The transformer is laid in the case with a small block of wood under the core at either side so as to raise the windings up off the bottom. The secondary terminals are connected to binding posts marked 1, 2 and 3 in Figure 66. These binding posts are mounted on insulating bushings which pass through the holes marked No. 1, No. 2 and No. 3 in Figure 64. The insulating bushings consist simply of fibre washers so that the binding posts will not short circuit on the metal case. One end of a piece of double conductor lamp cord is led through a hole in the back of the case and soldered to the two primary coil terminals. The other end of the lamp cord is connected to an attachment plug which may be screwed into a lamp socket. [Illustration: FIG. 66.—The completed Transformer.] The transformer case is then poured full of molten coil wax so that the space around the transformer is entirely filled. After the wax has cooled, fasten the cover on and it is complete. Arts and Science Series No. 8 Home-made Electrical Apparatus A Practical Handbook for Amateur Experimenters In Three Parts *Volume II* _Second Edition_ *BY* *A. M. Powell* PUBLISHED BY COLE & MORGAN, Inc. Publishers of the Arts and Science Series P.O. BOX 473 CITY HALL STATION NEW YORK, N. Y. Printed in U. S. A. Copyright 1918 by COLE & MORGAN, Inc. CHAPTER VI. ELECTRIC MEASURING INSTRUMENTS Galvanometers, Ammeters, Voltmeters. How to Make a Galvanometer. If several turns of wire are wrapped about a compass, and a current of electricity sent through the coil, the compass needle will be deflected. Such an instrument is called a *galvanometer* and may be used for detecting very feeble currents. Figure 67 shows a very simple form of galvanometer which may be made by winding about fifty turns of No. 36 B. & S. Gauge single silk covered wire around an ordinary pocket compass. The compass is set on a block of wood and the wire wound around both the compass and the block. The terminals of the wire are connected to two binding posts. [Illustration: FIG. 67.—A Simple Galvanometer.]