On receiving the boxes, cut a hole 3/4-inch diameter in the centre of the
bottom of the air vessel, and solder round it a piece of tubing, A, 1 inch
long, on the outside of the box. In the centre of the larger box make a
hole large enough to take a tube, E, with an internal diameter of 1/8 inch.
This tube is 8 inches long and must be quite straight. Next procure a
straight wire, C, that fits the inside of the small tube easily; make an
eye at the end, and cut off about 9 inches. Bore a hole for the wire in a
metal disc 1 inch across.
[Illustration: FIG. 166.--Perspective view of lung-capacity tester.]
The air container is then placed in the water box and centred by means of
wooden wedges driven in lightly at the corners. Push the small tube through
its hole in the water box, and thrust the wire--after passing it through
the disc and the projection on the air container--into the tube. The tube
should reach nearly to the top of the air container, and the wire to the
bottom of the water box. Solder the tube to the box, the wire to the disc,
and the disc to the container. A little stay, S, will render the tube less
liable to bend the bottom of the box.
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