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NATURE 



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2, 15 



force 2i times that of a Daniell's cell ; their internal 

 resistance was also very small, being from one-eighth to 

 one-twentieth of an ohm. These cells improved with use ; 

 the liberated gases attacking the surface of the lead elec- 

 trodes, so that they gradually became of a spongy texture, 

 while the surface of the plate at which oxygen was 

 liberated became covered with a film of brown peroxide 

 of lead. When both electrodes were thus " formed " by 

 charging the cell at intervals of a fcAv days in opposite 

 directions, the Plante cell became a veritable accumulator 



Represents tw 



separated by strips of thick felt, prepared 

 ogether round a roller. 



of electric currents, and was able to store up from a com- 

 paratively feeble source a supply which could yield vastly 

 stronger effects for a short time. In fact the secondary 

 battery became in Plant^'s hands a kind of Leyden-jar 

 for storing currents of electricity ; the essential point of 

 difference between the two being that while the Leyden- 

 jar accumulates a cliarj^e, and can be c barged or discharged 

 in an instant — or in other words possesses only an " in- 

 stantaneous capacity" — the secondary battery accumulates 

 currents which may flow into it for many hours, and which 

 may take also a considerable time for their discharge, its 

 "continuous capacity" being very great as compared with 

 its instantaneous capacity. The currents stored up in the 

 secondary battery are however not stored up as accumu- 

 lations of electricity. They are stored up in the form of 

 chemical work done in the cell, this chemical work being 

 capable of being retransformed at will into the energy of 

 electric currents. When the charging current from an 

 independent battery or from a dynamo-electric machine 

 (see Fig. 2) is passed through a Plante cell, the electrode 

 by which the current enters becomes more highly per- 

 oxidised than before, while a corresponding amount of 

 deoxidisation takes place at the electrode by which the 

 current leaves the cell. When the cell thus charged is 

 used as a battery it gives back a current which flows out 

 from the electrode by which it formerly flowed in ; passing 

 through the cell from the deoxidised to the peroxidised 

 electrode, until they are both reduced to a state of che- 

 mical similarity. If the cell is joined to the dynamo- 

 machine which charged it, in order to drive it round as 

 an electro-magnetic engine or motor, it will cause it to 

 rotate in the same direction as that in which it was driven 

 when used as a generator ; the principle of reversibility 

 applying both to the cell and to the machine. 



Several forms of secondary battery adapted for storage 

 of currents have been suggested in recent years. In 

 Philadelphia Professor, Houston and E. Thomson have 

 tried a modification of the Daniell's cell, in which sulphate 

 of zinc was electrolysed between electrodes of copper, the 

 metallic zinc so deposited afterwards serving as the 

 negative pole of the cell. Another suggestion, due to M. 

 d'Arsonval, was to use an electrode of lead along with 

 one of zinc, dipping into a solution of sulphate of zinc. 

 The charging currents deposited metallic zinc upon the 

 latter and liberated oxygen at the former, which, as in the 

 Plante cell, became coated with spongy peroxide of lead. 

 As this latter is not a very good conductor IVl. d'Arsonval 

 further proposed to increase the effective surface by laying 



the sheet of lead horizontal and covering it with leaden 

 shot, which should also become peroxidised. 



The latest form of secondary battery is that of M. 

 Camille Faure, described in Nature, vol. xxiv. p. 68, of 

 which there has been so much talk in the serai-scientific 

 press, and which is now being made the central point of 

 a great financial " operation" in Paris. There can be no 

 doubt that this instrument, though the accounts of its 

 performances have been grossly exaggerated, is an im- 

 proveinent upon that of Plantif, of which it is a slight 

 modification. The labour and difficulty of "forming" 

 the Plant(5 cell, that is to say of charging and re- 

 charging it until a sufficient film of peroxide of lead 

 should be produced, led M. Faure to try the effect 

 of coating the lead plates at first with a film of red 

 lead or minium, a lower oxide than the dark brown 

 peroxide. The two sheets, after having been covered 

 with minium, are rolled together precisely as in the 

 Plants cells, as shown in Fig. 3, a sheet of felt being 

 interposed to prevent internal contact. It was stated 

 by M. Reynier that the capacity of such cells was 

 forty times that of the Plante cell ; but four times 

 would have been nearer the mark if cells of equal 

 size were compared. M. Faure's cells are made of 

 large size and weigh 75 kilogrammes, or nearly 200 

 for lbs. It is stated th t one such cell would store a 

 sufficient amount of current as to be able afterwards 

 to yield in an hour an amount of work equal to one horse- 

 power. Confirmatory observations are yet needed. 

 Meantime let us just remind the enthusiast who brought 

 over to England the "million foot-pounds'' of energy 

 stored up in a Faure cell, that he would have imported a 

 dozen times as much stored energy if he had brought 

 over instead a lump of coal of the same weight. 



The uses for such secondary batteries may be of three 

 kinds : — i. They may serve as portable supplies of elec- 

 tricity to be left and called for to recharge when exhausted. 

 2. They may serve to accumulate supplies of electricity 

 from dynamo-electric machines, and store them until 

 required for furnishing electric light or motive power on a 

 small scale. 3. They may serve as equalisers of electric 

 currents in a system in which the supply is liable to 

 fluctuations. Suppose, for example, a dynamo-electric 

 machine is employed to produce electric light. Any least 

 thing which alters the speed of the machine, even for an 

 instant, makes the light flicker and change in intensity ;, 

 while the breakage of the engine-strap would at once 

 cause total darkness. But if a secondary battery of 

 suitable dimensions and power were inserted across the 

 circuit between the dynamo-machme and the lamp, the 

 inequalities of the current would be greatly modified. 

 When the light was not in use the battery would store up 

 the current. If the engine failed the battery would at 

 once put forth its power. It is probably in this direction 

 that the secondary battery will find no unimportant field 

 of usefulness. 



A SINGULAR CASE OF SHIPWRECK 



THE wreck of the Danish mail steamer P/iO'itlx; 

 which took place off the west coast of Iceland on 

 January 29, was attended by rather unusual circumstances 

 deserving of note. The vessel (about 450 tons burden) 

 sailed with cargo and the mails from Copenhagen for 

 Leith, the Faroe Islands, and Iceland, about the middle 

 of January. 



Nothing particular occurred until after leaving the 

 Faroes, when she ran into a severe gale, which rapidly 

 increased to a perfect hurricane, while at the same time 

 the temperature fell to about 50° F. of frost ( — 18° F.). 

 Such cold is not extraordinary in these latitudes in winter, 

 but fortunately it is seldom associated with very high 

 winds. Under the circumstances in which the PImnix 

 was placed every sea that she shipped frcize, and the 

 deck soon became covered with a foot or two of solid ice. 



