An Experimental Investigation into the Flow of Marble. 231 



opposite one another. The marble within was found to be still firm 

 and compact, and to hold the respective sides of the tube, now com- 

 pletely severed from one another, so firmly together that it was 

 impossible without mechanical aids to tear them apart. By means of 

 a steel wedge driven in between them, however, they could be separated, 

 but only at the cost of splitting the marble through longitudinally. 

 The half columns of the marble now deformed generally adhere so 

 firmly to the tube that it is necessary to spread the latter in a vice in 

 order to set them free. The deformed marble, while firm and compact, 

 differs in appearance from the original rock in possessing a dead white 

 colour, somewhat like chalk, the glistening cleavage surfaces of the 

 calcite being no longer visible. The difference is well brought out in 

 certain cases owing to the fact that a certain portion of the original 

 marble often remains unaltered and unaffected by the pressure. 

 This when present has the form of two blunt cones of obtuse angle 

 whose bases are the original ends of the columns resting against the 

 faces of the steel plugs, while the apices extend into the mass of the 

 deformed marble and point toward one another. These cones, or 

 rather parabolas of rotation, are developed, as is well known, in all 

 cases when cubes of rock, Portland cement, or cast iron are crushed 

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

 riments they seldom form any large portion of the whole mass. 



In order to test the strength of the deformed rock, three of the half 

 columns from different experiments, obtained as above described, were 

 selected and tested in compression. The first of these, which had been 

 deformed very slowly, the experiment extending over sixty-four days, 

 crushed under a load of 5350 Ibs. per square inch; the second, which 

 had been deformed in 1| hours, crushed under a load of 4000 Ibs. per 

 square inch ; while the third, which had been quickly deformed, the 

 experiment occupying only 10 minutes, crushed under a load of 2776 Ibs. 

 per square inch. As mentioned above, the original marble, in columns 

 of the dimensions possessed by these before deformation, was found to 

 have a crushing weight of between 11,430 and 12,026 Ibs. per square 

 inch. These figures show that, making all due allowance for the 

 difference in shape of the specimens tested, the marble after deforma- 

 tion, while in some cases still possessing considerable strength, is much 

 weaker than the original rock. They also tend to show that when the 

 deformation is carried on slowly the resulting rock is stronger than 

 when the deformation is rapid. 



Thin sections of the deformed marble, passing vertically through the 

 unaltered cone and the deformed portion of the rock, were readily 

 made, and when examined under the microscope clearly showed the 

 nature of the movement which had taken place. The deformed portion 

 of the rock can be at once distinguished by its turbid appearance, 

 differing in a marked manner from the clear transparent mosaic of the 



