Fossils, appeared; containing excellent figures of fossil shells from a part of the south coast of England; and similar works came forth in other parts of Europe. However exact might be the descriptions and figures thus produced, they could not give such complete information as the objects themselves, collected and permanently preserved in museums. Vallisneri says, that having begun to collect fossils for the purpose of forming a grotto, he selected the best, and preserved them as a noble diversion for the more curious.' The museum of Calceolarius at Verona contained a celebrated collection of such remains. A copious description of it appeared in 1622. Such collections had been made from an earlier period, and catalogues of them published. Thus Gessner's work, De Rerum Fossilium, Lapidum et Gemmarum Figuris, (1565,) contains a catalogue of the cabinet of petrifactions collected by John Kentman; many catalogues of the same kind appeared in the seventeenth century.7 Lhwyd's Lythophylacii Britannici Iconographia, published at Oxford in 1669, and exhibiting a very ample catalogue of English Fossils contained in the Ashmolean Museum, may be noticed as one of these. One of the most remarkable occurrences in the progress of descriptive geology in England, was the formation of a geological museum by William Woodward as early as 1695. This collection, formed with great labour, systematically arranged, and carefully catalogued, he bequeathed to the University of Cambridge; founding and endowing at the same time a professorship of the study of geology. The Woodwardian Museum still subsists, a monument of the sagacity with which its author so early saw the importance of such a collection. Collections and descriptions of fossils, including in the term specimens of minerals of all kinds, as well as organic remains, were frequently made, and especially in places where mining was cultivated; but under such circumstances, they scarcely tended at all to that general 6 p. 1. 7 Parkinson, Organic Remains, vol. i. p. 20. and complete knowledge of the earth of which we are now tracing the progress. In more modern times, collections may be said to be the most important books of the geologist, at least next to the strata themselves. The identifications and arrangements of our best geologists, the immense studies of fossil anatomy by Cuvier and others, have been conducted mainly by means of collections of specimens. They are more important in this study than in botany, because specimens which contain important geological information are both more rare and more permanent. Plants, though each individual is perishable, perpetuate and diffuse their kind; while the organic impression on a stone, if lost, may never occur in a second instance; but, on the other hand, if it be preserved in the museum, the individual is almost as permanent in this case, as the species in the other. I shall proceed to notice another mode in which such information was conveyed. Sect. 3-First Construction of Geological Maps. DR. LISTER, a learned physician, sent to the Royal Society, in 1683, a proposal for maps of soils or minerals; in which he suggested that in the map of England, for example, each soil and its boundaries might be distinguished by colour, or in some other way. Such a mode of expressing and connecting our knowledge of the materials of the earth, was, perhaps, obvious, when the mass of knowledge became considerable. In 1720, Fontenelle, in his observations on a paper of De Reaumur's, which contained an account of a deposit of fossil-shells in Touraine, says, that in order to reason on such cases, 'we must have a kind of geographical charts, constructed according to the collections of shells found in the earth.' But he justly adds, 'What a quantity of observations, and what time, would it not require to form such maps !" The execution of such projects required, not merely great labour, but several steps in generalization and classification, before it could take place. Still such attempts were made. In 1743, was published, A new Philosophico-chorographical Chart of East Kent, invented and delineated by Christopher Packe, M.D.; in which, however, the main object is rather to express the course of the valleys than the materials of the country. Guettard formed the project of a mineralogical map of France, and Monnet carried this scheme into effect in 1780,8 by order of the king.' In these maps, however, the country is not considered as divided into soils, still less strata; but each part is marked with its predominant mineral only. The spirit of generalization which constitutes the main value of such a work is wanting. Geological maps belong strictly to Descriptive Geology; they are free from those wide and doubtful speculations which form so large a portion of the earlier geological books. Yet even geological maps cannot be usefully or consistently constructed without considerable steps of classification and generalization. When, in our own time, geologists were become weary of controversies respecting theory, they applied themselves with extraordinary zeal to the construction of stratigraphical maps of various countries; flattering themselves that in this way they were merely recording incontestable facts and differences. Nor do I mean to intimate that their facts were doubtful, or their distinctions arbitrary. But still they were facts interpreted, associated, and represented, by means of the classifications and general laws which earlier geologists had established; and thus even Descriptive Geology has been brought into existence as a science by the formation of systems and the discovery of principles. At this we cannot be surprized, when we recollect the many steps which the formation of Classificatory Botany required. We must now notice some of the principal discoveries which tended to the formation of Systematic Descriptive Geology. 8 Atlas et Description Minéralogique de la France, entrepris par ordre du Roi; par MM. Guettard et Monnet, Paris, 1780, pp. 212, with 31 maps. CHAPTER II. FORMATION OF SYSTEMATIC DESCRIPTIVE GEOLOGY. Sect. 1.-Discovery of the Order and Stratification of the Materials of the Earth. THAT THAT the substances of which the earth is framed are not scattered and mixed at random, but possess identity and continuity to a considerable extent, Lister was aware, when he proposed his map. But there is, in his suggestions, nothing relating to stratification; nor any order of position, still less of time, assigned to these materials. Woodward, however, appears to have been fully aware of the general law of stratification. On collecting information from all parts, 'the result was,' he says, 'that in time I was abundantly assured that the circumstances of these things in remoter countries were much the same with those of ours here: that the stone, and other terrestrial matter, in France, Flanders, Holland, Spain, Italy, Germany, Denmark, and Sweden, was distinguished into strata or layers, as it is in England; that these strata were divided by parallel fissures; that there were enclosed in the stone and all the other denser kinds of terrestrial matter, great numbers of the shells, and other productions of the sea, in the same manner as in that of this island.' So remarkable a truth, thus collected from a copious collection of particulars by a patient induction, was an important step in the science. These general facts now began to be commonly recognized, and followed into detail. Stukeley the antiquary (1724), remarked an important feature in the strata of England, that their escarpments, or steepest sides, are turned towards the west and north-west; 1 Natural History of the Earth, 1723. and Strachey (1719), gave a stratigraphical description of certain coal-mines near Bath. Michell, appointed Woodwardian Professor at Cambridge in 1762, described this stratified structure of the earth far more distinctly than his predecessors, and pointed out, as the consequence of it, that the same kinds of earths, stones, and minerals, will appear at the surface of the earth in long parallel slips, parallel to the long ridges of mountains; and so, in fact, we find them.' 95 Michell (as appeared by papers of his which were examined after his death) had made himself acquainted with the series of English strata which thus occur from Cambridge to York; that is, from the chalk to the coal. These relations of position required that geological maps, to complete the information they conveyed, should be accompanied by geological Sections, or imaginary representations of the order and mode of superpositions, as well as of the superficial extent of the strata, as in more recent times has usually been done. The strata, as we travel from the higher to the lower, come from under each other into view; and this out-cropping, basseting, or by whatever other term it is described, is an important feature in their description. It was further noticed that these relations of position were combined with other important facts, which irresistibly suggested the notion of a relation in time. This, indeed, was implied in all theories of the earth; but observations of the facts most require our notice. Steno is asserted by Humboldt to be the first who (in 1669) distinguished between rocks anterior to the existence of plants and animals upon the globe, containing therefore no organic remains; and rocks superimposed on these, and full of such remains; 'turbidi maris sedimenta sibi invicem imposita.' Rouelle is stated, by his pupil Desmarest, to have made some additional and important observations. 3 Phil. Trans. 1719, and Observations on Strata, &c. 1729. 4 Fitton, Annals of Philosophy, N. S. vol. i. and ii. (1832, 3), p. 157. 5 Phil. Trans. 1760. Essai Céognastique. |