Geology, I should thus conclude, admits us a step nearer than any of the other sciences, even than astronomy itself, to the actings of the divine Architect. The revolution of every season demonstrates a providence—the workings of a perpetual miracle—in its sustaining energies. But geology shows us, not the mere annual renovation of things already existing, but the circumstances under which they began to exist. The fiat of Omnipotence peals through the bounds of creation. The earth and the seas obey. We see new things starting into being. We are present, as it were, at the moment of their birth. We see the molds out of which they are fashioned, and the first provision made to sustain them. Geology, in a word, hangs up before us one of the brightest and most diversified pages in the book of nature, inducing habits of thinking, and constantly reminding us of the facts and relations, that bodily and vividly keep before the mind the ever-active impress of the Divinity at whose bidding—
“Awakening nature hears
The new creating word, and starts to life
In every heighten’d form.”
FRANCE AND SWITZERLAND.
PART III.
CHAPTER I.
GEOLOGICAL STRUCTURE OF FRANCE—BASIN OF PARIS. ORGANIC REMAINS.
On the continental side of the Channel it will not be necessary to dwell, in minute details, upon any of the systems of rocks which are here presented. What is France? The tourist will say—A two hours’ voyage from the sister isle—a salt lake separates them—a pleasure trip is the measure of their estrangement. The geologist will add—And when safely landed, one finds himself among the sights and objects, the rocks and fossils, which engaged his attention on the coast of Albion, the cliffs and downs of both countries being composed of the self-same materials.
I. The Physical Union of France and England, although already adverted to, falls again to be noticed.
The geographical distribution of the respective rocks of France and Great Britain forms a remarkable coincidence in giving shape and contour to their general outline. Thus, the primary systems in both stretch along their western shores, presenting a vast barrier-wall of the oldest and hardest rock against the incessant encroachments of the Atlantic. Britanny and Normandy consist almost entirely of granite, gneiss, mica-schist, and silurian rocks; on these repose the upper suites of the secondary strata,—the lias, oolite, and chalk—training to the south and east. On the tertiary formations rest the secondary, narrowing in their basins, and preserving the same general line of bearing with the English beds, and in both cases reaching their maximum of thickness and exuberance of fossils around the capitals of Paris and London. The old red sandstone is not indicated on the maps, nor is it clearly ascertained to possess a habitat in the district in question. The coal-measures are of very limited dimensions, but in their due order of position at Hardinger, near Boulogne, and passing under the chalk and green sand, continue in an easterly direction by Valenciennes, Mons, Namur, and Liege, to Eschweiler, near Aix-la-Chapelle. The new red sandstone, of both divisions, is amply developed along the eastern boundaries from Semoy in Ardennes to Langrés and the borders of Switzerland. On the west again, the tertiaries prevail from the mouth of the Gironde to Bayonne on the Adour, where they are exposed to the constant tearing and erosion of the rude surges of the Bay of Biscay, while in the interior, and over the district of Auvergne, the granites and gneiss are widely overlaid by the overflowings of the most recent extinct volcanoes; the oldest and the newest plutonic rocks thus lying in immediate superposition and contact.