674 
of a white felspar and of a dark coloured mineral, both too 
much decomposed to be accurately identified. It is also 
interesting on account of being the largest pebble I have 
yet found, for it is nearly four inches in circumference. 
With the exception of a single pebble of very fine-grained 
mica-schist, which some would call clay-slate, I have not 
found good examples of any other decided and well-marked 
rocks. Of course the absence of some kinds does not prove 
that they did not constitute part of the ancient land from 
which those just described were derived; for those which 
were soft or easily broken up would not be able to withstand 
the wearing action of drifting to a distance. This is 
probably the reason why so very few pebbles of micaceous 
rocks are found, although they usually form so large a 
portion of districts where such rocks as I have described 
occur ; and the great amount of detached scales of mica 
in many of the associated finer grained beds makes this 
explanation still more satisfactory. Taking, then, all these 
facts into consideration, I think we are certainly led to 
the conclusion that the materials composing the millstone- 
grit in South Yorkshire, were, to a great extent, derived 
from the waste of land consisting of the so-called Primary 
rocks. 
As I have already stated, there is most excellent evidence 
to prove that the current which drifted the materials into 
their present resting-place came from the north-east, and, 
therefore, we are led to expect that the ancient land which 
furnished them lay in some such direction. Casting our 
eyes toward that part of the compass, the first locality 
where any such rocks now occur, is the Scandinavian 
peninsula. Perhaps this is too far removed to have been 
the source of the tolerably angular, and certainly not much 
water-worn, pebbles sometimes found, but still it is a matter 
of considerable interest to compare the rocks of that country 
with the pebbles in our millstone-grit. The coarse-grained 
