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What is required in this description of manufacture is, 
that the rim of the wheel and the inside of the tire should 
be turned to a standard gauge, accurately calculated to give 
the required amount of tightness with a larger margin of 
strength, and this done we should attain greatly increased 
security to the public, and a great saving in wear and tear — 
to say nothing of the large sums expended by companies in 
the shape of compensation for injuries and loss of life. 
“ On the Alleged Action of Cold in rendering Iron and 
Steel brittle,” by J. P. Joule, D.C.L., F.RS., & c., Vice- 
President. 
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 circum- 
stances. 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, al- 
though put forth in defiance, not only of all we know of the 
properties of materials, but also of the experience of every- 
day 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 wmre 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° F. than at about 12° F. 
2nd. I took twelve darning needles of good quality, 3in. 
long, -Ain. thick. The ends of these were placed against 
steel props, 2^in. asunder. In making an experiment, a 
