In the Tudor cell, Fig. 13, the positive plates are first treated by Plante's proeess, coating them with a layer of crystalline electrolytic peroxide ; the grooves are then partially filled with a paste of peroxide of lead. and pressure is applied to the ridges to expand them and partially close the mouths of the grooves.
Besides the improvements in the plates, various devices have been re sorted to with the view of decreasing, the resistance of the logs and se curing better contact between plates of the same sign, such as making connection by tinned copper rods passed through holes in the lugs. Lead is afterwards cast around the copper so that it is screened from the action of the acid.
Dr. Paul &hoop, of Switzerland, has produced a successful gelatinous electrolyte, by adding one volume of dilute sodium silicate (water glass), density 1-18, to two volumes of dilute sulphuric acid of 1.25o density. To prevent short circuiting between the plates by the material dislodged in working, they are now either slung or rested on supports which are so placed that the formation of a layer of mud between them is prevented. See Fig. 14.
Inactive material is sometimes packed between the plates to prevent short cir cuiting and to retain the active mate rial. In England Barber-Starkey has tried filling in between the plates with a mixture of plaster of Paris and sawdust ; Fuller used porous pots ; • and in the Unit ed States, in the Pumpellv battery, cellu lose, or wood pulp, is to separate the plates, which are arranged horizontally.
In the Atlas cell, Fig. 15, construct ed by Carl Hering. the plates consist of blocks made of oxides and salts of lead.
The use of storage batteries in central station work has begun to assume large proportions. In a recent work on Continental central stations, Mr. Killingworth hedges gives a list of stations in which batteries are a valuable adjunct. Most of the plants are small, but some of them are of quite respectable size. They run as follows : Barmen, 5.000 lamps of 16-candle power ; Hanover, 30,000 ; Düsseldorf, 20,000 ; Dessau, 2,500; Rheims, 540 ; Berlin, 800 ; Bad Kiisen, 600 ; Gevelsberg, 2,000 ; Bamberg, 2,700 ; Darmstadt, 5,800 ; Paris, 19,500; Gablonz, 1.500; Konigsberg, 1,600 ; • Blankenarg, 1,000 ; Berlin (Hospital), 2,000 ; Vienna, 10,000. To this list might be added, we believe, Salzburg, Lyons, Toulon, Montpelier, Mulhausen, Stockholm, Sundsvall, Munchen-Schwabing, Varese, Susa, Bremen, Breslau, and Stettin, although few details arc given with refrard to these ; while it appears that batteries are to be added to the Hamburg central station, which operates 12,000 lights ; Wildbad-Gastein, 1,200 ; Elberfeld, 14,000 ; Arco, 2,500. It is not understood from this list that the equipment of batteries is in any instance equal to the number of lamps named ; but in several cases the figures are large. Barmen, it seems, has four double sets of
batteries, 68 cells each, and is now going to erect five sub-stations which will be charged during the day by the main central station. This sub-station plan has not had any trial in America, except at Cheyenne, Wyo.; Germantown, Pa., and llaverford College, Pa. At Hanover. Germany, the accmnulators are placed on four floors, each battery consisting of 136 cells of 1,320 ampere hour capacity, and a discharge of 396 amperes. The Düsseldorf plant is already running three battery sub-stations ; the largest has two batteries of 140 cells, each with a discharge of 4S3 amperes, while the other two, with an equal number of smaller cells, discharge 248 amperes. An interesting feature of the Dessau installation is the employment of gas engines as primary power. It is stated that the addition of accumu lators of 1,700 ampere hour capacity to this plant increased the investment 15 per cent. and raised the output 38 per cent. The present batteries have been in use uninterruptedly for nearly two years without attention, so it is asserted, and more than once have been called upon for an output 20 to 25 per cent. above the normal.
As to the work done in Paris, France, with storage batteries in central stations, Mr. Stanley C. C. Currie says : " The principle adopted is that of casting chloride of lead com bined with a small proportion of chloride of zinc in tablets. These tablets are then placed in a special mold, and ordinary lead cast around them, thus forming a uniform plate. The plates weigh about 20 kilos (44 lbs.) each. The cells contain from 15 to 25 of these plates, making the average total weight of plates per cell about half a ton. The efficiency has averaged from 72 to 85 per cent." The following table gives the data of the tests of different cells: rFor more extended descriptions of storage batteries and the principles involved in their conStruetion and method of operation, the reader is referred to the following works : The Chemistry of the Secondary Batteries of Plante and Faure, by Gladstone and Tribe ; The Storage of Electrical Energy, by G. Plante ; The Electric Arra-mull/tor, by E. Reynier ; Complete Ilan(Thook on the Management of .Areumulators. by Sir D. Salmons ; Accumula tears Eleetriques, by Rene 'famine; Les Voltametres-llegulateurs, by E. Replier ; Die Aecumulatoren fuer Elektricitael, by E. Hoppe ; Storage Battery, by J. T. Niblett. Also the exhaustive researches of Ayrton (Ppoc. London List. Elec. Eng., 1890); Richardson (Jotan. Soc. Arts, London, December 4, 1891). Consult also the electrical journals.] Stoves. Air Healing : see Air Compressors.