Effects on First Loading a Wire. (>25 



being coiled would differ from that after a lapse of time 

 sufficient for recovery of its normal elastic properties. To 



Fig. 4. 



12 3 4 



(1) Normal behaviour of specimen. 



(2) After beiug on a cylinder of 2 cm. diameter. 



(3) After being- on cylinder of 2 cm. diameter and 



heated in steam for 15 minutes. 



(4) After being on cylinder again. 



investigate this, a long spiral of about 600 cm. length of iron 

 wire was wound on a cylinder of 1*5 cm., and its period 

 found with a small load. After being heated in steam for 

 some time, so that it might recover considerably, its period 

 was found to be still the same, so that the effect of the 

 internal stress was either relieved by the first few oscillations 

 or did not affect its torsional properties. It does not seem 

 probable that tne internal stress was relieved, as a wire after 

 being coiled on a cylinder, unwound, and then maintained in 

 transverse vibration under small tension with a tuning-fork 

 for an hour, showed similar behaviour to one which had not 

 been so vibrated. 



Poynting and Thomson suggest that microscopic investi- 

 gation may shed further light on the problem of these ano- 

 malous effects. With wires of such small section as have 

 been experimented on, there is considerable difficulty in 



Phil Mag. S. 6. Vol. 19. No. 112. April 1010. 2 S 



