34 EEPORT OF COMMISSIONER OF FISH AND FISHEI^IES. [32] 



it is pleased b}^ correct proportions, sound mecliauical ])rinciples, and 

 agreeable outlines. 



To preserve the uniformity of the current an adjustable resistance- 

 box is placed in the field circuit, so that when a number of lamps are 

 extinguished additional resistance may be thrown into the field by a 

 switch on the resistance-box, whereby the internal and external resist- 

 ance may be balanced, preserving not only tlie uniform brightness of 

 the lamps, but also the economy of the machine. 



THE WIRINa. 



The wires are all of copper; those well protected from dampness are 

 insulated with a woven cotton and white lead covering; where they 

 pass damp or wet places they are further incased in rubber tubes; where 

 they pass hot places (through the boiler room) they are run through 

 lead tubes; and where they pass through iron bulkheads they are pro- 

 tected by liard-rubber tubes. There are two comi:)lete circuits round 

 the ship ; in the event of an accident to one circuit (by collision, for 

 example) the lamps will be fed b3^ the other. These main circuits, on 

 board ship, are necessarily doubled or even tripled, as the short bend- 

 ing of a large wire or rod, or hauling it through boles iu iron or wood, 

 Avould be apt to injure the insulation besides increasing the labor. 'So. 

 10 is, therefore, the largest wire, and jSTo. 20 th e smallest wire used in 

 our circuit. 



Where a wire — main wire or branch — passes along a surface of iron, 

 as a lodger plate, it is fitted in a groove iu a wooden batten, and never 

 permitted to touch the iron; when it i^asses a wooden surface, a groove 

 is cut to let it in, and it is puttied and painted over; wherever possible 

 the wires are led out of sight. Wherever splicing or tapping of wires 

 was necessary, the ends were cleared of the insulation, cleaned with 

 sand-paper, soldered, and recovered with a bituminous mixture called 

 "insulation compound," and finally tightly covered with tape; tliese 

 joints are thus as well protected as any part of tlie wire. 



LAMP FIXTURES. 



The lamp fixtures are designed to suspend above and cast the unob- 

 structed rays of light do wnward. Handsome brass fixtures with por- 



FiG. 5. 



» 



celain shades of three kinds are used on board. Fig. 5 is called a 

 bracket, Fig. 6 a single-swing bracket, and Fig. 7 a double-swing 

 bracket. 



