AUTOMATIC SPRINKLERS
As these have been referred to several times a short description may appropriately be given. The building which they protect is fitted with a network of mains and branches ramifying into each room. At the end of each branch is a nozzle, the mouth of which is bridged over by a metal arch carrying a small plate. Between the bridge and a glass plug closing the nozzle is a bar of easily fusible solder. When the temperature has risen to danger point the solder melts, and the plug is driven out by the water, which strikes the plate and scatters in all directions.
This device has proved very valuable on many occasions. The Encyclopædia Britannica (Tenth Edition) states that, in the record of the American Associated Factory Mutual companies for the 5 1 / 2 years ending January 1, 1900, it appears that out of 563 fires where sprinklers came into play 129 were extinguished by one jet; 83 by two jets; 61 by three; 44 by four; 40 by five.
The fire-bucket is the simplest device we have as a first aid; and very effective it often proves. Insurance statistics show that more fires are put out by pails than by all other appliances put together. The important point to be remembered in connection with them is that they should always be kept full; so that, at the critical moment, there may be no hurried rushing about to find the two gallons of liquid which each is supposed to contain permanently. In Cassier's Magazine (vol. xx. p. 85) is given an account of the manner in which an ingenious mill superintendent ensured the pails on the premises being ready for duty. The hooks carrying the pails were fitted up with pieces of spring steel strong enough to lift the pail when nearly empty, but not sufficiently so to lift a full pail. Just over each spring, in such a position as to be out of the way of the handle of the pail, was set a metal point, connected with a wire from an open-circuit battery. So long as the pails were full, their weight, when hung on their hooks, kept the springs down, but as soon as one was removed, or lost a considerable part of its contents by evaporation or otherwise, the spring on its hook would rise, come into contact with the metal point, thus close the battery circuit and ring a bell in the manager's office, at the same time showing which was the bucket at fault. The bell continued to ring till the deficiency had been made right; and by this simple contrivance the buckets were protected from misuse or lack of attention.
FOOTNOTES:
[14.] Mr. W. H. Oatway.
[15.] Glasgow Evening News.
[CHAPTER XII]
THE MACHINERY OF A SHIP
THE REVERSING ENGINE — MARINE ENGINE SPEED GOVERNORS — THE STEERING ENGINE — BLOWING AND VENTILATING APPARATUS — PUMPS — FEED HEATERS — FEED-WATER FILTERS — DISTILLERS — REFRIGERATORS — THE SEARCH-LIGHT — WIRELESS TELEGRAPHY INSTRUMENTS — SAFETY DEVICES — THE TRANSMISSION OF POWER ON A SHIP
With many travellers by sea the first impulse, after bunks have been visited and baggage has been safely stored away, is to saunter off to the hatches over the engine-room and peer down into the shining machinery which forms the heart of the vessel. Some engine is sure to be at work to remind them of the great power stored down there below, and to give a foretaste of what to expect when the engine-room gong sounds and the man in charge opens the huge throttle controlling some thousands of horse-power.
By craning forward over the edge of the ship, a jet of water may be seen spurting from a hole in the side just above the water-line, denoting either that a pump is emptying the bilge, or that the condensers are being cooled ready for the work before them.
Towards the forecastle a busy little donkey engine is lifting bunches of luggage off the quay by means of a rope passing over a swinging spar attached to the mast, and lowering it into the nether regions where stevedores pack it neatly away.
In a small compartment on the upper deck is some mysterious, and not very important-looking, gear: yet, as it operates the rudder, it claims a place of honour equalling that of the main engines which turn the screw.
To the ordinary passenger the very existence of much other machinery—the reversing engines, the air-pumps, the condensers, the "feed" heaters, the filters, the evaporators and refrigerators, and the ventilators—is most probably unsuspected. The electric light he would, from his experience of things ashore, vaguely connect with an engine "somewhere." But the apparatus referred to either works so unobtrusively or is so sequestered from the public eye that one might travel for weeks without even hearing mention of it.
On a warship the amount of machinery is vastly increased. In fact, every war vessel, from the first-class battleship to the smallest "destroyer," is practically a congeries of machines; accommodation for human beings taking a very secondary place. Big guns must be trained, fed, and cleaned by machinery; and these processes, simple as they sound, need most elaborate devices. The difference in respect of mechanism between the King Edward VII. and Nelson's Victory is as great as that between a motor-car and a farmer's cart. It would not be too much to say that the mechanical knowledge of any period is very adequately gauged from its fighting vessels.
Photo] [Cribb, Southsea.
A gigantic sheer-legs used for lowering boilers, big guns, turrets, etc., into men-of-war. The legs rise to a height of 140 feet, and will handle weights up to 150 tons.
During the last twenty years marine engines have been enormously improved. But the advance of auxiliary appliances has been even more marked. In earlier times the matter considered of primary importance was the propulsion of the vessel; and engineers turned their attention to the problem of crowding the greatest possible amount of power into the least possible amount of space. This was effected mainly by the "compounding" of engines—using the steam over and over again in cylinders of increasing size—and by improving the design of boilers. As soon as this business had been well forwarded, auxiliary machinery, which, though not absolutely necessary for movement, greatly affected the ease, comfort, and economy of working a ship, got its share of notice, with the result that a tour round the "works" of a modern battleship or liner is a growing wonder and a liberal education in itself.
This chapter will deal with the auxiliaries to be found in large vessels designed for peaceful or warlike uses. Many devices are common to ships of both classes, and some are confined to one type only, though the "steel wall" certainly has the advantage with regard to multiplicity.
We may begin with