PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



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1856, had it not been that Baron Humboldt, in the recently piibHshed fomih 

 volume of his " Kosmos," applies the whole weight of his great authority to the 

 support of the theory of upheaval in contradistinction to eruption as the vera 

 causa of volcanic cones and craters, — a theory which the author, with Sir Charles 

 Lyell, M. Constant Prevost, and many others, believes to be not merely eiToneous, 

 but destructive of all clearness of apprehension as to the character of the subter- 

 ranean forces, and the part wliich volcanic action has played in the stnictiu-al 

 arrangement of the earth's surface. 



He showed, by reference to the works of Spallanzani, Dolomieu, Breislak, &c., 

 that the early observers of volcanic rocks and phenomena, together with the 

 imscientific world, looked upon volcanic cones and craters, whether large or small, 

 as the result of volcanic emptions ; but that of late years a new doctrine had been 

 propagated by MM. Humboldt, von Buch, Elie de Beaumont, and Dufrenoy, 

 which denies altogether that volcanic mountains have been formed by the accumu- 

 lation of erupted matters, and attributes them solely to a sudden " bubble-shaped 

 swelling-up " of pre-existing horizontal strata, — the bubble sometimes bimsting at 

 top and then leaving its broken sides tilted up around a hollow (elevation- 

 crater). 



The author expressed his belief that this notion originated in Baron Humboldt's 

 account of the eruption of Jorullo in 1759, in which (as the author showed in his 

 work on volcanos of 1825) a great error had been committed, — the convexity of the 

 Malpais and its five hills being simply a bulky bed of lava poured out on a flat 

 plain from five ordinary cones of eruption, and the "hornitos" common "fuma- 

 roles " coated over with black mud produced from showers of volcanic ashes mixed 

 with rain-water. But the idea of a " bladder-like swelling-up" of horizontal strata 

 into volcanic hills being thus started by M. von Humboldt, it was fm-ther extended 

 by M. von Buch ; and hence arose the " elevation-crater" theory. 



The author next proceeded to show the inconsistencies of the advocates of this 

 theory, who disagree among themselves as to the extent to wliich they apply it,— 

 MM. Humboldt, von Buch, and Dufi-enoy asserting both Somma and Vesuvius, 

 the Peak of Teneriffe, and all Etna, to be solely due to sudden upheval, while 

 M. de Beaumont declares Vesuvius, the Peak, and the upper cone of Etna to be 

 the products of eruption only. Again, while, except M. I)ufi-enoy, all admit the 

 minor cones and craters of Etna, Vesuvius, Lanzarote, and Central France to be 

 eruptive, all declare the similar cones and craters of the Phlegrsean fields to be due 

 only to upheaval. They offer no reliable test by which upheaved can be distin- 

 guished from eruptive cones ; or, when they attempt tliis, differ again from one 

 another, and even from themselves. Thus, Von Buch considers the extreme regu- 

 larity of the slopes of Etna a proof of its upheaval. M. de Beaumont asserts 

 regularity of outline to be the distinguishing feature of an eruptive cone, and 

 yet declares the upper and the lower portions of Etna, which are its least sym- 

 metrical parts, to be of eruptive origin, and the intermediate cone, the slope of 

 which is extremely regular, to have been upheaved ! In respect to the tuft-cones 

 and craters of the Phlegrsean fields, the series from Somma to the Monte Nuovo 

 is so evidently of similar character, that, to avoid classing the first as an eruption- 

 cone, the upheavalists have been driven to deny that the Monte Nuovo itself was 

 the product of eruption, and even to assert that it existed in the Roman era, and 

 was only sprinkled with a few ashes by the eruption which, from all contem- 

 porary authorities, threw it up in two days of the year 1538 ! The author describes 

 the circular antichnal dip of the strata of the Monte Nuovo and other tuff-cones of 

 the Campi Phlegrsei as utterly inexphcable upon the theory of upheaval, while it 

 is the natural result of the fall and accumulation of fragmentary materials pro- 

 jected upwards by eruptions. 



He then disputes the truth of M. de Beaumont's dogma, that lava cannot con- 

 solidate into a solid bed upon a slope exceeding 5° or 6°, and shows from number- 

 less instances in Auvergne and the Vivarais, on Etna, Vesuvius, Teneriffe, &c., 

 that bulky beds of lava have congealed on steep slopes, — in some cases, as for 

 example in that of Jomllo itself, in the form of a massive promontory projecting 

 far from the side of the cone of the crater from which it issued ; in others, when 

 liquidity was at the minimum, in that of a dome or bell (Boiu-bon, Puy de Dome, 



