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16 length, from the tank to the burner is steam jacketed. The system adopted for the burner is a steam spray on the principle of an ejector, so that there is no pressure in the tanks, and no pumps are required. The oil in its fluid state passes through the central cone surrounded by steam, and is thus atomized, and is sprayed into the fur- nace on to what may be termed a "tar- TER LEVEL BoiLter oF OJFL-FIRED LAUNCH, get" of fire brick: Here the jet is broken up and passes through holes in the fire-brick arch on to the tube plate, which is thus protected from direct im- pingement of the exceedingly hot gases. Air is forced into the ashpan by means of a fan, driven off the main engine by a steel belt, and from the ashpan passes into the combustion chamber through holes in the surrounding fire-brick. The amount of air entering can be con- trolled by a slide, whilst the amount of steam and oil passing through the burn- er is also regulated by a stop valve, so that the fire is under complete control and is found to be absolutely smokeless at all rates of combustion. The official tests called for one hour's continuous run at 40. indicated horse- THe Marine REVIEW power, and a one hour's run at 35 I. H. P. with a tow rope attached to the shore and these resulted as fol- lows: Seam Wbss ie. eee - Vacuum, in..----+-++++: See ewe see se Revolutions. <2. 6062 2s oe ee Pe ae FO Pe ee re : ye Fuel consumed in 1 hour, Ibs... 86.5 ; Fuel consumed in 1 hour per - Bo Ee i eo a a ee oe 212 8.14 7.9 Sb ey 0 8 88: eerereeceere Speed, knots April, 1999 The boats have now been on their station for some six months, and ac- cording to the latest reports have been giving complete satisfaction in ordinary working. The hulls of these launches were designed by and the whole of the work carried out under the supervision of Mr. Archibald Hogg, of Newcastle- on-Tyne. &e- + | Effect of Bossing on the Resistance of Ships. By SsqIN THE course of testing some y y models of twin screw ships x hj with different shaped sterns, PD)| the writer had occasion to try the effect upon the resistance placing the bossing at different an- gles, and it was thought that the re- sults might be of interest to the mem- bers of this Institution. Before proceeding to discuss the re- sults obtained in these experiments, the writer would call attention to the important part that some of these appendages might play in connection with the resistance of a modern ves- sel. Most of the passenger vessels of to-day are fitted with bilge-keels, and nearly all with two, if not, in the case of turbine-driven vessels, three or four lines of shafting. The stream-line flow around a vessel is still somewhat of an unknown quantity, although in a valuable paper by Naval Constructor D. W. Taylor,. United States Navy, _ before the Society of Naval Architects and Marine Engineers in New York in 1907, the probable path of the water has' been indicated for a number of different types. A casual glance at these lines will show how easy it is to-place an appendage in a most dis- advantageous position so far as resist- ance is concerned; in fact, the resistance might easily be increased 20 per cent by improper design. The following experiments, although applying directly only to the form tested, nevertheless indicate in a gen- eral way the course to be followed in placing the bossing for a twin-screw ship. The following are the particulars of the model .used:--Length, 10 ft.; *Paper read before the Institution of En- gineers and Ship Builders in Scotland, Feb. 23, 1909. Of. Prof Herbert C. Sadler breadth, 1 ft. 3 in.; draught, 6 in, and Fan Block Draught Pris. Mid. Sect. Coeff. Coeff. Coeff. 6 in. 0.635 0.663 0.958 7 in. 0.653 0.677 : 0.964 The model was first run "naked" at the above draughts, representing the medium and deep-load draughts in the actual vessel. The bossing was after- wards added to the same model. The two types of bossing tried are shown in Figs. 1 and 2, and represent. prac- tically the two extreme cases, viz., one with the appendage horizontal, and the other inclined at an angle of 45 deg. to the vertical. The form of the bossing is that in common use, the top 'being kept as straight as possible, while most of the curvature is on the underside, an arrangement which gives a more simple construction in connec- tion with the plating than that where both the top and bottom have the same form. The tests with the bossing wefe made at the same displacement as that corresponding to the 6-in. and /-in. draughts of the naked hull. This method was adopted in preference to that of equal draughts as giving 4 more direct comparison. The differ- ence in draught, due to the displace- ment in the ibossing, is not great, as the additional displacement is only 0.84 per cent for No. 1, Fig. 1, and 0.88 per cent for No. 2 bossing, Fig. 2. The net addition to the wetted sur- face is about 3 per cent for the hori- zontal type, and about 3% per cent for the inclined type. The curves for total resistance are shown im @e = plotted to a speed-length ratio base, and give the for both the medium and deep draughts. Observation of these curves shows that at all practical speeds for this results