The electric heater is just large enough to allow a space about 1/2 in. on all edges. This makes it 23 in. square. A piece of 1/4-in. asbestos of the above size should be secured, on which to place the heating wire. The amount of wire depends on the size and kind. As it is not necessary to heat the wire very hot, iron or steel wire may be used. The length of wire may be determined by the following method:
Wind the wire on a long stick, making sure that no one coil touches its neighbor. Connect one wire of the current supply at one end of the coil and run the other end of the current supply along the coils, starting at the extreme opposite end and drawing toward the center until the iron wire gets too hot to hold with the bare hand. This will be the right length of wire to use. The length being known, a number of tacks are placed in the asbestos board to hold the wire, as shown in Fig. 2. Cover the wire with a sheet of asbestos and attach binding-posts, E and F, at each end.
The asbestos inclosing the heating wires is covered with a thin piece of sheet iron, which is made to fit tightly over the bottom and sides. This will spread the heat evenly. Be careful to have the binding-posts insulated from the sheet metal. In the cross section of the heater, Fig. 2, A represents the 1/4-in. asbestos board; B, the heater wire; C, the asbestos paper, and D the sheet-metal covering.
The most important part of the incubator is the thermostat which regulates the current to maintain a steady heat. It is not advisable to make this instrument, as a good one can be purchased for less than $1. Place the thermostat in the end of the box at B, Fig. 1. A small door, E, is made in the box for easy adjustment of the thumbscrews.
Suspend the heater from the cover of the box with bolts 2-3/4 in. long, as shown in Fig. 1. A base receptacle, G, and a snap switch, H, are fastened on top of the cover and connected up to the thermostat B, the condenser C, the heater F, and lamp I, as shown. Another snap switch, J, is used on the light only. The condenser C is to prevent sparking, thus saving the platinum points on the screws. Do not use more than a 2-cp. lamp for lighting purposes, as a brighter light blinds the young chicks.
The incubator should be run for a day or two so that the current may be well regulated before placing the eggs in the tray. The incubator is operated the same as with lamp heat.—Contributed by M. Miller, Lansing, Mich.
A Cover for Magazines
As soon as Popular Mechanics, or any other magazine of similar size, arrives and before any member of the family looks through it, strip off the front cover and carefully remove the narrow strip on the back as shown in Fig. 1. Strengthen the back with a piece of bookbinding tissue, A, Fig. 2, and then paste a piece of heavy manila paper, B, over the covers and back. Over this paste a piece of dark blue cambric, Fig. 3, carefully turning the edges even with the book. The picture from the cover and the date added to the left corner of the picture are neatly pasted on, Fig. 4, and the narrow strip is glued to the back.
Removing the Cover, and Binding with Heavy Paper (Fig. 1, Fig. 2)