HARDENED BY OVERSTRAIN. 
3 
Position of the Pyrometer. 
Times in 
minutes. 
Pyrometer 
readings. 
Pyrometer on the right ... 
0 
562° C. 
5 ) ,, ... ... 
2 
582 
— 
3 
592 
— 
55 55 55 
4 
599 
Bunsens slightly removed. 
Pyrometer on the left 
k 
574° C. 
_ 
55 55 55 
8 
580 
- - 
10 
584 
Bunsens slightly closer on the left. 
55 55 55 
12 
595 
Pyrometer on the right ... 
13 
597° C. 
55 55 55 
14 
605 
Bunsens slightly removed. 
55 55 55 
15 
605 
— 
Pyrometer on the left 
16 
598° C. 
5 5 5 5 5 5 • • • • • • 
17 
607 
Gas supply turned oft‘. 
55 55 55 
18 
604 
— 
From tlie above series of readings tlie specimen in tlie furnace would Ije said to 
have been heated to 605° C. 
Preliminarij Examination of the JSLaterial in the State as siijoified. 
The elastic properties of the materials to be employed were examined not only in 
the usual fasliion Ijy breaking a specimen in the testing machine, and recording the 
breaking load and the ultimate elongation, but also in a manner which has already 
been described in a paper by the present author on the recovery of iron from 
overstrain.^ Diagram No. 1 of the present ])aper illustrates this method of 
examination, the material examined being a rod of steel ratlier under half an inch in 
diameter. 
A specimen about a foot long was cut from this rod, and was turned down in the 
centre for a length of 5 inches to a diameter just over fths of an inch. Sufficient 
length was left unturned at each end to enable the specimen to be securely gripped in 
the jaws of the testing machine. The diameter of the turned portion of the specimen 
was then accurately measured ; a 4-inch length was marked off by means of a 
marking instrument of Professor Ewixg’s design ; the extensometer was attached to 
this 4-inch length, the specimen was put into the testing machine, and load was 
applied. Extensometer readings were taken after the addition of every ton per 
* The diagram in ‘Phil. Trans.,’ A, vol. 195, p. 31, 1899, shows this method of examining iron and 
steel. 
