* * *

THE INFLUENCE OF INTENSE COLD ON STEEL AND IRON.

[Condensed from Nature.]

There has recently been a most interesting discussion at the Literary
and Philosophical Society, Manchester, on the above subject.

The paper which gave rise to the discussion was by Mr. Brockbank, who
detailed many experiments, and ended by stating his opinion that iron
does become much weaker, both in its cast and wrought states, under
the influence of low temperature; but Mr. Brockbank's paper was
immediately followed by others by Sir W. Fairbairn, Dr. Joule, and Mr.
Spence, which at once put an entirely new complexion on the matter.

Dr. Joule says:

"As is usual in a severe frost, we have recently heard of many severe
accidents consequent upon the fracture of the tires of the wheels of
railway carriages. The common-sense explanation of these accidents is,
that the ground being harder than usual, the metal with which it
is brought into contact is more severely tried than in ordinary
circumstances. In order apparently to excuse certain railway
companies, a pretence has been set up that iron and steel become
brittle at a low temperature. This pretence, although put forth in
defiance, not only of all we know, of the properties of materials, but
also of the experience of everyday life, has yet obtained the credence
of so many people that I thought it would be useful to make the
following simple experiments:

"1st. A freezing mixture of salt and snow was placed on a table. Wires
of steel and of iron were stretched, so that a part of them was in
contact with the freezing mixture and another part out of it. In every
case I tried the wire broke outside of the mixture, showing that it
was weaker at 50 deg. F., than at about 12 deg. F.

"2d. I took twelve darning needles of good quality, 3 in. long, 1/24
in. thick. The ends of these were placed against steel props, 2-1/8
in. asunder. In making an experiment, a wire was fastened to
the middle of a needle, the other end being attached to a spring
weighing-machine. This was then pulled until the needle gave way. Six
of the needles, taken at random, were tried at a temperature of 55 deg.
F., and the remaining six in a freezing mixture which brought down
their temperature to 12 deg. F. The results were as follow:--

Warm Needles. Cold Needles.
64 ounces broke 55 ounces broke
65 " " 64 " "