Miss M. S. Johnston — Geological Notes on Central Fnmce. 61 



as an isolated hill in the centre of a circular valley. This is the 

 Roche Vendeix. 



After traversing some woods the road opens on to a fine 

 panorama, an immense circle bounded by the mountains of Mont 

 Dore, the Cantal and Cezallier, and the hills of lesser heights, the 

 Orgues de Bort and the Limousin. The village of Latour is built 

 on a basaltic promontory. The columns of basalt are magnificent ; 

 their broad tops serve as excellent foundations to the houses, and are 

 especially well seen in the small hill, on which once stood a castle. 



Here the road descends into the valley, and the sceneiy is changed. 

 Eounded and striated hills of granite betoken the presence of 

 ancient glaciers, and between them stretch marshy fields of peat, 

 whose undersoil is formed of scratched pebbles and erratic blocks of 

 every size. The glaciers were of Pliocene age and when the 

 volcanoes of Auvergne were at their highest. The glaciers have 

 scooped out curiously shaped valleys, and the moraines lie along 

 successive hills, whose contours are rounded and lowered as fur 

 as La Pradelle, when the materials spread themselves out over 

 a flat tableland, which constitutes the plateau of Lanobre and 

 extends to the Orgues de Bort, whose precipitous escarpment 

 dominates the left bank of the Dordogne. It may be added that 

 at Bagnols erratic blocks, forming immense heaps, repose oa 

 rounded, polished, or striated cordierite gneiss. 



From Bort a short drive brings one up to the Orgues de Bort; 

 these 'orgues' are of phonolite (PI. II, Fig. 1). A cap of phonolite, 

 rising in immense columns, overspreads a hill of augen gneiss. Many 

 of the ' eyes ' in this gneiss are very large and in regular and con- 

 tinuous layers. 



The view from this hill is very fine. The massifs of Mont Dore 

 and the Cantal are both seen ; the Dordogne and the Rhue have cut 

 narrow precipitous valleys on the north and east, but on the south, 

 after the junction of the two streams, the valley widens and there 

 are some small glacier-formed lakes, which are filling with peat. 



On leaving Bort by train for Aurillac the line, a marvel of 

 engineering skill, winds between the spurs of the Cantal, which 

 the train crosses, ascends, and descends in constant succession. 

 Before reaching the slopes of the Cantal a small Carboniferous 

 deposit is crossed, in which mines are worked at Chanjpagnac. 



Aurillac is built on the banks of the Jordanne, and on 

 crossing the railway to the south of the town the alluvial terraces 

 of Quaternary age, with the rounded hills of mica-schist rising- 

 above them, are very noticeable. There is also in this valley other 

 evidences of glacial action, and at Vezac a Quaternary moraine 

 is prominent, forming waterfalls and rapids in the small stream. 



The next interesting section on the road to Carlat is an andesitio 

 conglomerate at Cahanes. This conglomerate is found in great 

 blocks amongst tuft's and andesitic dust, and forming a high hill. 

 The theory concerning this deposit is, that it may be the projection 

 of what was the last effort of the volcano. From this hill is also, 

 seen u wonderful promontory of basalt. This promontory is furnK'(f, 



