Grotto del Cane. 257 



proximity of the volcano which has produced the deposit, it would be 

 easy to refer the whole to an alluvial origin, so characteristic are the 

 undulating lines of deposition, the alternation of coarse and fine mate- 

 rials interstratified, including now large angular masses of rock, and 

 again graduating into the finest silt and mud. In some places the 

 lines of deposition are curved in regular undulations, and in others 

 they meet at a sharp unconformable angle. Close observation alone 

 detects that the whole material is volcanic — pumice, scoria, sand and 

 fine dust, including large blocks of inflated lava and tufa. 



It IS impossible to see any difference in the general character of these 

 deposits and of those which cover Pompeii, only that the latter being 

 niostly the result of one eruption are less varied than the former, and 

 more regularly stratified. In both, the evidence of aqueous action is 

 very obvious; and we have historical as well as geological evidence of 

 the eruption of vast volumes of aqueous vapor with the lapilli, scoria 

 and fine ashes from Vesuvius, which, condensing into rain, produced a 

 deluge of hot mud, filling the most intricate recesses of the Pompeian 

 houses and producing the appearance of an aqueous deposit in the ash 

 hills of the flanks of Vesuvius. In Herculaneum we see the same 

 phenomena in a more remarkable manner. Here owing to a much 

 V larger accumulation of material — to subsequent overflows of lava and 



the superincumbent weight thus produced, with the aid of water, the 

 ashes were consolidated into so compact a mass that some writers 

 have even doubted whether Herculaneum had not been destroyed by an 

 overflow of lava in the first instance. That such was not the fact is 

 ^ell known, and the condition of the antiquities imbedded there quite 

 Jorbid the idea were no other evidence attainable. ' 



2. Grotto del Cane and Lake Agnano. 



has been so much cited for its 

 - s,. ^^...yu.v. a^iu -aa i;u>ciiiig tho floof, that all gcological 

 travellers who visit Naples feel an interest in seeing it. Unfortunately, 

 like some other grottos, its enchantment disappears on a near view. It 

 js a little hole dug artificially into the foot of a hill facing Lake Agnano. 

 i Ihe aperture is closed by a door, and the space within is barely suffi- 



cient for one person to stand erect. Into this narrow cell a poor little 

 ^og is very unwillingly dragged and placed in a depression of the 

 "oor, where he is soon narcotized by the carbonic acid. The earth is 

 ^'^fm to the hand, and the volume of gas given out is very constant. 

 ^LJch is the world-renowned Grotto del Cane, which if it did not equal 



our anticipations, at least afforded us the opportunity of some mer- 

 nt ! 



Lake Agnano, as is well known, fills the bottom of an ancient crater 



The Grotto del Cane or dog grotto, 

 stratum of carbonic acid gas coverin 



rime 



}vhose walls are still distinctly to be traced. On the shore of ihe lake 

 immediately opposite the Grotto del Cane there is a constant and copi- 

 ous discharge of carbonic acid, and the water of the lake at that part 

 J^ in great agitation from its escape. Nor is other evidence wanting of 

 Jhe present operation of the ancient causes which have characterized 

 ^his region. At the foot of the hill on the east are numerous vents of 

 steam and sulphur. Over some of these, vapor baths (Sudatorise) have 

 oeen established, which are held in some repute in cases of rhcuma- 



Secoxd SEsxi:s, YoL XII, ^o. 35.-Sepi, 1851. 33 



