Voltaic BatterieSi 8jc. 1 39 



the amount of action obtained at any of the three different 

 positions in a is the same as the ratio found for these positions 

 respectively in h and c, 



90. 12 : 26 (in c) : : 21 : 4!5'5 (in h) being as near an ap- 

 proach to 46, the real number, as could be looked for in ac- 

 tual experiment ; and the same ratios are maintained with no 

 material alteration throughout. 



91. These preliminary trials show, therefore, that I may 

 select any-sized couple which may appear most convenient 

 for the following more extended experiments upon the effects 

 of distance ; and that the results obtained by the couple now 

 to be used will be true equally for this one condition and for 

 every other as regards the dimensions of the couple em- 

 ployed. 



92. To facilitate references to positions and numbers in 

 the following experiments, let the mass of liquid in which 

 they are conducted be represented by the following diagram, 

 in which the horizontal line is supposed to pass through the 

 centre of the mass contained in the graduated trough already 

 described (36. p. 64), and the vertical line, also passing through 

 the centre, to represent its depth. 



Fig. 1. 



H 1 1 ' 1 1— H 1— J 1 i 1 i 1- ! i i- 



10 II 12 13 14 15 16 17 18 



D 



93. The position of the fixed zinc plate is at Z, whence 

 the graduation commences ; the first division being a quarter 

 of an inch from the zinc, and the amount of voltaic action 

 obtained at this first position is used throughout as the 

 standard of comparison of the effects of distance. The plates 

 used in these experiments, whether of zinc or copper, are each 

 one inch square, and only that surface of the zinc plate which 

 is opposite to the copper presents a clear amalgamated sur- 

 face; the contrary surface, as well as the connecting wire, 

 being well covered with wax to preclude the contact of the 

 acid, and to restrict its action to the clear amalgamated sur- 

 face alone. But both surfaces of the copper are clear, and 

 consequently brought into operation. 



94. The experiments are first gone through with an acid 

 mixture composed of 1 part by measure of sulphuric acid, and 

 100 of water, its specific gravity being 1*013; and are after- 



