352 TENTH ANNUAL REPORT OP 



Batteries composed of zinc and copper plates buried in the moist 

 ground are said to be very constant. Sucb batteries, however, yield 

 very weak currents, because the resistance to conduction between the 

 plates is very great. Thus it is evident that the current of this 

 battery v/ill remain constant longer than when the plates were im- 

 mersed in acid. 



Prince Bagration placed plates in vessels filled with sand, w^hich he 

 moistened moderately with a solution of sal-ammoniac. Garnier used 

 such batteries successfully to keep electrical clocks in motion (Ding- 

 ler's Journal, vol. 110, p. 177) ; here a very feeble current was pow- 

 erful enough to impart sufficiently strong magnetism to a small 

 electro-magnet. 



Garnier's apparatus was constructed as follows : The sand was in 

 a small tub ; the zinc and copper had the form of a cylinder, the 

 zinc being on the inside. The surface of the copper was 1.5 and that 

 of the zinc 1.3 square decimetres. Such an element kept the appa- 

 ratus in motion two months and a half. By using a battery of many 

 such elements the construction could be so arranged that a single pair 

 of plates might be removed, and renewed v/ithout interrupting tli^e 

 current. 



Koppinsky (Dingler's Journal, vol. 101, p. 222 ; Technologiste, 

 March, 1840, p. 241) was disappointed in his expectation of this bat- 

 tery. He probably wished to produce strong currents with it. The 

 vapor of ammonia also annoyed him. The unfavorable results are to 

 be ascribed, in his opinion, to insulation ; because the battery cannot 

 supply itself with electricity from the ground, and because it is not 

 protected from exposure to the air, which neutralizes the electricity 

 generated by contact of the plates. 



I cite this as an example of the loose and inconsiderate disquisitions 

 on the galvanic current and battery to be met with in technical periodi- 

 cals. The editors of these journals should be more critical in such 

 cases, and statements v>^hich are only calculated to lead astray those 

 having no well-founded physical knowledge should either not be 

 permitted to appear, or should be accompanied with the requisite ex- 

 planations. 



After condemning all other batteries, Koppinsky finally proposes to 

 use for galvano-plastic purposes, zinc and copper elements, the plates 

 of which are one square metre in surface, and immersed two or three 

 millimetres apart in dilute snlpliuric acid. This is one of the oldest 

 forms of the battery with large plate, to which Hare subsequently gave 

 the very convenient form of a spiral ; thus, in this respect, Kop- 

 pinsky's efforts resulted in nothing new. On the other hand, the 

 proposal to place the acid in vessels of other than resinous VFOod and 

 set them on moistened earth, is new, but of no value. 



The experiments of Weekes (Dingler's Journal, vol. 97, p. 194) 

 show the feebleness of tho current produced by burying in tolerably 

 moist ground, plates of zinc and iron, each being 54 square decime- 

 tres in surface. A current was obtained which deflected the astatie 

 needle of a multiplier 87"^, but the deflection soon fell to 61° ; the cur- 

 rent was therefore exceedingly weak. 



A pile of 36 pairs of this kind gave, between coal points, a light 



