59 
Thus we see that in the South of England, in Wales, in 
Scotland, and in Ireland, the carboniferous rocks are sepa- 
rated from the silurian by a great thickness of strata, and 
wherever the junction can be seen, the lower beds of these 
intervening strata are found to graduate downwards into the 
upper silurian, and the upper to pass upwards, without any 
break, into the carboniferous. In Cumberland, there is 
another silurian district, and around it are carboniferous 
rocks, but here the enormous thickness of red strata is nearly 
absent. The carboniferous limestone dips in all directions 
from the silurian lake district as a centre, and only in isolated 
patches is there anything which can by any means be com- 
pared with the old red sandstone of Wales and Scotland, the 
limestone, for the most part, lying unconformably upon the 
contorted, metamorphosed, and denuded silurian rocks. It is 
the same in the Isle of Man ; the carboniferous limestone, 
the most recent formation not tertiary in the island, is 
separated from the silurian schists by a few comparatively 
thin red beds. It is these isolated patches of red, which in 
these localities intervene between the silurian rocks and the 
carboniferous limestone, which are more especially the subject 
of this paper. 
First, as to their character and mode of occurrence. The}' 
foi'm almost always a coarse conglomerate. The included stones 
vary much in size, and some are v^ery large. They are angular 
or subangular, rarely well rounded. In mineral character they 
are the same as the underlying silurian rocks, and appear to 
have been always derived from the immediate neighbourhood. 
The matrix is generally red, but is sometimes of a light grey 
or green, and sometimes a deep purple, and it contains a 
large quantity of iron. The conglomerate presents a rough 
stratification, and often contains thin, irregular, false-bedded, 
and ripple-marked beds of sand or sandy clay. No fossils 
have been found in it, except silurian fossils in the included 
