The bitumen which has been so extensively used for pavements, &c. is found in considerable abundance, and of the best description, at Bastenne, a small village in the south of France, about fifteen miles north of Orthez. The geological circumstances connected with its appearance being somewhat interesting, a short account of them may be desirable.
The country about Bastenne is formed of numerous small conical hills two or three hundred feet high, separated from each other by deep narrow valleys or ravines; they are chiefly composed of a coarse sandy limestone, which M. de Fresnoy places in the cretaceous system; their upper part consists of variously coloured sands and clays from fifty to sixty feet in thickness, the whole being covered by gravel and sand, which extends for many miles in every direction. The sands and clays are usually horizontal, but are occasionally much disturbed and highly inclined; whenever this occurs it is evidently owing to the protrusion of igneous matter, which is then found in connexion with them. The bitumen is worked in three localities near to each other, and the following section was made at the principal mine:—
5 to 15 feet of bitumen which varies much in character, the upper part consisting of looser and coarser sand, with a less proportion of sand, and being chiefly composed of bitumen.
10 or 15 feet of sand without bitumen occurs in some places, although where the bituminous sand is found of the greatest thichness, it the rests upon the
MAGAZINE OF NA'l'URAL I-IISTOl1Y. No. 51). K0\7E;\IBER 1841. XI~.-Dcscriptio~r of s o i m iteiu Species of rliiifaonifes fouizd ilb !he Oxford Ciay 011 the h e of fhe Greal ll'esler~r I(ailiony near Christiarr dIaiJoo,d.
The general aspect of the Spanish Province of Catalonia is a series of hills, which take a direction from the north-east to the south-west, nearly parallel to the coast; they are separated from each other by undulating plains or valleys of nearly the same width as the ridges, varying from five to twelve miles. These hills occasionally rise to a considerable elevation, from 2000 to 3000 feet. As great disturbance has taken place near the chain of the Pyrenees, these parallel ridges do not assume their predominant character nearer than about twenty miles from the base of these mountains; but even beyond this distance, they are considerably disturbed here and there throughout their extent by igneous action and the protrusion of masses of granite. The pass of the Pyrenees by Bellegarde to Jonquera represents the general character of several other ridges in the province, the base being granite, covered by gneiss, and surmounted by very thick deposits of schistose beds, with occasional masses of limestone and red marly sandstone.
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