being so pivoted that they can swing round when the cells require to be taken out of their compartments. In Fig. 81 will be seen 3 of the 6 pipes leading from battery box into chimney Z, which ought to be about 28ft. high, and which terminates with a large ventilating cowl to ensure always a thorough draught through battery box, and of the other parts shown in Fig. 80. W is a receptacle for any water condensed in chimney, X being a damper contained in it, T being a small tap or outlet for condensed water. It will also be seen, from Fig. 3D the position of cells allows of a clear 25/8in. space behind for draught. In Fig. 81 M is is a brass tube fitted with 18 nozzles end taps, by which to conduct hydrogen gas to cells, these being connecled by means of short lengths of 1/4in. rubber tubing. The brass tube terminates at the top with a pressure-gauge P, and has at its bottom end a regulator K, which regulates both the pressure and quantity of gas, for it will be seen that when the gas is turned on, the float H, which is made of Ihin iron, rises until a series of small perforations, halfway along its length, Gome opposite the opening of pipe leading gas to cells; then on any lamp being turned on in the main S, a shunt current R passes through regulator and controls the gas according to the resistances of the lamps in parallel; the regulator can also easily be adjusted by turning screw-It may seem unnecessary to have both a pressure gangs and taps to all the nozzles; but, apart from the convenience of shutting off some cells, in case of a leakage of hydrogen gas, which has no smell, it can at once be determined and the cell eat off It will also be perceived that the bobbin of regulator is a shunt on the main leading wires, V being a lamp inserted in shunt; but this is quite optional, as by reversing the regulator and readjusting screw-cap, it can be used direct on the main leads.

Batteries Part 7 50067Batteries Part 7 50068Treeby's battery.

Treeby's battery.

A, vulcanised frame; C, grooves for sliding glass partitions; D, overflow drip tubes; K, gas regulator; L, screw cap; H, core float; M, gas-cocks leading into cells; N, brackets for fixing gaspipe; P, pressure indicator; R'R, shunt binding-screws; S, main binding-screws; T, tap for condensed water; W, condenser; V, lamp; X, damper for draught; Y, binding-screws from cells.

Now to come to one of the roost important parts of the battery - viz., the wire mesh frames to fit into glass cell. For these are required 36 pieces of vulcanite, 12 1/2in. by 3/8in. by 3/8in., 36 pieces 9 1/2in. by 3/8in. by 3/8in., and these will make the 18 topor positive frames, and for the bottom frames will be required the same number of pieces, 12 1/4n. by 3/8in. by 3/8in. and 9 1/4in. by 3/8in. by 3/8in. respectively. All these can be nicely cut out of two half-sheets of vulcanite Jin. thick. Inadditionto the above will be required 18 pieces, 12 1/4in. by 9|in., of silver wire gauze, 120 mesh, and 18 piece, 12in. by 9in., together with several lengths of copper or silver wire, No. 18 gauge, and a good many gutta-percha whip-lashes for sealing in with, and 36 strong elastic bands 1/2in.

The first thing to do is to mitre, mortise, and tenon all the vulcanite strips, and to take a saw-cut 1/8in. deep down the inside 3/16in. from the edge, boring a hole on one side, 4in. from top aide, for the connecting wire to pass through (Figs. 82 and 83). On the other side in the centre on outside of frame file a small groove about 1/4 in. wide across it; this is for the rubber tubing.

The next thing, after fitting all the frames, is to fii the silver-wire mesh inside them, and to do this first take the gauze and turn it up 1/5in. all round, running a silver or copper wire, No. 18 B.W.G. under the lap, twisting the two ends together where they meet (Fig. 83); then taking the shorter piece of vulcanite with the hole in it, pass the twisted wires through and press the wire edging into saw-cat by means of a blunt screw-driver. This also do on the opposite aide with the other piece, soldering the wires to the mesh with metallic putty, and sealing over the saw-cut with a piece of gutta-percha whiplash; then take the two longer pieces, and having placed the other side of the wire mesh into their respective saw-cuts. fix the ends of the pieces in their place, with a solution of gutta, passing a rubber band all round the frame. Now press the wire edging home on either side to bottom of saw-cuts, soldering as before, and sealing with gutta-percha. This will strain the wire mesh, and make it quite tight - an absolute necessity for the proper working of the cell. The wire mesh-plate is now nearly completed, but will have to be placed in a silver bath until the wires of gauze are cemented together, when it will have to be transferred to a platinum bath.

All the other frames must be treated in the same way. When the smaller frames have been sealed in the bottom of their respective glass cells, place the larger ones over them, on the upper side of which has previously been placed about 1 Jib. granulated platinised carbon, about the size of 4 or 5 shot. The cells are now practically finished, except for the addition of a dilute acid, and can be placed in their different compartments.

Batteries Part 7 50070

No doubt the above is capable of many improvements, such as the corrugation of the plates, closing up the face of battery and using forced draught; but the wire gauze plates will only be beaten by thin porous metal ones made of'some less costly metal. The difficulty of the cell is that it must be kept absolutely level, so that the positive or upper plate is never out of capillary attraction with the dilute acid in the cell, and yet it must be never underneath the surface. To remedy this 1 tried floating the positive plate; but this so diminished the available surface that I prefer the level kept constant by overflow tubes, such as D, the evaporation being also kept constant by turning damper X. This latter will be fairly rapid, as the air not only passes over, but permeates through the layer of carbon in cell.