194 PROF. BONNEY ON THE RELATION OF BRECCIAS | May 1902, 
' 
IX. Jurasstc Breccras. 
We are indebted to Prof. Judd! for a very full and precise 
‘description of the remarkable beds of breccia which occur in the 
Upper Oolite of Sutherland, As they bear in many respects a 
very close resemblance to those which I am about to describe in. 
the next section, I shall content myself with referring to his paper 
for particulars, merely stating that these breccias are not quite so diffi- 
cult to explain as some others, because the source of their materials 
is more easily determined. He concludes that they were deposited 
in a sea in the neighbourhood of its shore, and were brought down 
from a mountainous region by flooded streams, but that the great 
size of occasional blocks—some measuring 20 by 10 feet—suggests 
that ice aided in the transport. 
X. Breccras IN THE ALPINE FLyscu. 
The breccia-beds in the Flysch may be traced practically over the 
whole length of the Alpine chain,” but the more remarkable 
developments are on the northern side. The Flysch itself is ob- 
viously a result of physical conditions which were not simultaneous, 
but set in and ended earlier in the east than in the west, the 
breccias being sporadic in distribution. I select for description 
two localities which I have myself examined, and believe to be 
among the most remarkable instances. 
The first is the noted one in the Habkerenthal. As this has 
been frequently described, I shall restrict myself to mentioning the 
points which seem to me to bear more immediately on the question 
of its origin. Here the Flysch itself is a brownish to blackish, 
rather gritty, fissile® mudstone. It contains occasionally thin bands 
of hard sandstone and lenticular masses of breccia or conglomerate. 
The fragments in this are commonly subangular or subrotund ; 
sometimes it becomes a coarse grit, and sometimes contains boulders 
bigger than a man’s head. The material of the matrix (generally 
indurated) apparently has been derived from granitic rocks; in 
parts it becomes a fairly uniform quartz-felspar grit, which occa- 
sionally might even be mistaken for a granite, but when the 
fragments vary much in size a few represent sedimentary rocks. 
Thin streaks of mudstone sometimes interrupt the lenticular masses 
towards the outside, and the mudstone itself may contain isolated 
boulders or fragments.* I was unable in the time at my disposal 
to find one of the very large boulders actually im sztw in the Flysch, 
but several lay in the bed of the stream, the biggest of which 
1 Quart. Journ. Geol. Soe. vol. xxix (1878) p. 187. 
> Erratics are said to occur in the Flysch of the Carpathians and Apennines: 
Lyell, ‘ Principles of Geology’ 11th ed. vol. i (1872) p. 209. 
3 Whether due to cleavage or bedding I could not be certain, in the time at 
my disposal. I do not remember to have seen a clear statement in print. 
The term schist of course, as used by Continental geologists, tells us nothing. 
4 In one or two places I suspected this to be the result of the shearing of a 
band. 
