014 



ERUPTION OF MONTE NUOVO. 



[Ch. XXIV. 



seen breaking through the walls of the crater, widening as 

 they approach the centre. (See fig. 64, a, b.)* Not a single 



fissure of this kind is observable in 

 the interior of Monte Nuovo, where 

 the walls of the crater are continu- 

 ous and entire ; nor are there any 

 dikes implying that rents had ex- 



Fig. 64. 



isted, which were afterwards filled 

 with lava or other matter. 



It has moreover been often urged 

 by Yon Buch, De Beaumont, and 

 others, who ascribe the conical form of volcanos chiefly to 

 upheaval from below, that in such mountains there are a 

 great number of deep rents and ravines, which diverge on 

 all sides like the spokes of a wheel, from near the central 



axis to the circumference or base of the cone, as in the case 

 of Palma, Cantal, and Teneriffe. Yet the entire absence of 

 such divergent fissures or ravines, in such cases as Monte 

 Nuovo, Somma, or Etna, is passed by unnoticed, and appears 

 to have raised in their minds no objection to their favourite 

 theory. 



It is, indeed, admitted by M. Dufrenoy that there are some 

 facts which it is very difficult to reconcile with his own 

 view of Porzio's record. Thus, for example, there are cer- 

 tain Roman monuments at the base of Monte Nuovo, and on 

 the borders of Lake A vermis, such as the temples of Apollo 

 (before mentioned) and Pluto, which do not seem to have 

 suffered in the least degree by the supposed upheaval. ' The 

 walls which still exist have preserved their vertical position, 

 and the vaults are in the same state as other monuments on 

 the shores of the Bay of Baise. The long gallery which led 

 to the Sibyl's Cave, on the other side of Lake Avernus, has 

 in like manner escaped injury, the roof of the gallery re- 

 maining perfectly horizontal, the only change being that the 

 soil of the chamber in which the Sibyl gave out her oracles 

 is now covered by a few inches of water, which merely indi- 

 cates a slight alteration in the level of Lake Avernus. 9 f On 



* Mem. de la Soc. Geol. de France, torn. ii. p. 91. 

 f Dufrenoy, Mem. pour servir, &c. p. 277. 



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