244 
Proceedings of the Royal Society of Edinburgh. [Sess. 
This research was accordingly undertaken in conjunction with that 
previously begun, the general aim of the work being to ascertain to what 
extent the two treatments produced similar effects. 
The present paper therefore falls into two parts : — 
I. An account of the effect of thermal treatment in inducing sensitive 
state in five different specimens, and a comparison of the results obtained 
for the different specimens. 
II. An account of the effect of longitudinal strain in inducing sensitive 
state in five different specimens, and a comparison of these results among 
themselves, and with the results given in Part I. 
I. Effect of Thermal Treatment in inducing Sensitive State. 
The specimens used in this investigation were with one exception in the 
form of cylinders 20 cm. in length, and about 0’9 cm. in diameter, the 
exception being a piece of steel wire of the same length, but only about 
0’2 cm. in diameter. 
The following table gives the composition of the specimens : — 
Description of Material. 
Percentage Composition. 
Carbon. 
Mn. 
Si. 
P. 
S. 
Tung- 
sten. 
Medium carbon steel 
0-80 
0-20 
0-075 
0-012 
0-02 
Hard steel 
1-321 
0-339 
0-143 
2-745 
0-023 
Steel wire .... 
0-755 
0660 
0-066 
0-027 
0-017 
Cast iron ..... 
3-15 
0-15 
013 
Tungsten steel .... 
0-51 
0-13 
0-19 
4-01 
Previous to being tested, each specimen was carefully annealed from 
900° C. in a Fletcher gas furnace, care being taken to exclude air from 
contact with the specimen during the process. For the magnetic tests, 
a Gray-Ross magnetometer* provided with an electric furnace f was 
employed, and in the case of each specimen the procedure was as follows : — 
The specimen was first carefully demagnetised by what is known as the 
process of reversals — that is to say, it was submitted to the action of 
an alternating magnetic field of gradually diminishing strength ; the initial 
value of this field being great and the final value zero, the specimen was . 
left devoid of residual magnetism and magnetic history. 
* Proc. Roy.' Soc. Edin., vol. xxix. p. 182, 1909. 
t Proc. Roy. Phil. Soc. Glasg ., vol. xii,, 1910. 
