A Treatise On The Principles And Practice Of Harbour Engineering

HARBOUR ENGINEERING. 258 difficulty in making such a wick automatically raise iteelf as combustion proceeded. Mr Wigham, therefore, designed his wick to barn horizontally, passing it slowly over a small roller, the light being obtained from the flat side instead of from the end or edge. One end of the wick passes up through an oil-tight brass tube, receiving its supply of oil from the main reservoir1 by means of feed-holes, and the other end of the wick is brought down through another tube soldered or otherwise secured at its lower end, and standing above the level of the oil in the lamp. A circular float, to which this end of the wick is attached, rests upon the surface of the oil in a copper cylinder at the foot of the lamp. The oil in the cylinder is slowly withdrawn, drop by drop, through a valve of special construction, and the float, in descend- ing with the falling level of the oil, draws the wick in its train, and so causes a constant change in the part of the latter exposed to the action of the flame. The light may thus be arranged to burn without attention for periods of one, two, or even three months. The consumption of oil for both illumination and automatic working, together, is at the rate of about half a gallon per day of twenty-four hours. Turning to the alternate system of vapour lighting, we find that oil gas is manufacturable from shale oil, petroleum, or other oils. Heavy oils generally produce a smaller quantity of gas, but of richer quality than light oils. One gallon of oil yields from 70 to 90 cubic feet of gas, and the cost of production per 1000 cubic feet varies (subject to fluctuations in the price of materials) from 6s. 6d. on a large scale to 10s. on a small one. As manufactured on the Pintsch System, the gas is produced in two Q-shaped cast-iron retorts, arranged one above the other, connected by a double mouthpiece and set in a suitable furnace. The furnaces are heated by coal, coke, or other fuel, until the retorts have become cherry red. The oil, previously stored in a wrought-iron tank, is pumped into a small vessel, or cistern, near the furnaces, from which it flows by gravitation in a thin stream regulated by a micrometer coek, through a syphon into the upper retort. In order to protect this retort and somewhat retain the oil, a sheet-iron tray is inserted, into which the oil drops and is immediately converted into a brownish vapour. Passing through the connecting mouthpiece and along the heated sides of the lower retort, this vapour is further decomposed and made into permanent gas, full of impurities. The only outlet of the lower retort is a short pipe, called the descension pipe, through which the gas passes into the hydraulic main, depositing here a certain amount of tar, and thence into a circular condenser. Issuing from a small pipe into the large space of the condenser, the gas cools down and frees itself from the lighter tarry matters. It then passes into the washer, where it is forced through about an inch of water, and, afterwards, through two or three layers of lime and saw- dust in the purifier. In small installations, the washer and purifier are generally combined in the same apparatus, one above the other. Tn the 1 Divisions are made in the reservoir to prevent the oil from flooding the wick during momentary disturbance, such as is inevitable in the case of buoys and other floating vesseis.