A 1-inch sight hole was drilled through each block at its center. A
ring of cardboard, on which Uncle Ed marked with radial lines the 360
degrees of the circle, was placed over the compass socket, with the zero
and 180 degree marks pointing toward the sight blocks. The outer faces of
the end blocks were now wet with mucilage and a hair was stretched
vertically across the center of each sight hole. The hairs were then
adjusted by sighting through the holes and moving the nearer hair sidewise
until it was exactly in line with both the zero and the 180 degree marks
on the cardboard. Then a hair was stretched horizontally across the center
of each sight hole. Great care was taken to place the hairs at exactly the
same height above the baseboard. To protect the hairs after they were
adjusted, they were covered with a piece of glass, which was secured in
place by tacks driven into the wood with their heads projecting over the
edges of the glass.
Spirit Levels.
From one of his pockets Uncle Ed produced two small bottles, the kind used
for holding homeopathic pills. These he filled nearly to the top with
water, corked them and wedged them into grooves cut lengthwise in the
baseboard at opposite sides of the cardboard ring.
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