The Volcanic Region of Auvergne

THE VOLCANIC REGION OF AUVERGNE. By CANON T. G. BOKNEY, D.Se., LL.D.. F.R.S., etc., late Professor of Geology in University College, London. (Read July stll, 190L) UVERGNE, SO far as my experience goes, is the most A interesting region in France, if not in Europe. It can teach the geological student more about the natural history of volcanoes than the Eifel, or even than the neighbourhood of Naples, though not a single vent is now in action. Impressive as Vesuvius must be during an eruption, we have then to con template it from a respectful distance, so that, although I would gladly have witnessed this, I probably learnt more from being able to stand on the crater rim. Auvergne offers to our examination a wonderful series of preparations, the handiwork of nature, illustrative of the anatomy of a volcano, from crater-cones as perfect as that of Monte Nuovo to ruins as complete as those on the Fifeshire coast. These will principally attract your attention during your visit, but they do not exhaust the geological interests of the region. The volcanic cones rise from a great upland plateau-a huge insular mass of ancient, and to a large extent, crystalline rocks surrounded by Secondary and later strata. Depressions in this plateau were occupied towards the middle of the Tertiary era by extensive lakes, which were gradually filled up by beds of sand stone, marls and freshwater limestones, the earlier of which are contemporaneous with the Headon, Bembridge and Hamstead beds of our country. You will frequently come across sections of them, especially on the western flank of the broad valley of the Allier, sealed up sometimes under sheets of basalt. As the lakes disappeared, probably owing to changes of level about the beginning of the Miocene period, volcanoes became active on the 'central plateau, and continued in eruption, with occasional pauses, during the rest of the Tertiary era, and almost down to historic times. It is this episode in the history of Auvergne which has made it classical ground since the middle of the eighteenth century, for here especially the weapons were forged which early in the following one gave the death blow to those Wernerian dogmas which had been so serious an impediment to progress in geology. Here Scrope and Lyell, Murchison and Sedgwick learned to read aright Nature's book of hieroglyphics, and here also during the last third of a century the details and relations of the rocks have been worked out by some of the ablest geologists in France. It will be my endeavour, while not passing over other topics in absolute silence, to lay before you a brief outline of their principal conclusions. ':' • As it is now, I regret to say, a quarter of a century since I was in Auvergne, I have trusted far more to the works of these authorities (of which a brief list is appended by way of postscript) than to my own notes written when I was little more than a beginner in petrology T. G. BONNEY ON As the traveller approaches Clermont Ferrand along the broad valley of the Allier, he is greeted by a view no less impres sive than characteristic. The fertile river plain is bounded by the steeply sloping scarp of an undulating plateau rising more than a thousand feet above it." This scarp, consisting partly of the granitic substructure, partly of lacustrine beds, to which sheets of basalt often form a coping, is seamed by gullies and furrowed hy the deeper glens of the stronger streams, and sometimes has been carved by rains and rivers into bastion-l ike promontories. Above this long but irregular fortress -wall rises a line of boldly outlined hills, most of which are obviously volcanic cones, though two or three, and notably the highest one, have a less distinctive, though still peculiar, outline. This singular view, more than any other characteristic of the" Puy "t region, though attractive at all hours of the day, is never so impressive as at sunset, when these strange, almost weird, summits loom out in purple shadow against the glowing western sky. The upland plateau, no doubt, some times wears a barren aspect, with its rugged surfaces of lava, its wild moors and its coars e vegetation, but the volcanic cone s, apart from their geological interest, never allow the view to become monotonous; the valley slopes, here craggy, there richly wooded, are often picturesque, and their beds in broadening out present a charming contrast by their fertility, while the mountain scenery around Mont-Dore (Fig. 17). and occasionally in theCantal, is really