When water is poured in to make up for evaporation, the equilibrium of the fluids is not disturbed. The deposit on the zinc thus protected is easily removable, requiring no hacking or scraping. One zinc will endure two charges of sulphate of copper. The band around the rim is one of the most important features of the cell, as it prevents zinc sulphate from creeping over. It offers simply a mechanical obstruction. It works perfectly in bsnds may be applied to any battery requiring them. They serve equally well for Leclanche battery; and, to attach them to cells of any kind already up, it is only necessary to see that the rims of the jars are clean and dry. The sticky side of the strip should be heated slightly and pressed on firmly all Friedlander's -Fig. 77 shows this portable battery with incandescent lamp attached for ordinary use, but various modifications of a more or less ornamental character are manufactured. Pig. 78 illustrates the manner in which the electrodes are arranged. They consist of carbon blocks and zinc rods attached to an axis which can be turned from the outside by means of a knob, so that when the light is not required the electrodes are turned into a horizontal position clear of the liquid. By lowering them more or less, the intensity of the light can be regulated.

The exciting fluid is a solution of chloride of zinc and bichromate of potassium, and has no fume or smell. With a 3 c.p. lamp, one charge of the electrolyte will last for about 3 1/2 lamp hours. The exhausted liquid must then be poured away and fresh solution filled in, an operation requiring no more skill than the filling of an ordinary oil lamp. The carbon electrodes, which are specially prepared, do not need renewal, but the zinc rods must of course from time to time be replaced. This portable battery and lamp is intended for use in warehouses and other places where ordinary lamps are inadmissible on account of fire risk, and also for use in bedrooms and other places where light is only required for a short time.

Chromic odd battery.

Chromic odd battery.

Delamy 's battery.

Delamy 's battery.

Batteries Part 6 50064Batteries Part 6 50065Batteries Part 6 50066

Gas

Following are details concerning an 18-cell battery of Treeby's design, using material which can be easily obtained, and which requires no special construction, though it would be better if the glass cells were less deep, as it would reduce the height of the battery more than 1ft. The cells are placed in a framework made of vulcanised fibre, as it is strong and easy to work.

For the construction of the frame are required 4 pieces of fibre 50 1/2in. by 2in. by lin., and these will make the uprights; 4 pieces 15 1/8 in. by 2in. by lin., for cross bars; 2 pieces 13fin. by 13in. by fin., for the top and bottom of frame; 2 pieces 46in. by 9 1/2in. by fin., for the sides; and a piece of 1/4in. plate-glass, 45 1/2in. by 13 5/8in. for the back, together with 19 pieces of 1/8in. patent plate-glass, 13 1/2in. by l0in. To construct the framework, first take one of the uprights, and having mitred one end across the thickness, take a saw, cut immediately below the mitre, 3/8in. deep, and another fin. below that, and plough out the groove with a plough plane (Fig. 79, top end); then 3 1/2 in. and 4in. respectively from bottom of upright take 2 saw-cuts 3/8in. deep, and plough out between them, making 1/4in. below lower groove a mortise hole 1/2in. by 3/4in. This do to all the 4 uprights, afterwards cutting a fin. rabbet on either side between the upper and lower grooves in the case of two, the other two being rabbeted on one side only as shown by dotted line, Fig. 79. When this is done, take the two last uprights and cut 17 grooves 2 1/2in. apart, 3/16in. deep, by 1/8in. broad; these will then have the appearance of Fig. 79. Now take the two side-pieces, 46in. by 9 3/4in. by 3/8in., and plane a mortise cut 1/2in. deep along the top and bottom of each, and after laying one of the grooved uprights upon them, mark off and cut 17 grooves corresponding to the ones made in uprights.

These must exactly meet when fixed in their places. Again, take one of the sides, and, marking off lin. from the top, bore exactly in centre of side a Jin. hole and 17 other ones 2 1/2in. from each other; these holes are for the rubber tubing which conveys the gas to the cells, and which are connected to the gas-taps M, Fig. 81. On the other side mark off in the same way, boring two 1/8in. holes 3in. from either side. These are for the connecting wires from cells (Fig. 80), Y being binding screws, the small dots above being the holes. This having been done, take the two top and bottom pieces 13 7/8in. by 13in. by 1/2in. and cut two rabbets 3/8in. deep on the bottom side of the top piece and the top side of the bottom respectively at the back - these rabbets being for the glass back to fit into - afterwards fitting them both to the sides by cutting their corresponding mitres on right and left. Now when two of the cross-bars have been mitred at their ends and the other two have had their ends shaped to tenons so as to fit into the mortise-hole at bottom of uprights, the framework ought to be completed and merely require fixing,, which had better be done with bichro-mated isinglass glue, being careful to rough the parts to be glued with sandpaper or a coarse file, using small brass screws 7/8in. long for fixing the sides and cross-bars, and red lead putty for fixing the glass back.

When thoroughly secure, varnish with a stiffish solution of shellac in spirit, to which has been added, whilst warm, 10 per cent, of solution of rubber in chloroform and 2 per cent, of copaiba oil. When the varnish is dry, slide the glass plates into their grooves. Fig. 84 will perhaps give a general idea of the battery when fitted with cells, G being zinc wings sloped forward in order to concentrate the draught, and on which are hung two leaden tubes E, with branches terminating in little cups to catch drips from battery cells, the above.