An EoLperliiK'iital Investigation into the Flow of Marble. 233 



When the deformation is carried out at 400 C., no trace of cata- 

 clastic structure is seen. 



An experiment was then made in which the marble was deformed 

 at 300 C., but in the presence of moisture, water being forced through 

 the rock under a pressure of 460 Ibs. per square inch during the 

 deformation, which extended over a period of fifty-four days, or nearly 

 two months. Under these conditions the marble yielded in the same 

 manner as when deformed at 300 C., in the absence of moisture, that 

 is, by movements on gliding planes and by twinning, but without 

 cataclastic action. The deformed marble, however, when tested in 

 compression, was found actually to be slightly stronger than a piece of 

 the original marble of the same shape. The structure developed was 

 identical with that of the marble deformed at 300 C. in the absence 

 of water. The presence of water, therefore, did not influence the 

 character of the deformation. It is quite possible, however, that there 

 may have been a deposition, of infinitesimal amount, of calcium 

 carbonate along very minute cracks or fissures, which thus helped to 

 maintain the strength of the rock. No signs of such deposition, how- 

 ever, were visible. 



By studying the marble deformed at a temperature of 300 C., or 

 better at 400 C., it will be seen that structures induced in it by the 

 movements, and the nature of the motion, are precisely the same as 

 those observed in metals when they are deformed by impact or by com- 

 pression. In a recent paper by Messrs. Ewing and Rosenhain, 

 " Experiments in Micro-metallurgy : Effects of Strain," which ap- 

 peared in these Proceedings, three photographs of the same surface of 

 soft iron, showing the results of progressive deformation under pressure, 

 are shown, which photographs could not be distinguished from those of 

 thin sections of the marble described in the present paper, at corre- 

 sponding stages of deformation. In both cases the movements are 

 caused by the constituent crystalline individuals sliding upon their 

 gliding planes or by polysynthetic twinning. In both cases the 

 motion is facilitated by the application of heat. The agreement 

 between the two is so close that the term "flow" is just as correctly 

 applied to the movement of the marble in compression under the 

 conditions described, as it is to the movement which takes place in 

 gold when a button of that metal is squeezed flat in a vice, or in iron 

 when a billet is passed between rolls. 



In order to ascertain whether the structures exhibited by the 

 deformed marble were those possessed by the limestones and marbles 

 of contorted districts of the earth's crust, a series of forty-two speci- 

 mens of limestones and marbles from such districts in various parts of 

 the world were selected and carefully studied. Of these, sixteen were 

 found to exhibit the structures seen in the artificially-deformed marble. 

 In these cases the movements had been identical with those developed 



