GEOLOGICAL SOCIETY OE DUBLIN - . 
63 
them to their parent rocks, which are all to he found within a moderate 
extent of country. Their decrease in number , according to the remoteness 
from their native localities, might, indeed, he accounted for on glacial 
principles; hut not so easily their diminished she: for though the ice-raft 
may waste away by degrees, and its powers of buoyancy become less, 
still this must he thought to effect the total quantity , rather than the in¬ 
dividual parts of the load that it bears. As its cliffs succumb in its pro¬ 
gress through the warm sea-waves, its burden may gradually he reduced; 
but there is no reason why the largest masses should not still he found 
among the mixed materials that are carried on its contracting area. If, 
to meet this objection, the inveterate glacialist would have recourse to 
the manipulation of various icebergs for the shaping of each diminished 
boulder, asserting that its reduced form was due to the lines of bedding, 
or divisional joints of the original mass, which rendered it liable to split 
into fragments when alternately let fall and taken up by successively 
advancing icebergs,—he may he told, that however applicable his expla¬ 
nation might he to the erratics of other regions, the short-travelled boul¬ 
ders of our district will be more simply, and therefore more probably, 
accounted for, by conceding, in this instance at least, the motive power 
to the ordinary waves and currents of the sea. 
If ice were the transporting cause of our drift, we should expect to 
see scattered over the surface of the land even a few large blocks that 
escaped those conjectured vicissitudes of the smaller in their journey 
from distant localities ; but they are never found so situated. The great 
boulders must be looked for near their source, and we have nothing 
like erratics of 100 tons, whose route must have been 100 miles or 
upwards. 
I have already alluded to the unbroken lines of escar hills as a proof 
of their subsequency to the other drifts, and it is hard to imagine how 
they could escape the levelling action of icebergs, had these been float¬ 
ing about and impinging against the shores at the time of the final 
rise of the land. Of course, this remark applies also to Scandinavia and 
to other countries; and generally I would say, that the existence of 
escar chains seems to suggest the prevalence of a climate unfavourable to 
icebergs at the period of emergence from the waters; and this was pre¬ 
cisely the time when I believe that the escars were formed. 
Though the striation of rock-surfaces which I have observed in some 
parts of my district may be thought indicative of glacial action, still it 
does not follow that we must refer to that cause the various phenomena 
of the drifts. The comparatively local character of those deposits which 
I have alluded to above is unfavourable to such a,n idea; and the strati¬ 
fication that the drift so often shows is a proof that, however it had been 
originally accumulated, it comes finally under the action of the waves 
and currents, so that its present condition, or that with which we have 
to deal, must in any case be attributed to aqueous causes. At the same 
time, I do not think that the parallel striation of surface rocks can al¬ 
ways he so confidently ascribed to the operation of icebergs. On account 
of the probable unevenness of the sea bottom, it is likely that when an 
