ith the inner surfaces of the posts
parallel and 5 ft. 8 in. apart. The holes around the posts are
filled with earth and well tamped.

The hickory piece which is to form the bar should be planed,
scraped and sandpapered until it is perfectly smooth and round
except for 3 in. at each end. Bore a 9/16-in. hole through each
square end 1-1/4 in. from the end. The bar may be fastened at any
desired height by slipping the 1/2-in. bolts through the holes
bored in both the bar and channel.

Each post must be well braced to keep it rigid while a person is
swinging on the bar. Four anchors are placed in the ground at the
corners of an imaginary rectangle 9 by 16 ft., in the center of
which the posts stand as shown in Fig. 2. Each anchor is made of
one 2-ft. piece of wood, around the center of which four strands
of the heavy galvanized wire are twisted, then buried to a depth
of 2 ft., the extending ends of the wires coming up to the surface
at an angle.

The heavy screw eyes are turned into the posts at the top and
lengths of ropes tied to each. These ropes or guys pass through
the pulley blocks, which are fastened to the projecting ends of
the anchor wire, and return to the posts where they are tied to
cleats. Do not tighten the guy ropes without the bar in place, as
to do so will strain the posts in the ground. Do not change the
elevation of the bar without slacking up on the ropes. It takes
but little pull on the guy ropes to make them taut, and once
tightened the bar will be rigid.

[Illustration: Ground Plan]

Oil the bar when it is finished and remove it during the winter.
It is well to oil the wood occasionally during the summer and
reverse the bar at times to prevent its becoming curved. The wood
parts should be well painted to protect them from the weather.

** Electrostatic Illumination [299]

Anyone having the use of a static machine can perform the
following experiment which gives a striking result. A common
tumbler is mounted on a revolving

[Illustration: Illuminated Tumbler]

platform and a narrow strip of tinfoil is fastened with shellac
varnish to the surface of the glass as follows: Starting beneath
the foot of the glass from a point immediately below the stem, it
is taken to the edge of the foot; it follows the edge for about 1
in. and then passes in a curve across the base, and ascends the
stem; then it passes around the bowl in a sinuous course to the
rim, which it follows for about one-thir