624 Mr. A. I. Steven on Anomalous 



The recovery of iron from elastic overstrain on warming 

 to a temperature of 100° 0. for a short time, investigated by 



Fig. 3. 



5 



(1) Normal behaviour of specimen. 



(2) After coiling on cylinder of 4*5 cm. diameter. 



(3) Six days after coiling on a cylinder 4*5 cm. 



(4) Two months after coiling on a 4"5 cm. cylinder. 



Muir, suggested that the same recovery might be found in 

 this particular type of bending overstrain. Fig. 4 is illus- 

 trative of this effect. (1) shows as usual the normal behaviour 

 of a straight homogeneous wire, (2) the effect of winding on 

 a 2 cm. cylinder. After again obtaining curve (1) the 

 specimen was wound on the cylinder, and unrolled so that 

 the wire was pulled straight up a long straight glass tube. 

 Steam was then passed along the tul>e for 15 minutes, when, 

 after cooling, the wire showed the behaviour indicated by (3). 

 A second experiment showed (4) for the effect of the cylinder 

 again without st<am-heating. None of the samples showed 

 complete recovery, even though the steam-heating was con- 

 tinued for as long as an hour, but all showed some recovery, 

 this diagram (fig. 4) being a fair example. 



These effects suggest that the condition of internal stress 

 in the material alt< j r bending overstrain might affect the 

 period of a spiral spring, so that its period immediately after 



