For the present we shall pass over these more humble whisperers of things
curious and strange, and turn to those massive fragments of rocks which,
far removed from their original site, are now scattered either singly or
in groups over a large portion of the earth’s surface, resting sometimes
on the slopes of hills composed of materials totally different from
their own, seen sometimes on the sand and gravel of extensive plains,
and distant from the mountains of which they were once a part, sometimes
from one to three hundred miles: they are Boulders. Can we not picture
to ourselves, in that remote period of our island’s history when forest
and morass occupied the place of its bogs, and when the winds sighed
over comparative desolation, an ancient inhabitant, imbued with nature’s
living poetry, pausing before one of those grey lichen-covered masses
which had withstood the warrings of the elements for perhaps thousands
of years, and, as the awe of the surrounding solitude came like a charm
over his soul, gazing with growing veneration at the venerable rock?--to
him it would appear as if cast down from heaven, or planted where it now
stands by some supernatural or giant hand. What spot, then, more fitted
for the simple worship of nature’s child?--what temple, what altar more
suited to his simple rites?
A rock such as we have here described may have been found supported in
part by lesser fragments, or such supports may have been introduced by
partial excavations under favourable projections of its surface; and
in either case, the superfluous earth, sand, or stones under and about
it, being removed, this ancient monument of the operations of Nature
would henceforth become an instrument in the worship of Nature’s God--a
Cromlech!
Whether, however, this be, or not, a correct view of the original impulse
which led to the selection of these giant stones, or of the purpose to
which they were applied, it is for our antiquarian friends to decide.
Suffice it here to add, that the transportation of such huge masses from
their native beds, by the power of man or of giants, was at such a remote
epoch, and under the circumstances of the country, impossible; nor will I
stop to inquire whether a work so mighty was performed by spirits light
as air.
Let us turn to the consideration of the phenomenon of Boulders, as it
has appeared to the eye of science. And perhaps there are no two facts
which place it in so strong a light, and embrace so fully the reasonings
founded upon it, as the dispersion of blocks of the granite and other
rocks of Sweden over a large portion of Northern Europe, the boulders,
either singly or in clusters, being disposed in long parallel lines
or trainées, for upwards of two hundred miles from the mountains of
Scandinavia, to which, by identity of mineral composition, they have
been traced, although separated from them by the Baltic Sea; and the
occurrence of boulders of alpine granite resting on the secondary rocks
of the Jura chain, between which and the Alps are situated the deep
valley of the Rhone, the Lakes of Geneva and Neufchatel, the distance
travelled by the boulders being sixty miles. Saussure, struck by the
spectacle of clusters of these fragments so far removed from any rock
resembling them, declared that they looked as if rained down from heaven;
a sentence strikingly expressive of the difficulties which attend on an
explanation of their occurrence. De Luc rightly speaks of such travelled
masses of stone as being “one of the most important of geological
monuments, since they offer a rigorous criterion of the different systems
concerning the revolutions which have happened on our globe;” and in
describing the vicinity of Cuxhaven, situated at the extremity of the
Bremen country, which lying between the Gulfs of the Elbe and Weser, is
as it were a peninsula, he cites the very forcible example it affords of
a vast abundance of boulders at a distance of more than two hundred miles
from the Scandinavian chain, the outlet, itself sixty miles wide, of the
Baltic, forming part of the intervening space.
At the time of De Luc’s visit to Cuxhaven (1797), a dike was constructing
to secure the port from the violence of the sea, and the plan of
employing blocks for this purpose was suggested by the quantity which
were scattered over all the neighbouring country. From the vicinity alone
of Hornburg, an inland town between the ports of Stade and Harborg,
600 lasts of blocks, amounting to 240,000 quintals, or 23,679 tons,
had at that time been brought and consumed in the dike, which, with
the thickness necessary to resist the utmost impetuosity of the waves,
and a height of about eight feet, already extended three leagues to
the westward of the town. The country in which these accumulations of
erratic boulders had taken place, is an expanse of sand covered with
heath, except where broken by cultivated patches around the scattered
villages, the surface being undulated by hills composed either of sand or
of heaps of boulders. De Luc adds, “that he travelled ten miles without
perceiving in the whole horizon any house, or even a hovel, or a single
tree”--desolate and dreary indeed to the eye of painter or poet, yet rich
in all the elements of sublimity to the eye of the geologist.
It is quite unnecessary to adduce other and less imposing examples
from Great Britain and Ireland of similar facts, the difficulties of
explanation being fully embraced by those selected. How have they been
brought to their present places? is then the question mentally asked, as
well by the learned as the unlearned.
Saussure, celebrated for his examination of the Alps, imagined a great
debacle and retreat of the sea from the strata that had been formed, as
he supposed, by chemical precipitations; and to the violent rush of the
vast current he ascribed the excavation of the valleys, and the transport
of immense masses of stones from the central chain of the Alps, beyond
the precincts of those mountains, to the Jura. Here, then, the excavation
of the valleys of the Alps, and the transport of the boulders, are
considered results of one great catastrophe, by which the bottom of the
sea became hard dry land, its waters descending into huge abysses which
had burst open around the Alps. The phenomenon of Boulders is general in
a large portion of the northern hemisphere; the explanation however is
local and hence insufficient; whilst the philosopher’s machinery, of huge
abysses, like the peasant’s giant, is born of necessity, not deduced from
experience.
