waves. Such joints as there are will be well flushed and pointed with cement, for it can be readily understood that slipways are subjected in a peculiar manner to the most destructive action of breaking waves, which renders it im- perative to present thereto as hard, smooth, and unbroken a surface as possible. Where slipways are paved with cubes, or setts, these latter must be thoroughly grouted and bedded in a perfect manner upon a sub- stantial concrete foundation. Slipways are provided with a bottom landing, and times with one or two mediate landings — all platforms. Stairways and some- inter- level Lad- ders.—Access to the water- line may also be obtained by stairways and ladders. The former are simply steps set in the wall in the ordinary manner, and not uncommonly Fios. 172, 173.— Steps in Quay Wall. at corners,, where they are least likely to interfere with the use of the quay by shipping. The latter generally consist of galvanised wrought iron vertical sides and circular rungs, recessed within the face line of the quay so as to 1 Dock Engineering, Chapter V.