118 FRANK D. ADAMS 
to expose the transverse hole. This latter is seen to have been unaffected 
by the pressure. 
Fic. b.—This is a column of Solenhofen limestone (Exp. 520) which has 
been submitted to a pressure of too tons to the square inch equivalent to a 
depth of 31 miles below the surface of the earth, for half an hour. The steel 
which enclosed it has been completely removed. There has been a slight 
movement of the nature of plastic flow developed in the rock, owing to which 
the transverse hole originally circular in outline has been flattened so that it 
now presents a lenticular cross-section. 
Fic. c.—This is experiment 383. The column of Solenhofen limestone 
was submitted to a pressure equivalent to a depth of 40 miles below the earth’s 
surface—for seven hours. The steel tube was then removed but in the pro- 
cess the column broke in two along the line of the transverse hole (seen at the 
top of the photograph) and also split vertically along the line of the vertical 
hole. A vertical section of one-half of the column is shown. For about one- 
half its length along the central part of the column the vertical hole remains 
unaltered but from this unaltered part, and with increasing intensity toward 
either end of the column minute crescentic cracks form on the wall of the hole, 
along which cracks little fragments of the rock separate and fill the hole more 
or less completely. 
Fic. d.—This is a reproduction of a photograph of a thin section cut ver- 
tically through the column of Solenhofen limestone of experiment 360. It 
shows the walls of the vertical hole with the minute cracks referred to in Fig. c. 
Prate II 
Fic. a.—Shows a column of Westerly granite (Exp. 373) which has been 
submitted to a pressure equivalent to a depth of 25 miles below the surface of 
the earth for 2 months. The steel tube has been partially removed exposing 
the transverse hole, which has been absolutely unaffected: by the pressure. 
Fic. 6.—Shows a column of Westerly granite (Exp. 358) which has been 
exposed to a pressure equivalent to a depth of 35 miles below the surface of the 
earth, for 24 months. Under this pressure, as seen, the transverse hole has 
been filled in. The irregular dark spot, marking the original position of the 
hole, is caused by the breaking away of a little granite when the steel tube was 
being removed. 
Fic. c.—This shows the cracks referred to in the description of Plate I, 
Figs. c and d; but they are especially pronounced because in this case (Exp. 
384) the steel tube was thinned away about the middle of the column of Solen- 
hofen limestone, permitting the latter to bulge out laterally, thus giving a 
greater freedom of movement. It was submitted to a pressure of 204,000 lbs. 
per square inch, equivalent to a depth of rather over 31 miles below the surface 
of the earth. 
