OF DENISON UNIVERSITY. 
17 
battery to any one of a great number of combinations," The irlstru- 
ment illustrated is adapted to control a battery of twelve, twenty-four, 
or some multiple of twelve cells. 'Vw 
It consists of a base of thoroughly seasoned wood or ebonite, 
upon which is fixed a double row of flat, rectangular pieces of brass, 
I, 2, 3, etc., each two or three centimetres long, one centimetre wide 
and one half centimetre thick. Each is fixed to the base by two 
round-headed machine screws, d and e, which fit into holes bored 
nearly through the brass from the under side and tapped out to fit the 
screws. The plates are so placed that the spaces between the rows are 
of the same width as the spaces between single plates. All are of 
equal size except two, 12 and 13, at opposite ends of the upper and 
lower rows ; these are twice as long as the others. The plates may be 
connected like the coils of a^TCsistance box, by flat plugs of brass 
shown in end and side elevation at and c. Fig. 2. Binding screws 
are soldered on at that end of each row which terminates in a short 
piece of brass. From these wires lead current to any desired point. 
Each plate in the upper row is connected to the positive terminal of a 
battery of one or more cells and each corresponding plate in the lower 
row with the negative terminal of the same battery. Thus, plates i 
and 13 form the terminals of one battery, and 2 and 14 of another. 
The battery wires are firmly held by one of the two screws of each 
plate, as shown at /. It is well to glue strips of wood, g under the 
ends of the base so that the screw heads will not have to be counter- 
sunk. To show how connections are made, suppose the simple case 
where each brass plate is the terminal of a single battery cell. In Fig. 
3 we see at a., how the plugs must be inserted to give, an arrangement 
of twelve cells in series, at b the arrangement of twelve cells parallel, 
at c, the combination of six cells in series and two parallel, and at d, 
of three cells in series and two parallel. If the cells are of the Leclanche 
type, each with an electromotive force of 1.4 volts and internal resist- 
ance .7 ohm, we would have in the several combinations 
abed 
Electromotive force. 
— 16.8 
1.4 
8.4 
Internal resistance. 
- 8.4 
, 06 
2. 1 
Current with no external resistance. 
— 2.0 
23-3 
4 - 
“ 1 ohm “ 
— 1.8 
1-3 
2.71 
' “ 5 ohms ‘^ 
— 1-3 
.27 
1.04 
This table shows the range of ] 
power possible 
by a 
4.2 volts. 
.53 ohms. 
8. amperes. 
2.74 
.96 
moment’s ad- 
