The course of creation

by John Anderson

The rocks of this class consist of a group of argillaceous, calcareous, and arenaceous deposits, varying in color and texture. They are of great thickness and severally impressed with their own written story, the fossil memoranda of the changes and events that occurred betwixt the formation of each. These are the transition rocks of Werner. The newly-adopted term of Silurian implies no peculiar theory as to their origin. It simply expresses the fact that in the district in question a complete succession of fossiliferous strata is interpolated between the oldest slaty crystalline rocks and the old red sandstone. The system is divided by their discoverer and historian, Sir R. I. Murchison, under the ascending series, into the Cambrian System, Llandeilo-flags, Caradoc Sandstone, Wenlock Shales and Limestones, and Lower and Upper Ludlow Rocks.

Do the equivalents of all, or of any, of these groups exist in the Grampian range? Geologists for the most part have been answering these questions in the negative. Hitherto no true silurian deposits have been recognized as existing among the northern Scottish mountains, and no well-authenticated organism of the system has been detected in any of their localities. This, however, will hardly be taken as a conclusive argument after the admission into the family of the Skiddaw slate, in which the faintest traces of organized matter have only very recently been observed, while the over-lying series consisting of chlorite-slate, and alternating beds of porphyry and greenstone, from twenty to thirty thousand feet thick, have not yet been proved to contain a single fossil. “Good fossil groups,” Professor Sedgwick argues, “are the foundation of all geology; and are out of all comparison the most remarkable monuments of the past physical history of our globe, so far as it is made out in any separate physical region.”

We are convinced that the clayslates and graywackes which repose on the southern flank of the Grampians, as well as abundantly in the interior, will, upon strict examination, have their place assigned among the Silurian class. Mr. Nicol, who has done so much for the Lammermuir deposits, will find ample scope for his investigations, and all his ingenious speculations, in determining the true position of these argillaceous beds, which are of prodigious thickness and vast extent. This is not the place to enter into details, but in support of the view now advanced, the following among other reasons may be given.

First of all, the clayslate of the Grampians resembles in its lithology the slates of Wales and Cumberland, admitted to be silurian. In hand specimens they cannot easily be distinguished from each other: practical men consider the slates of Dunkeld and Glenalmond as softer and less flinty than those of the south. They pass from extremely coarse into the finest grained varieties, when the graywacke character is entirely lost in the homogeneous mass. Their position in reference to the crystalline rocks, in the next place, is very distinct, never alternating with, nor lying conformable to, either the gneiss or mica-schists. They form the outer zone, from east to west, of the Grampian range, where feldspar, porphyries, and trappean rocks are along the whole line mixed up or associated with them. Then overlying the clayslate, precisely as in Cumberland, the old red sandstone is found in immediate succession and resting unconformably. Shall we add that, even in a topographical point of view, these beds will be admitted to vindicate their claim to Silurian origin, constituting, as they do, in extension, a portion of the great primary belt that encompasses the western shores of Great Britain, and beyond the channel, stretches through Brittany and Normandy?

From considerations such as these there are sufficient grounds, we think, for constituting the clayslates and porphyries of the Grampians into a “physical group,” existing in a “separate physical region.” The absence of organic remains may be accounted for by the fact of the vast disturbance prevailing in the seas at the period, and indicated by the prodigious quantity of igneous matter spread repeatedly over their bottom. These causes would act in so far in preventing the existence and increase of living things, over all these parts, and most certainly in obliterating the traces of their remains, if any were deposited. But as future explorers may yet detect them in abundance we proceed to consider the nature and classes of fossils elsewhere discovered in the Silurian strata.

Animal Remains. Here, in this series of rocks, we are carried back to the beginning of life upon the globe, in which we see the very dawn and commencement of earthly enjoyment, the first forms and races of creatures which were privileged to eat at the banquet of creation. As matter of history, therefore, nothing can be more interesting; as a subject of mere curiosity concerning ancient relics, the most ardent archæologist will be amply gratified; and as showing the manner of the divine actings in replenishing the earth with living things, the word and the works of Deity are again to the devout inquiring mind brought into pleasing harmonious comparison.

