482 Adams <& Coker — Investigation into the Flow of Rocks. 



sesses very different elastic properties from the same iron in 

 its original condition. The iron so treated assumes a more 

 plastic character and a bar thus stretched will on the applica- 

 tion of small additional loads undergo a further elongation or 

 creeping, producing a permanent set. It is a well-known fact 

 moreover that iron when thus over-strained will, if allowed to 

 rest for a sufficiently long time, revert to its former state of 

 normal elasticity, and Muir* has shown that tin's recovery is 

 greatly hastened by raising the temperature of the bar even a 

 few degrees, and if the temperature be raised to 100° C, the 

 reversion to the state of normal elasticity is very rapid, being 

 accomplished in a few minutes instead of requiring several 

 days. 



As has been shown, the movement set up in marble under 

 the conditions of deformation secured in these experiments is 

 essentially of the same character as that which takes place in 

 iron or other metals when they are deformed, for while there 

 is in marble, when deformed at ordinary temperatures and at 

 comparatively low pressures, a certain amount of granulation, 

 this is very subordinate to the movement of the calcite on its 

 gliding places or by twinning, as before described. It was 

 therefore conjectured that if the marble was rapidly deformed, 

 thus giving rise to a comparatively weak product, this deformed 

 rock might, following the analogy of the metals, become 

 stronger if allowed to rest for a certain time. If the analogy 

 to metals holds, it might still further be expected that the 

 application of heat would bring about a more rapid recovery 

 of strength on the part of the deformed rock than mere rest 

 alone. 



The results of three experiments in which the strength of 

 the deformed column was tested after a rest of 100 days, as 

 well as the results of four other experiments in which the 

 marble after deformation was heated to 100° C. for 20 hours, 

 and two experiments in which the marble after deformation 

 was heated to 350° C. for 20 hours, are given in the table on 

 page 479. As will be seen from an examination of the figures, 

 the marble became distinctly stronger as the result of a rest of 

 100 days, but the application of heat, whether it be 100° C. 

 or 350° C.j does not noticeably accelerate the recovery of 

 strength as it does in the case of the iron. In fact, the figures 

 seem to show that the heating of rock to 100° C. for 20 hours 

 rather weakens it and that it recovers this loss at a higher 

 temperature. 



Another series of three experiments was then made in which 

 columns of marble and steel tubes of the same dimensions were 



*On the Kecovery of Iron from Over-strain, Phil. Trans. Koyal Soc, 

 series A, vol. xciii, pp. 1-46. 



