─────────────────────────────────────────────────────────────────── Size Length Width Length Width No. of No. of of of of of of Paper Tinfoil Coil Paper Paper Tinfoil Tinfoil Sheets Sheets ─────────────────────────────────────────────────────────────────── 1/4 30 in. 4 3/8 30 in. 4 in. 5 4 in. in. ─────────────────────────────────────────────────────────────────── 1/2 30 in. 4 3/8 30 in. 4 in. 5 4 in. in. ─────────────────────────────────────────────────────────────────── 1 in. 30 in. 4 3/8 30 in. 4 in. 7 6 in. ─────────────────────────────────────────────────────────────────── The paper placed between each two layers of the secondary winding should be the special waxed paper which is made for that purpose. Start and end each layer of wire one-half inch from the edges of the paper. Wind the wire in smooth, even layers, permitting each turn to touch the other, but none to lap over. Wind on two layers of waxed paper between each layer of wire and the next. The paper must be put on smoothly and evenly so as to afford a firm foundation for the next layer of wire. The wire should never come nearer to the edges of the paper than one-half inch or the insulation of the secondary will be weak and the coil not liable to give a long spark. The utmost care should be used not to break the wire. If it should break, the ends must be very carefully connected. The number of turns that each layer averages should be carefully noted so that by keeping a record of the number of layers it is possible to tell how many turns have been wound on. When five to six thousand turns have been wound on the secondary it is sufficiently large, and the outside end of the wire should be fastened and prevented from unwinding by securing it with a drop of sealing wax. When winding a secondary remember that if at any point in the work, you allow the winding to become irregular or uneven, the irregularity will be much exaggerated on the succeeding layers. For this reason do not allow any irregularities to occur and if the wire tends to go unevenly, wind on two or three extra layers of the waxed paper to smooth it out. [Illustration: FIG. 113.—Details of the Wooden Coil Heads.]