Prof. T. G. Bonney—On some Breccias and Crushed Rocks. 437 
Many of the serpentine breccias are thus formed. This rock is a 
brittle one, and seems to crush readily. Instances are frequent, but 
the most notable case has already been described by me in this 
Magazine (Vol. VI. Dee. II. p. 365), at the quarries near Levanto. 
Here there could not be a doubt as to the nature of the breccia, 
although specimens might be selected here and there in which the 
fragments were in great confusion, and no one, who had not 
examined the rock in situ, could have determined its origin. I had 
no doubt that a breccia of lherzolite in a mass of that rock in the 
Ariége was of the same kind; and think it possible that the same 
origin may be assigned to a very singular breccia containing frag- 
ments of lherzolite and crystalline limestone which occurs in that 
neighbourhood. As however I could not in the time at my dis- 
posal find this in situ, I am unable to express a positive opinion. 
“Crush breccias” also occur in sedimentary rocks. Some years 
since, I observed a very curious case in a slaty rock near the Pont 
Napoleon, St. Sauveur (Pyrenees). First, in a bedded slaty to arena- 
ceous rock, occurred a number of narrow, nearly vertical, bands filled 
with a rather sandy-looking material, separated by wider bands— 
from 4" to 1" across and 6" to 8” long—of the normal dark calcareo- 
argillaceous rock. They closely resembled worm tubes—and at first I 
inclined to this opinion—but a little further down it became evident 
that they were only joints which had been made to gape, and then filled 
up by pulverized matrix and mineral infiltrations. A little lower 
Incipient brecciation in slaty rocks near Pont Napoleon. The granulated portion 
consists of more arenaceous material in part squeezed up from below, but probably 
in part fragmental. 
down occurred a further displacement, as in the diagram, where A Bis 
the direction of the joints already mentioned, filled as above described 
—in part apparently, a squeezing up of a more sandy bed below, 
and a new set of separation planes were developed parallel to the 
line A CO. These as a rule did not gape, but one fragment had often 
slipped over the other. Yet nearer. the bridge “the joints were more 
irregular, not seldom those parallel to A B were curved in form, 
the fragments were more displaced, twisted and pulled about so as 
closely to resemble an ordinary breccia.” From what I saw some 
