362 MEMOIR OF LEOPOLD VON BUCH. 



situated quite near tlic summit of mountains.* The sagacious and patient de Saus- 

 sure had too long meditated and suftcred among the snows of Mont Blanc to con- 

 cede much influence to mountains of fire. Werner, averse to what might disturb 

 the regular order of nature, which he had 'elaborated, and interrupt the tranquil 

 flow of his instructions, accepted volcanoes but as local and limited accidents. 

 It was thus that matters stood, and would perhaps have long stood, had not 

 two travellers, who happened to be detained on the road to Moulins, been 

 struck at observing the great difficulty experienced by a mason at work near 

 them, in breaking the stones v/ith which he Avas constructing a fountain : their 

 hardness, color, and porous structure recalled to one of the observers the lavas 

 of Vesuvius. " Whence do you bring these stones ? " he asked. " From Volvic, 

 near Riom." " Volric/ Vulcani, vicus ; there must have been a volcano 

 there," said our celebrated naturalist, Guettard,t to his friend Malsherbcs ; "let 

 us take the road to Auvergne." This they did; it was in 1751. Guettard 

 discovered a whole chain of extinct volcanoes, and revealed to his fellow-citi- 

 zens that they trod a soil once on fire ; the lavas, the cinders, the scorioe, the 

 mountains, with their craters, all lent confirmation to the fact. The unexpected 

 announcement was received, we are told, with astonishment, and even with 

 alarm. 



Twelve years later, the practical and sagacious Desmarets, in the course of 

 one of those excursions in which he traversed the whole of France on foot, 

 made a visit to the Puy de Dome, and clearly distinguished the pillars of 

 black stone, whose figure and position struck him with their resemblance to 

 what he had read respecting basalts and giant causeways. In their regularity, 

 these columns bore the indications of a melted product ; t and further investi- 

 gation left no doubt on the miud of Desmarets that they had been cast by the 

 action of fire. 



" "Perpendicular fissures, some larger, some smaller, have doubtless been formed in vast 

 numbers in the body of the mountain. The rain, of course, penetrated into all these fissures, 

 and taking up or dissolving whatever siibstances were callable of being thus acted on, have 

 iormed pyrites, sulphurs, and other combustible materials ; and when, in a long succession 

 of ages, these had accumulated in immeuse quantity, fermentation and conflagration have 

 taken place, producing the explosions and other effects of volcanoes. Perhaps, also, there were 

 masses of these mineral substances already existing before the rains could reach them, but 

 whenever openings or crannies, by which the. water and air could penetrate, have been 

 formed, ignition has taken place in the inflammable matter and a volcano has been the 

 result." — Buffon, 1, p. 287. " The fire of the volcano comes rather from the summit than 

 from the lower depths of the mountain." — Id., 1, p. 285. (The author cites here and else- 

 where his own edition of Puffon, just published in ]2 vols. 8vo. ) 



t Guettard, (Jean Etienne,) born ]7I.^), died 1786: Memoirc sur quelques montagnes de 

 la France qui out cte des Volrans. ]\Iem. do 1' Academic des Sciences, 1752. 



X That the columns were almost always found at the termination of long courses of lava 

 which had themselves issued from craters still discernible, carried conviction to the mind of 

 Desmarets. "In 1763," he says, " I traversed a part of Auvergne, where traces of volcanoes 

 are to be seen, and particularly from Volvic to the Monts Dor. On the route from Clermont 

 to the Puy de Dome, I perceived prisms of a black and compact stone, like that which cov- 

 ered a great part of the surface, the prisms resting on a bed of scoriae. It was evident that 

 they pertained to the crust of black stone enveloping the high plain which leads to the foot 

 of the celebrated mountain. When I considered the inconsiderable thickness of this crust 

 established on a bed of scoriaj and overlying a mass of granite which had undergone no 

 action of fire, the idea at once occurred to me that here was the product of a current which 

 had escaped from a neighboring volcano. Proceeding on this idea, I ascertained the lateral 

 and extreme limits of the deposit, and still found the prisms, presenting in the perpendicular 

 section their faces and angles, and on the surface their bases perceptibly distinct from one 

 another. I was thus decided in the belief that the prismatic basalt belongs to the products 

 of volcanoes, and that this constant and regular form is the result of the state of fusion in 

 which the lava once existed. There can, I think, be no doubt that the groups of prismatic 

 coliunns in Auvergne pertain to the same conformation with those of the county of Antrim, 

 in Ireland, and that the constant and regular form is in Antrim the result of a cause similar 

 to that which announces itself in so uniform a manner in Auvergne." — Desmarets : Mcmoire 

 sur Voriginc et la nature dii hasaltc a grandes colonncs polygoncs, &c. — (Mem. de I'Acade- 

 mie des ISciences, 1771.) 



