Plug the tube at the bottom.
The wire sliding in the tube will counteract any tendency of the container
to tilt over as it rises.
A nozzle, D, for the air tube is soldered into the side of A, as shown.
The counterweight is attached to the container by a piece of fine strong
twine which passes over two pulleys, mounted on a crossbar of a frame
screwed to the sides of the water box, or to an independent base. The
bottom of the central pulley should be eight inches above the top of the
container, when that is in its lowest position.
For recording purposes, make a scale of inches and tenths, and the
corresponding volumes of air, on the side of the upright next the
counterweight. The wire, W, is arranged between counterweight and upright
so that an easily sliding plate, P, may be pushed down it by the weight, to
act as index.
[Illustration: FIG. 167.--Apparatus for showing lung power.]
Notes.--The pulleys must work easily, to reduce friction, which renders
the readings inaccurate. Absolute accuracy is not obtainable by this
apparatus, as the rising of the container lowers the water level slightly,
and the air has to support part of the weight of the container which was
previously borne by the water.
Pages:
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291