Scientific American Supplement, No. 362, December 9, 1882 by Various
page 64 of 140 (45%)
page 64 of 140 (45%)
![]() | ![]() |
|
wires a little stronger, and varying generally from one to two-tenths
of a millimeter in diameter. The current then requires to be a little intenser. The requisite intensity is easily obtained with elements of large surface, which have a much feebler internal resistance than porous-cup elements; and since, for a given number of elements, the intensity of the current decreases in measure as the internal resistance of the elements increases, it becomes of interest to diminish such internal resistance as much as possible. The platinum wires are usually rolled spirally, with the object in view of concentrating the heat into a small space, in order to raise the temperature of the wire as much as possible. There is thus need of a less intense current to produce the inflammation than with a wire simply stretched out. In fact, the same wire traversed by a current of constant intensity scarcely reaches a _red_ heat when it is straight, while it attains a _white_ heat when it is wound spirally, because, in the latter case, the cooling surface is less. [Illustration: FIG. 2--RANQUE'S NEW FORM OF LIGHTER WITH EXTINGUISHER.] We shall now proceed to the examination of a few practical forms of electric lighters. In Fig. 1 will be seen quite a convenient spirit or naphtha lighter, which has been devised more especially for the use of smokers. By pushing the lamp toward the wall, the wick is brought into proximity with the spiral, and the lamp, acting on a button behind it, closes the current. Pressure on the lamp being removed, the latter moves back slightly, through the pressure of a small spring which thrusts on the button. Owing to this latter simple arrangement, the spiral never comes in contact with the flame, and may thus last for a long time. Mr. |
|