65 
and fragments from the granite are found in them. These 
facts tell of a long period during which these old silurian 
rocks were exposed to denudation and igneous action, and 
during which the country received the great general features 
of hill and valley which it now presents. Judging by 
the work done, this must have been a period of very long 
duration. In the southern silurian district, on the other 
Jiand, 10,000 feet of strata were deposited conformably upon 
the upper silurian. These periods of denudation and deposi- 
tion must have been contemporaneous. By far the greater 
part of the materials removed from the Cumbrian region 
would be carried out into the Devonian sea and form new 
rocks elsewhere, but some would remain, choking up the 
valleys, and when the land began to sink the first thing 
done by the encroaching sea would be the sorting out and 
rearranging of these valley deposits. The work would be 
done with more or less thoroughness, according to the 
amount and nature of the deposit and its position with refer- 
ence to the advancing waters. In some cases, as at Shap, it 
was sorted and spread out along the valley ; in others, as at 
UUeswater, it was left piled up as a great bank. Then, as the 
land still continued to sink, overlapping deposits of sand and 
mud were thrown upon and against the coarser deposits, 
becoming more and more interstratified with limestone as 
the water deepened, sometimes the sandy and muddy deposits 
predominating, and sometimes the limestone, till finally the 
latter prevailed over the former, and the carboniferous 
limestone was deposited in thick masses round the sinking 
land. 
There can be little doubt that the conglomerates, sand- 
stones, and shales, represent a part of the waste of this old 
silurian region. This material would be brought down into 
the valleys either by water or ice. Everyone must be struck 
on first seeing the conglomerate, both in the Isle of Man and 
