402 Scientific Intelligence. 



When the experiment was completed, the tube was slit longi- 

 tudinally along two lines opposite to each other and the marble 

 within exposed. It was uniformly found to be so firm and com- 

 pact that a steel wedge was needed to split it through the middle, 

 the half column adhering firmly to the sides of the tube. The 

 deformed marble, while firm and compact, differs in appearance 

 from the original rock in possessing a dead white color, some- 

 what like chalk, the glistening cleavage surfaces of the calcite 

 being no longer visible. The difference was well brought out in 

 certain cases where a certain portion of the original marble 

 remained unaltered by the pressure. This had the form of two 

 blunt cones of obtuse angle whose bases were the original ends 

 of the columns resting against the faces of the steel plugs, while 

 the apices extended toward one another into the mass of the 

 deformed marble. 



Special experiments on certain samples showed that, mak- 

 ing all due allowance for the difference in shape of the specimens 

 tested, the marble after deformation, while in some cases still pos- 

 sessing considerable strength, was much weaker than the original 

 rock. It also appeared that when the deformation was carried on 

 slowly the resulting rock was stronger than when the deforma- 

 tion was rapid. 



By the study under the microscope of thin sections of the 

 deformed marble, passing vertically through the unaltered cone 

 and the deformed portion of the rock, the nature of the change 

 that had taken place, could be seen clearly. The deformed por- 

 tion of the rock could be at once distinguished by its turbid 

 appearance, differing in a marked manner from the clear transpar- 

 ent mosaic of the unaltered cone. This turbid appearance was 

 most marked along a series of reticulating lines running through 

 the sections, which when highly magnified were seen to consist 

 of lines or bands of minute calcite granules. These were lines 

 along which shearing had taken place. The calcite individuals 

 along these lines had broken down, and the fragments so produced 

 had moved over and past one another, and remained as a compact 

 mass after the movement ceased. In this granulated material 

 were enclosed great numbers of irregular fragments and shreds 

 of calcite crystals, bent and twisted, which had been carried 

 along in the moving mass of granulated calcite as the shearing 

 progressed. This structure was therefore cataclastic, identical 

 with that seen in the feldspars of many gneisses. 



Between these lines of granulated material the marble showed 

 movements of another sort. Most of the calcite individuals in 

 these positions could be seen to have been squeezed against one 

 another and in many cases a distinct flattening of the grains had 

 resulted, with marked strain shadows, indicating that they had 

 been bent or twisted. They showed, moreover, a finely fibrous 

 structure in most cases, which, when highly magnified, was seen 

 to be due to an extremely minute polysynthetic twinning. The 

 chalky aspect of the deformed rock was in lact due chiefly to the 



