November 23, IS&J.] 



SCIENCE. 



673 



iron bulkheads aud beams, close to the boilers 

 or hot steam-pipes, and through damp places. 



To bend the heavy main 

 ■wires at short ladii ^\ ith- 

 out breaking the insula- 

 tion, was also a question 

 that presented itself. But 



all these had been apjirehended. Where the 



wires past^ed damp places, they were incased 



in rubber tubes, besides their insulation of cot- 

 ton-cloth and white le.ad ; in all hot places thej- 



were incased in 



lead pipe ; where 



they jiasscd through 



iron liulk-hcads or 



beams, ferrules of 



hard rubber or 



gutta-percha were 



used; and the 



mains, instead of 



being single wires 



of large size, were 



composed of a 



number of smaller 



wires, wliicli, of 



course, made them 



more flexible. 



Where the wires 



passed an iron sur- fio. 



face, such as a 



lodger-plate or stringer, they were fitted to 



a groove in a wooden batten ; and, where tliej' 



passed a wooden surface, thej* were embedded 

 into a groove cut in the wood ; and, when 

 carefuUj- painted over, it is difficult to detect 

 their presence. The main wires, as far as 

 possible, were led behind the wooden lining 

 of the ship. Where the wires were spliced or 

 ' tapped,' their insulation was removed, and the 

 naked metallic surfaces brightened with sand- 

 paper, to insure metallic contact. Thej- were 

 then twisted together tightl}', and soldered. 

 The naked place was then covered with insula- 

 tion-tape, which is common cotton tape satu- 

 rated with a bituminous insulation compound 

 manufactured by the Edison company, the 

 components of which are kept a profound 

 secret, and which an irreverent young man 

 lias named ' gulloot. ' 



The lamp-fixtures are designed to suspend 

 the shade above, and to cast the unobstructed 

 rays of the light downward. Handsome brass 

 fixtures of three kinds, with porcelain shades, 

 are used on board. Fig. 8 is called a bracket, 

 and figs. 9 and 10 are single and double swing- 

 brackets respectivelj-. 



The wires are run through the tubes of these 

 brackets ; but in the joints of the swing-brack- 

 ets the current is transmitted through insulated 

 hinges, to whicli the wires are fixed b3' bind- 

 ing-screws, as shown at a in fig. 11, by which 

 arrangement the wires are not twisted in swing- 

 ing the bracket. 



The wires are brought to the binding-posts 

 in the lamp-socket, fig. 12, between their 

 liinding-posts and brass conductors. One of 

 tliese brass conductors 

 is soldered to the thin 

 si)un bi'ass socket into 



which the lamp is 

 screwed, while the other is con- 

 nected, tluough the key, to a 

 brass disk, jilaccd centrally in the 

 bottom of the socket, against 

 which one pole of the lamp presses 

 when screwed in place. The key 

 is mounted on a screw-thread of 

 such pitch that one-fourth of a convolution will 

 give it suflQcient axial motion to open and close 



