No. III. — Pmisilipo and the Lago (TAgnano. 259 



curately treated of, named the " Grotto del Cane ;" and the 

 reader need not fear that I shall trouble him with a long drawn 

 narration of this simple phenomenon. Ever since the de- 

 scription by Pliny of these " Charoneae Scorbes^' and " Spira- 

 cula Ditis *, travellers seem to have tried to outvie one another 

 in their description of the wonders of this little spot. Spallan- 

 zani exhausts almost as much space upon it as on Vesuvius ; 

 and in all the topographical works it receives its meed of ad- 

 miration or mystery. Professor Vairo of Naples long ago 

 asserted, that in the Grotto del Cane, the muscular fibres of 

 animals have no irritability ; that there is no electricity ; that 

 the loadstone draws no iron ; and that the needle is remark- 

 ably declining -[- ; — absurdities, to refute which, if they are 

 worth refutation, it is sufficient to consult the decisive experi- 

 ments of Breislak J. Without wasting time upon past errors, 

 we may collect in a few words the principal facts ascertained 

 regarding this grotto, and we may notice in the first place, 

 that it is certainly excavated from Pozzuolana,, and not out of 

 lava, as Ferber asserts §. It is about ten feet long and four 

 broad, and the height of the carbonic acid vapour at a mean, 

 eight Paris inches. Its temperature is considered by Breislak as 

 8° R. above that of the air ; but Mr Adolphus Murray found no 

 difference ; and I am disposed to consider the heat as accidental, 

 for which the great want of circulation in the cavern, and the 

 quantity of combustibles, burnt there by way of experiment, 

 will pretty well account. The composition of the mephitic va- 

 pour may be taken as follows : Oxygen 10 per cent, j car- 

 bonic acid 40 per cent. ; azote 50 per cent. It appears to 

 contain no sulphureous matter. 



The editor of the French edition of Sir William Hamilton's 

 works II, who has subjoined numerous notes, justly remarks, 

 that one of the most surprising phenomena of the Grotto del 

 Cane is the continuance of its exhalations during so many 



• II. 93. 



T Ferber 's Travels, 177. 



t Campanie, ii. 56 ; and in Spallanzani's Travels, i. 108. 



§ P. 177. This author lays particular weight on this point, in which, 

 from the testimony of Breislak and my own observation, I am convinced 

 he is mistaken. 



II The Abbe Giraud-Soulavie. Svo- Paris, 1781. 



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