ELECTROPHORUS—Plate 18.

ELECTROPHORUS—Plate 18.

The electrophorus consists of two parts, a pan filled with a resinous mixture, and a cover which has been completely covered with tinfoil. Under favorable conditions, a spark of electricity 1/2" long can be obtained from this electrophorus. The favorable conditions are these: The air should be dry; both parts of the electrophorus should be warm, dry, and clean; and the tinfoil and rosin should be perfectly flat, so as to come in close contact with each other.

Make the pan and its sides as shown in Plate 18. Glue and nail the sides in place and round their upper edges well with sandpaper. To make the resinous mixture, melt a half teacup of rosin with two teaspoons of turpentine and about the same of paraffin in a rather deep dish, and pour the mixture into the pan. As all these materials are inflammable, perhaps the safest place to melt them is in the oven. After the pan is cold, test the surface of the rosin to see that it is flat every way. If it is not flat, sandpaper the high parts slowly with coarse sandpaper.

When making the cover, observe the directions on page 20, then round the edge to a good half-circle. Test the cover also to see that it is flat, especially on its under side, for to get good sparks, the tinfoil and rosin must come just as close together as possible. Cut two circles of tinfoil 4-1/2" in diameter. Smooth them carefully on a piece of paper, spread glue thinly on the cover, lay the tinfoil on the glue, and smooth it with the fingers. Press the edges as smooth as possible because electricity escapes easily from sharp corners. Cover the larger open spaces with bits of tinfoil. Hard rubber (ebonite), being a non-conductor of electricity, makes the best handle. A piece of an old rubber comb or a fountain pen can be used for this purpose.

To get a spark of electricity, rub the rosin with soft leather, fur, or woolen; place the cover on it; touch the top of the cover with the finger (to remove the negative electricity); lift the cover by the top of the handle; bring the edge of the cover near a finger, or other conductor, and a spark will fly off with a snap. It is a miniature flash of lightning. Some books on electricity describe many other experiments which can be tried.

ELECTROPHORUS — Plate 18

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