The lamp shown in the engraving will be recognized as an Edison
lamp, the vacuum globe and the carbon horseshoe being the principal
elements. Mr. John H. Guest, a well known electrical inventor of
Brooklyn, N. Y., judging from his own experience in fusing platinum
with glass in the manufacture of thermostatic fire alarms, concluded
that the principal trouble with the Edison lamp would be the entrance
of air around the wires passing through the glass of the vacuum globe,
devised a simple plan of sealing the joint between the wires and the
glass by means of mercury, thus interposing an effectual barrier to
the entrance of air at that point.
[Illustration: GUEST'S IMPROVED ELECTRIC LAMP, Fig 1 and Fig 2]
The invention is so clearly shown in the engraving that scarcely a
word of explanation is necessary. In the lamp shown in Fig. 1, the
wires that convey the current to the carbon horseshoe are sealed in
the ends of curved glass tubes communicating with the globe, and these
joints are inclosed in small globes formed on the ends of the glass
tubes and filled with mercury.
In this lamp Mr. Guest has made provision partially or wholly
preventing the circulation of air, should any remain in the globe
after exhaustion with the air pump. The device by which this is
accomplished is simply a small globe connected with the lower portion
of the lamp globe by a contracted passage, the theory being that the
cooler and heavier portion of the air will be drawn into the auxiliary
globe by its own gravity.
Fig. 2 shows a lamp in which the tubes that support the wires extend
downward into the lamp globe. These tubes at their junction with the
vacuum globe are fused to the platinum conducting wires, and the tubes
act simply as lateral supports to the wires inside the globe, allowing
the wires to expand freely lengthwise. The tubes are sealed outside
the globe in the manner shown in Fig. 1.
Another improvement made by Mr. Guest consists in inclosing the ends
of the platinum wire conductors in the ends of the material of the
carbon before it is carbonized, the wire being formed into a loop to
increase the conducting surface and to insure a good connection with
the carbon.
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