ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
Ill 
The deflection produced by different potentials, per 100 cells, was as follows 
Number of cells 
used. 
Sections. 
A to D. 
A to C. 
A to B. 
divisions. 
divisions. 
divisions. 
10,980 
1-226 
3-613 
22-66 
9780 
1-339 
3-569 
19-84 
8580 
0-9790 
3-368 
18-53 
7380 
0-7995 
3"035 
16-12 
6180 
0-5825 
2 - 655 
14-40 
4700 
0-2979 
2-106 
11-68 
3240 
0-1235 
1-666 
9-23 
2160 
0-0000 
1-250 
7-36 
1080 
0-0000 
o-ooo 
5-64 
The deflection is read for-the battery without the tube and again when the tube is connected. If the tube- 
potential approaches that of the whole number of cells it may at once be calculated, but if the tube- 
potential is much less than that of the battery a shorter length of the line-resistance is taken and a new 
reading obtained with the tube connected; this new deflection is reproduced approximately by lessening 
the number of cells and reading the deflection again without the tube ; the tube-potential is then calculated 
from the new data. The pencil-line-resistance has been found to change from time to time, but this is not 
of the least moment, because, in every observation, the tube-potential is balanced, as it w-ere, at the time 
it is made. 
In fig. 88 T T', is the tube; Z A, the battery; L L', the line-resistance; A C, B C, C D, sections of 
this resistance; G, the galvanometer; K, a key for connecting on the tube when required. The movable 
wire is shown to be inserted into the hole D so as to include the whole resistance A D, but it may be inserted 
into either C or B. 
Note B, relating to Page G 9. 
The second method of obtaining the tube-potential, suggested to us by Professor Mascart, is a modifi¬ 
cation of that described (Part II., p. 165); the change consisting in detaching the induction apparatus 
from the electrometer, as showm in fig. 89 ; for it was found in the former arrangement that the in¬ 
fluence of the induction-plate on the pair of quadrants opposed to that over which it was placed was 
detrimental, especially when much raised. Moreover, it was found to be advantageous to charge the 
needle and not one of the quadrants with the induced charge; and, on the other hand, to connect each pair 
of quadrants respectively with the + or — terminal of two chloride of silver batteries, each of 20 or more 
cells. The other terminal of each battery being connected to the earth ; each pair of quadrants becomes 
constantly charged to the same potential, one with positive the other with negative electricity, and their 
influence on the needle is perfectly symmetrical. 
The figure shows clearly the arrangement. The lower plate is in connexion with the needle through the 
insulated wire I; the Z terminal of one battery, and the Ay terminal of the other are connected to their 
respective quadrants. When an observation has to be made, one terminal of the battery of high potential 
is brought into connexion with T, which is in metallic communication with the upper or inducing plate of 
the induction apparatus, the other terminal of the battery being to earth ; the swing of the needle is 
observed and the apparatus is afterwards discharged by connecting the needle and the inducing plate to 
earth, the tube is then attached to the terminals and the swing observed when T is again touched. The 
ratio of the latter to the former gives the ratio of the tube-potential to the number of cells used. If the 
