which, as already mentioned, generally run E. and w., have there less elevation, and present greater facilities of access, and less irregularity in the stratification of their component beds. The Dobra range, which may be looked upon as the southern boundary of this belt, is cut perpendicularly by several of the principal rivers which water the province, the Deva, the Nansa, the Besaya, and its confluent the Saya, etc. Thus the valleys of those rivers offer a series of excellent natural sections, so that by following either of the latter to its point of junction with the range in question, and carefully examining the lofty and precipitous rocks which overhang and close in their torrential beds, the peculiar geognostical features of the different formations may be studied. We propose first to study those sections in detail, and then to summarize the conclusions which may be drawn from their study respecting the geological relations of the rocks of this belt, which to a certain extent may be looked upon as the key of those of the whole province.

The most natural order in which to study our sections will obviously be, to begin at that one which traverses chiefly the oldest rocks. We shall accordingly commence with that afforded by the valley of the Deva. This order will present the additional advantage of illustrating, by the description of the rocks occurring along the section, what we have just said concerning the rocks of the main chain.

The coast at the mouth of the Deva is formed by a hard white quartzose sandstone, which is a continuation of those remarkable high platforms formed by alternations of hard limestone and quartzose sandstone, which give such a peculiar character to the Asturian coast, and which will be fully described at p. 358. This sandstone is in contact with nummulitic beds from near Pesues westward to Columbres beyond the Deva. The nummulitic series is particularly remarkable between Unquiera and Pesues, on account of the high dip of the beds, their great mass, and their relation to the platform just alluded to. It consists of the usual limestone containing Conoclypus conoïdeus, Ag., Ostrea latissima, Desh., Serpula spirulæa, Sow., etc., yellow sand and sandstone. To the south these beds rest upon the usual succession of cretaceous rocks.

To the south of Columbres limestone rocks, hitherto considered to be carboniferous, rise into a considerable mountain, having an elevation of about 350m to 400m at least, and forming part of the east and west range called the Sierra de Cuera. On the south of this mountain, and near its summit, is situated the village of Alevia. Here the limestone, which dips to the north at an angle varying from 40° to 45°, forms a bold and precipitous

declivity towards the valley. This limestone is nearly black, and seemingly much fractured, the joints being filled up with a rose coloured calc spar. The colour of the spar may be due to the neighbourhood of a bed of manganese which occurs nearly at the top of the mountain, and which, from its strike being east and west, and its dip about the same as that of the beds of enclosing rocks, may be contemporaneous. The ore would seem to have been chiefly manganite. This circumstance, joined to the almost inaccessible position of the mine, defying all attempts at road-making, and leaving no other method of transport practicable but the shoulders of the vigorous inhabitants of the village, contributed to render the works unprofitable.

According to Don G. Schultz, another patch of cretaceous rocks occurs in the valley to the south of Alevia, but we have had no opportunity of examining the locality, nor have we any reliable data as to their precise nature. It is certain, however, that beds of limestone containing numerous fossils, and nearly vertical, occur near the eastern extremity of this valley, the high road which leads to Unquiera being cut in their vertical beds. The rock in question is of a dark grayish-blue internally; a thin zone of about one inch thick, of a somewhat brownish colour, evidently due to weathering, being found at each side of the several beds. The texture is saccharoidal, and in that respect is very similar to that of certain limestones found in the neighbourhood of the principal dolomite bed of the province, while, on the other hand, it is quite distinct from that of the great limestone mass already described.

Following the line indicated on the section, and traversing the valley in which the Deva flows, bending towards the east for about a mile, and then returning to the direction of its former course, the first crests of the lower ranges of the Peñas de Europa are met with. The stratification may be still observed, having the same general strike, but a higher dip than at Alevia. Those nearly inaccessible mountains, which present an extremely uneven surface, generally clothed with trees peculiar to those high ranges, rise continuously in elevation up to Tresviso, to the south of which a very deep and narrow valley occurs, running east and west, and forming a bed for a wild mountain torrent, fed by the melting snow of the Europa chain. Between the point of junetion of this stream with the Deva and the valley of Alevia, the underlying hard gray sandstone presents itself on both sides of the bed of the river Deva, apparently forming an anticlinal axis, as indicated in the section. About one mile to the south of this point of junction, and consequently higher up the course of the river, occur the hot springs of La Hermida, of which mention

will be made hereafter. Here the dip of the limestone can scarcely be determined, the bedding being still less marked. The colour becomes darker in that part which overhangs the Deva, and still more so near its contact with the beds of shale in the valley of Potes; bands of black limestone are also frequent in it.

The line of section passes over the Peñas de Europa, which form the highest peaks in the province, attaining, as already mentioned, an elevation of 2600m, and whose mines of calamine, blende, and galena are extremely interesting. The limestone here presents the same general aspect as in the lower ranges, but becomes whiter and more marble like, and is also much more highly fissured. On the north side of the valley of Potes the limestone beds are almost vertical, inclining about 10°-12° to the north; they form as it were an immense wall, so bold and clear is their outline, and so precipitous their declivity. Immediately underlying the limestone are found beds of hard shale and clay, out of which the valley of Potes has been eroded; these beds are also nearly vertical. Associated with these shales in the inferior beds are found quartz conglomerates, derived no doubt from the denudation of the gray sandstone or quartzitelike rock which underlies conformably the shale and clay just described, and in which are found veins of copper associated with veins of quartz, as will be more fully indicated in the description of the mines of Pico Jano.

