Fig. 172.—Lupea pelagica.
The lignites, which we find in the Miocene, as in the Eocene period, constitute, however, a combustible which is worked and utilised in many countries, especially in Germany, where it is made in many places to serve in place of coal. These beds sometimes attain a thickness of above twenty yards, but in the environs of Paris they form beds of a few inches only, which alternate with clays and sands. We cannot doubt that lignites, like true coal, are the remains of the buried forests of an ancient world; in fact, the substance of the woods of our forests, often in a state perfectly recognisable, is frequently found in the lignite beds; and the studies of modern botanists have demonstrated, that the species of which the lignites are formed, belong to a vegetation closely resembling that of Europe in the present day.
Another very curious substance is found with the lignite—yellow amber. It is the mineralised resin, which flowed from certain extinct pine-trees of the Tertiary epoch; the waves of the Baltic Sea, washing the amber out of the deposits of sand and clay in which it lies buried, this substance, being very little heavier than water, is thrown by the waves upon the shore. For ages the Baltic coast has supplied commerce with amber. The Phœnicians ascended its banks to collect this beautiful fossil resin, which is now chiefly found between Dantzic and Memel, where it is a government monopoly in the hands of contractors, who are protected by a law making it theft to gather or conceal it.
Amber,[91] while it has lost none of its former commercial value, is, besides, of much palæontological interest; fossil insects, and other extraneous bodies, are often found enclosed in the nodules, where they have been preserved in all their original colouring and integrity of form. As the poet says—
“The things themselves are neither rich nor rare,
The wonder’s how the devil they got there.”
The natural aromatic qualities of the amber combined with exclusion of air, &c., have embalmed them, and thus transmitted to our times the smaller beings and the most delicate organisms of earlier ages.
The Miocene rocks, of marine origin, are very imperfectly represented in the Paris basin, and their composition changes with the localities. They are divided into two groups of beds: 1. Molasse, or soft clay; 2. Faluns, or shelly marl.
In the Paris basin the Molasse presents, at its base, quartzose sands of great thickness, sometimes pure, sometimes a little argillaceous or micaceous. They include beds of sandstone (with some limestone), which are worked in the quarries of Fontainebleau, d’Orsay, and Montmorency, for paving-stone for the streets of Paris and the neighbouring towns. This last formation is altogether marine. To these sands and sandstones succeeds a fresh-water deposit, formed of a whitish and partly siliceous limestone, which forms the ground of the plateau of La Beauce, between the valleys of the Seine and the Loire: this is called the Calcaire de la Beauce. It is there mixed with a reddish and more or less sandy clay, containing small blocks of burrh-stone used for millstones, easily recognised by their yellow-ochreous colour, and the numerous cavities or hollows with which their texture is honeycombed.
This grit, or silex meulier, is much used in Paris for the arches of cellars, underground conduits, sewers, &c.
The Faluns in the Paris basin consist of divers beds formed of shells and Corals, almost entirely broken up. In many parts of the country, and especially in the environs of Tours and Bordeaux, they are dug out for manuring the land. To the Falun series belong the fresh-water marl, limestone, and sand, which composed the celebrated mound of Sansan, near Auch, in the Department of Gers, in which M. Lartet found a considerable number of bones of Turtles, Birds, and especially Mammals, such as Mastodon and Dinotherium, together with a species of long-armed ape, which he named Pithecus antiquus, from the circumstance of its affording the earliest instance of the discovery of the remains of the quadrumana, or monkey-tribe, in Europe. Isolated masses of Faluns occur, also, near the mouth of the Loire and to the south of Tours, and in Brittany.