It was formerly remarked, that organic remains were found in the primary argillaceous schists. But it is pro per also to observe, that this only happens in the upper parts of the series, and that they have never yet occurred in the deeper seated or more ancient strata of this nature that alternate with gneiss and quartz rock.
Thus we have gone through, in as much detail as is ne cessary for the present purpose, the series of the primary or ancient strata ; and thus it appears that organic re mains not only exist in abundance in the upper parts of it, but that there are indications of their presence even in the lower ; and that if these are imperfect or scanty, we are not unprovided with reasons to account for it, without its be ing necessary to suppose that there is any point of time in that series at which they did not exist in the waters of that ocean under which these rocks were originally de posited. We do not indeed see how any one can presume to point out a time in which animals did not inhabit the globe, of such kinds, at least, as were adapted to its condition ; nor how we can limit even the natures or ca pacities of such beings ; ignorant as we are of the former conditions of the earth, and certain as we are that it undergone revolutions by which many of them must have been utterly destroyed.
Excepting in the crystalline rocks, for the reasons al ready assigned, there appears none in which they may not be found ; or none, at least, under which they may not be discovered, should we find substances in the ma torials of which they might have lived. If that is a cor rect view of the possibilities in this case, it is incumbent on geologists to search for facts to confirm these, not to reject them without an adequate examination. The whole of the ancient strata, in a general view, at least, appear to have been formed under one sea during one long interval of time, and to have been displaced by one exten sive revolution. If it were admitted that organic remains are decidedly found only in the upper parts of the series, still there is no apparent reason why the creation of these animals should have taken place at one particular point of time in this interval. It is more probable, that at all its
periods that ocean contained those animals, of which the remains are now chiefly, if not exclusively, found in those parts which are peculiarly favourable to their propagation, or, subsequently, to their preservation. Yet, that they were less abundant, and perhaps also less numerous as to their tribes, may easily be allowed. If their actual absence from the ancient rocks has not here been admitted as a proof of that, the comparative variety of ancient lime stones seems a valid argument. Had they been as abun dant in ancient as in more recent times, we might expect that, in the same proportion, the older calcareous rocks would be no less extensive than the newer ones.
Having thus brought this inquiry through the ancient strata, that which remains to be said on the more recent will admit of being comparatively brief. Organic bodies are so rarely found in the lowest, or old red sandstone, that the few instances in which this has occured must be con sidered in the light of exceptions. Nor is it difficult, per haps, to explain this, when it is recollected how rarely they exist in any rocks of this character. A very obscure question might be started on this subject; but it is im possible, for want of facts or arguments, to enter on it to any useful purpose. It might be supposed, that the great revolution which took place at that period which first ele vated the primary strata, had destroyed all the pre-existing races. And certainly, if that revolution was as universal and simultaneous as has often been supposed, and if, as Dr. Hutton thinks, it was the consequence of a general eruption of fused rocks from beneath the stratified ma terials, or strata, which it elevated, such races must in all probability have been destroyed by the heated state of the ocean. Thus, the organic bodies of the secondary strata might be supposed to belong to a new creation ; and thus it would be easy to explain why they did not begin to appear in the first of the strata that were formed after this revolution. But on questions of this nature it is perhaps in vain to speculate.