NoVF.MnEK Hi, IS&i.) 



SCIENCE. 



643 



of drodgiiig in great depths often canies the 

 daj-'s labor past midnight. To provide for 

 these emergencies, which arc frequent, and 

 to alford ample illumination for the natural- 

 ists, not only in assorting the contents of the 

 dredge as it is delivered on deck, but to illu- 

 minate their microscopes, delicate balances, 

 «tc., in the laboratory, the commissioner of fish 

 and fisheries determined to employ the best 

 artificial illumination the eountr}' afforded. 

 As the vessel is essentially a steamer, using 

 steani for every labor where it is practicable, 

 the iilea of electrical lighting from a dynamo- 

 electric machine, driven hy a steam-engine, 

 was readily conceived, and an examination of 

 the different systems was at once entered in- 

 to. The Edison company for isolated light- 

 ing, we found, was prepared to enter into 

 a contract for a complete plant, including 

 the engine and the wiring ; and being able to 

 divide the light into eight - candle power 

 lamps, besides giving guaranties, their bid 

 was accepted. 



The arc-lamp, though admirable for our deck, 

 where a great quantity of light in a limited 

 space is necessary, can never, from its great 

 brilliancy, be utilized for twelve or fifteen nat- 

 uralists, each at a special work, in the labora- 

 tory. It also occurred to the commissioner, 

 that a lamp which could be lowered into the 

 sea, to attract fishes, would be useful, thus 

 afl'ording another reason for preferring the in- 

 candescent light. 



Fig. 1 shows the way in which the arc- 

 lights are placed iu circuit. And as each arc 

 offers a considerable opposing electromotive 

 force, it is necessar3', in order to get light in a 

 number of such lamps placed in series, to use 

 cunents of high tension. 



Kig. 2 shows the incandescent lamps in 

 mnltii)le arc. The main wires, a and b, are 

 tapped at pleasure, and the lamps are hung in 

 the short circuits. The carbon threads in the 

 lamps (described beyond) offer so much resist- 

 ance that the current heats them to incan- 

 descence. The electromotive force in the 

 circuit is low, which renders shocks impos- 

 sible. 



The plant on board the Albatross consists 

 of an eight and a half by ten Armington and 

 Sims engine, an Edison Z dynamo having its 

 fielil-magnets vertical, a resistance-box in the 

 cii-cint of the magnetic field, the main and 

 branch wires, lamp-fixtures, safet3'-catches, and 

 lamps. 



The steadiness and uniformity of brightness 

 of the lamps depend largely on the engine 

 driving the dynamo; and the success of the 



system lies more in the attention paid to the 

 engine, when the plant is correctl.y installed, 

 than in any thing else. Uniformity of speed 

 is the great object sought; and, to scciu'C this, 

 Mr. Edison has wisely adopted a high-speed 

 engine with a sensitive governor, which is 

 found in the Armington and Sims engine, 

 represented in fig. 3. 



The superiority of this engine lies in its well- 



V" 



(b 



0) -^ 





balanced working- parts, its relatively large 

 bearing-surfaces, its sensitive automatic gov- 

 ernor, and in its simple and well-balanced 

 valve. 



To secure high speed without the noise of 

 ' thumping,' great lap has been applied to the 

 exhaust side of the valve, where1\v ' cush- 

 ioning' is effected. This cushioning, or early 

 exhaust closure, also effects a saving hy re- 

 taining, in the clearance spaces, steam which 

 would otherwise have been exhausted and 

 wasted. To prevent an unequal expansion 

 between the piston-valve an<l its chest, the 

 castings are so made as to allow live steam to 

 surround that part of the chest which surrounds 



