ON AN EXPERIMENTAL INVESTIGATION INTO THE FLOW OF MARBLE. 367 
and the surfaces of fracture also had a vitreous lustre. The calcite, however, was 
observed to have been forced into little depressions and cracks which existed in the 
collar, but in such cases the calcite occupying the depressions and cracks, as well as 
the portions of the cylinder adjacent to them, was reduced to a finely pulverulent 
condition, and did not show the cleavage possessed by other portions of the mass. 
The alabaster deported itself in a similar manner under pressure. Gumbel con¬ 
sidered that these experiments proved an entire absence of plasticity on the part of 
the several minerals in question, except possibly in the case of the alabaster, and 
concluded from their results, fortified by extended observations in the field, that the 
folding of the older crystalline rocks had taken place before they had become 
hardened. He also believed that in cases where a folded rock shows distinctly under 
the microscope that it has been crushed, its coherence is due to a recementation of 
the crushed mass by subsequent infiltration of mineral matter. It was shown by 
Rosenbitsch,* however, in reviewing Gum cel’s work, that while in the case of the 
quartz and orthoclase the minerals had undoubtedly been crushed to powder; in the 
experiment with the calcite column it was by no means proved that deformation 
without rupture, or “ flow,” would not equally well account for the phenomenon 
observed. Unfortunately, no examination of the microscopical characters and optical 
properties of the several minerals, before and after they had been submitted to 
pressure, was made. 
Somewhat similar experiments on limestone were carried out by P faff, f He 
enclosed a small column of lithographic limestone from Solenhofen in a steel block, 
except at the top where a piston of the same metal came down upon it. A very 
small hole was drilled through the side of the block to the limestone, and this was 
filled with wax. The marble was then submitted to a pressure amounting to 9970 
atmospheres, which was continued for seven weeks. The wax was not displaced, and 
the limestone suffered no alteration. In another experiment, a specimen of the same 
limestone] having a polished surface, was submitted to a pressure of 21,800 atmo¬ 
spheres, delivered by means of a small ring-shaped steel die. The limestone did not 
flow into the centre of the ring, and only a slight depression was left on the polished 
surface of the rock. From these experiments Peaff drew the conclusion that 
pressure alone is incapable of inducing any plasticity in limestone. 
Kick,| in his experiments on deformation, made use of many different materials, 
the only rock investigated being marble. One of his experiments reproduces very 
closely the conditions in the first of Pfaff’s experiments just described; but the 
result obtained was entirely different. A stout casting was bored out to receive a 
piston, the hole being closed at the lower end. In the bottom of the hole a steel die, 
* ‘ Neues Jahrbuch fur Mineralogie,’ 1882, 1, 222. 
t ‘ Der Mechanismus cler Gebirgsbildung,’ pp. 16-19. 
X “Die Principien der mechanischen Tec-hnologie und die Festigkeitslehre,” ‘ Zeit. des Vereines 
Deutscher Ingenieure,’ Bd. 36, p. 919 (1892). 
