Vestiges of the Natural History of Creation (Chapter 5)
by Robert Chambers
Era of the Old Red Sandstone—Fishes abundant.
e advance to a new chapter in this marvellous
history—the era of the Old Red Sandstone System. This term has
been recently applied to a series of strata, of enormous thickness in the
whole mass, largely developed in Herefordshire, Shropshire, Worcestershire,
and South Wales; also in the counties of Fife, Forfar, Moray, Cromarty, and
Caithness; and in Russia and North America, if not in many other parts of
the world. The particular strata forming the system are somewhat different
in different countries; but there is a general character to the extent of
these being a mixture of flagstones, marry rocks, and sandstones, usually
of a laminous structure, with conglomerates. There is also a schist shewing
the presence of bitumen; a remarkable new ingredient, since it is a
vegetable production. In the conglomerates, of great extent and thickness,
which form, in at least one district, the basis or leading feature of the
system, in closing waterworn fragments of quartz and other rocks, we have
evidence of the seas of that period having been subjected to a violent and
long-continued agitation, probably from volcanic causes. The upper members
of the series bear the appearance of having been deposited in comparatively
tranquil seas. The English specimens of this system shew a remarkable
freedom from those disturbances which result in the interjection of trap;
and they are thus defective in mineral ores. In some parts of England the
old red sandstone system has been stated as 10,000 feet in thickness.
In this era, the forms of life which existed in the
Silurian are continued: we have the same orders of marine creatures,
zoophyta, polypiaria, conchifera, crustacea; but to these are added
numerous fishes, some of which are of most extraordinary and surprising
forms. Several of the strata are crowded with remains of fish, shewing that
the areas in which those beds were deposited had swarmed with that class of
inhabitants. The investigation of this system is recent; but already[1] M. Agassiz has ascertained about twenty genera, and
thrice the number of species. And it is remarkable that the Silurian fishes
are here only represented in genera; the whole of the species of
that era had already passed away. Even throughout the sub-groups of the
system itself, the species are changed; and these are phenomena observed
throughout all the subsequent systems or geological eras; apparently
arguing that, during the deposition of all the rocks, a gradual change of
physical conditions was constantly going on. A varying temperature, or even
a varying depth of sea, would at present be attended with similar changes
in marine life; and by analogy we are entitled to assume that such
variations in the ancient seas might be amongst the causes of that
constant change of genera and species in the inhabitants of those seas to
which the organic contents of the rocks bear witness.
Some of the fossils of this system,—the
cephalaspis, coccosteus, pterichthys, holoptychius—are, in form and
structure, entirely different from any fishes now existing, only the
sturgeon family having any trace of affinity to them in any respect. They
seem to form a sort of connecting link between the crustacea and true
fishes.
The cephalaspis may be considered as making the
smallest advance from the crustacean character; it very much resembles in
form the asaphus of lower formations, having a longish tail-like body
inserted within the cusp of a large crescent-shaped head, somewhat like a
saddler's cutting-knife. The body is covered with strong plates of bone,
enamelled, and the head was protected on the upper side with one large
plate, as with a buckler—hence the name, implying buckler-head.
A range of small fins conveys the idea of its having been as weak in motion
as it is strong in structure. The coccosteus may be said to mark the
next advance to fish creation. The outline of its body is of the form of a
short thick coffin, rounded, covered with strong bony plates, and
terminating in a long tail, which seems to have been the sole organ of
motion. It is very remarkable, that, while the tail establishes this
creature among the vertebrate and the fishes, its mouth has been opened
vertically, like those of the crustaceans, but which is contrary to the
mode of vertebrate generally. This seems a pretty strong mark of the link
character of the coccosteus between these two great departments of the
animal kingdom. The pterichthys has also strong bony plates over
its body, arranged much like those of a tortoise, and has a long tail; but
its most remarkable feature, and that which has suggested its name, is a
pair of long and narrow wing-like appendages attached to the shoulders,
which the creature is supposed to have erected for its defence when
attacked by an enemy.
The holoptychius is of a flat oval form,
furnished with fins, and ending in a long tail; the whole body covered with
strong plates which overlap each other, and the head forming only a slight
rounded projection from the general figure. The specimens in the lower beds
are not above the size of a flounder; but in the higher strata, to judge by
the size of the scales or plates which have been found, the creature
attained a comparatively monstrous size.
The other fishes of the system,—the osteolepis,
glyptolepis, dipterus, &c., are, in general outline, much like fishes still
existing, but their organization has, nevertheless, some striking
peculiarities. They have been entirely covered with bony scales or plates,
enamelled externally; their spines are tipped with bone, and, as one
striking; and unvarying feature, the tail is only finned on the lower side.
