So it seems that exercise
strengthened the wire nearly twenty-seven per cent.
While those atoms are hustling about, lengthening the wire and getting
a better grip on one another, they grow warm with the exercise. Hold a
thick rubber band against your lip--suddenly stretch it. The lip
easily perceives the greater heat. After a few moments let it
contract. The greater coldness is equally perceptible.
A wire suspending thirty-nine pounds being twisted ninety-five full
turns lengthened itself one sixteen-hundredth of its length. Being
further twisted by twenty-five turns it shortened itself one fourth of
its previous elongation. During the twisting some sections took far
more torsion than others. A steel wire supporting thirty-nine pounds
was twisted one hundred and twenty times and then allowed to untwist at
will. It let out only thirty-eight turns and retained eighty-two in
the new permanent relation of particles. A wire has been known to
accommodate itself to nearly fourteen hundred twists, and still the
atoms did not let go of each other. They slid about on each other as
freely as the atoms of water, but they still held on. It is easier to
conceive of these atoms sliding about, making the wire thinner and
longer, when we consider that it is the opinion of our best physicists
that molecules made of atoms are never still.
Pages:
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49