198 PROF. BONNEY ON THE RELATION OF BRECCIAS [May 1902, 
XI. Breccias oF Recent AGE. 
We must next enquire what physical conditions at the present 
or in post-Tertiary ages are most favourable to the formation of 
breccias like those that I have described. We find no such deposits 
either now forming in Europe, or among those of Glacial or later 
days in the Alps, Pyrenees, or Scandinavia. One instance only is 
known to me, which presents any resemblance—the breccia-beds at 
the Rock of Gibraltar. The late Sir Andrew Ramsay and Prof. 
James Geikie, after a lucid discussion of the evidence, concluded that 
these were mainly formed by frost and transported by melting 
snow. In fact, as more than one observer has informed us, the 
physical conditions now existing in the Arctic regions are par- 
ticularly favourable to the production of breccias.” 
XII. Sront-Rivers or THE FaLtxuanp Istks.? 
In the Falkland Isles the land, generally low, rises in places into 
ridges which are seamed by the basset-edges of a white quartzite, 
like stone walls: the ground elsewhere being peaty and boggy. In 
the East Island most of the vallevs* are occupied by pale-grey 
glistening masses, from a few hundred yards to a mile or two in 
width, which at a distance look hke glaciers, apparently descending 
from the adjacent ridges, and being gradually increased in volume 
by tributary streams, till they reach the sea. They are composed 
of blocks of quartzite, angular and irregular in form, and often 
rudely diamond-shaped, but edges and points in most cases are 
slightly rounded. In length they measure from 2 to 8 or 10 
feet, and perhaps half as much in width; their thickness corresponds 
with that of the quartzite-beds. A stream often makes its way 
beneath them along the valley-bottom. ‘The following is Sir Wyville 
‘Thomson’s explanation:—As some of the quartzite-beds are much 
softer than others, these crumble readily away, leaving the harder 
projecting, till at last they fall, when they are quickly embedded in 
a peaty soil, which under the combined action cf the rain, of 
expansion, and of contraction, creeps down the slope, carrying with 
it the embedded blocks. On reaching the bottom they continue 
their crawling motion, though more slowly, down the valley, and 
percolating water gradualiy removes the peaty material from among 
them, leaving little more than the blocks of quartzite. Though 
these islands approximately correspond in latitude with England 
between Stafford and Salisbury, their mean temperature is about 
7 degrees lower ; the winters indeed are not at all severe, but the 
thermometer in summer does not often rise above 65° Fahr., and 
fog or rain are far more frequent than sunshine. 
1 See Quart. Journ. Geol. Soc. vol. xxxiv (1878) p. 505. 
2 See especially E. J. Garwood, Quart. Journ. Geol. Soc. vol. lv (1899) 
p. 683 (Spitsbergen) ; H. W. Feilden, <bid. vol. xxxiv (1878) pp. 564-65 (Smith 
Sound District). 
8 This account is condensed from a very clear and precise description by 
Sir Wyville Thomson, in ‘ Voyage of the Challenger: Atlantic’ vol. ii (1877) 
pp: 245 et SCQQ- 
