chap. v. Craters of Tuff. 121 



flowed as mud. 1 This mud may have been formed 

 either within the crater, or from ashes deposited on 

 its upper parts, and afterwards washed down by torrents 

 of rain. The former method, in most of the cases, 

 appears the more probable one ; at James Island, how- 

 ever, some beds of the friable kind of tuff extend so 

 continuously over an uneven surface, that probably 

 they were formed by the falling of showers of ashes. 



Within this same crater, strata of coarse tuff, chiefly 

 composed of fragments of lava, abut, like a consoli- 

 dated talus, against the inside walls. They rise to a 

 height of between 100 and 150 feet above the surface 

 of the internal brine-lake ; they dip inwards, and are 

 inclined at an angle varying from 30 to 36 degrees. 

 They appear to have been formed beneath water, pro- 

 bably at a period when the sea occupied the hollow of 

 the crater. I was surprise to observe that beds having 

 this great inclination did not, as far as they could be 

 followed, thicken towards their lower extremities. 



Ba/iiks' Gove. — This harbour occupies part of the 

 interior of a shattered crater of tuff larger than that 

 last described. All the tuff is compact, and includes 

 numerous fragments of lava ; it appears like a sub- 

 aqueous deposit. The most remarkable feature in 

 this crater is the great development of strata con- 

 vergiug inwards, as in the last case, at a considerable 

 inclination, and often deposited in irregular curved 



1 This conclusion is of some interest, because M. Dufrenoy 

 (' Mem. pour servir,' torn. iv. p. 274) has argued from strata of tuff, 

 apparently of similar composition with that here described, being 

 inclined at angles between 18° and 20°, that Monte Nuevo and some 

 other craters of Southern Italy have been formed by upheaval. 

 From the facts given above, of the vaulted character of the separate 

 rills, and from the tuff not extending in horizontal sheets round 

 these craterif orm hills, no one will suppose that the strata have here 

 been produced by elevation ; and yet we see that their inclination is 

 above 20°, and often as much as 30°. The consolidated strata, also, 

 of the internal talus, as will be immediately seen, dips at an angle 

 of above 30°. 



