Adams <& OoTcer—The Flow of Marble. 487 



meaning that there had actually been a permanent condensa- 

 tion of the calcite by the greater pressure to which it had been 

 subjected in folding. Further investigation, however, showed 

 that the slightly lower specific gravity of the rock on the outer 

 side of the fold was due to the presence in it of minute rifts 

 or pores which were wanting in the rock on the more highly 

 compressed inner side, the limestone itself really being of the 

 same specific gravity throughout. 



Conclusions. 



1 . Marble when deformed at ordinary temperatures will flow 

 readily by distortion of the original calcite grains, accompanied, 

 if the differential resistance be low, with the development of a 

 certain amount of cataclastic structure. 



2. The marble when deformed at ordinary temperatures will 

 increase in strength if allowed to rest. 



3. The marble, if deformed at ordinary temperatures, will be 

 much stronger if the deformation be carried on slowly than if 

 the deformation be rapid. There is every reason to believe 

 that with the extreme slowness of deformation to which the 

 rock is subjected in nature, and the long rest which it subse- 

 quently undergoes, the change in shape would be accomplished 

 without any loss of strength. 



4. If the deformation be carried on at a higher temperature, 

 the calcite develops freer movement on its gliding planes, and 

 the deformed rock will be relatively stronger than if deformed 

 at the ordinary temperature. 



5. Under the conditions to which the rock is subjected in 

 these experiments, — although not under all conditions, — the 

 presence of water has no recognizable influence on the char- 

 acter of the deformation. 



6. The specific gravity of the rock is not increased by the 

 pressure to which it is subjected during deformation. 



McGill University, Montreal, Canada. 



EXPLANATION OF PLATES. 

 Plate II. 

 a. Wrought iron tube enclosing marble column after compression. 

 6. Column of marble, before and after compression, under a load of 

 296,725 pounds per square inch (20,875 kilos, per square centimeter). The 

 finer lines of the scale are 1 millimeter apart. 



Plate III. 



a. Carrara marble, original, x 60. 



b. Carrara marble, caused to flow under pressure of 296,725 pounds per 

 square inch, x 40. 



Plate IV. 

 Tube with its enclosed column of Carrara marble, cut open after deforma- 

 tion. The finer lines of the scale are 1 millimeter apart. 



