The means for supporting and turning the coil in order to wind on the secondary may be left somewhat to the ingenuity of the young experimenter. The following suggestion, however, is one which experience has proved to be well worth following out, and may be applied to other things than the construction of an induction coil. It seems to be the nature of most boys, for some reason or other, to be unwilling to spend time and labor on anything which will aid them in their work. They are always in such a hurry and so anxious to see something completed that they direct all their energy to that end rather than spend part of their time in constructing some little device which would really lighten the other work and go a long way towards insuring its successful completion. I have frequently given instructions for building an induction coil and placed particular stress upon winding the secondary, only to have such suggestions ignored in the anxious endeavor of boys to finish the coil as soon as possible. In every such instance the coil has been a failure. [Illustration: Fig. 162.—Simple Winding Device for winding the Secondary.] The illustration shows a simple form of winder, with which the operation of winding the secondary is a very slow one, but, on the other hand, it is possible to do very accurate, careful winding with the aid of such a device. The parts may all be made from wood. The chucks fit tightly over the ends of the core so that when the handle is turned, the coil will revolve also. The spring serves to keep the chucks snugly against the coil ends, so that they will not slip. From one-half to five-eighths of a pound of wire will be required to wind the coil. A large number of strips of thin paraffined or waxed paper must be cut five inches wide. The inside terminal, or "beginning" end of the wire is tied around the insulating tube near the left-hand end. The spool of wire must be placed in a position where it will revolve freely without strain on the wire. No. 36 is very fine and easily broken, so use the utmost care to guard against this mishap. [Illustration: Fig. 163.—Completed Secondary Winding.] Wind on a smooth, even layer of wire, permitting each turn to touch the other, but none to lap over. Carry the winding to within one-half inch of the ends of the insulating tube and then wind on two layers of the waxed paper.