liquid fuel.

Ordinary coal bunkers are of course not suitable, as the riveting and plating is not oil-tight. In the Flannery-Boyd system the oil is carried in all the ballast tank spaces throughout the ship, namely, the fore and aft peaks, the double bottom ballast tanks under the engines and boilers, the forward ballast tank adjacent to the fore peak, and the forward and aft cofferdam.

The main difficulty in carrying liquid fuel in these spaces is that some water always remains in a ballast tank, owing to the difficulty of completely draining it. This water becomes mixed with the liquid fuel, and passing to the burners causes dangerous explosions, and generally puts out flame. It is therefore necessary to eliminate the water. To do this two settling tanks of large capacity are placed in the 'tween decks amidships, adjacent to the boiler room bulkhead. These tanks are fitted with heating coils to enable the liquid fuel to be heated to a sufficient temperature to allow of the water freely separating. The water then settles to the bottom of the tank, and can be drained off.

Each tank is made of sufficient size to contain half a day's supply, so that half a day is allowed for the water to become separated. From these separation or service tanks the oil gravitates to the burners, and is sprayed by a jet of steam.

Each furnace is fitted with two burners, and the furnace arrangements are such that the complete coal burning gear remains intact when burning liquid fuel, so that the system of either coal burning or liquid fuel burning can be resorted to at will.

If the vessel is burning liquid fuel, and it is found necessary from economical reasons to resort to coal burning, it is only necessary to rake a few broken firebricks from the bars and disconnect the burners and light a coal fire. This operation can be carried on, without stopping the vessel, at sea; the whole operation in a large vessel can be carried out within an hour.

The ss. Trocas has three large single-ended boilers and one donkey boiler. The large boilers have each three furnaces, and the small boiler has two furnaces. All are fitted for liquid fuel.

In Chapter XXXI. a recent example of an oil tank steamer will be found illustrated.

Use of Liquid Fuel at Sea.

Sir Fortescue Flannery states in his 1902 paper to the Institution of Naval Architects that the use of astatki was commenced in 1870 on the Caspian Sea and Volga, and about 400 vessels are now equipped. As the Volga is a fresh-water river, steam can be used as the pulverizing agent without evil results in scale. Progress has been slow because the supply of oil was for years very small, but over 7,000,000 tons annually are now used as fuel in Russia, and the world's production has much increased of late years, and in addition to the British Admiralty, the Italian and German Admiralties have taken up the study and experiment. The Hamburg-American Line have four steamers fitted for liquid fuel, and the North German Lloyd have two. The Dutch Navy have combined liquid fuel with coal in two destroyers, and Dutch mail and cargo boats in the East are regular users of oil.

Supply.

"Storage and supply systems of this fuel are in regular use, or in course of arrangement, at the ports of London, Barrow, Southampton, Amsterdam, Copenhagen, New Orleans, Savannah, New York, Philadelphia, Singapore, Hong Kong, Madras, Colombo, Suez, Hamburg, Port Arthur, Texas, Rangoon, Calcutta, Bombay,

Alexandria, Bankok, Saigon, Penang, Batavia, Surabaya, Amoy, Swatow, Fuchow, Shanghai, Hankow, Sydney, Melbourne, Adelaide, Zanzibar, Mombassa, Yokohama, Kobé, and Nagasaki, and storage arrangements are projected in South African and South American ports.

"The supply to these stations will be drawn as regards the ports east of the Suez Canal from Borneo and Rangoon, and as regards those west of the Canal and in South America from the Texas fields, South African stations being neutral as regards the heavy charges of the Suez Canal, and therefore likely to draw their supply from Borneo or Texas with equal economy. The South American stations will probably be supplied from the Texas and Californian fields."

The question of safety and flash-point is of importance. The British Admiralty have hitherto required a flash-point of 270°F., Lloyds' register of 200° now reduced to 150°, while the German authorities have accepted as safe 150°. Fuel of the lower flash has been in constant use for four years in British and Dutch mercantile vessels with complete immunity from accident. It is not desirable to fix a flash point higher than is really necessary for safety, because high-flash points are obtained by removing the more volatile parts of the liquid, so as to leave a thick and sluggish residuum, which requires much power to pulverize it into spray.

Comparative Advantages for War Vessels.

Sir Fortescue continues: "The problem that confronts every designer of a warship is the combination of the maximum speed, armament, ammunition supply, protection, and range of action in the smallest and least expensive hull, and any reduction of weight and space of these is a saving which acts and reacts favourably upon the problem. The comparisons between coal and oil fuel realized in recent practice are that 2 tons weight of oil are equivalent to 3 tons weight of coal, and 36 cubic feet of oil are equivalent to 67 cubic feet of coal as usually stored in ships' bunkers; that is to say, if the change of fuel be effected in an existing war vessel, or applied to any design without changing any other of the data than those affecting the range of action, the range of action is increased 50 per cent. upon the bunker weight allotted, and nearly 90 per cent. upon the bunker space allotted.

"The coal protection of cruisers, if an advantage—a matter of opinion-would disappear with the use of liquid fuel, because it would be for the most part stowed below the water line, if not wholly in the double bottom. The double bottom and other spaces, quite useless except for water stowage, would be capable of storing liquid fuel, and the space now occupied by coal bunkers would be available for other

uses.

