1859.] SCROPE CONES AND CEATEES. 519 



own theory; for (as Sir Charles Lyell and M. Prevost have both 

 remarked) the peculiar characteristic of a starred opening is the 

 formation of fissures radiating from the centre of impulsion, but all 

 widening inwardly towaixls it, which is precisely the reverse of the 

 universal character of the fissures, ravines, or " barancos," radiating 

 from the centre of volcanic mountains, all of which, without ex- 

 ception, I believe, widest outwayxlly towards the base of the moun- 

 tain, according to the usual habit of waterworn ravines, which they 

 no doubt are for the most part, though some may have had their 

 origin in earthquake-cracks. Indeed these radiating clefts or 

 ravines, which are very characteristic of volcanic mountains (being 

 the natural result of their regailarly conical or pyramidal form, and 

 the rapid degradation from rain- fall to which their fragmentary 

 materials are generally liable), rarely penetrate the rim or border of 

 the central crater at all. And how a^ cone possessing an unbroken 

 annular central crater can be supposed to represent an etoilement 

 or starred fracture, or to have been raised by a sudden and violent 

 impulse from beneath, acting upon solid horizontal superficial strata, 

 passes comprehension. 



It seems indeed strange that the upheavaHst should fail to per- 

 ceive that his own arguments and illustrations tell strongly against 

 his own theory — that the generally unbroken and regularly circular 

 lip of a volcanic crater, as well as the extremely regular and uni- 

 form inclination of the outer slopes and parallel component beds of a 

 volcanic cone (which is so remarkable that observers can almost 

 always recognize a volcanic mountain at any distance by its pecu- 

 liar talus-like outhne), so far from serving as arguments in his 

 favour, and distinctive characteristics of upheaval, are, to ordinary 

 minds, the very reverse. 



But there is more yet to be said on this part of the subject. In 

 many volcanic districts, for example near Naples, in the Galapagos 

 Isles, and several other localities, cones and craters occur composed 

 of beds of tuif or pumice- ash and scoriae, through which the abrasion 

 of torrents or of the sea-waves has exposed favourable cliff-sections, 

 exhibiting, besides the usual outward concentric anticlinal dip, an 

 inward synclinal one, equally concentric, toivards the interior of the 

 crater. The Capo di Miseno, and the isles of Msida and Procida, 

 and the Monte Barbaro near Pozzuoli, are examples of this remark- 

 able arrangement, which, on a httle consideration, will appear to be 

 the natural result of the process of eruptive accumulation, — the 

 fragments that fall upon or roll down the outer slopes of the cone 

 from the beginning forming beds with an outward quaquaversal 

 dip, — those that fall in the interior of the crater, especially as the 

 eructations diminish in violence towards the close of the eruption 

 (and consequently become unequal to the clearance of the whole 

 area of the channel of discharge), accumulating in an inner talus 

 having a concentric dip towards the centre. (See fig. 6.) 



In my volume on Yolcanos, published in 1825, 1 gave both an ideal 

 section of a cone so formed (of course, by a single eruption) (fig. 6), 

 and a sketch of the natural sections of some actually exhibited, for ex- 



