TABLE OF HEIGHTS

IN THE

VOLCANIC DISTRICT OF CENTRAL FRANCE.

[N.B. The greater number of these heights are extracted from Ramond's Nivellement Barométrique des Monts Dore et Dôme; the remainder are derived from articles in the Journal des Mines, by M. Cordier, &c., and from the work of M. Bertrand Roux.]

Eng. feet above the Sea.

Ramond 6217

..

Trachyte
Clinkstone..
Clinkstone..
Clinkstone..

.6096

Cordier 5820

..

5545

..

Clinkstone ..
Granite

Road from Le Puy to Pradelles, Haute Loire Basalt on granite

"THE VOLCANIC DISTRICT OF CENTRAL FRANCE."

Comprising the greater part of the primary platform, and containing the departments Puy de Dôme, Loire, Rhône, Haute Loire, Cantal, Ardèche, Lozère, and parts of the Aveyron, Corrèze, Creuse, and Allier. The areas occupied by the volcanic products are distinguished in colours, as well as those of the principal crystalline and sedimentary formations, and the several coal-basins. This map is

copied for the most part from the Carte Géographique de la France,' omitting the subdivisions, which would have been too complicated for the scale employed.

No. 2.

"THE MONTS DÔME AND PART OF THE LIMAGNE."

Exhibiting the chain of puys rising from the granitic platform which separates the Allier and Sioule. The extent of surface covered by the volcanic cones and their lava-currents is indicated by colours, as well as the limits of the primary and freshwater formations, and the more ancient basaltic currents which have flowed from the Mont Dore in that direction.

PLATE I.

Panoramic View of the Environs of Clermont, taken from the summit of the Puy Girou, a conical peak of columnar basalt, about four miles south of that town. The chain of puys of the Monts Dôme is seen to the west, with the Puy de Dôme in the centre, rising from the surface of the granitic platform. To the north lies the basin of Clermont, eaten out of the freshwater formation, and overlooked by the primary escarpment, on the edge of which rises the recent volcanic cone of Graveneire. Beyond Clermont are seen the basaltic platforms of Les Côtes and Chanturgues; in front, a basaltic peak crowned by the Castle of Montrognon. Eastwards, and above the village of Opme, rise the Puy de Jussat and the plateau of Gergovia, both in all probability once continuous with the basalt of Girou. To the south is seen in its whole extent the basaltic platform of La Serre, partly resting on granite, partly on the freshwater marls, and terminating at the village of Le Crest. Beyond it rise the trachytic heights of the Mont Dore, and its basaltic embranchments; with the insulated basaltic plateaux or peaks of St. Sandoux, St. Saturnin, Coran, Monton, &c.

The horizon is closed by the mountains of the department of the Haute Loire. Immediately below these distant heights the valley of the Allier appears narrowed by the quantity of basalt which has flowed in that direction from the vicinity of the Mont Dore. Beyond the river rises an insulated group of hills capped by basalt and chiefly composed of freshwater limestone, but partly of granite and secondary sandstone. They are called the Puys de Millefleur, St. Romain, Mauriac, Dallet, &c. At the foot of this range flows the Allier, and immediately enters the wider expanse of the Limagne d'Auvergne, which, bounded only eastwards by the distant granite range of the Forèz, stretches to the horizon on the north-east of the station. The cone of Graveneire, and the lava-current bursting from its side and spreading thence over a large surface of the lower plain, are remarkable objects to the north of the spectator.

PLATE II.

Distant View of the Chain of Puys, or Monts Dôme, taken from a remnant of basalt crowning the western bank of the Sioule, a short distance below Pont Gibaud. Nearly all the cones are visible; the most conspicuous are those of Louchadière and Côme. The lavastreams poured forth by these two vents may be seen spreading in broad sheets from the base of the cones over a wide extent of the granitic platform, and uniting immediately above the Castle of Pont Gibaud to pour over the banks of the valley of the Sioule in a spreading sheet, which is, however, partly hidden by forest and underwood. That part of the lava-current which occupies the former bed of the Sioule is, on the contrary, still bare and rugged, its surface appearing like a series of heaps of loose basaltic blocks. Between this and the granite cliffs to the right, the river dashes and foams through the narrow channel it has excavated by undermining the granite. At the angle immediately beneath the spectator the basalt exhibits a regularly columnar structure.

In the distance to the right is the outline of the central trachytic eminences and plateaux of the Mont Dore, from amongst which the Sioule takes its rise.

PLATE III.

Transversal View of the Northern Chain of Puys, from the Summit of the Puy Chopine. The cone of La Goutte, which half encircles the Puy Chopine, forms the foreground. The Puy de Côme and the commencement of its lava-current are seen to the extreme right. The Puys de Dôme, Cliersou, Suchets, Pariou, with the beginning of its lava-stream, &c., in the front; and the group of Les Goules and the Sarcouis, with the Puy Chaumont, on the left. The Mont Dore and the mountains of the Forèz and Haute Loire. skirt the horizon to the right and left. The observer looks due south.