328 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 23, 



amount of elevation in mass of the pre-existing superficial rocks ; 

 and moreover that the rents they cause in the solid substance of the 

 cone of a volcano in repeated eruption, into many of which rents 

 liquid lava will be injected from the column rising in the central 

 chimney, and cool down afterwards into more or less vertical dykes 

 of solid rock, must have added considerably to the bulk and elevation 

 of such a mountain, by a sort of inward distension. 



This was no closet-theory, — because, as respects the cone and 

 crater of Vesuvius at least, I had the advantage, in the years 1818, 

 1819, and 1820, of watching with my own eyes the outward growth 

 of that cone, through a series of almost continual eruptions of a 

 comparatively tranquil character, which during those years added 

 considerably to its height and bulk by external accretions of ejected 

 scoriae and lava-currents. These last, the lava- streams, issued from 

 small cones and craters formed upon the solid platform which then 

 composed the summit of the great cone, and dribbled slowly down 

 its slopes, consolidating so rapidly there as in few instances to reach 

 the base of the cone at all ; although night after night they were to 

 be seen flowing from the summit in streams of considerable breadth 

 and bulk, and glowing with a bright light on its steep sides. 



Afterwards, in the latter part of the year 1822, I had seen the 

 upper portion of this solid cone blown into the air (by which it lost 

 a full third of its height), and a crater of vast dimensions drilled 

 through its axis by continuous eruptive explosions of twenty days* 

 duration. 



I had previously made a close examination of the cones and craters 

 of Etna, the Phlegrsean Fields, the Lipari Isles, Central France, and 

 the Rhine district ; and their appearances accorded so completely 

 with the supposition of an analogous mode of formation in their 

 instances, that, upon the principle of explaining the unknown by the 

 known, it seemed impossible, or at least unnecessary, to imagine any 

 other origin for them. 



" Elevationi"" ^' Denudation,^^ and " Engulf ment^^ Theories of 

 Crater-formation. — It was, therefore, with no small surprise that I 

 have since found this simple and natural mode of production denied 

 to all cones and craters — including those of Vesuvius itself; and an 

 hypothesis substituted of their originating in some sudden elevation 

 ojp previously horizontal beds around a centre, — not (it would seem) 

 of eruption, but of maximum elevation. I allude, of course, to the 

 " Elevation-crater theory" of MM. Von Buch and EUe de Beau- 

 mont. 



Sir Charles Lyell, M. Constant Prevost, and others, have amply 

 refuted this unphilosophical theory; which, however, still appears 

 to hold its ground to some extent on the Continent, through the 

 prestige of the great names attached to it. It may, therefore, not 

 be wholly useless to adduce some additional proofs of its unwarrant- 

 able character. But I must first be permitted to remark, that even 

 Sir Charles Lyell, while supporting the view indicated above, of the 

 generally eruptive origin of volcanic cones, has had recourse, in the 

 case of some craters, to another agency, the influence of which I am 



