A liquid comes in handy sometimes in measuring the volume of a
substance where the length, breadth, and thickness is difficult to get
at. It is a very simple operation, only requiring the material to be
plunged under water and measure the amount of displacement by giving
close attention to the overflow. It is a process that was first
brought into use in the days when jewelers and silversmiths were
inclined to be a little dishonest and to make the most of their
earnings out of the rule of their country. If we remember rightly, the
voice of some one crying "Eureka" was heard about that time from
somebody who had been taking a bath up in the country some two miles
from home. Tradition would have us believe that the inventor left for
the patent office long before his bathing exercises were half through
with, and that he did the most of his traveling at a lively rate while
on foot, but it is more reasonable to suppose that bath tubs were in
use in those days, and that he noticed, as every good philosopher
should, that his bathing solution was running over the edge of the tub
as fast as his body sunk below the surface. Taking to the heels is
something that we hear of even at this late day.
[Illustration]
It was not many years ago that an inventor of a siphon noticed how
water could be drawn up hill with a lamp wick, and the thought struck
him that with a soaking arrangement of this kind in one leg of the
siphon a flow of water could be obtained that would always be kept in
motion. Without taking a second thought he dropped his work in the hay
field, and ran all the way to London, a distance of twenty miles, to
lay his scheme before a learned man of science. He must have felt like
being carried home on a stretcher when he learned that a performance
of this kind was a failure. Among the others who have given an
exhibition of this kind we notice an observer who was more successful.
Being an overseer in a cotton mill, he had only to run over to his
dining room and secure two empty fruit jars and pipe them up, as
shown. He had had trouble in measuring volume by the liquid process by
having everything he attempted to measure get a thorough wetting, and
there were many substances that were to be experimented upon that
would not stand this part of the operation, such as fibers and a
number of pulverized materials. One of the jars was packed in tight,
nearly half full of cotton, and the other left entirely empty. The
question now is to measure the volume of cotton without bringing any
of the fibers in contact with the water. The liquid is poured into the
tunnel in the upright tube under head enough to partially fill the
jars when the overflow that stands on a level with the line, D E, is
open to allow the air in each jar to adjust itself as the straight
portions are wanted to work from. The overflow is then closed and head
enough of water put on to compress the air in the empty jar down into
half its volume. It may take a pipe long enough to reach up into the
second story, but it need not be a large one, and pipes round a cotton
mill are plentiful. In the jar containing cotton the water has not
risen so high, there being not so much air to compress, and comes to
rest on the line, C. Now we have this simple condition to work from.
If the water has risen so as to occupy half of the space that has been
taken up by the amount of air in one jar, it must have done the same
in the other, and if it could have been carried to twice the extent in
volume would reach the bottom of the jar in the one containing nothing
but air, and to the line, H I, in the jar containing cotton.
The fibers then must have had an amount of material substance about
them to fill the remaining space entirely full, so that a particle of
air could not be taken into account anywhere. The cotton has produced
the same effect that a solid substance would do if it just filled the
space shown above the line, H I, for the water has risen into half the
space that is left below it. This enables an overseer to look into the
material substance of textile fibers by bringing into use the
elasticity of atmospheric air, reserving the liquid process for
measuring volume to govern the amount of compressibility.--_Boston
Journal of Commerce._
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