Gold Leaf Electroscope
Fig. 5.—Electroscope parts.
Obtain a square glass pickle or preserve jar, to the mouth of which has been fitted a large cork bung (A, [Fig. 4]). Next take a 7-inch length of 1⁄8-inch brass wire (B, [Fig. 4]) (similar to that used for the Leyden jars above), and flatten one end by hammering (F, [Fig. 5]), after having bent it triangular-shape, as in (C, [Fig. 4]).
A 21⁄2 inch length of cycle valve-tubing (A, [Fig. 5]) is to be slipped over the brass rod B ([Fig. 5]), and then strips of gummed brown paper, 2 inches wide, lapped round and round the rubber-tubing until a paper cylinder some 1⁄4-inch across the outside is formed (C, [Fig. 5]). Anyway, this paper cylinder must be a good fit for a hole bored through the center of cork (D, [Fig. 5]), into which, moreover, it must be glued when dry. The stopper, paper, &c., must then be allowed to soak in hot candle wax for an hour or so, wiped clean and put aside to cool. Excess of grease must be particularly removed—with paraffin if necessary—from the plain end of the metal rod, to which we must next solder a brass knob (D, [Fig. 4]) or, as an alternative, tinfoil may be twisted round a loop in the wire until a ball is formed, as in the case of the Leyden jar.
The next operation is to cut two strips of Dutch metal—or, better, gold leaf—size 3⁄4-inch by 2 inches, and gum them on either side of the flattened brass rod triangle (E, [Figs. 4] and [5]). This is best managed by laying the brass, after being lightly gummed, upon the Dutch metal strips in the correct position, and when fixed trimming off the corners of the leaves close to the sides of the triangle—not, of course, at the base, or no strips will remain to hang down. Dutch metal and beaten gold are both employed in gilding, and should be obtainable in small quantities at any picture-framer’s shop.
If the cork be now fixed in the mouth of the jar and the brass rod adjusted so that the gold leaves hang free of the interior, our electroscope is practically complete. However, a few pieces of calcium chloride, or pumice stone soaked in strong sulphuric acid, may be included at the bottom of the jar (F, [Fig. 4]), in order to absorb moisture; and lastly, as a brass ball is not always the most satisfactory terminal for this instrument, one other small accessory may be made. This consists of a 2-inch circle of tin, or, preferably, brass (G, [Fig. 4]), exactly like that fitted to one of the Leyden jars, and to the under side of which is soldered a ring of springy brass (H, [Fig. 4]) about 3⁄4-inch deep, so made as to fit securely on the brass ball terminal. Thus the metal table is adaptable to the brass knob, whenever such an arrangement is required.
Fig. 6.—The electrophorus.