DEEr-SEA EXPLORATION. 
287 
Portable electric Wjht.s : There are two small reels carrying 50 feet each ol‘ 
insulated Ilexible cable, to which 50-candle’ incandescent lamps are attached; one 
reel is in the pilot-house, the other under the forecastle, and both can be concen- 
trated upon the table sieve, where a bright light is required tor collecting and 
assorting specimens at night. These lamps have replaced the arc lights used for the 
same purpose during the hrst cruise of the Albatross. They are more easily managed 
and answer the purpose e(iually well. 
Submarine electric lamjis are improvised on board the Albatross by connecting an 
ordinary 10 or 50-caudle lamp to one end of an insulated cable, carefully wrapping 
the joint to make it water-tight; a plug on the other end forms a convenient connection 
wherever a lamp socket is found. They are especially useful in collecting at or near 
the surface, lighting up the sounding machine, dredging gear, or any part of the deck 
remote from fixed lamps. 
LAMP FIXTURES. 
There are combination electroliers in the cabin and ward-room arranged to burn 
either mineral sperm oil or electricity or both. The bracket fixtures are designed to 
be suspended above and cast unobstructed rays of light downward; they are hand- 
somely made of brass with porcelain shades, three kinds being used, called brackets, 
swing brackets, and double swing brackets, as shown in figs. 1, 3, and 3 (plate xiii). 
The wires are run through the tubes of these brackets, but in the joints of the 
swinging brackets the current is transmitted through insulated hinges, to whicii the 
wires are fixed by binding screws, as shown at a in fig. 4, by which arrangement 
the wires are not twisted in swinging the bracket. The wires are brought to the 
binding ]>osts in the lamp socket, fig. 5, between their binding screws and brass con- 
ductors; one of these brass conductors is soldered to the thin-spun brass socket into 
which the lamp is screwed, while the other is connected, through the key, to a brass 
disk jilaced centrally in the bottom of the socket, against which one iiole of the lamp 
ju'esses when screwed in place. The key is mounted on a screw thread of such pitch 
that one-fourth of a revolution will give it sufficient axial motion to open or close the 
circuit. 
The lamps are of thin glass, pear-shaped, containing a thread of bamboo carbon 
about as thick as a horsehair. The small end of the lamp (fig. 0) contains glass of 
sufficient thickness to make a tight joint on the idatiiium wire conductors which 
carry the current to the carbon. The atmosphere is exhausted by Edison’s modifi- 
cation of the Sprengel pump, through a tube at the lower eml of the lamp, and the 
tube is then fused and broken off. Platinum wire is used because its index of expan- 
sion is the same as that of glass, thus preventing any breakage or leakage from the 
heat. The bamboo carbon and platinum wire are soldered together by electrically 
deposited copper. One wire, passing through the glass, is soldered to a small brass 
disk which is centered on the top of the lamp (fig. 0), while the other wire is soldered 
to the spun brass screw thread which surrounds the cylindrical part at the top of the 
lamp, and when the lamp is screwed into the socket (fig. 7) the circuit is completed 
or broken by the switch or key already described. 
When the circuit is closed the carbon thread becomes heated to incandescence — 
from its high resistam;e — and continues to glow, in vacuum, without burning, so long 
as the current continues to liow. Eig. 8 shows a lamp screwed into its socket. 
By varying the length, and also the sectional area of the carbon thread, keeping 
the electro motive force constant, Edison has varied the candlepower of his lamps. 
