responding to the draught of water which was maintained without sensible variation during all the trials: Length on water-line from forward edge of rabbet of stem to after side of the sternpost, . 96 feet. Greatest breadth on water-line, Extreme breadth, Draught of water from bottom of keel, Mean, Depth of keel below lower edge of its rabbet, Aft,. Mean depth of hull from water-line to lower edge of Area of the greatest immersed transverse section, Displacement (35 cubic feet per ton), 2 ft. 6 in. 25.28 sq. ft. 861.44 sq. ft. 42.87 tons. Displacement per inch of draught at water-line, 2.051 tons. Ratio of length to breadth on water-line. 7.1111 Ratio of the greatest immersed transverse section to its circumscribing parallelogram, 0.7490 Ratio of the water-line to its circumscribing paral The vessel had one vertical, direct-acting, compound, condensing steam engine, with the two cylinders placed side by side and acting on cranks at right angles to each other. Diameter of the small cylinder, Diameter of piston rod of the small cylinder, Space displacement of the piston of the small cyl- Diameter of the large cylinder, Diameter of the piston rod of the large cylinder, 12 inches. 1 inches. 112.2140 sq. in. 16 inches. 1.0390 cu. ft. 20 inches. 13 inches. 313-2764 sq. in. Stroke of the piston of the large cylinder, Ratio of the space displacement of the piston of the large cylinder, per stroke, to that of the piston of the small cylinder, BOILER. 16 inches. 2.9007 cu. ft. 2.97178 There was one cylindrical boiler, with cylindrical furnaces, and horizontal fire tubes returned over them. A large portion of the steam. room was in a steam-chimney or drum placed above the shell and traversed by the chimney, so that the steam in the drum was, in a measure, superheated by the escaping hot gases of combustion. Area of water-heating surface, calculated for out side of tubes, Calorimeter, or aggregate cross area of tubes, for Steam room in boiler shell and in steam-chimney, Square feet of water-heating surface per square foot of grate surface, Square feet of grate surface per square foot of cross area of tubes, SCREWS. 5 ft. 6 in. 2 2 ft. 4 in. 5 feet. 233 sq. feet. 519 sq. feet. 3.14 sq. feet. 94.54 cu. feet. 22.2429 7.4310 The screws experimented with were seven in number, and are designated by letters from A to G, both inclusive. In the tables hereinafter given, the columns headed with these letters contain the data and results of the experiments made with the screws of corresponding letters. All the screws were of cast brass with the exception of screws B and G which were of cast iron and had blades about two and a half times thicker than the brass ones. All the screws had four blades and a uniform pitch, which varied for the different screws from 7.50 to 9:08 feet. The mean fraction used of the pitch varied also from 0·1994 to 0.5736. The diameter of all the screws, except A and F, was 5 feet; that of A was 46458 feet and that of F was 43 feet. When the vessel was at rest, a small portion of the 5 feet diameter screws protruded above the water; but when the vessel was in motion at the experimental speeds, all the screws were submerged, owing to the dropping of the stern. The following table shows the principal dimensions of the screws: The following are detailed descriptions of each screw, wherein the form of the blade, or its outline, is given, together with its thickness and the diameter of the hub, etc. SCREW A. This screw was of cast brass and had a uniform pitch. The blades, when viewed in projection on a plane parallel with the axis, increased gradually in length from the hub to a radius of 13 inches, from which their length gradually decreased to the periphery. The hub was square and the blades-which were cast separately--were bolted to it. The thickness of the blades at the fillet of the hub was 16 inches. Length of the screw at the hub, in the direction of the axis, 4.6458 feet. 0.8333 feet. 8.4 feet. 4. 0.5625 foot. Length of the screw at radius of 13 inches, in the direction of the axis, 0.9167 foot. angles to the axis, Length of the screw at the periphery, in the direction of the axis, Mean fraction used of the pitch, Projected area of the blades on a plane at right Helicoidal area of the blades, SCREW B. This screw was of cast iron, and had a uniform pitch. The hub and blades were cast together. The blades, when viewed in projec 0.3125 foot. 0.3325 5.4551 sq. ft. 7.9447 sq. ft. tion on a plane parallel with the axis, had their edges parallel from the hub to a radius of 6 inches. From this point to a radius of 18 inches the length of the blades gradually but irregularly increased. From the radius of 18 inches to the periphery the length of the blades gradually decreased. The outer corners of the blades were excessively rounded. The hub was cylindrical, and the thickness of the blade at its fillet was 3 inches. Length of the screw at the hub, and to radius of 61 inches, in the direction of the axis, 5.00 feet. 0.70 foot. 7.5 feet. 4. 0.6667 foot.. Length of the screw at radius of 18 inches, in the direction of the axis, 1.1875 feet. of the axis, to the axis, Length of the screw at the periphery, in the direction Mean fraction used of the pitch, Projected area of the blades on a plane at right angles Helicoidal area of the blades, |