The evidence derived from organic remains in the case of the coal strata, is of the highest importance, not only as marking the mode in which this important substance was produced, but as indicating some very extraordinary re volutions in the disposition of the earth at large, or at least in very considerable portions of its surface. For example, it is observed that the organic remans found with coal are principally those of terrestrial vegetables with, more rarely, fresh-water shells, and in some cases it is thought, marine shells. Here then are the data from which we must deter mine how and where the coal series was produced. In the first place, it must have been deposited under water, as all strata have been ; and that water, from the nature of the remains, must have been fresh. The plants are often of characters that prove them to be aquatic; and hence, also, we must conclude, that coal was formed in fresh water lakes, on the surface of emerged land ; since the re mains of trees, ferns, and other plants, prove that there was dry land near them.
But we need not pursue all the deductions that may be derived from these facts, as it would be to give a history of the coal strata. Yet we cannot pass it by without still pointing out the conclusions that follow from the presence of marine remains. While the coal strata themselves con tain terrestrial aquatic bodies, the strata that lie above them include marine ones. Hence it is certain that, after the formation of these, the sea had covered the land deeply, and for so long a time, as to have been enabled to to deposit the great depth of strata, which in England and in many other countries, lie above the coal or fresh-water series. It is not for us to inquire here, whether in this case the sea has risen or the land has subsided, as that would be to lead us into geological disquisitions beyond the hounds of the present undertaking.
There are other cases, also, in which examinations of organic remains serve to indicate particular facts with re spect to rocks which we might otherwise find it difficult to understand or prove. Thus they show the modes and places in which these were deposited, in how far they are of mechanical origin, and w hat chemical changes they have undergone. Thus they may also serve to discriminate in difficult cases between the rocks of aquatic and those of igneous origin, or to determine whether particular sub stances are to be referred to one or the other of these causes.
We might here show how the study of organic fossils enables us to determine important points with respect to revolutions of the earth's surface whether ancient or recent, were there not danger of our prolonging these remarks too much. Yet, that we may not altogether pass over that subject, in the alternations of marine and fresh-water shells we have proofs either of alterations of the relative level of A 2 sea and laud, or of changes which, if of a different nature, are not of less magnitude. In a similar manner the state
of extreme integrity in which some of the maritime re mains of the upper soils of Italy are found, together with other circumstances in the condition of that country, show that it has been raised by sonic sudden, and probably vol canic action, from the bottom of the sea.
In geological reasonings, the nature of fossils affords evi dence with respect to the identifications of certain strata, whether these are distant, or whether near to each other but interrupted and disturbed. If it does not in these cases do all that has been fondly expected of it, it is still an as sistant and collateral evidence. But as this is a question which especially belongs to the very subject and design of this essay, it will be fully considered hereafter. We shall therefore terminate for the present these general remarks on the geological bearings of this subject, and proceed to give a sketch of the history of the opinions respecting it, as they arc worthy of the reader's notice.
Opinions of the early Observers respecting Organic Remains.
It is not very long since Ray, Lister and others, imagined that fossil shells were lopides sui generis, produced in the earth by some extraordinary plastic virtue. Such also were the opinions entertained by Dr. Plott, in his History of Oxfordshire, and by Langius, in his Historia La/tidum Figuratorum Helvetic. This visn/astica was supposed to be a power peculiarly delegated for this purpose, and con ferred on certain parts of the earth, or species of matter, while it was also known by the terms vis formativa nnd vi8 la/tidUicativa.
In other hands, the versatile doctrine of lulus nature served to reconcile and explain every thing; and as this was a favourite doctrine about a century ago, when this question was in agitation, it is not surprising that it became an object for the humorous criticisms of Swift,—applying this universal solution of all difficulties, of whatever nature, to account for the stature of Gulliver among the philoso phers of Brobdignag. By others it was supposed that these fossils were produced by the seeds of fishes and shells, evaporated into the air, and then conveyed, by means of the rains and dews, through crevices into the earth. Here they grew, by some means unexplained, into the various forms determined by their semina ; the process being of a nature that partook at once of mineral, animal, and vegetative life. The animal principle determined the form ; the pro cess was vegetative ; and the material was directed by the mineral action.