92 
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 ° F., 
and the remaining six in a freezing mixture which brought 
down their temperature to 12° F. The results were as 
follow : — 
Warm Needles. Cold Needles. 
64 
oz. 
broke. 
55 
OZ. 
broke. 
65 
)) 
64 
5J 
>> 
55 
>> 
72 
62 
>> 
60 
bent. 
44 
68 
broke. 
60 
>> 
bent. 
40 
Average 68J Average 59f 
I did not notice any perceptible difference in the perfec- 
tion of elasticity in the two sets of needles. The result, as 
far as it goes, is in favour of the cold metal. 
3rd. The above are doubtless decisive of the question at 
issue. But as it might be alleged that the violence to 
which a railway wheel is subjected is more akin to a blow 
than a steady pull ; and as, moreover, the pretended brit- 
tleness is attributed more to cast iron than any other 
description of the metal, I have made yet another kind of 
experiment. I got a quantity of cast iron garden nails, 
inch and quarter long, and ^in. thick in the middle. These 
I weighed, and selected such as were nearly of the same 
weight. I then arranged matters so that by removing a 
prop I could cause the blunt edge of a steel chisel, weighted 
to 41bs. 2oz., to fall from a given height upon the middle of 
the nail as it was supported from each end, 1 ,Vin. asunder. 
In order to secure the absolute fairness of the trials the 
nails were taken at random, and an experiment with a cold 
nail was always alternated with one at the ordinary tem- 
perature. The nails to be cooled were placed in a mixture 
