536 PLIOCENE VOLCANOS. [Ch. XXXI. 



I shall describe one more section to elucidate the phenomena of this 

 district. A lava-stream, flowing from a ridge of hills on the east of 

 Olot, descends a considerable slope, until it reaches the valley of the 

 river Fluvia. Here, for the first time, it comes in contact with running 

 water, which has removed a portion, and laid open its internal structure 

 in a precipice about 180 feet in height, at the edge of which stands the 

 town of Castell Follit. 



By the junction of the rivers Fluvia and Teronel the mass of lava has 

 been cut away on two sides ; and the insular rock B (fig. 474J has been 

 left, which was probably never so high as the cliff A, as it may have con- 

 stituted the lower part of the sloping side of the original current. 



From an examination of the vertical cliffs, it appears that the upper 

 part of the lava on which the town is built is scoriaceous, passing down- 

 wards into a spheroidal basalt ; some of the huge spheroids being no less 

 than 6 feet in diameter. Below this is a more compact basalt, with crys- 

 tals of olivine. There are in all five distinct ranges of basalt, the upper- 

 most spheroidal, and the rest prismatic, separated by thinner beds not 

 columnar, and some of which are schistose. These were probably formed 

 by successive flows of lava, whether during the same eruption or at dif- 

 ferent periods. The whole mass rests on alluvium, ten or twelve feet 

 in thickness, composed of pebbles of limestone and quartz, but without 

 any intermixture of igneous rocks; in which circumstance alone it 

 appears to differ from the modern gravel of the Fluvia. 



Bu/adors. — The volcanic rocks near Olot have often a cavernous 

 structure, like some of the lavas of Etna ; and in many parts of the hill 

 of Batet, in the environs of the town, the sound returned by the earth, 

 when struck, is like that of an archway. At the base of the same hill 

 are the mouths of several subterranean caverns, about twelve in num- 

 ber, called in the country " bufadors," from which a current of cold 

 air issues during summer, but which in winter is said to be scarcely 

 perceptible. I visited one of these bufadors in the beginning of August, 

 1830, when the heat of the season was unusually intense, and found a 

 cold wind blowing from it, which may easily be explained ; for as the 

 external air, when rarefied by heat, ascends, the pressure of the colder 

 and heavier air of the caverns in the interior of the mountain causes it 

 to rush out to supply its place. 



In regard to the age of these Spanish volcanos, attempts have been 

 made to prove, that in this country, as well as in Auvergne and the 

 Eifel, the earliest inhabitants were eye-witnesses to the volcanic action. 

 In the year 1421, it is said, when Olot was destroyed by an earthquake, 

 an eruption broke out near Amer, and consumed the town. The re- 

 searches of Don Francisco Bolos have, I think, shown, in the most 

 satisfactory manner, that there is no good historical foundation for the 

 latter part of this story ; and any geologist who has visited Amer must 

 be convinced that there never was any eruption on that spot. It is true 

 that, in the year above mentioned, the whole of Olot, with the exception 