The internal skeleton, of which no traces have been preserved, is presumed
to have been cartilaginous. They therefore unite the character of
cartilaginous fishes with a character peculiar to themselves, and in which
we see pretty clear vestiges of the pre-existent crustaceous form.
With regard to the link character of these animals, some
curious facts are mentioned. It appears that in the imperfect condition of
the vertebral column, and the inferior situation of the mouth in the
pterichthys, coccosteus, &c, there is an analogy to the form of the dorsal
cord and position of the mouth in the embryo of perfect fishes. The
one-sided form of the tail in the osteolepis &c. finds a similar analogy in
the form of the tail in the embryo of the salmon. It is not premature to
remark how broadly these facts seem to hint at a parity of law affecting
the progress of general creation, and the progress of an individual
fœtus of one of the more perfect animals.
It is equally ascertained of the types of being
prevalent in the old red, as of those of the preceding system, that there
are uniform in the corresponding strata of distant parts of the earth; for
instance, Russia and North America. In the old red sandstone, the marine
plants, of which faint traces are observable in the Silurians, continue to
appear. It would seem as if less change took place in the vegetation than
in the animals of those early seas; and for this, as Mr. Miller has
remarked, it is easy to imagine reasons. For example, an infusion of lime
into the sea would destroy animal life, but be favourable to
vegetation.
As yet there were no land animals or plants, and for
this the presumable reason is, that no dry land as yet existed. We are not
left to make this inference solely from the absence of ]and animals and
plants; in the arrangement of the primary (stratified) rocks, we have
further evidence of it. That these rocks were formed in a generally
horizontal position, we are as well assured as that they were formed at the
bottom of seas. But they are always found greatly inclined in position,
tilted up against the slopes of the granitic masses which are beneath them
in geological order, though often shooting up to a higher point in the
atmosphere. No doubt can be entertained that these granitic masses, forming
our principal mountain ranges, have been protruded from below, or, at
least, thrust much further up, since the deposition of the primary
rocks.
The protrusion was what tilted up the primary rocks; and
the inference is, of course, unavoidable, that these mountains have risen
chiefly, at least, since the primary rocks were laid down. It is remarkable
that, while the primary rocks thus incline towards granitic nuclei or axes,
the strata higher in the series rest against these again, generally at a
less inclination, or none at all, shewing that these strata were laid down
after the swelling mountain eminences had, by their protrusion, tilted up
the primary strata And that it may be said an era of local upthrowing of
the primitive and (perhaps) central matter of our planet, is established as
happening about the close of the primary strata, and beginning of the next
ensuing system. It may be called the Era of the Oldest Mountains,
or, more boldly, of the formation of the detached portions of dry land over
the hitherto watery surface of the globe—an important part of the
designs of Providence, for which the time was now apparently come. It may
be remarked, that volcanic disturbances and protrusions of trap took place
throughout the whole period of the deposition of the primary rocks; but
they were upon a comparatively limited scale, and probably all took place
under water. It was only now that the central granitic masses of the great
mountain ranges were thrown up, carrying up with them broken edges of the
primary strata; a process which seems to have had this difference from the
other, that it was the effect of a more tremendous force exerted at a lower
depth in the earth, and generally acting in lines pervading a considerable
portion of the earth's surface. We shall by-and-by see that the protrusion
of some of the mountain ranges was not completed, or did not stop, at that
period. There is no part of geological science more clear than that which
refers to the ages of mountains. It is as certain that the Grampian
mountains of Scotland are older than the Alps and Apennines, as it is that
civilization had visited Italy, and had enabled her to subdue the world,
while Scotland was the residence of "roving barbarians." The Pyrenees,
Carpathians, and other ranges of continental Europe, are all younger than
the Grampians, or even the insignificant Mendip Hills of southern England.
Stratification tells this tale as plainly as Livy tells the history of the
Roman republic. It tells us—to use the words of Professor
Philips—that at the time when the Grampians sent streams and detritus
to straits where now the valleys of the Forth and Clyde meet, the greater
part of Europe was a wide ocean.
The last three systems—called, in England, the
Cumbrian, Silurian, and Devonian, and collectively the palaeozoic rocks,
from their containing the remains of the earliest inhabitants of the
globe—are of vast thickness; in England, not much less than 30,000
feet, or nearly six miles. In other parts of the world, as we have seen,
the earliest of these systems alone is of much greater depth—arguing
an enormous profundity in the ocean in which they were formed.
Notes
[ Robert Chambers,
Vestiges of the
Natural History of Creation, 1st edition, 1844; Reprinted in James Secord,
ed., Chicago: University of Chicago Press, 1994, pp. 66-75. ]
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