[12] Atlas et Description Minéralogique de la France, entrepris par ordre du Roi, par MM. Guettard et Monnet, Paris, 1780, pp. 212, with 31 maps.
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 discoveries which tended to the formation of Systematic Descriptive Geology. [511]
CHAPTER II.
Formation of Systematic Descriptive Geology.
Sect. 1.—Discovery of the Order and Stratification of the Materials of the Earth.
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.”[13] So remarkable a truth, thus collected from a copious collection of particulars by a patient induction, was an important step in the science.
[13] Natural History of the Earth, 1723.
These general facts now began to be commonly recognized, and followed into detail. Stukeley the antiquary[14] (1724), remarked an important feature in the strata of England, that their escarpments, or steepest sides, are turned towards the west and north-west; and Strachey[15] (1719), gave a stratigraphical description of certain coal-mines near Bath.[16] Michell, appointed Woodwardian Professor at Cambridge [512] 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.”[17]
[14] Itinerarium Curiosum, 1724.
[15] Phil. Trans. 1719, and Observations on Strata, &c. 1729.