200 PROF. BONNEY ON THE RELATION OF BRECCIAS [May 1902, 
parts of the Karakorams and Himalayas (see my paper in Geol. Mag. 
1902, p. 8), are by no means identical with these breccia-beds. In 
these the proportion of mud is very much larger, so that they bear 
closer resemblance to an ordinary boulder-clay. Mr. R. D. Oldham,! 
in a most suggestive paper, expressly identifies the Permian breccias 
of the Midlands with the ‘gravel-fans’ of Western and Central Asia; 
but I venture to think that he does not quite sufficiently emphasize 
this distinction, between the breccias in question and the ordinary 
‘mud-avalanche ’ or ‘ glacial-schotter.’ 
XIV. INFERENCES AS TO THE PREVAILING Puysrcat ConprTions WHEN 
THE BRECCIAS WERE FORMED. 
My apology for describing these breccias at some length must be 
that inferences as to the physical conditions which led to their 
formation are dependent on the details. Those of the Rothliegende 
are fringe-like in distribution, attain considerable thickness, and 
can be traced occasionally for some few miles from their source. 
The area of this often is not large, compared with the volume of 
the breccia-bed ; so that they were more probably derived from a 
highland region with bare rocky slopes, than from a lofty mountain- 
range. The close resemblance between these and certain Asiatic 
breccias suggests that the climate of both our islands and Germany 
was then distinctly continental in character ; perhaps hot in summer, 
but cold in winter, possibly with a considerable snowfall at that 
season, though this, as we see, is not an absolute necessity, for occa- 
sional torrential rains might produce the same effect. Remembering 
that contact with a sheet of water would greatly check the move- 
ment of scree-like material, we infer that, as a rule, these breccia- 
beds were subaérial rather than subaqueous deposits; and it is not 
impossible that even the intercalated beds of finer material may 
be wind-borne. There is no proof of the existence of glaciers, but 
floating ice is sometimes suggested as a possible agent of transport ; 
in any case, these breccias indicate that the epoch of the Rothlie- 
gende was characterized by a considerable range of temperature 
and rather cold winters.” 
When the breccia-fringe extends continuously from the moun- 
tainous district for 4 or 5 miles, it is probably a subaérial 
deposit. It is certainly so in Persia, where I was perplexed to 
explain how the fragments could travel so far on an almost level 
surface. At moderate distances we might attribute it to melting 
snow, which imparted a sort of fluidity to the mass, so that it 
spread out laterally under the action of gravity, somewhat as a 
mud-avalanche may ultimately do. But for the Persian breccias 
1 Quart. Journ. Geol. Soc. vol. 1 (1894) p. 463. 
2 I have not referred to the glacial deposits of Permo-Carboniferous age 
in Australia, Hindustan,-and, perhaps, South Africa, because they are outside 
the purview of my paper, and the question of their exact age might introduce 
complications. 
