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Aft, :

responding to the draught of water which was maintained without sensible variation during all the trials : Length on water-live from forward edge of rabbet of stem to after side of the sternpost, .

96 feet. Greatest breadth on water-line,

13 ft. 6 in. Extreme breadth,

16 feet.

Forward, 2 ft. 9 in. Draught of water from bottom of keel, Mean,

3 ft. 8 in. Aft,

4 ft. 7 in.

6 in. Depth of keel below lower edge of its / Forward,

Mean,

1 ft. 2 in. rabbet,

1 ft. 10 in. Mean depth of hull from water-line to lower edge of rabbet of keel,

2 ft. 6 in. Area of the greatest immersed transverse section,

25.28 sq. ft. Area of the water-line,

861:44 sq. ft. Displacement (35 cubic feet per ton),

12:87 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 parallelogram,

0.6647 Ratio of the displacement to its circumscribing parallelopipedon,

0 4631

ENGINE.

.

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,

12 inches. Diameter of piston rod of the small cylinder,

1} inches. Net area of the piston of the small cylinder, 112.2140 sq. in. Stroke of the piston of the small cylinder,

16 inches. Space displacement of the piston of the small cylinder, per stroke,

1.0390 cu. ft. Diameter of the large cylinder,'

20 inches. Diameter of the piston rod of the large cylinder, 1} inches. Net area of the piston of the large cylinder, 313-2764 sq. in.

16 inches.

2.9007 cu. ft.

Stroke of the piston of the large cylinder, .
Space displacement of the piston of the large cyl-

inder, per stroke,
Ratio of the space displacement of the piston of

the large cylinder, per stroke, to that of the piston of the small cylinder,

2:97178

BOILER.

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. Diameter of the boiler shell,

7 feet. Length of the boiler shell,

8 feet. Diameter of the steam-chimney,

4 ft. 6 in. Height of the steam-chimney,

Ō ft. 6 in. Number of furnaces,

2 Diameter of the furnaces,

2 ft. 4 in. Length of the grates,

5 feet. Area of grate surface,

23. sq. feet. Area of water-heating surface, calculated for outside of tubes,

519
sq.

feet.
Calorimeter, or aggregate cross area of tubes, for
draught,

3.14 sq. feet. Steam room in boiler shell and in steam-chimney, 91:54 cu. feet. Square feet of water-heating surface per square foot of grate surface,

22:2429 Square feet of grate surface per square foot of cross area of tubes,

7:4310

SCREWS.

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 Jetters.

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 4:658 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:

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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 131 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 116 inches.

4.6158 feet. 0.8333 feet. 8:1

feet. 4.

.

.

Diameter of the screw,
Diameter of the hub,
Pitch of the screw,
Number of blades,
Length of the screw at the hub, in the direction of

0.5625 foot.

the axis, Length of the screw at radius of 13} inches, in the

direction of 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

angles to the axis, Helicoidal area of the blades,

0:9167 foot.

0.3125 foot. 0:3325

5.4551 sq. ft. 7.9447 sq. ft.

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

tion on a plane parallel with the axis, had their edges parallel from the hub to a radius of 64 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.

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.

Diameter of the screw,
Diameter of the hub,
Pitch of the screw,
Number of blades,
Length of the screw at the hub, and to radius of 61

inches, in the direction of the axis,
Length of the screw at radius of 18 inches, in the

direction of 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 angles

to the axis, Helicoidal area of the blades,

1.1875 feet.

0:5080 foot. 0:5283

.

10:1693

sq.

ft. 13-5266 sq. ft.

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