126 



THE GEOLOGIST. 



&c.). In regard to Etna, he leaves 31. de Beaumont's misrepresentations of fa<:t 

 to be dealt -with by Sir C. Lyell. caily remarking that, on M. de Beaimiont's owu 

 sho^\Tiig, the portion of Etna which he supposes to have been upheaved, is 

 positively eucrasted -with a coating lavas." 



The uiapphcaljility of the ele^"ation theory to the Cantal, ]Mt. Dore, and ]\Iezenc 

 in France, is then sho^vu. iuasmuch as, by de Beaumont's own admission, the 

 angle of slope of their l">asaltic and trachytie beds is even less than that of the 

 recent and acknowledged lava-tlciws in the same district. Finally, he asks what 

 has become of the products of the repeated eruptions of volcanos, if they have not 

 accumulated in the com'se of ages mto the mountains Avhich we find there, com- 

 posed of uTegiilar alteruatmg beds of lava and conglomerate just such as we see to 

 be erupted fi'om the central oritices I 



The author next shows that the upheavahsts have no coiTect idea of the 

 mode of formatiijn of craters, which are not formed, as they assert, at one blow, 

 by a single explosirai. like the bm'sting of a bubble, or of a mine of gimpowder, 

 but by the rei'etition of explosions or flashings of steam from the smiace of 

 ebullient la^-a within the volcanic vent (like those of a colossal Perkins's steam- 

 mortar\ contumed f jr weeks and mouths, or more, by which the mountain is often 

 iiltimatfly evis.erate'i. its summit and heart being bio v^ii into the air, and scattered 

 in fi'agments or ashes ai-'juiid— fjundering into the cavity and remaining there 

 as they represent. lie in>t;inces the great crater of Vesuvius formed under liis 

 eyes m 1S2-2 by explosi^jiis lastnig twenty days ; and judging from the quantity of 

 fi'agmentaiy matter then ejected and falling around, conrparing it with the far 

 gTeater cpiantities tlu'own up occasionally by eruptive paroxysms in other cpiarters 

 of the gLjV'e. he asseits his belief that in the latter cases craters may be, and are, 

 formed of several miles in diameter, nothing remaining of the whole mountain 

 except the wreck of its l iase. as we see in Santorini, the Circpie of Tenerifte, and 

 so many other cu-cular cUti:-ranges surrounding extinct or active volcanic vents. 

 He expresses Ids astcaiishment that Yon Buch^and Humboldt should have sup- 

 posed Yesuvius to have " sprung up hke a bubble in one day, just as we now see 

 it," iji the year 79 a.d., and not to have mcreased smce ; and shows that even 

 witliin the last hundi-ed years gi'eat changes have taken place in the form of that 

 mountain, and that the relation of Pliny of the phenomena witnessed by him is 

 inconsistent with the idea of upheaval, and demonstrative of the occuiTence of an 

 emptive par.jxysm by which the upper part of Somma was blown by degTees into 

 the ah', and the crater of the Atrio furmed, in which the subsequent eruptions of 

 eighteen centuries have raised up the cone of Yesuvius. 



In recapitulation, the author declares that the characters of all volcanic moun- 

 tains and rocks are simply and natm-ally to be accounted for hy their emptive 

 origin, the lavas and fi-agmentaiy matters accumidatmg round the vent in forms 

 determined m great degree hy the more or less imperfect fluidity of the former, 

 which, as in the case of some trachytie lavas, glassy or spongy, may and do con- 

 geal in domes or bulky masses immediately over, or in thick beds near the vent, 

 or, as in that of some basaltic lavas, may flow over very moderate declivities, to 

 gi'eat distances ; and consequently that the upheaval- ur elevation-crater theory is 

 a ^atuitous assumption, unsupported by direct observation and contrary to the 

 evidence of facts. He concludes by representing its continued acceptance to be 

 discreditable to science, and an impediment to the progress of sound geology, 

 inasmuch as folse ideas of the bubble-like inflation, at one stroke, of such moun- 

 tains as Etnaor Chimborazo must seriously aftect all oiu' speculations on Geological 

 Dynamics, and on the nature of the subterranean forces by which other mountain- 

 niuges or continents are formed. 



