16
We therefore have to resort to methods which; while they differ somewhat from this arrangement in detail^ are practically the same.
In the first place we must have a large number of these wire loops, and as the wire is soft and easily bent, we must wind it about a core so as to hold it rigidly in place, as it has to be revolved very rapidly. Again, the ends of each wire loop must be brought out and attached to plates or blocks of metal, arranged upon some kind of non-conducting substance at one end of the shaft upon which the whole will turn. Sometimes the ends of the loops are attached to each other in such a manner as to combine all the loops as though they were one wire, and then separate pieces of wire are attached to them where they join each other, and these short wires terminate in plates at the end of the shaft as before described. As each loop of wire (which may be made of one or more coils) comes into the space between the ends of the mag« net, a current is set up in it; this current
