As the
gas is made it passes into the balloon or is collected in the inner
vessel, which acts as a bell jar if the stop cock to the balloon
is closed.
The arrangements for utilising the balloon are very pretty.
An instrument weighing only 2 1/4 oz. and recording the temperature and
pressure is attached beneath a small flag and hung 10 to 15 ft. below
the balloon with balloon silk thread; this silk thread is of such fine
quality that 5 miles of it only weighs 4 ozs., whilst its breaking
strain is 1 1/4 lbs. The lower part of the instrument is again attached
to the silk thread, which is cunningly wound on coned bobbins from
which the balloon unwinds it without hitch or friction as it ascends.
In order to spare the silk any jerk as the balloon is released two
pieces of string united with a slow match carry the strain between
the instrument and the balloon until the slow match is consumed.
The balloon takes about a quarter of an hour to inflate; the slow
match is then lit, and the balloon released; with a weight of 8
oz. and a lifting power of 2 1/2 lbs. it rises rapidly. After it
is lost to ordinary vision it can be followed with glasses as mile
after mile of thread runs out. Theoretically, if strain is put on the
silk thread it should break between the instrument and the balloon,
leaving the former free to drop, when the thread can be followed up
and the instrument with its record recovered.
Pages:
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284