The sketch we have last given shows three batteries connected in
multiple. These we will call set No. 1.
Now, suppose we take three more batteries exactly similar and connect
them together just in the same manner. Let us call this set No. 2. Now
take the wire leading from the carbon of set No. 2 and connect it with
the wire leading from the zinc of set No. 1. Then take a wire leading
from the zinc of set No. 2, and a wire leading from the carbon of set
No. 1, and connect them with the lamps or motors. These two sets being
connected in multiple series, we shall get 4 volts and 30 ampères.
This is called connecting in multiple series, and may be extended
indefinitely with any number of batteries.
We should add that one of the elements in a battery is called
"positive," and the other "negative."