20 EEPOET OF COMMISSIONER OF FISH AND FISHEEIES. [18] 



C— STEAM MACHINERY AND MECHANICAL APPLIANCES. 



By Passed Assistant Eugineer G. W. Baied, U. S. N. 



The designs and specifications of the motive engines, as well as the 

 hull, were drawn by the distinguished engineer, Mr. C. W. Copeland, 

 of New York, and they were built by the Pusey and Jones Company, 

 of Wilmington, Del. There is a two-cylinder compound engine for each 

 of the two proxjellers ; the engines are independent, and are provided 

 with steam reversing gears ; they are upright but not vertical, the cyl- 

 inders inclining towards each other (Plate XV) to give more room on 

 the working platform. There is one condenser, common to both en- 

 gines, which is mounted on a bed-plate, and which forms the framing 

 and cross-head guides for the engines ; the single bed-plate supports 

 the pillow-blocks of both engines. The condenser is of the type known 

 as " surface condenser," and is arranged in three nests of horizontal 

 tubes, the water passing successively through each nest, and the steam 

 is condensed on the outside of the tubes. 



There are two plunger air-pumps, placed horizontally, forward of the 

 main engines, one plunger being worked from a concentric on the for- 

 ward end of each crank-shaft. Both pumps are in one casting. The 

 feed-pumps are worked from rods extending from the air-pump plungers. 



The valves of the high-pressure cylinders are locomotive slides, over 

 which gridiron cut-off valves are placed, while the low-pressure valves 

 are donble ported and are without cut-offs. All these valves are actu- 

 ated by eccentrics and Stephenson links, in the usual manner. 



The engines are provided with a system of valves by which they may 

 be converted from compound to single expansion or simple engines. 



There are two outboard deliveries, one for the circulating water and 

 one for the air-pump or fresh water. 



The circulating pump is a Davidson light-service pump. No. 26. 

 (Plate XVII.) 



There is a flexible coupling connecting each crank shaft to its line- 

 shaft, and the thrust-bearings are on the line-shafts. 



The screw-propellers are right and left, with four blades each, the 

 blades curving radially and axially , according to the style of the designer. 



The shaft-brackets are of wrought iron; one is placed near the hub of 

 the screw and the other half way between this and the hull. The jour- 

 nals of the bracket are lined with bronze and lignum-vitae, and the 

 shaft in these journals is covered by a bronze jacket in the usual way. 



The stern pipes are of cast iron, the after floors bored to receive them, 

 and the frames bent round them. The stern bearings are also of cast 

 iron, with flanges fitting the hull; they are 3 feet 4 inches in length, 

 lined with lignum-vitse staves, and are recessed to receive the stern 

 pipes; the usual stuffing-boxes are provided. 



The sea- valves are of bronze with bronze stems, seats, and glands, 

 with cast-iron chambers, and have outside threads. 



