60 
Mr. Bolton was unable to give any clue to the manner in 
which such remarkable sections as the above had obtained. 
The occurrence of the superficial deposits, as shown in 
the foregoing section, is, I believe, to be explained by the 
theory of glacial action, and is evidently a part of the great 
change wrought upon the surface, by the agency of ice, 
during the “glacial epoch”; coeval with the boulder drift. 
The great ice sheet, which then covered all the north of 
England, descended from the lake mountains, grinding 
down the surface rocks, and depositing the clays and 
gravels in its course. The evidence of this is most strik- 
ingly displayed in the above section, each line of which 
apparently marks out a period, and a pause, in its course. 
The iron ore occurring in these deposits is of a dark 
colour, and of much lighter specific gravity than that from 
the veins of limestone ; and it has the appearance of having 
been all ground to powder. After exposure to atmospheric 
influence it soon falls again into that state. The clays are 
of a bright yellow colour, and of exceedingly fine grain, 
being evidently the “ flour of rocks,” ground down by the 
glacier in its passage over the clay-slates. The unfossilized 
wood is in a remarkable state of preservation, occurring in 
large fragments, as if it had been rudely broken up and 
crushed, probably also by the ice. It is principally birch, 
and some of the trees have been found of 2ft. diameter. In 
one of the pits there was also a layer of peat, giving evidence 
of a long period of rest and stagnation. 
The iron ore was thus, by glacial agency, transferred from 
its original place of occurrence, from the outcrop of one reef 
to another, and redeposited as drift; covered up by clays 
and the debris of rocks, wherever there was a cavity to 
receive it. The water resulting from the thaw of the ice 
would carry the ore down with it into the crevices and 
caverns of the limestone, where it is now found as soft or 
“ puddling” ore. Aggassiz points out in his work on glaciers 
