G 
MR. J. MUIR ON THE TEMPERING OF IRON 
so to effect recovery of elasticity the specimen was, as before, heated to about 
200° C. and slowly cooled. It was known as the result of earlier experiments that 
the yield-point had been raised by this j^i'ocess through a second step of 11 tons,^ 
Diagram No. 1. (Steel as supplied.) 
Curve No. 1—Primary test. 
,, „ 2—Shortly after No. 1. 
,, ,, 3 days ,, ,, 1. 
Curve No. 4—2 weeks after No. 1. 
,, „ 5—After heating to 200° C. 
„ „ 6- „ ,r 200° C. 
SO that the sjrecimen should not yield until a stress of 60 tons per sq. mch had 
been applied. Curve No. 6, Diagram 1 shows that the specimen bore the stress 
of 60 tons, but that with 60|- tons per sc[. inch a yield-point and fracture occurred. 
* “On the Recovery of Iron from Overstraiip” ‘Phil. Trans.,’ A, vol. 193, p. 34, 1899. 