We find that the creatures belonging to this first epoch of organic existence are, generally, low in the scale of animated being. The rocks in which their remains are imbedded are, in some instances almost entirely composed of organic matter, showing that life at first was not bestowed sparingly, or, through some hidden mysterious processes, stealthily introduced upon the stage; it rather appears in an abundance and variety, speaking of a purpose in obedience to a designing creative act. As suitable to the condition of the planet, not at once but by successive arrangements brought into a state of adaptation for sustaining life, the animals now formed appear to have been chiefly of the invertebrate division, that is, animals of comparatively simple structure, destitute of a bony skeleton, suited to live in shallow waters and muddy bottoms, and to be content with such fare as an infant state of things over the young earth could produce. Among these ancient families are graptolites,—many of them zoophytic bodies, allied to the modern sea-pen; crinoids, or lily-shaped animals, of beautifully-developed forms; and trilobites, crustacean creatures divided into three dorsal lobes. There are several species of each. And so accurately has nature adhered to her plan of operations, that we find the corals of that early age doing the same offices, and piling up similar submarine reefs, by which these busy little architects are still distinguished. The mollusca of the period are very numerous, embracing almost every order and form of shell that are found in our present seas, though wholly of different species; conchifera, brachiopoda, gasteropoda, cephalopoda, pteropoda, beside the heteropoda, of which there are no existing analogues. The habits of all these orders must have been nearly the same as those of our modern types. The cephalopoda, embracing the nautilus and orthoceras tribes, were then as they are now, the tyrants of the deep, furnished with eyes and ears, and armed with powers that enabled them to roam and prey at will in the bays and estuaries of the primeval world. There have been named and catalogued of these first forms of the moving creatures of the deep about three hundred and fifty distinct species.

But, beside these, there have been discovered in the silurian rocks six or seven genera, involving a still greater number of species, of fishes of the order of the Placoids, so denominated from the broad scales or plates with which they are covered. The probability is, that more of these higher organisms will yet be brought to light, as all the strata of the system consist of marine deposits, and only the most limited sections have anywhere been explored. They constitute the lowest of the fossiliferous beds; are generally found, except in Russia, in a vertical or highly inclined position, and consequently but little of their superficial area is exposed. Here, however, geologists have named and described an Onchus Murchisoni, a Thelodus parvidens, and other four genera of equally erudite-sounding names. The onchus type is continued, and greatly multiplied in species, in the two succeeding formations, when it dies out, or at least no trace of the genus is found in later times; while the rest appear to come and to depart within their own geological epoch. These organisms are all as yet termed Ichthyolites, that is, simply fossil fragments of fish, as no entire animal has been anywhere detected, while of their true class M. Agassiz affirms with confidence. Teeth, fins, spines, occur so abundantly in a stratum of the Upper Ludlow series in Wales as now to be termed “the bone-bed,” giving assurance that the seas were thus early stocked with the finny tribes. The families of most of these fishes have yet to be determined. But nature, though in her operations “simpler than man’s wit would make her,” was still pretending enough to be shaping out thus early the higher types of life.

The science which introduces to such sights and studies, occupies no mean place among the various branches of human inquiry. To neglect to decipher what is so indelibly recorded on these pages of creation, is willfully to shut oneself out from what has been actually preserved for information—a voice from the past, which speaks in the same distinct articulate language as the present of the fiat of Omnipotence. No object is mean or contemptible which divine wisdom has formed, and no subject is unworthy of investigation which illustrates His ways and works during any period of creation.

The mind, at this starting point of life, is curious to know what amount of information can be obtained as to the organic structure and specific characters of these first denizens of earth, so as to compare them with the forms and species of the analogous families now existing. The information derived from this first chapter in palæontology, we believe is, that the earliest specimens of organization are as perfect as the latest, each after its kind; and that, in these morning-days of existence, nature at once stamped, with her plastic hand, her lineaments of beauty and adaptation on everything she made. There is nothing omitted to be afterward supplied—nothing formed defective in a single part or organ that requires to be corrected. The first discoveries in geology at once speak conclusively of a plan or course of creation derived from the beginning—a power, not delegated, but linked forever with the first intelligent cause—a world, through all its changes, continually presided over and ruled by Him who made it.