The Floiv of Marble. 431 



visible. The difference is well brovight 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 experiments 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 lbs. per 

 square inch ; the second, which had been deformed 

 in 1-| hours, crushed under a load of 4000 lbs, per 

 square inch ; while the third, which had been quickly 

 deformed, the experiment occupying only 10 minutes, 

 crushed under a load of 2776 lbs. per square inch. 

 As mentioned above, the original marble, in columns 

 of the dimensions possessed by these before deforma- 

 tion, was found to have a crushing weight of between 

 11,430 and 12,026 lbs. per square inch. These 

 figures show that, making all due allowance for the 

 difference in shape of the specimens tested, the 

 marble after deformation, while in some cases still 

 possessing considerable strength, is much weaker than 

 the original rock. They also tend to show that when 



