GERARD'S INCANDESCENT LAMP.
The part in which the energy is expended is homogeneous, as might be supposed from the mode of manufacture, and as may be ascertained from a microscopical examination, and it is exempt from those variations in composition that are found in carbons of a vegetable nature, like the Edison. Besides, being of relatively large diameter, the lamp is capable of supporting a very great increase of temperature.
The process employed for fixing the lamps is as simple as can be. Each platinum wire is soldered to a piece of copper that surrounds the base of the lamp and that is fixed to the glass with a special cement. These two armatures intertwine, but at a sufficient distance apart to prevent contact. They carry a longitudinal projection and an inflation that fit by hard friction into two copper springs connected electrically with the circuit. It is only necessary to lift the lamp in order to remove it from the support; and the contrary operation is just as easy.—Le Genie Civil.
A NEW REFLECTING GALVANOMETER.
Fig. 1 shows an elevation of the instrument and a horizontal section of the bobbins. Two pairs of bobbins, cc, cc, are so arranged that the axes of each pair are parallel and in the same vertical plane. Each pair is supported by a vertical brass plate, and the two plates make an angle of about 106° with each other, so that the planes containing the axes of the bobbins make an angle of about 74°. Two horseshoe magnets, m m, made of 1/25 inch steel wire, are connected by a very light piece of aluminum and placed at such a distance from each other that, on being suspended, the two branches of each of the magnets shall freely enter the respective bores of the two bobbins fixed upon the same plate, and, when the whole system is in equilibrium and the bobbins free from current, the two branches of each of the magnets shall nearly coincide with the axes of such bores. The magnets are not plane, but are curved so as to form portions of a vertical cylinder whose axis coincides with the direction of the suspension wire, and to which the axes of the bobbins are tangent at their center, approximately to the points where the poles of the magnets are situated.
FIG. 1. GRAY'S GALVANOMETER.
The needles have been given this form so that their extremities shall not touch the sides of the bore during considerable deflections.