132 Prof. J. A. Ewing. On Measurements of small [May 16, 



reduced in consequence of the hardening and recovery of elasticity 

 which the overstrained material undergoes with the mere lapse of 

 time. 



The following observations were made with a turned rod of com- 

 mon wrought iron, the original diameter of which was 0*697 inch 

 (section O381 square inch). Length under measurement, 9 inches. 

 Each ton of load corresponds to 2'65 tons per square inch. The rod 

 was annealed after being turned. The first loading, after annealing, 

 gave the following results : 



(3A.) Common Iron, annealed. 



Differences. 



Per half -ton. 



50 

 49 

 48 

 48 

 46 

 47 

 48 

 46 



Per ton. 



47 

 51 



(Set=l) 



95 

 95 



94 



(Set = 8) 



Creeping to 703 in 1 minute. 

 Creeping to 724 in 1 minute. 

 Creeping to 750 in 10 seconds. 

 Creeping to 774 in 10 seconds. 

 Creeping to 820 in 1 minute. 



With this load of 6 tons the yield point was reached. The creep- 

 ing under the load was at first slow, then gradually became acceler- 

 ated, and, finally, the sighted wire of the extensometer ran quickly off 

 the scale. At the same time the oxide formed in annealing began to 

 come off in the way characteristic of the yield point. The scaling 

 of the oxide began at one place in the bar and spread gradually in 

 both directions. The load of 6 tons was kept on without altera- 