§. 2. Description of Section II., Pl. 2, corresponding to Section CD of the map.

We have already mentioned that between San Vicente de la Barquera and the Asturian border village of Columbres, is found a considerable development of nummulitic beds. These are indicated in the cross section I., Pl. 2, which is marked on the map by the line CD, which passes through San Vicente. The dip of these nummulitic beds is about 20° to 25° N., passing under the newer formation situated between its outcrop and the sea, and disappearing apparently in the direction of Cabiedez, near a village called Roiz, under the overlying rocks. The estuary which runs by San Vicente, and which receives a mountain stream near the point called Peña Candil, about three miles south from the coast, has cut through the bed, and thus laid bare a section on each side. Near the point of junction just mentioned, a very fine specimen of Hemipneustes radiatus, Ag., was found, which the action of the stream had left in situ, the enclosing marly limestone having been eaten away. Between this point and that more to the south, where the beds constituting the

Florida mountain crop out, the dip of the strata varies from that already described, tending to become horizontal, and even apparently to incline towards the south, and then rising again, so that the beds present anew their original dip to the north. There is thus naturally formed a synclinal trough, slightly marked in the lower beds, but quite recognizable in the upper ones of sandstone, their castellated outlines forming conspicuous objects, when viewed either from the valley on the north side of the synclinal axis, or from that to the south. It is this irregularity in the continuity of the dip of the strata which brings the underlying beds, characterised by the abundance of Micraster coranguinum, Ag., to the surface as well to the north as to the south in front of the Florida mountain, and also the overlying beds of sandstone, and the thick underlying beds of greenish sandstone and ochreous clay. From under these, limestone beds come out with a dip of 40° to 45°, and form the Florida mountain, in which a remarkable mass of dolomite occurs, which will be more fully described when we come to the description of the Florida mines; the mountain itself has an elevation of about 550TM to 600m above the sea. The dolomite crops out near the south side of the crest of the mountain, and rests conformably on beds of limestone. Immediately underlying the limestone are found beds of shales and clay, which form the bottom of a deep narrow valley that separates the Florida from the Escudo mountain, where terminates the section, and which consists of the red sandstone beds hereafter to be described, as occupying the interval between the beds of Mercadal and the limestone of the Dobra range (Sect. IV. Pl. 3).

Between the Escudo mountain, which rises to an elevation of about 700, and the underlying Dobra limestone formation, intervenes a valley in which is situated the village of Celis, not far from the junction of the sandstone and limestone. Very large crystals of quartz are found here, some being clouded, and others perfectly transparent. This is perhaps the only place in the province where transparent crystals occur, although quartz crystals with other peculiarities are elsewhere abundant, and will be noticed in connection with the limestone of the Dobra range.

The beds of nummulitic limestone above described as sinking near Roiz, rise again to the surface with a north-east strike, and, in conjunction with other rocks of the same age, seem to form the headland called Cape Hoyambre, which lies between San Vicente de la Barquera and the Rabia stream, to the westward of which they run out into the sea towards the north-east, forming a very remarkable reef about a mile and a half in length, well known to the fishermen of the coast, on account of the safe anchorage

which they find behind this natural mole during the north-west gales. Apparently they do not again reappear along the coast, not being recognizable at Comillas, nor yet still farther to the east, where the transverse section FG (on the Map, sect. III., Pl. 2) is supposed to be taken. If we suppose a plane of section to pass through the beds forming the eastern side of the bay of San Vicente, at about 1 from the last described section, and parallel to it, we have the following succession of beds:

1. Beds of limestone dipping N. 45° or 50°, forming the great mass of the Cape Hoyambre, which bounds the bay on the E. They apparently correspond to the beds upon which is built the Castle of San Vicente, and in which Orbitolinas are very abundant. 2. A thin bed of dolomitic limestone, less brown and more rosy or pink, as also more compact, than that of Comillas. It forms a bold escarpment on the road to San Vicente, near its junction with the old road del Tejo. This rock appears to form a part of the next series of beds.

3. Red ochry clay, very plastic, and consequently producing very good tiles and bricks. Some beds are almost white, others blue and mixed with gypsum, which is generally transparent, and also with grains of quartz. A bed or beds of a red conglomerate, formed of pebbles of quartz, cemented by carbonate of lime, occurs here also, fragments of which exist as large boulders on the strand between Cape Hoyambre and San Vicente, forming very conspicuous objects. Some other rocks, chiefly limestone and alternating with dark gray marls in which lignite has been repeatedly found, intervene between the ochry clays and the nummulitic limestone No. 4.

4. Nummulitic limestone, the dip of which is somewhat lower than that of the clay beds No. 3, and containing Hemipneustes radiatus, Ag. 5. Sandstone in immediate contact with the nummulitic beds; some of them, particularly in the lower portion of the group, are coarse grained, almost conglomerates, and nearly white in colour. 6. Marly limestone, full of fossils, Micraster coranguinum, Ag., being extremely abundant.

7. Thick beds of limestone, generally presenting a grayish colour, a sub-crystalline or dolomitic grain, distinct however from what is known as saccharoidal. The outside of the beds is generally weathered, the colour there changing and becoming brownish gray. Intercalated beds of marly black clay also occur.

8. Beds of ochry sandstones and clay, one of which is black and slaty, being also highly impregnated with iron pyrites.

9. Thick beds of limestone, some of which near the base of the group are very marly, of a grayish, black colour, apparently hydraulic in their character, and containing large oysters imbedded in the mass.

10. Principal bed of dolomite, consisting of a bed of brownish gray