grand. On my second visiq 1 was there for a full fortnight without a companion and never felt lonely, for one's thoughts were always occupied and eyes delighted, even when one rested from work in the field. I have seldom seen a view which has struck me as more beautiful than that from the edge of the volcanic zone across the rich river-valley of the Allier to the blue line of the Forez hills. Geologically and geographically Auvergne is an insulated region, and that fact has left an impression on its history. Here, the primitive and the archaic have lingered longest ; here, any importation from without has been resisted and modified by that which was indigenous. Its archreology, its architecture, its chronicles, and its peopl e-all are marked by distinct and home born characteristics. Auvergne is rich in prehistoric remains. It is not without those of Pal seolithic man, but to find them in abundance we must look beyond its western border to the • The height of Clermont F errand above sea level is 1,335 feet, of Ger govla 2,44' feet, and the mean elevation of th e pl ateau is give n as rather more than 3,000 feet. t PUY,or pue, a name for a hill . ap parently used in the southern part of France, is conne cted with the Italian poggio an d th e L ati n podium, one meaning of which (espe cially in II L ow Latin") is a hill or high place. The wo rd, as applied to isolated cr ater-con es, or lava-domes, has of late years made its way into geology, the « puy stage " d esignati ng th e one (usually late in th e v olcani c hi st or y of a region) sign ali sed by numerous sp ora dic outb reaks. ~ On th is occasion I sp ent a sho rt time at L e Puy en Vetay. just glanced at the Cantal, and devo te d th e re mainder of the time to the Mont-Dare and Pu y de Dome distric t. My firs t visit was no more than a br ief halt at Cler mont Ferrand in order to get a general idea of a volcanic region. THE VOLCAN IC R EG IO N OF AUV ER GN E. 193 limestone gorges of the Dordogne and neighbourin g rivers. There, in the caves of Aquitaine, the hunters dwelt, like the Horites of Palestine, but no doubt they often pursued the reindeer, the auro chs, the horse, and even the mammoth into the wild uplands of Auvergne. But the relics of their succcssors- the people of the Neolith ic, the Bronze, and the Early FIG. 18 .-;\ DYKE 1:-; Til E HI GII VA LI. EY OF Iron ages- are ab undant. Such an up CIIAI;nEFO\; H. land as Auvergne forms a natural camp of refuge when a native race is being pressed back by a stronger invader. Thus it is a land where the prehis toric is overlapped by the historic. The hill forts of the home-born Gauls may be contemporaneous with the camps of the Italian soldiers. Cesar was driven back by Vercingetorix from the ramparts of Gergovia, and was obliged to raise a siege which brought him no credit, though he was ultimately victorious. The Roman s ruled Auvergne and have left their mark, not to name other localities, on the great " high place " of the Puy de Dome and in the road not far from its base, ab out the sprin gs of Mont-Dore, and in the subs oil of Clermont Ferrand. To the lover of architecture, Auvergne is hardly less attractive than to the geologist. Ru ined castles, often picturesquely perche d on a crag of volcanic rock, are abundant. So also are ancient churches, and their features are not less characteristic tha n those of the 194 T. G. BONNEY ON region. The Romanesque architecture of this province, according to Fergusson", attained a degree of independent completeness which enables us to class it among the more perfected styles in Europe. Fine examples are to be found at Issoire, Orcival, and St. Nectaire, in the church of Notre Dame du Port at Clermont Ferrand and the cathedral at Le Puy. Nor must we forget St. Michel's Church in that town, on its rocky pinnacle, or the fortified church of Royat, or the cathedral of Clermont Ferrand though that is in the Pointed style, for it was begun in 1248-with its fine stained-glass windows dating from the later part of that and the following century. The insulated character of the region has also impressed itself on the people. A highland race, they preserved for long a cer tain independence, and may still be reckoned among the nearest representatives of the ancient inhabitants of Gaul. The Auvergnat of the original stock is a member of the short, dark, brachy cephalic race which entered France in early Neolithic times and still survives in ethnological islands such as this hill region.

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