The Story of the Earth and Man

by Sir John William Dawson

Our picture of the Permian World has not been inviting, yet in many respects it was a world more like that in which we live than was any previous one. It certainly presented more of variety and grand physical features than any of the previous ages; and we might have expected that on its wide and varied continents some new and higher forms of life would have been introduced. But it seems rather to have been intended to blot out the old Palæozoic life, as an arrangement which had been fully tried and served its end, preparatory to a new beginning in the succeeding age.

Still the Permian has some life features of its own, and we must now turn to these. The first is the occurrence here, not only of the representatives of the great Batrachians of the coal period, but of true reptiles, acknowledged to be such by all naturalists. The animals of the genus Protorosaurus, found in rocks of this age both in England and Germany, were highly-organised lizards, having socketed teeth like those of crocodiles, and well-developed limbs, with long tails, perhaps adapted for swimming. They have, however, biconcave vertebras like the lizard-like animals of the coal already mentioned, which, indeed, in their general form and appearance, they must have very closely resembled. The Protorosaurs were not of great size; but they must have been creatures of more stately gait than their Carboniferous predecessors, and they serve to connect them with the new and greater reptiles of the next period.

Another interesting feature of the Permian is its flora, which, in so far as known, is closely related to that of the coal period, though the species are regarded as different; some of the forms, however, being so similar as to be possibly identical. In a picture of the Permian flora we should perhaps place in the foreground the tree-ferns, which seem to have been very abundant, and furnished with dense clusters of aërial roots to enable them to withstand the storms of this boisterous age. The tree-ferns, now so plentiful in the southern hemisphere, should be regarded as one of the permanent vegetable institutions of our world—those of the far-back Lower Devonian, and of all intervening ages up to the present day, having been very much alike. The great reed-like Calamites have had a different fate. In their grander forms they make their last appearance in the Permian, where they culminate in great ribbed stems, sometimes nearly a foot in diameter, and probably of immense height. The brakes of these huge mares'-tails which overspread the lower levels of the Permian in Europe, would have been to us what the hayfields of Brobdingnag were to Gulliver. The Lepidodendra also swarmed, though in diminished force; but the great Sigillarise of the coal are absent, or only doubtfully present. Another feature of the Permian woods was the presence of many pine-trees different in aspect from those of the coal period. Some of these are remarkable for their slender and delicate branches and foliage.[X] Others have more dense and scaly leaves, and thick short cones.[Y] Both of these styles of pines are regarded as distinct, on the one hand, from those of the coal formation, and on the other from those of the succeeding Trias. I have shown, however, many years ago, that in the upper coal formation of America there are branches of pine-trees very similar to Walchia, and, on the other hand, the Permian pines are not very remote in form and structure from some of their modern relations. The pines of the first of the above-mentioned types (Walchia) may indeed be regarded as allies of the modern Araucarian pines of the southern hemisphere, and of the old conifers of the Carboniferous. Those of the second type (Ulmannia) may be referred to the same group with the magnificent Sequoias or Redwoods of California.

[X] Walchia.

[Y] Ulmannia.

It is a curious indication of the doubts which sometimes rest on fossil botany, that some of the branches of these Permian pines, when imperfectly preserved, have been described as sea-weeds, while others have been regarded as club-mosses. It is true, however, that the resemblance of some of them to the latter class of plants is very great; and were there no older pines, we might be pardoned for imagining in the Permian a transition from club-mosses to pines. Unfortunately, however, we have pines nearly as far back in geological time as we have club-mosses; and, in so far as we know, no more like the latter than are the pines of the Permian, so that this connection fails us. In all probability the Permian forests are much less perfectly known to us than those of the coal period, so that we can scarcely make comparisons. It appears certain, however, that the Permian plants are much more closely related to the coal plants than to those of the next succeeding epoch, and that they are not so much a transition from the one to the other as the finishing of the older period to make way for the newer.

But we must reserve some space for a few remarks on the progress and termination of the Palæozoic as a whole, and on the place which it occupies in the world’s history. These remarks we may group around the central question, What is the meaning or value of an age or period in the history of the earth, as these terms are understood by geologists? In most geological books terms referring to time are employed very loosely. Period, epoch, age, system, series, formation, and similar terms, are used or abused in a manner which only the indefiniteness of our conceptions can excuse.

A great American geologist[Z] has made an attempt to remedy this by attaching definite values to such words as those above mentioned. In his system the greater divisions of the history were “Times:” thus the Eozoic was a time and the Palæozoic was a time. The larger divisions of the times are “Ages:” thus the Lower and Upper Silurian, the Devonian, and the Carboniferous are ages, which are equivalent in the main to what English geologists call Systems of Formations. Ages, again, may be divided into “Periods:” thus, in the Upper Silurian, the Ludlow of England, or Lower Helderberg of America, would constitute a period. These periods may again be divided into “Epochs,” which are equivalent to what English geologists call Formations, a term referring not directly to the time elapsed, but to the work done in it. Now this mode of regarding geological time introduces many thoughts as to the nature of our chronology and matters relating to it. A “time” in geology is an extremely long time, and the Palæozoic was perhaps the longest of the whole. By the close of the Palæozoic nine-tenths of all the rocks we know in the earth’s crust were formed. At least this is the case if we reckon mere thickness. For aught that we know, the Eozoic time may have accumulated as much rock as the Palæozoic; but leaving this out of the question, the rocks of the Palæozoic are vastly thicker than those of the Mesozoic and Cainozoic united. Thus the earth’s history seems to have dragged slowly in its earlier stages, or to have become accelerated in its latter times. To place it in another point of view, life changes were greater relatively to merely physical changes in the later than in the earlier times.

[Z] Dana.