it for yards--to an immense boulder in its
base--by far the largest stone I ever saw in an Old Red conglomerate.
The mass is of a rudely rhomboidal form, and measures nearly twelve feet
in the line of its largest diagonal. A second huge pebble in the same
detached spire measures four feet by about three. Both have their edges
much rounded, as if, ere their deposition in the conglomerate, they had
been long exposed to the wear of the sea; and both are composed of an
earthy amygdaloidal trap. I have stated elsewhere ["Old Red Sandstone,"
Chapter XII.], that I had scarce ever seen a stone in the Old Red
conglomerate which I could not raise from the ground; and ere I said so
I had examined no inconsiderable extent of this deposit, chiefly,
however, along the eastern coast of Scotland, where its larger pebbles
rarely exceed two hundred weight. How account for the occurrence of
pebbles of so gigantic a size here? We can but guess at a solution, and
that very vaguely. The islands of Mull and Kerrera form, in the present
state of things, inner and outer breakwaters between what is now the
coast of Oban and the waves of the Atlantic; but Mull, in the times of
even the Oolite, must have existed as a mere sea-bottom; and Kerrera,
composed mainly of trap, which has brought with it to the surface
patches of the conglomerate, must, when the conglomerate was in forming,
have been a mere sea-bottom also. Is it not possible, that when the
breakwaters _were not_, the Atlantic _was_, and that its tempests, which
in the present time can transport vast rocks for hundreds of yards along
the exposed coasts of Shetland and Orkney, may have been the agent here
in the transport of these huge pebbles of the Old Red conglomerate?
"Rocks that two or three men could not lift," say the Messrs. Anderson
of Inverness, in describing the storms of Orkney, "are washed about even
on the tops of cliffs, which are between sixty and a hundred feet above
the surface of the sea, when smooth; and detached masses of rock, of an
enormous size, are well known to have been carried a considerable
distance between low and high-water mark." "A little way from the
Brough," says Dr. Patrick Neill, in his 'Tour through Orkney and
Shetland,' "we saw the prodigious effects of a late winter storm: many
great stones, one of them of several tons weight, had been tossed up a
precipice twenty or thirty feet high, and laid fairly on the green
sward." There is something farther wort