_The GEOLOGY of Touraine_, being of a nature particularly worthy the attention of the scientific enquirer, we may properly close these restricted remarks, by a few cursory observations on so interesting a subject. In contemplating the geognostic structure of this department, the eye of the investigator encounters none of those strikingly bold and sublime operations of nature, almost every where to be met with in the primitive and volcanic regions of the globe.
Here with but a few solitary exceptions, the whole surface of the province presents a continuous series of rounded and gentle undulations, exhibiting to the careless glance of the unobservant, and to the uninitiated, one vast homogeneous mass of earthy and stony materials.
But when this wide spread, and apparently uninvestigable aggregation of particles, comes under the scrutinizing _eye of science_, a beautiful and systematic arrangement of undigenous formations are clearly developed. Individually containing within themselves the marvellous and decisive evidence of their comparative existence, in their present relative positions.
Those «_medallions of Nature_,» the fossils which they contain not only furnishing us with a chronological knowledge of the progressive formation of the Earth's crust, but recording in language the most intelligible, what were the peculiar states, and characteristics of animal and vegetable existences at the distinct, and distant epochs of the World.
By the aid of these silent but eloquent intelligencers, we discover that the strata which now constitute the table lands of Touraine, were among the last, in the whole geological series, that emerged from the waves of the Ocean. That, that grand instrument of transposition and renovation, has in a general sense, ever since been restrained within its mighty confines. And that at the time its waters last prevailed over these regions now high and dry, many of the types of living testacea, etc. were become identical with those of existing species.
Touraine, or the department of Indre-et-Loire, may be said to be the grand repository of the _tertiary_ formations of central France. It constitutes the southern divisions of the great _Paris basin_, formed by a vast depression in the chalk, and which is about 180 miles long and 90 miles broad. This cretaceous or chalk basin terminates to the south a short distance from Poitiers, where the oolites and certain other formations older than the chalk, crop out from beneath it, and thence forward, principally constitute the formations of the more southern departments of the kingdom: and occasionally extend to the summits of the gigantic Pyrénées.