474 Adams & Colter — Investigation into the Flow of Bocks. 



1. Deformation of the dry rock at ordinary temperatures. 



(a) Deformation at comparatively loic pressures. Structure 

 of the deformed marble. 



The pressures employed ranged from 120,000 to 130,000 

 lbs. to the square inch. A series of experiments was first made 

 in which the marble was enclosed in wrought iron tubes. The 

 walls of these tubes immediately surrounding the marble had 

 a thickness varying from 1/8 to 1/4 of an inch, and the load 

 was slowly applied until deformation, indicated by the bulging 

 of the tube, had commenced. So soon as movement ceased 

 the load was increased slightly and the movement was thus 

 resumed, and in this manner the deformation was carried on at 

 a rate which was kept as nearly as possible constant. 



The experiments were arranged so that in some cases the 

 deformation went forward rapidly and in other cases very 

 slowly, the time occupied being from ten minutes to sixty-four 

 days. 



In later experiments, as has been mentioned, the wrought- 

 iron tubes were replaced by tubes of steel. These latter had 

 the advantage of offering a higher resistance and also of being 

 more easily prepared and more uniform in strength than those 

 of wrought iron. This latter quality was of especial impor- 

 tance in cases where experiments were carried on in series 

 under identical conditions for purposes of comparison. Plate 

 IY shows such a tube with the enclosed marble column, cat 

 open after deformation. 



The deformed marble was uniform and compact and seemed 

 to break with equal ease in all directions. It differed some- 

 what in appearance from the original rock in possessing a dead 

 white color, the glistening cleavage surfaces of the calcite being 

 no longer visible, and the contrast being well brought out 

 when the deformed column is split or cut through vertically, 

 owing to the fact that a portion of the original marble often 

 remained unaltered and unaffected by the pressure. This, 

 when present, had the form of two cones of obtuse angle whose 

 bases are the original ends of the column resting against the 

 faces of the steel pistons, while the apices extend into the 

 deformed marble and point toward one another. These cones, 

 or rather parabolas of rotation, are also developed, as is well 

 known, where cubes of rock, cement or cast-iron are crushed 

 in a testing machine in the ordinary manner. In the present 

 experiments they sometimes constitute a considerable propor- 

 tion of the whole mass ; in other cases they are absent or but 

 faintly indicated ; but there is always in immediate contact with 

 the ends of the steel pistons at least a thin cake of marble pos- 

 sessing the character of the ordinary rock. 



