EXPERIMENTS ON FLOW OF ROCKS 457 



interior of the tube, and so arranging it that the marble would only pass half way 

 into the tube when cold. The tube was then expanded by heating, so as to allow 

 the marble to pass completely into it and leave about 1"25 inch of the tube free at 

 either end. On allowing the tube to cool a perfect contact between the iron and 

 the marble was obtained. In some experiments the tube was subsequently turned 

 down, so as to be somewhat thinner immediately around the marble. Into either 

 end of the tube containing the column an accurately fitting steel plug or piston 

 was then inserted, and by means of these the pressure was applied. The high 

 pressure required was obtained by means of a powerful press especially constructed 

 for the purpose, consisting of a double hydraulic " intensifier," the water pressure 

 being in the first instance obtained from the city mains. By means of this ma- 

 chine pressures up to 13,000 atmospheres could be exerted on the columns having 

 a diameter of 0-8 inch, and the pressures could be readily regulated and maintained 

 at a constant value for months at a time if required. 



It having been ascertained that the columns of the marble 1 inch in diameter 

 and l^^ inch in height crushed at a pressure of from 11,430 to 12,026 pounds to the 

 square inch, the column inclosed in its wrought-iron tube, in the manner above 

 described, was placed in the machine and the pressure applied gradually, the ex- 

 terior diameter of the tube being accurately measured at frequent intervals. No 

 effect was noticeable until a pressure upon the marble, varying of course with the 

 thickness of the inclosing tube, but generally about 18,000 pounds to the square 

 inch, was reached, when the tube was found to slowly bulge, the bulge being 

 symmetrical and confined to that portion of the tube surrounding the marble. 

 The distension was allowed to increase until the tube showed signs of rupture, 

 when the pressure was removed and the experiment concluded. The conditions 

 under which the marble was submitted to piessure were four in number: 



1. At the ordinary temperature in the absence of moisture (cold dry crush). 



2. At 300 degrees centigrade in the absence of moisture (hot dry crush). 



3. At 400 degrees centigrade in the absence of moisture (hot dry crush). 



4. At 300 degrees centigrade in the presence of moisture (hot wet crush). 

 Eight experiments were made on marble columns at the ordinary temperature 



in the absence of moisture, the rate at which the pressure was applied dilBfering in 

 different cases, and the consequent deformation being in some cases very slow 

 and in others more rapid, the time occupied by the experiment being from 10 

 minutes to 64 days. In plate 42, figure 1, is seen, on the left, the iron tube 

 inclosing the marble and ready to be placed in the machine; on the right, the 

 same tube after the marble had been slowly deformed during a period of 64 days. 

 The amount of deformation was not in all cases equal, as some of the tubes showed 

 signs of rupture sooner than others. On the completion of the experiment the 

 tube was slit through longitudinally by means of a narrow cutter in a milling 

 machine along two lines opposite one another. The marble withm 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 w^edge driven in between 

 them, however, they could be separated, but only at the cost of splitting the marble 

 through longitudinally. In plate 42, figure 2, the deformed marble inclosed in 

 the tube shown in figure 1 is seen freed from latter, and beside it is a marble 

 column of the dimensions which it originally possessed (natural size). The half 

 columns of the marble, now deformed, generally adhere so firmly to the tube' that it 



