A. S. Kimball— Physical Properties of Steel. 111 
Many manuals of practical mechanics give a higher modulus 
for tempered than for untempered steel. Reuleaux in “Der 
Constructeur,” (page 4,) states that it may be increased 50 per 
cent by hardening. Coulomb and Tredgold state that harden- 
ing has no influence whatever, while Styffe finds that the 
modulus is diminished. For our first experiment, five pieces 
of good tool-steel, each 18” long, were cut from a half-inch 
= bar. These were carefully annealed, squared, and pol- 
ished. No. 1 was laid aside and the others were hardened 
LB) 
ona 
It is well known that the deflection of a bar left under stress 
will increase for a long time. I am not aware, however, that 
Comparative tests of the rate of increase in steel of different 
tempers have previously been made. 
The immediate set increases with the hardness of the steel. 
In the experiments each bar was of course loaded with the 
Same weight which was allowed to act for the same number of 
Minutes, 
ee — recovers from a temporary set with greater rapidity the 
b The remarkable fluctuations in the line of the bar observed 
Y Prof. Norton, (this Journal, April, 1876,) became more 
marked and had a wider range as the hardness of the bar in- 
creased. In none of the experiments referred to was a perma- 
a set produced, though in some cases 48 hours had elapsed 
Pe ore the bar recovered its original line. In a few experi- 
eae an attempt was made to determine the approximate 
hess of the bars by grinding. The results obtained, how- 
ever, could not be considered very reliable. A more satisfae- 
eae method was found in the determination of the tempera- 
pes employed in hardening and drawing, by the specific heat 
atinum, or by the use of the pyrometer. : 
m indebted. to Mr. F. ©. Blake for the accuracy with 
ch the experiments referred to in this note, have been con- 
+ a 
which ¢ 
ducted, 
