87 
Dr. Joule communicated to me the discussion which 
took place at the last meeting of the Society, on the 
question of the effects of intense cold on steel tires. This 
enables me to refer to a series of experiments which had 
for its object the effects of various degrees of temperature 
on wrought iron. These inquiries are to some extent 
analogous to the cause of the recent accident which occurred 
on the Great Northern Railway, near Hatfield, by the 
breaking of a steel tire, which caused the death of a number 
of persons. 
It has been asserted, in evidence given at the coroner’s 
inquest, that the breaking of the steel tire was occasioned by 
the intensity of the frost, which is supposed to render the 
metal brittle, and of which this particular tire was composed 
This is the opinion of most persons, but judging from my 
own experience such is not the fact, and provided we are 
to depend on actual experiment, it would appear that 
temperature has little or nothing to do with it. 
Some years since I endeavoured to settle this question by 
a long and careful series of experiments on wrought iron, 
from which it was proved that the resistance to a tensile 
chain was as great at the temperature of zero as it was at 
60° or upwards, until it attained a scarcely visible red heat. 
To show that this was the case, and taking, for example, 
the experiments at 60°, it will be found that the mean 
breaking weight, in tons, per square inch, was in the ratio 
of 19 '930 to 2T879, or as 1 : 1*098 in favour of the speci- 
mens broken at the temperature of zero. 
The generally received opinion is, however, against these 
facts, and it is roundly asserted that the strength of iron 
and steel is greatly reduced in strength at a temperature 
below freezing. The contrary was proved to be the case in 
wrought iron plates, and assuming that steel follows the 
same law, it appears evident that we must look for some 
other cause than change of temperature for the late fracture 
