In the first illustration (fig. 267), A and B are the positive and negative carbon-holders respectively, and the carbon points are controlled by an armature, which is, in its turn, adjusted by the screw, D. When it happens that the magnetic force is reduced the spring acts and permits the points to approach again, and the light is rekindled; the carbons are then locked till required to move. The second illustration (fig. 268) shows a section of the lamp with the wheel arrangements for controlling the advance of the carbon points as they waste away. [Illustration: Fig. 269.—Wallace lamp] [Illustration: Fig. 270.—Houston lamp.] In the “Brush” light, which is in use in London, and is fitted for large spaces, the carbon points are held by a regulator side by side, and they last eight hours without renewal. The power is generated by an electro-dynamic engine. We give illustrations of the lamps of Wallace and Houston (figs. 269, 270). The current is conveyed through _b_ and the magnet, _m_. The armature, _a_, separates the electrodes, and the weakened current is restored by _b_, and the light continues. The pillar, _p_, is hollow, with a wire running through it. The positive electrode is supported by J, the negative by C; V is a button which comes in contact with the lever, T, when the carbon points are exhausted, and cuts the lamp out of the circuit by passing it direct through mercury cups. The Jablochkoff candle and chandelier are also represented (figs. 271, 272). The candles consist of carbons connected at the top, but otherwise insulated, and fixed in a socket. They do not last very long without renewal. The exhibition at the Crystal Palace will be essentially an Electric Light Exhibition, and all the latest forms can be studied there. The great attraction will doubtless be, as at Paris, the varied and numerous inventions of Mr. Edison. The early career of that American “magician” is now tolerably well known; his tremendous energy and application are fully appreciated. With only a few months schooling all his life he has taken a foremost place in the scientific world. In ten years he has invented the phonograph, the electric pen, a system of fast telegraphy, the electro-motograph, the telephone, a tasimeter, and other useful applications of electricity, besides solving the problem of electric light for domestic purposes. Mr. Edison’s electric light[18] requires something more than a passing notice, and we will therefore endeavour to give a sketch of the general subject. Now that the electric light has been made available for domestic purposes, and the very simple lamp (consisting of an exhausted glass globe, two platinum wires, and a piece of charred paper) can be obtained, people will no doubt soon largely adopt electric lighting in their houses. The light has found a success at the theatre, in the streets, and in the train; there is no reason why it should not be adopted generally, being more economical and more healthy than gas.