stated to last from 1000 to 1500 hours. Mr. Swan's lamp is of similar construction, but the filament is prepared from cotton fibre charred in oil of vitriol, and has a kink or complete turn in it.

The incandescent lamp of Mr. Maxim, another American, is similar to that of Edison in appearance, but in this case the filament is prepared by taking a thin charcoal fibre and depositing carbon upon it from a hydro-carbon gas or liquid. This is done by passing the current through the fibre until it becomes white hot and decomposes the surrounding gas. When the filament has become properly built up in this way, the residual gas is exhausted and the lamp is ready for use. The carbon loops, which are made of a double form, are joined to the platinum conductors through the glass by little clamps of platinum. Maxim's lamp is shown in Fig. 71. Mr. Lane-Fox has invented a somewhat similar lamp, in which the fibre is a piece of charred bass-broom, on which carbon has been deposited by the process described. It is joined to the platinum wires by a carbonaceous paste or cement; and the globes are sometimes made of opal glass, to screen the eyes from the dazzling brilliance of the glowing loop. The Lane-Fox lamp is usually fed by the Brush machine. The Swan lamp by that of Gordon: but different machines will answer. The Maxim lamp is fed by the Maxim generator, which resembles that of Siemens. Edison's lamp is fed from the Edison generator; and there is a fifth incandescent system devised by Mr. Wright, which is fed by the Gramme machine. In this lamp the carbons are joined to the platinum wires by small ferrules of carbon. The Maxim, Lane-Fox, and Wright lamps are constructed to

give a higher candle-power than the Edison and Swan because of their thicker carbons. The Maxim lamp gives out thirty candles ordinarily, but it can readily be made to give out fifty without fear of breaking the loop or wick. The Lane-Fox lamp is made to twenty candles, but it will safely yield thirty candles.

In the "Duplex" lamp of Dr. S. H. Emmens there are two "loops" or filaments, and the current can be sent through one or both together at will, thus yielding two grades of illumination.

Another lamp is that of Mr. Gatehouse, in which a resistance of platinum wire is added to the circuit of

the filament, in order that the lamp shall keep its resistance to the current carbon practically constant. The filament falls, but the platinum rises in resistance as the current increases, and hence they counteract each other, and give a steady resistance to the lamp.

Such incandescent lamps are especially suitable for buildings very liable to fire, such as theatres, museums, and public libraries, because the red-hot wick is protected from the outer air, and if by accident the bulb should break, the inrush of the atmosphere at once dissipates the filament in dust. They are equally applicable to fiery mines, and Swan's lamps have been introduced with success into the Earnoch Colleries; the bulb being further guarded by a lantern of stout glass which is kept under lock and key. Moreover, as they will burn as well under water as in the upper air, they have been employed in diving operations to illuminate the sea-depths. Translucent balloons, lit inside by incandescent lamps, and the current flashed off and on according to a code of signals, have also been proposed for signalling by night; and many other possible uses for these lights could be suggested.

There are two ways of arranging electric lamps in

order to distribute the current to them. They can be placed one after another in a single circuit or wire connecting the two poles or brushes of the generator, as shown in Fig. 72, where м is the generator or

machine, and L L the lamps. In this case the current requires to have a high electro-motive force in order to overcome the added resistance of the whole number of lamps. Such a current is supplied by the Brush generator or the peculiar form of Gramme generator employed by Jablochkoff. These are the currents which are dangerous to life and limb unless they are properly insulated; and it is by these that one or two fatal accidents have occurred through negligence. The other way of arranging the lamps is to connect them singly or in little groups by cross wires between two main conductors joined to the brushes of the generator м, as shown at L L in Fig. 73. Then the current, instead

of traversing one lamp after another, splits up between the lamps, part going through one lamp or group, and part through another. The resistance of any particular path or channel for the current is in such a case not very great, and the electro-motive force of the current need not be dangerously high. It is on this plan that incandescent lamps are generally arranged for domestic purposes, and the current flowing in the wires about a house would of course be harmless. These lamps can be mounted on an ordinary chandelier.

The aim of electric lighting companies is to found central stations in different districts of a town, and there manufacture electricity, which would be distributed to all the houses in the district, just as gas is

now.

In order to carry this out properly, a means of storing the electric power is necessary, in order that there should be a stock in hand for use by day, when the generators were not working, or in case of accident. In the so-called "secondary batteries," or accumulators, of M. Faure, MM. Sellon and Volckmar, and others, we have a means of doing so. The Faure accumulator, Fig. 74, consists of two lead plates, overlaid with red-lead and sheathed in felt, then rolled up together and plunged in a vessel containing acidulated water. When these two plates are connected by their terminal wires (+), to the poles of a generator, electric energy can be pumped into the cell, so to speak, and there magazined. On disconnecting the generator and joining the plates of the cell through a wire or through electric lamps, as the case may be, an electric current is found to flow out of the cell in the reverse direction to that which flowed in from the generator. The Sellon-Volckmar accumulator is similar to Faure's, but the plates are simply placed side by side in the acidulated water, and the red-lead is filled in the form of paste into round holes cast in the metal plates.

The Sellon-Volckmar cell is made in the form of a wooden case containing the liquid and the plates. These plates are an alloy of lead, and the paste is filled into the perforations. The absence of the coating of red-lead and the cloth sheathing, reduces the internal resistance of this battery and makes it restore some 80 or 90 per cent. of the current put into it. Binding-screws are fitted on the cover to connect up the wires which run to the lamps.

At the Electric Exhibition in the Crystal Palace during the summer of 1882, the Lane-Fox incandescent