4.G 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[44] 



Large Tjoat. i Small Ijoat. 



I 



Diameter of furnane inches 



Area of grate surface square feet 



Diameter of smoke-pipe inches 



Height of smoke-pipe above grate bars - . . feet 



Diameter of separator inches 



Height of separator - do. ., 



Steam cylinders number 



Diameter of high-pressure cylinder ' inches 



Diameter of low-pressure cylinder do . . 



Stroke of pistons do . . 



Diameter of the piston rods do.. 



Diameter of the air pump (single-acting) do . . 



Stroke of air pump do.. 



Diameter of circulating pump-plunger do. . 



Diameter of feed pump-plunger do.. 



Stroke of pumps do.. 



Length of condensing pipes feet 



Condensing surface square feet 



Main j ourn als number 



Diameter of main journals inches 



Length of main journals ? do . . 



Crank -pin journals number. 



Diameter of crank-pin journals : 



High-pressure inches 



Low-pressure. do. . 



Length of crank -pin journals : 



High-pressure do . . 



Low-pressure do.. 



Space occupied by the engine : 



Length fore and aft do.. 



Width. do.. 



Height do.. 



Diameter of the screw propeller do. . 



Pitch of the screw propeller (uniform) do.. 



Projected length of the screw on line of its axis do.. 



Blades of the screw number 



Friction of the pitch used 



Helicoidal area of the screw blades square feet, 



Weight of the screw pounds 



DBt^DGING ENGINE. 



Plates XXIII and XXIY represent the dredging engine, the principal 

 use of which is to hoist the trawls and dredges, but it is provided with 

 additional " gypsy heads " for hoisting boats, &c. It was built by 

 Copeland & Bacon, of New York, according to their patents. It has 

 three gypsy heads (the large one of steel) mounted on the same hori- 

 zontal shaft, and driven by a double-cylinder half-trunk steam-engine 

 through the intervention of toothed gearing and a modification of 

 Mason's friction clutch. The engines have locomotive valves which are 

 actuated by Stephenson's links and eccentrics ; the cranks are cast-iron 

 disks ; each pair of eccentrics is cast in one ; the cut-off is effected by 

 the lap on the valves. The machine has a friction brake to regulate the 

 "paying out" of the dredge rope, and also a roller guide, with treadle 

 motion, to press the rope aside and prevent the turns from riding. The 

 engine is placed on the main deck, forward of the foremast ; it takes its 

 steam from the main boilers and may be exhausted either into the 

 main condenser or into the atmosphere. 



Its principal dimensions are as follow : 



Greatest diameter of the large gypsy head inches . . 36^ 



Least diameter of the hxrge gypsy head do 25i-{-| 



, Length of the large gypsy head on line of its axis do 24 



Diameter of the inboard end of the small gypsy heads do 21-i 



