while, in climates like our own, all the forest-trees are dicotyledonous. Should we then conclude that the present tropical forests are both of a lower organic type, and of an older date, than those of our own climate? We know that such a conclusion would be false. Why then should we venture to affirm a similar conclusion while we are reasoning on the Carboniferous flora? Analogy, our best guide while we are deprived of any other, rather tells us, that the numerical proportions among the organic types of the Carboniferous flora depended not on the time that had elapsed after the several species had come into being, but on the physical conditions under which they flourished.

But great injustice is sometimes done to the rank of the Carboniferous flora while we are comparing it with that of the living world. The ancient flora is but a mere fragment of an organic series produced during one almost unvaried set of conditions; while the present flora consists of species, counted by tens of thousands, and derived from every condition of climate, from the arctic to the tropical, compatible with vegetable life. No wonder, then, that the present flora should seem to lord it over the older, and give an appearance of inferiority to the ancient types, which belongs not to their collective nature because they are ancient; but depends, more probably, on the conditions under which they grew, and on the mutilated state in which we find their scattered fragments.

Conclusion.-In this section of the Preface I have endeavoured to shew in what manner geologists try to

clear their way among the broken fragments of a former world. They examine these fragments one by one, and learn to arrange them, in the exact order of their history and taking the analogies of living nature as their clew through the dark labyrinths of the earth, they do their best to interpret the past by help of the present-what is dark by what is light-what is unknown by what is known. They are not anxious to form any theory: and if as a matter of speculation they do construct a theory, they profess to base it on allowed facts, and not on vague assumptions, which the progress of knowledge may prove to be untrue; and at every moment of their progress they are ready either to modify it, or to abandon it altogether, as new phenomena rise up before them.

First Forms of Vegetable and Animal Life as described in "The Vestiges," &c.

Let us now cast an eye over the shorter method by which the Author of The Vestiges professes to give colour to his hypothesis, and to bring the successive organic types, whether animal or vegetable, into a seeming accordance with it. I wish not to misrepresent him, and I should gain nothing by the attempt.

First, he supposes that the humble vegetable types of the sea were the oldest of their Class. This conclusion may be true; but, as we have seen, it rests not on good direct evidence.

Secondly, he supposes the vegetable types to have undergone a gradual transmutation, during a long lapse

of ages to have come out from the sea, and to have been spread over the dry land under modified organic forms. Of this derivation of our earliest land-plants we have no proof. Its assumption is nothing better than a begging of the whole question in debate; and it is both gratuitous and unnecessary to the hypothesis of development. It certainly accords not with any phenomena of our living flora. We have innumerable opportunities on our own coasts of testing the truth of this rash hypothesis. We find marine and land-plants growing side by side. In a few years the sea gains upon the land, and marine plants now grow where only land-plants grew before. In other cases the sea retires, and we now find landplants where before we only found either marsh-plants, or those that were purely marine. But who, that is in his senses, refers such changes to specific transmutations? Or who that has seen marine and land-plants struggling side by side, as they have done for centuries, under conditions unfavourable to both, will dare to tell us that one set gradually gets the mastery by specifically transforming and naturalizing the other*?

Thirdly, he assumes that monocotyledonous plants passed by gradual transmutation into dicotyledonous— that the Carboniferous flora was of an humble and imperfect type-and that its antiquity and inferiority is proved by the excess of its monocotyledonous types. Of this part of the scheme we may affirm that it is defective in the statement of fact and erroneous in inference; and it derives no probability from the succession

* See Supplement to the Appendix No. IV. and No. VI.

of organic types in our older strata. The succession of vegetable types is, however, so broken and imperfect as to be of comparatively small value to the argument. Most of our Palæozoic rocks are marine; and among them, as before stated, we have no right to look for, nor do we find, any thing like a continued sequence of such plants as might have grown contemporaneously on the land. If there be any show of probability in the application of our Author's scheme to the Paleozoic epochs, it must be derived analogically from some different source. The theory is not shadowed forth among the vegetable phenomena of the Secondary or Tertiary rocks; and I know not of any source of good evidence, bearing upon the question, beyond that which flows from the vegetable kingdoms of the present world.

Let us next glance at our Author's method of interpreting the history of the animal kingdom, from succession of organic types among our oldest Palæozoic strata. In the first four editions of The Vestiges he stated, without any reserve, that the animals of the old world appeared, among the successive strata, in a natural ascending organic scale; and what he asserted then he now only insinuates. "The first animals, (as he tells us, Vestiges, 6th Ed. p. 52), we are called on to notice, are Polyparia”—the creatures producing coral-reefs. Next he notices Graptolites; and then Crinoïdia. Now Graptolites do appear at the base of our known organic series; but the Polyparia which produce coralreefs do not; neither do Crinoïdia. When he afterwards adds, that these latter animals may hereafter

be discovered in the place he has given them, he writes in the language of theory, and not of chronological history." Of the Articulata we have," (he says, p. 54), “first a few examples of its lowest class, the Anellides or sea-worms;" and he quotes the wellknown case of the Lampeter species. These Lampeter Anellides are undoubtedly of great antiquity; but they belong not to a low type of Anellides, but to the highest type of their class; and there are found in Wales other creatures of far higher organization, such as Trilobites, and Cephalopods, several thousand feet below them*.

He adds, "that Trilobites stand low in the Crustacea; nor were there any higher animals of the order (such as crabs and lobsters) yet in existence." I have never seen Crabs among the fossils of the great Cambro-Silurian groups; but the gentlemen of the Government Survey tell me that they have.

He then notices the Brachiopoda, Pteropoda, Gasteropoda, and Cephalopoda, in their natural order on an organic scale; and he reasons on this order as if it were historically true. A Brachiopod (Lingula) is one of our oldest known Mollusks; but it occurs, as stated above, along with the Tellinomya, which is a Lamellibranch; and the Cephalopods are found quite as

• In the frontier chain of Scotland I found sixteen species of Graptolites. Four of them are new; the others (with one exception) are described by Hall (Palæontology of New York) from the Utica slate. These Graptolites of Scotland are associated with Anellides; and they are, beyond doubt, of great antiquity, and perhaps not far from the parallel of the Lampeter fossils. They are, I think, not so old as the Graptolites found in the Skiddaw slate. (Supra, note p. 59.) The species have been carefully determined by Mr M'Coy; and the specimens in the Cambridge Museum prove, beyond any doubt, that Graptolites belong to the Order of Hydroida, as was first asserted by Neilson.