ON AN EXPERIMENTAL INVESTIGATION INTO THE FLOW OF MARBLE. 373 
the square inch, was reached, when the tube was found to slowly bulge. This bulge 
was symmetrical and confined to that portion of the tube surrounding the marble. 
This distension was allowed to increase until the tube showed signs of rupture, when 
the pressure was removed and the experiment concluded. 
B. Deformation oj the Dry Rock at Ordinary Temperatures. 
Eight experiments were made in this manner on the dry rock at ordinary tempera¬ 
tures, the rate at which the pressure was applied differing in different cases, the con¬ 
sequent deformation in some cases being very slow and in others taking place more 
rapidly, the time occupied by the experiment being from 10 minutes to 64 days. 
The pressure was regularly increased so soon as the movement ceased, and in this 
way the rate of motion was kept as nearly constant as possible. The final amount of 
deformation was not in all cases equal, as some of the tubes showed signs of rupture 
sooner than others, thus requiring the experiment to be brought to a close. 
Plate 23, fig. 1, shows one of the tubes enclosing a marble column before the pres¬ 
sure has been applied, and beside it the same column after the completion of the 
experiment. The deformation in this case was carried out very slowly, the time 
occupied by the experiment being 64 days. 
After the bulging of the tube had been carried as far as possible, consistent with 
safety, the tube was removed from the press, the pi ugs taken out, and the tube was 
slit through longitudinally by means of a narrow cutter in a milling machine along 
two lines opposite one another. The marble within, however, was found to be still 
firm and compact and to hold the respective sides of the tube, now completely 
severed from one another, so firmly together that it was impossible without mechani¬ 
cal 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. Columns so split, with the portions of the tube adhering to 
them, are shown in Plate 23, figs. 3 and 4, the marble column in the former case 
having been reduced to one-half of its original height in 4 hours, while in the latter 
case the deformation occupied 17 days. The marble was in one or two instances 
detached from the tube without breaking it further, by striking the latter a smart 
blow on the back with a hammer, but usually it adhered so firmly that it could be 
released from the tube only by spreading the latter in a vice. The exterior surface 
of the marble where it had been in contact with the tube was smooth and conformed 
to the curve of the bulging iron, its surface reproducing perfectly all the fine tool 
marks on the latter. 
Fig. 2 of Plate 23 shows the deformed marble, freed in this way from the tube 
shown in fig. 1 of the same plate, and beside it a marble column of the dimensions 
which it originally possessed, for purposes of comparison. 
The deformed marble is uniform and compact, and seems to break with equal ease 
