144 
PROFESSOR DANIELL ON VOLTAIC COMBINATIONS. 
2 an infinitely small zinc rod in the axis. Let the area of the copper-plate be 100, 
the area of the mean section of the electrolyte ( m s) will be = 50. The distance 
of c from 2 , or the thickness of the electrolyte, will be 2 inches. Let the rod z be re- 
placed by a cylinder of zinc z z, two inches in diameter, fig. 4. The mean section will 
be increased to 75? and the thickness of the electrolyte will be decreased to 1 inch. 
The force would, therefore, be increased in the proportion of 50 : 75 for the first, 
and of 1 : 2 for the second : consequently, compounding the proportions, the force 
circulating in the first arrangement would be to that in the second as 1 : 3. 
In the preceding observations the cylinders and rods have been taken of equal 
heights ; when one is shorter than the other, it will be obvious, from a little conside- 
ration, that the decrease of length is equivalent to an increase of distance between 
the two. 
Fig. 5. 
Z C 
Let c c c' c' represent a section of a copper cylinder, and z z’ a zinc rod of half its 
height ; in any action which may take place from the point of the rod z 1 to the lower 
half of the cylinder c', the distance between the metals z' c’, or virtual thickness of 
the electrolyte being greatly augmented, the influence of the lower half will be pro- 
portionally diminished. 
In some experiments which were carefully made with the calorific galvanometer, an 
amalgamated zinc rod was successively immersed in the electrolyte in a copper cy- 
linder 3^ inches high to the following depths, and with the results set down in the 
Table : — 
Length of Zinc. Degrees of galvanometer. 
\ inch 
7 
^ inch 
19 
§ inch 
35 
1 inch 
49 
1 \ inch 
67 
3^ inches 
- 
97 
In a copper cylinder, twenty-one inches in height, charged with dilute sulphuric 
acid and sulphate of copper, an amalgamated zinc rod lost 51*5 grains in five minutes ; 
a rod of half the length lost in the same time 26T grains. In a similar cylinder, six 
inches in height, charged in a similar manner, a zinc rod of equal length lost 12 
