382 
PROFESSOR F. D. ADAMS AND DR. J. T. XICOLSOX 
that gives rise to the phenomenon of the “ flow” of metals as described in Section IY. 
Calcite, however, is apparently much more prone to twin during this deformation 
than metals are, although the greater difficulty of recognising twinning in metals— 
the latter being opaque—may have led to the frequency of this phenomenon in their 
case being- underestimated. 
The character of the movement in the case of quick deformation at a high tempera¬ 
ture shows therefore that calcite has freer movement in its gliding planes at a high 
temperature and breaks less readily than when cold. A microphotograph of a 
section of this deformed marble (400° C.), taken in ordinary light and magnified 
70 diameters, is seen in Plate 24, fig. 3. The evenness of movement and freedom from 
all fracturing or cataclastic action is well seen. The flattening of the grains is also 
distinctly shown and is especially noticeable if it be compared with the section of the 
original marble beside it, forming fig. 1 of the same Plate. 
d. Deformation of the Rock at 300° C. in the presence of Water. 
It was next sought to introduce the third factor above mentioned as possibly 
having an influence on rock deformation, namely, moisture. 
For this purpose a modification of the apparatus employed in the experiments just 
described was used. A drawing of this is given in fig. 8. A hole was bored through 
the cast-iron jacket (B), as well as through the end of the wrought-iron cylinder (A) 
which contained the marble, so as to reach the surface of the steel piston at H, just 
above its contact with the marble column. Through this hole a stout copper 
pipe (K) was passed and having been screwed into A was brazed. Water was then 
forced through this tube by means of a hydraulic accumulator, similar in construction 
to that marked D in fig. 1 of Plate 22, while at the same time the required 
temperature was obtained by means of a gas flame as before. Even under the great 
hydraulic pressure employed, the water passed so slowly that the temperature could 
be easily maintained at 300° C. ; the water making its way between the side of the 
steel piston and the tube (A) to the marble and passing through the latter and out of 
the lower steel piston by the hole (N) drilled through it. In order to prevent the 
water entering at H from passing upwards along the piston instead of downward into 
the marble and thus escaping, a heavy brass cap (P) was screwed on the end of the 
ring (Q), which in its turn was screwed into the jacket (B). The cap was turned 
with a projecting ring on its lower surface, while the upper surface of Q was slightly 
hollowed. In the space (M) thus intervening between the two, a ring of lead was 
placed, which, on screwing down the cap (P), was forced to occupy the whole space 
and to make a perfectly water-tight joint around the piston. This arrangement was 
repeated in the case of the lower steel piston. 
The Callendar thermometer was inserted at C as before. In this way a column of 
