A Treatise On The Principles And Practice Of Harbour Engineering

rgo HARBOUR ENGINEERING. Scale ofinches and Peet tns aocso 1 2 3 ^5 c Feet r^-H-— tei — -te^—7-feis^ Scale of millimétrés 250 500 1000 1500 _______________2000 'm Fig. 160. —Port Light and Mast. Where the light is of minor im- portance and lacks the rotative mech- anism which demands a protective lantern, a mast (fig. 160) may be used for the purpose of elevating it to the required focal plane. A steel column, tapering in form and fitted into a strong cast-iron base, will gener- ally be used in such cases. The base must be securely bolted into the pier- head structure. At the head of the mast there will be a curved bracket, or yard arm, to support the lamp, which may be raised or lowered by a chain or wire rope, leading to a winch at the foot. Apart from any guiding signals for the night-time, such as the above, or for the daytime, sucli as séma- phores or other indicators, the pier- head needs to be equipped for general purposes with a capstan or two, with snatch - blocks, mushrooms, or fair- leads, and also with mooring-posts at frequent intervals. Steps leading down to the water level should also be provided in a sheltered spot. The provision of life-belts and life-lines is almost too obvious a duty to call for mention. Pierhead at Toulon.—The pier- head of the St Mandrier Jetly at Toulon has a diameter of 92 feet, comparable with the 42 feet width