centre of the coldest part of the burning mass, thus supplying the fire with fuel, without checking the evolution of gases produced by the combustion in the middle and end of the furnace. At Cairo, in March 1874, the consumption of begass by a 10-HP. portable engine was found to be 17.77 lb. per H.P. per hour, which, taking the average consumption of coal by this engine at 6 lb. per H.P. per hour, gives the proportionate consumption of coal and begass as I to 2.96. When the begass was dried in the sun, it made an excellent fire, and required no larger air-space between the grate-bars than was necessary for burning wood. Sir Frederick Bramwell and Dr. Letheby, reporting on the Khedive's sugar-factories, stated 377 lb. of dry begass (the produce of I ton of canes) to be equivalent to 180 lb. of Welsh coal.

It

It is necessary to refer the reader for a moment to the analyses of canes, given on pp. 27-8. There he will find that from 26 to 54 per cent. of the total ash of the cane consists of silica. This silica forms a deposit upon the bars of furnaces burning straw, begass, and such substances. does not collect in hard masses on the bars, so as to prevent the ingress of air, until the boiler has been for some time at work; and experiment shows that if an apparatus can be made to act before the silica becomes agglomerated, the space between the bars can be kept as free and open as when burning coal or wood.

With this object, many trials have been made of variouslyshaped grate-bars, self-acting bars, and rotary prickers turned by a handle outside the boiler. The result has been the adoption of a simple apparatus, whose position in the furnace is shown in Fig. 26. It consists of a rake with 5 or 6 teeth, according to the width of the fire-box, the top of these teeth projecting about 2 inches above the fire-bars. One end of this pricker is attached to a handle, which extends outside the ashpan, and can be worked by the stoker, and the whole apparatus slides backwards and forwards upon 2 wrought-iron guides

underneath the fire-bars. When the apparatus is used, it is drawn from the back to the front of the fire-box, along one side of the fire-bars. It is then shifted to the other side of the 4-inch space, and travels from the front to the back of the fire-box

FIG. 26.

along the other side, and thus cuts away all the deposit of silica, which falls into the ash-pan. There is also liable to be a slight deposit of silica and slag in some of the tubes of the boiler, especially in the 2 lower rows, thus impeding the

generation of steam.

To obviate this and the necessity for

stopping the engine and cleaning the tubes, a steam jet (Fig. 27), consisting of a wrought-iron pipe with a brass rose at one end, may be attached, with an indiarubber pipe, to a tap in front of the boiler. When the tubes are furred, this rose-jet

is inserted through the flaps in front of the boiler, and the whole of the silicious deposit is blown through the tubes into the smoke-box.

Some modifications of the boiler grates were adopted at the Khedive's sugar factories for more completely burning the

FIG. 27.

begass. The modifications, as applied to a 60-H.P. boiler, are shown in section and plan in Figs. 28 and 29. The lower half of the number of fire-bars was removed, the other half was raised, and two D-shaped mouthpieces, 2 feet 6 inches long and 14 inches wide, were placed side by side, with their bottoms level with the floor of the stoke-hole. The natives, squatting as usual on the floor with the begass piled around them, pushed the fuel down the mouthpieces by the aid of short sticks. The fuel was thus put into the fire, and not over it, and the result was such an improvement in the combustion of the begass and the amount of heat generated from it, that auxiliary coal could be dispensed with.

A stir has recently been made by the introduction of the Marie furnace for burning undried begass, in such a condition as it presents on leaving the cane-mill. It is the invention of Marie Jean Léon Marie, of Saint Pierre, Martinique, and

is made in this country by Manlove, Alliott, Fryer & Co., of Nottingham. Figs. 30 and 31 represent a longitudinal vertical section and horizontal section respectively of the begass furnace, while Fig. 32 illustrates the application of the begass furnace to the fire-box of a locomotive boiler.

furnace. A coal fire having been first lighted in the furnace A, its walls become highly heated; the wet begass is then fed in through the hopper C, whose balance-door D opens to give passage to and spread the begass uniformly upon the grate g, the door D closing again immediately to re-establish the natural draft through the grate. The flame of the fire immediately envelops the fresh fuel, and owing to the high temperature in the furnace, the gases at once begin to be liberated. As the surfaces of internal boiler furnaces do not exceed the relatively low temperature of the surrounding water, a great part of the gases is carried off unconsumed, and becomes partly condensed on the cooler surfaces, and partly passes away in the form of dense smoke; whereas in this furnace, the heat which in the former case would go to heat the water is stored up in the walls of the furnace, which quickly become hot enough to almost instantly dry the begass, and render it eminently fit for burning. As all the gases are compelled to pass through the mouth or aperture leading to the boiler furnace s, perfect combustion is ensured, and there is little or none of the usual deposit in the boiler tubes.

The advantages of a furnace which will burn wet begass are not confined to the mere saving of the time and outlay required for drying, but extend to the equally important gain represented by the avoidance of that risk of fire, which is so constantly to be feared when begass is stored in large quantity, and by the utilization of the combustible qualities of the saccharine matter left in the canes, before it is destroyed by fermentation. The furnace is simple to construct and manage, and little likely to get out of repair. It is independent of the fire-place to which it is desired to attach it, and has been very successfully applied not only to the boiler furnaces for the cane-mills, but also to the "copper walls" for making muscovado sugar.

Norbert Rillieux, of Paris, has also devised a plan for effecting the drying of the begass on its way to the furnace.