VRS nee A 
: 29) 
190 PROF. BONNEY ON THE RELATION OF BRECCIAS _[ May 1902,. 
age, underlie the Coalfield. Moreover, the area covered by the 
higher Permian deposits in the immediate neighbourhood of the 
breccias, even if augmented by that now occupied by the Lower 
Bunter, seems, under the most favourable circumstances—that is. 
supposing the ranges of this old land-mass to run athwart it,\—to 
afford a very straitened site for a really important hill-mass. The 
Bunter also, as it is thinning rapidly, can hardly exceed 1000 feet 
in any part of this district and must often be much less, so that 
any buried summit cannot rise high above the general level. Though 
a large land-mass undoubtedly occupied this part of England during: 
the earlier half of the Carboniferous Period, the distribution of the 
Coal-Measures proves that very much of it was afterwards buried, 
and was not laid bare again before the Permians were deposited. 
Thus the masses of more ancient rock from which the breccias 
were supplied cannot have extended far, or risen high ; so that to call 
this region the ‘Mercian Highlands’ seems to me more picturesque 
than accurate, for I should expect it to be comparable rather with 
the Southern Uplands of Scotland than the great hill-masses farther 
north.” If then we are compelled to restrict, vertically as well as. 
horizontally, the area which supplied these masses of Permian 
breccia, we are driven to assume that agencies have been at work 
which were capable of shattering the bare rocky slopes andi 
transporting the materials for some few miles, 
VI. Tue Devon Breccias.’ 
Mr. Ussher has given a very full description of these interesting 
deposits,’ from which I extract the following facts as having most 
bearing on their origin and formation. They vary considerably in 
shape and in mineral character, being generally angular, as, for 
instance, about Dawlish and Teignmouth,’ but subangular or 
rounded in the neighbourhood of Bradninch and Roundham Head 
| As suggested by Mr. Wickham King. 
2 Some may reply that these Mercian Highlands were destroyed during the: 
Jater Permian and earlier Triassic periods. But, if so, they must have been 
planed away, work which takes rain and rivers a long time to perform, and it 
is very doubtful whether, during this interval, the sea ever overflowed this. 
district. [A speaker in the discussion mentioned Charnwood as a truly ‘ High- 
land’ mass. But this is some 35 miles away: the highest summit also at the. 
present day does not rise more than 400 or.500 feet above the Coalfield and the. 
overlying Permians (which here are thin), and we have no reason for supposing. 
that the relative levels have been materially altered since the end of the Palzo- 
zoic era. 
= ail oh these as Permian, in accordance with the views of Conybeare, 
Buckland, and Murchison, which since Dr. A. Irving’s excellent paper in 
vol. xliv (1888) of this Journal (p. 149) have regained fayour. It would not 
affect their general significance even if they were Trias. 
' Quart. Journ. Geol. Soe. vol. xxxii (1876) p. 387. 
5 In this district, according to the late Mr. R. N. Worth, the biggest boulders 
occur (sometimes 4 or 5 feet in diameter) in the Dawlish, Valley ; here also 
they are most varied in composition, and contain the largest proportion of 
granitic rock. 
