246 Proceedings of the British Association. 



limestone contains numerous fossils which indicate a period older 

 than the mountain limestone, although several species are found in- 

 termixed, which can scarcely be separated from it. Hard grits and 

 shales, highly inclined, succeed, and form the higher parts of the 

 Pass, extending about a league beyond it to the north, when coal 

 plants are found abundantly in the grits and shales ; no coal, how- 

 ever, is seen until near Pola de Lena situate about three leagues from 

 the top of the Pass ; from hence following the road to Oviedo, in a 

 distance of 10 miles, more than 70 seams of good workable coal are 

 crossed near the upper part of the series a bed of conglomerate oc- 

 curs, formed of rolled masses of grit, and limestone, and coal ; 

 another such deposit, probably exceeding 1,500 feet in thickness, ap- 

 pears near the lowest part of the series, in which the coal boulders 

 are more abundant, varying from the size of an egg to a foot in dia- 

 meter, and possess the same character with the coal of the associated 

 beds ; one good coal-seam occurs in the conglomerate, and two or three 

 below it. The coal deposits are terminated by a narrow valley, be- 

 yond which the limestone rises from beneath them to a considerable 

 elevation ; a depression of the surface soon after occurs, forming a 

 plain of cretaceous deposits of the Hippurite period, upon which the 

 city of Oviedo stands, and which extends for 20 or 30 miles east 

 and west. Beyond Oviedo to the north, the limestone again rises, 

 and coal deposits appear between this point and the coast ; in one of 

 these the coal forms beds of from three to seven feet, interstratifi- 

 ed with the limestone, which, with the shales that occur in it, con- 

 tains an abundance of fossils, chiefly shells and corals, with but few 

 traces of plants, whilst those before mentioned in the series south of 

 Oviedo, were chiefly calamites, sigillarise, and other coal-plants. 

 Another of these deposits, containing the same fossils, crops out on 

 the sea-shore near the port of Aviles, which is to form the termination 

 of the north of Spain Railroad to Madrid. It appears, therefore, that, 

 besides extensive coal-beds corresponding with those of England and 

 other countries, this province possesses a considerable deposit belong- 

 ing to an earlier period, which was probably the source of the boulders 

 occurring in the conglomerate of the upper series. Connected with 

 the coal, and always below it, are several beds of haematite, one of 

 which is extraordinary, the pure unmixed ore being 50 feet thick, and 