Others, and even yet they are many, attribute the transport of both
gravel and boulders to the Noachian deluge, which is their great
geological catastrophe. The application, however, of that great
historical event to such physical agencies, is beset with great
difficulties. The words of scripture do not support, but rather oppose,
the notion of a huge wave rising in the north to a great height, then
rushing southwards over the dry land, and rooting up or sweeping before
it, by hydrostatic pressure, fragments of the earth’s crust. Nor are
facts more in accordance with that notion--the boulders of Scandinavia
were moved from north to south--the boulders of the Alps from south
to north, passing over the Jura mountains into Franchcomté--the
stratification of many of the heaps of sand and gravel--the position
of the boulders generally on the surface, whether of rocks, of sand,
or of gravel--and the valleys, lakes, and seas now lying in the line
of movement, which, if existing before the catastrophe, must have been
filled up before the boulders could have travelled farther, if formed
after, must have required the action of a second catastrophe of equal
violence for their formation. And if, which is more in accordance with
scripture, we consider the waters rising from the surrounding seas over
the dry land, and then suppose them urged on with immense velocity, the
effect would be a heaving up and moving forward of fragments from the
lower land, by which the surface of the higher would be partly covered
and protected; and at the return of the waters to their ancient beds,
these fragments would be swept off, and carried back the same way they
came. Neither, then, the words of scripture, nor the facts themselves,
require us to seek in the Noachian deluge for an explanation of these
phenomena. Another theory, still adhered to by many modern geologists,
is, the action of submarine currents, at a time when the present dry land
had only in part emerged from the sea. This theory has the advantage
of dealing with bodies of diminished gravity, in consequence of their
immersion in a fluid, and consequently of having to provide for the
movement of weights less by one-half or one-third than they would have
been in air. In conjunction with the theory of raised beaches, it
explains many of the phenomena of accumulations of sand and gravel, but
not all. And as regards the transport of boulders, it fails; the great
size and angular form of some--their occurrence at various levels,
resting on various strata--sometimes connected with, and sometimes
unconnected with sand or gravel--their position frequently on the top of
heaps and ridges of gravel, being facts in seeming opposition to such an
explanation, even were it conceded that all the depressions now existing
on the line of travel, as lakes and seas and valleys, were scooped out
subsequently to their transport.
The geological system of the illustrious Hutton assumed as an essential
principle, that as the present continents and dry land were once the
bottom of the ocean, and have been formed, either in greater part or
entirely, of fragments of pre-existing continents now submerged, so is
the work of destruction and renewal still continuing, the substance of
our present dry land being loosened, abraded, or worn down by meteoric
agencies, and carried by torrents and rivers to the ocean, to be there
by currents distributed over the bottom of the sea, and by internal heat
consolidated into new strata, which in time will be elevated into new
continents and islands. To apply this theory in the case of the Jura
boulders, Playfair assigned their transport to an epoch anterior to the
formation or excavation of the deep valleys and lakes which would now
form an insurmountable obstacle to such transport, and thus obtained a
greatly inclined plane, extending from the summit of the Alps to the
Jura, on which to trundle the fragments gradually downwards, by aid of
the numerous streams and torrents descending from the higher to the
lower ground. But as this theory would, as thus applied, premise that
the land had been raised above the sea-level prior to the transport of
the boulders, no means of effecting the great excavations, including the
Lakes of Geneva and Neufchatel, which are supposed to have been formed
subsequently, are left, except the slow erosive action of rains, frost,
torrents, and such-like agents--means which few will consider adequate to
the desired object; and hence the explanation of Playfair, resting solely
on a bold hypothesis, must be rejected. As most of the preceding theories
referred to the usually rounded condition of the granite boulders (many
boulders of other rocks are angular), as an evidence of movement through
the agency of water, De Luc, preparatory to the promulgation of his
own theory, thought it expedient to show that blocks of granite, even
as they stand tranquilly braving the storms, are gradually weathered
into a rounded form. He thus cites the granite of Darmstadt as an
example:--“Here I found a striking example of the manner in which blocks
and even rocks of granite are rounded by the decomposition of the angles
of their masses. I perceived it first in some angular pieces that had
been detached and lay at the foot of the rock, surrounded with rubbish;
for, on giving them a strong blow with an iron at the end of my stick,
the angles fell off, detaching themselves with a concave surface on their
inner side; and I thus produced rounded blocks, exactly resembling those
which I had seen scattered on the plains.” This spherical concretionary
structure has been noticed in the granite of Dublin and Down, and is
common in trap rocks. Having smoothed away this difficulty, De Luc tacks
on the boulders as a corollary to his theory of subsidences. Immense
masses of strata, subsiding into huge caverns or hollows beneath them,
fragments of the lower strata were broken off and blown upwards by the
force of the pent-up air and gases rushing through the cracks of the
sinking strata, the weight of which continued more and more to compress
them, so that the boulders of M. De Luc came from below, and not from
above. This is also a gratuitous hypothesis; and as the localities of
many boulders exhibit no signs of such subsidences and explosions, it
has obtained few if any adherents. So far, then, it would appear that
philosophers, though armed with all the powers of mind invigorated
by study and sharpened by research, have fought in vain against the
difficulties which like a rampart fence in this rugged problem. For a
moment they have appeared illumined by the light of knowledge, and have
then sunk into the darkness of ignorance. But though philosophy may
yield, she never will despair. And now, having marshalled new forces for
the combat, we shall see her, with brighter hopes and prospects, again
renew the assault. To the consideration, therefore, of a widely different
class of explanations, I shall proceed to direct attention in a second
paper.