"The ship's complement would be reduced by the almost complete abolition of the stoker element and the substitution of men of the leading stoker class to attend to the fuel burners under the direction of the engineers, and the space of stokers' accommodation, the weight of their stores, together with the expense of their maintenance, would be saved. The number of lives at risk and of men to be recruited and trained over a long series of years would be reduced, without reducing the manoeuvreing or offensive or defensive power of vessels of any class in the fleet. Re-bunkering at sea-so anxious a problem with coal--would be made easy, there being no difficulty in pumping from a store ship to a warship in mid-ocean in ordinary weather. Three hundred tons an hour is quite a common rate of delivery in the discharge of a tank steamer's cargo under ordinary conditions of pumping. The many parts of the boiler fronts and stokehold plates, now so quickly

corroded by the process of damping ashes before getting them overboard, would be preserved by the action of the oil fuel, and the same remark applies to the bunker plating, which now so quickly perishes by corrosion in way of the coal storage.

Liquid fuel, if burned in suitable furnaces with reasonable skill and experience on the part of the men in charge, is smokeless. It is easy to produce smoke with it, but this is evidence of its being forced in combustion, or of the detailed arrangements of the furnace being out of proper proportion to each other. In regard to smokelessness, it is, when used under conditions customary in the merchant service, not inferior to Welsh coal, and superior to any other coal ordinarily in use.

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The cost of oil in the East is less than the cost of Welsh coal when the cost of transport and Suez Canal dues are added to the original price of coal as delivered in a Welsh port."

It is only since Texas oil has been discovered that the successful competition of oil has appeared probable to the west of the Suez Canal. In the mercantile marine advantage is gained by a reduction of the stokehold complement, a crew of thirty-two being reducible to eight.

The big and fast Atlantic liners find it difficult to get coal to their boilers in sufficient quantity for the firemen to burn, and they lose time in consequence, even when their engines and boilers are in perfect order. This difficulty disappears with oil, and there is a saving of space previously occupied by men and stores.

Allowing 3 tons of coal to be equal to 2 tons of oil, a first-class Atlantic liner will gain 1,000 tons for freight, as well as the whole of the bunker space. That is, with oil in the peaks and ballast tanks, there will be a gain of 100,000 cubic feet of paying space, and for most ships at least a fourth of the coal bunker space could be used for cargo. There is in addition the saving in time when coaling. Oil is pumped in without the help of a man. No fires require to be cleaned; there are no ashes to be removed.

The advantages are thus summed up by a firm of engineers who instal liquid fuel apparatus, and as the statements they make are perfectly true, they may printed practically in extenso, and are applicable to both marine and locomotive practice, as well as to stationary work.

"Aside from the economy over the use of coal resulting from the less actual cost of oil, where this is the case, and the amount of which can be readily figured out for each locality, there are fundamental economies resulting from the facts that oil is much more readily handled than coal; it can be stored at a less cost, does not deteriorate when stored (as does coal), and the fire room cost is much reduced. Fires made by oil are perfectly steady, and the steam pressure is constant, while the temperature of the stoke-hold in steamships is lower, owing to the fact that the furnace doors are never opened and hot cinders and ashes are not pulled out into the In addition to these fundamental advantages, there are also other more particular advantages resulting from the use of this fuel.

room.

"1. Diminished loss of heat up the stack, owing to the clean condition of the tubes and to the smaller amount of air which has to pass through the furnaces for a given calorific capacity of fuel.

"2. More equal distribution of heat in the combustion chamber, as the doors do not have to be opened; consequently there is a higher efficiency. The heat is easier on the metal walls of the boiler, being better diffused over the whole surface.

"3. Reduction in cost of handling fuel, which is done mechanically by pumps.

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"4. No firing tools or grate bars are used,1 consequently the furnace lining

suffers no damage.

"5. No dust or ashes to fill the tubes or diminish the heating surface, or to be handled and carted away.

"6. Liquid fuel does not suffer when stored, while deterioration of coal under atmospheric influence is well known, not to mention the expense and shrinkage in handling, labour of feeding fires, removing clinkers, etc.

"7. Ease with which the fire can be regulated from a low to an intense heat in a short time.

"8. Lessening of manual labour to the firemen.

"9. Great increase of steaming capacity, as conclusively proved by many factories in Pennsylvania and Ohio having to increase their boiler capacity by about 35 per cent. when returning to the use of coal on account of the high cost of oil."

1 Grate bars may be employed, under certain conditions, as explained elsewhere.

THE

Chapter XV

MARINE FURNACE GEAR

severe a drain

HE use of steam or of air for atomizing is a mixed question. Steam is more convenient and is naturally first used, but it becomes so on the fresh water supply that it is practically inadmissible at sea.

The claim that its oxygen is set free by the fire and burned with advantage to the evaporative efficiency of the boiler cannot be for a moment entertained or maintained. Needless it is, almost, to say that the dissociation of water or steam absorbs exactly as much heat from the fire as is given back by the recombination.

Some makers of atomizing apparatus claim to secure a softer flame with steam, but so far as our chemical and physical knowledge extends, air ought to be superior. It requires, however, to be first compressed, and it also seems desirable that it