18 
MR. J. MUIR ON THE TEMPERING OF IRON 
semi-plastic nature of the material immediately after the fourth overstrain. All these 
curves were obtained from second loadings at the various times. 
Diagram No. 4. (Lovmoor Iron as supplied.) 
Curve No. 1—Primary test. 
„ ,, 2—Shortly after No. 1. 
„ „ 3—1 hour ,, 2. 
55 
„ 4—4 hours „ „ 2. 
f)_0] 2 
55 ^ 55 5 5 5 5 
,, „ 6—After heating to 230° C. 
Curve No. 7—Immediately after No. 6. 
,, „ 8—After heating to 150° C. 
„ „ 9— „ „ „ 110° C. 
„ ,, 9'—Shortly after No. 9. 
,, ,, 10—After heating to 140° C. 
The first series of curves (A) in Diagram No. 5 gives the history of another 
specimen from the same bar of Lowmoor iron, hut after the specimen had been heated 
to 770° C. and allowed to cool down in the air. The primary yield-point is shown to 
have been lowered from 17 to about 15 tons per sq. inch, and the step by which the 
