The boiler is vertical and cylindrical; from the crown-sheet depend water-tubes having in them concentric circulation-tubes, causing in each tube a strong central downward current of water, which, mostly converted into steam, ascends in a thin film in the annular space between the outer tube and the inner or circulation tube. These drop-tubes are ranged in concentric circles, those in the outside rows being longer than the others, thus better utilizing the space in the combustion chamber. The gases of combustion pass from the combustion-chamber or furnace through vertical smoke-flues set concentrically, a conical smoke chamber, properly jacketed, connecting with the stack ; and the draft being regulated by a varia ble exhaust-nozzle, from which the rapid succes sion of discharges makes, in effect, a steady blast, which does not "pull fire," and thus endanger neighboring property. This variable exhaust nozzle has several outlets, each controlled by a conical plug, all of which are regulated at once by a suitable lever.
The shell and fire-box are of tough steel, hav ing a tensile strength of 60,000 lbs. to the sq. in. The water-tubes are inclined outward at the bot tom, so as to assist the draft and to present the tube - heating surface to the best advantage, They are screwed into the crown-sheet, and the eireulation-tubes have at their lower ends trian gular easements, to prevent the lifting of the water by the rapid circulation. The steam made in the outer annular passages in the drop-tubes and elsewhere is dried and further heated by the smoke-flues passing through the steam-chamber. The steam is taken from a circular perforated dry pipe running around the steam-space of the boiler. The water-level is carried about one third way up in the steam-chamber.
It is claimed that this boiler will raise steam from cold water in four to six minutes, will burn coal or wood, will not foam nor prime, and will use salt water if necessary.
The engine contains two rotating pistons or cams, both alike, and each of which is in effect a gear-wheel having eight short teeth arranged in pairs, with one long tooth and one deep space between each two pairs of short teeth. The short teeth are for the purpose of in suring that the two cams rotate exactly together. The long teeth are in effect abutments for the steam, forming as they do steam-tight joints with the walls of the case in which they rotate, and with the deep spaces in which they engage. The steam, entering at the bottom of the case, tends to press the abutments apart, and thus cause rotation of the pistons in oppo site directions.
The construction of the pump is upon the same general principle as that of the engine, only there are three long teeth to each cam, and fewer short or guide-teeth. The water enters
at the bottom of the case by the suction-opening. and is discharged at the top by the outlet. Th3 revolution of the pump-pistons in opposite directions causes a vacuum in the case, and the water rushes up to fill it, and is then caught by the long teeth or abutments and swept out of the ease.
The main pump, if the engine is to be used in connection with water-works. has a churn valve by which the stream may be led from a hydrant through the suction-hose into the dis charge-hose, without revolving the pump or any portion of the machinery.
The following is a record of trials at Cedarville, Ohio. of a F1RE-B0ATS.—The latest type of floating steam fire-engine is illustrated in Fig. 15.' This is the boat New-Yorker. built for and in use by the Eire Department, and serving to protect vessels at the city piers and property on the water-front.
The boat and machinery are built of iron and steel throughout, under full specifications furnished by the department. The length over all is 125 ft. 5 in.; on load water-line, 115 ft. The beam molded is 2G ft.; on load water-line, 25 ft. 2 in. The depth molded is 14 ft. li in., and the extreme draft is 10 ft. The displacement is 351 tons. At the load water-line the displacement is 52 tons to the inch.
The boilers, two in nnmber, arc of the '• Scotch " type. cylindrical, with corrugated fur naces. They are built for a? working-pressnre of It lbs. Each is 12 ft. diameter and 15 ft.
long, with 204 tubes of tlf in. outside diameter. The out •tide sheets are in. thick, and other portions of reduced thickness. Artificial draft is provided, and the boilers can be worked titget her or indeptqulently.
The ItroPt'llint-t-NUZine is of the triple-expansion direct inverted type. 24 in. stroke, with 15, 24, and 39 in. cylinders. The high-pressure cylinder has a piston-valve, Ilse others have slide-valves. 11 can work up to 135 revolutions per min., with 135 to 150 Ills. The propellors are two in number. The fixed or forward screw is 7 ft. 9 in. diameter by 12 ft.
pitch. Back of this comes the " Kunstadter " swiveling-screw and gear. This is connected by a universal joint to the shaft, which joint comes in line with the axis of rotation of the rudder. Thus the screw is swung to right or left with the rudder, and aids in matactivring the boat. It has been found highly efficient. One independent air-pump and a circulating pump for the condenser are provided. The condenser is of the tubular pattern, with about 2.000 sq. ft. of condensing surface. Steam-steering gear and engine are provided in addition to the regular hand-steering apparatus. For signaling, a steam-chime whistle and a steam calliope are provided.