248 
THE HARDENING AND TEMPERING OF STEEL. 
A N announcement was made some time ago that the Institution 
of Mechanical Engineers had resolved to devote a sum of 
money to experimental research on mechanical questions. The 
first-fruits of this resolution have since appeared in the shape of 
a First Report on each of the three subjects selected by the 
Council for examination, viz., the hardening, tempering, and 
annealing of steel ; the best form of riveted joints ; and friction 
between solid bodies at high velocities. 
It will be seen that these subjects are all of great impor- 
tance, and that two at least — the first and the ]ast — possess a 
scientific as well as a practical interest. The reports upon them 
do not describe any new experiments actually undertaken by the 
Institution. They are preliminary and historical; giving a 
digest of the theories that have been broached, and the experi- 
ments that have been made, by former labourers in each subject, 
and going on to point out wherein these .are imperfect, and 
what remains to be done in order to achieve in each case the 
final solution of the problem. This historical element is itself 
of much interest, as showing the mode in which such questions 
have been attacked, both from the theoretical and the practical 
side ; and we regret that our limits do not allow us to reproduce 
the reports in extenso. We must, however, content ourselves at 
present with a short resume of the first subject on the list, viz., 
the hardening, tempering, and annealing of steel ; pointing out 
first its essential features, and then noticing the light which is 
thrown upon it by the report in question. 
The facts relating to this subject are extremely well 
known, and are continually acted upon ; their importance is 
almost unique. Probably there is hardly a known process, 
scientific, surgical, mechanical, or industrial, which does not 
at some stage depend for its success on the use of properly 
tempered steel tools. It seems strange, therefore, that the 
theory of the subject should be in a state of the utmost un- 
certainty and confusion ; and that even the direct experiments 
