First procure a wide-mouthed bottle about 4 in. high, provided
with a rubber stopper. This stopper should be pierced, making two
holes about 1/4 in. in diameter. From a sheet of lead 1/16 in. in
thickness
[Illustration: The Completed Instrument]
cut a piece shaped like A, Fig. 1. Common tea lead folded several
times will serve the purpose. When in the bottle this lead should
be of such a size that it will only reach half way around, as
shown in B. To insert the lead plate, roll it up so it will pass
through the neck of the bottle, then smooth it out with a small
stick until it fits against the side, leaving the small strip at
the top projecting through the neck of the bottle. Bend this strip
to one side and fit in the stopper, as shown in C. A small
binding-post is fastened at the end of the strip.
Having fixed the lead plate in position, next get a piece of glass
tube having a bore of about 1/32 of an inch in diameter. A piece
of an old thermometer tube will serve this purpose. Insert this
tube in the hole in the stopper farthest from the lead plate. Get
a piece of wire that will fit the tube and about 6 in.
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