Heat the mixture until it is reduced to a liquid, stirring it until it is perfectly smooth. Add a teaspoonful of powdered bichromate of potash to the glue.
The glue must now be kept in the dark, for sunlight will "set" the glue so that it becomes insoluble.
The Frame of the machine is composed of two strips twenty-five inches long, three inches wide, and an inch and one-half in thickness, and two cross-pieces of the same thickness and width fifteen inches long.
Fig. 37.—The Frame.
Notches are cut at both sides of the base to admit the feet of the uprights.
The Uprights are seventeen inches long, three inches wide, and one and one-half inches thick.
Fig. 38.—The Upright.
The notch at the foot is cut the same width as the thickness of the long members of the frame and is arranged so that when fitted in place, the foot of the upright will rest on the table in line with the bottom of the cross-pieces.