32 



KEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



[30] 



and Sims engine, an Edison Z dynamo (Plate XXII) having vertical 

 field magnets, a resistance-box in the magnetic field-current, the neces- 

 sary wiring, lamp fixtures, safety-catches, and lamps. 



THE ENGINE. 



The steadiness and uniform brilliancy of the lamps depends so largely 

 on the engine driving the dynamo that Mr. Edison has adopted the best 

 (though quite expensive) engine he could find, which is manufactured at 

 Providence, E. I., by Armington & Sims. The great success of this engine 

 lies in the correct balancing and lightness of its working parts, large 

 bearing surfaces, early exhaust closure, and in its extremely sensitive gov- 

 ernor. It has a piston valve, which has considerable exhaust lap, which 

 serves not only to " cushion " the piston past its centers but to save the 

 steam , thus compressed in the clearance spaces. The engine runs 300 

 revolutions per minute, and is belted to and drives the dynamo 1,200 revo- 

 lutions per minute. The governor of the engine is fixed in the fly-wheel, 



Fig. 3. 



which is keyed to the shaft ; there are two eccentrics, one within the 

 other, and both movable on their axis ; there are two weights, with their 

 centers of motion opposite, and fixed in arms of the wheel; these weights 

 are each connected to one of the eccen tries and connected by an arm or 

 rod ; spiral springs (Fig. 3), to resist the centrifugal force of the weights, 

 are provided ; the system is so constructed that any centrifugal motion 

 of the weights will throw one eccentric ahead and the other back, thus 

 diminishing the throw of the eccentrics and effecting a shorter cut-off, 

 without changing the lead of the valve. When the main engines of 

 the ship are in motion, we use a boiler pressure of 50 pounds above the 

 atmosphere and exhaust all engines (including the dynamo engine) into 



