1848.] DARWIN ON THE TRANSPORTAL OF ERRATIC BOULDERS. 317 
his high authority, I do not consider it necessary to give in detail ; 
I will only mention that the grauwacke was planed down level, be- 
fore the thick mass of mountain-limestone on the surface of which 
the boulders lie was deposited on it, and that at a short distance the 
grauwacke is quite cut off by the Craven fault: the conglomerate 
beds, whence the boulders at a height of 900 feet on Stainmoor were 
derived, are horizontal. 
With respect to subsequent unequal elevation having caused the 
boulders now to lie above their parent rocks, the simple fact of the 
number of points, irregularly placed both in Great Britain (namely, 
in northern and central Scotland, in the Lake district, North Wales, 
Isle of Man and Ireland,) and likewise in the United States, appears 
to me to render this view extremely improbable ; for on such a view 
it must be admitted that in Great Britain and America several great 
mountains and mountain-chains have been formed so lately as during 
the glacial period, and this is a proposition to which few geologists 
will be inclined to assent. Moreover, in the case of Stainmoor, it is 
known that its crest now holds, one part with another, the same re- 
lative level as it did during the glacial period, for the boulders have 
crossed it only in one notch or gap, which is now the lowest part ; 
and certain chains of hills which would at present intercept boulders 
coming from one quarter likewise did so at the glacial epoch. 
In the Isle of Man the parent granite and the boulders which lie 
788 feet above it are scarcely more than two miles apart, and in the 
intermediate tract, thickly covered with the boulders, Mr. Cumming 
has in vain searched for evidence of a fault. In the Lake district 
there is, I think, conclusive evidence that unequal elevation is not the 
true explanation, for the boulders there lie so close to the rocks in 
situ that there would necessarily be, if the boulders had been subse- 
quently upraised, a fault or abrupt flexure, in one case of 900 and in 
the other of 500 feet. Hence we must conclude, in accordance with 
the views of the several authors who have described the above cases, 
that the boulders have really been drifted nearly as many feet up- 
wards (that is, making in almost every instance some allowance for 
the subsequent denudation of the parent rock) as they now lie above 
their original source. 
Those who believe in the powerful agency of ice in moving boulders 
will probably at first conclude that icebergs have in some manner 
transported them from a lower to a higher level. But the most ob- 
vious method by which fragments of rock can get on icebergs is by 
their having first fallen from the surrounding precipices on glaciers 
entering the sea, and therefore they must have come from a higher 
to a lower level. It seems impossible, owing to the temperature of 
the water, that at any considerable depth, boulders could be frozen 
into the bottom of icebergs; and even if at lesser depths they did 
become so frozen* or mechanically wedged in, and if by the icebergs 
being overturned they were saved from being soon thawed out, yet 
they could be deposited above their former level only by so much as 
* See some excellent remarks on this subject in Sir H. De la Beche’s Anniver- 
sary Address for 1848, p. 68 ef¢ seg. 
