JS6 Physical Notices of the Bay of Naples. 



simple and uniform action, the flow of a stream of liquefied 

 matter, (liquefied by water, not by heat,) while the various 

 and remarkable structure of the original tufas, in swelling ba- 

 sin-shaped stratifications, filled up with perfectly horizontal 

 layers, as I have often, with great satisfaction, contemplated 

 in the neighbourhood of Naples, leads me to attribute their 

 origin to the action of submarine volcanos. In the ancient 

 tufas. Sir William Hamilton describes various fossil remains 

 as being found, particularly oyster shells, which he has beau- 

 tifully illustrated in coloured plates of his Campi Phlegral*. 

 I am not aware whether such remains are, or are not, met 

 with in the tufa above Herculaneum ; but it is not of great 

 importance, for we are well assured that all volcanos hold a 

 particular communication with the sea, which would appear to 

 be a requisite agent in the production of their effects; for 

 they " seem in general to be situated near the sea-coast, and 

 rarely or never in the interior of large continents. Cotopaxi, 

 in South America, is perhaps of all volcanic mountains the 

 most distant from the ocean ; and yet it is only 140 miles from 

 the shores of the Pacific f." If I do not mistake, shells are occa- 

 sionally ejected from Vesuvius itself; and Humboldt assures us, 

 that in the Andes fish are frequently thrown from the craters 

 of volcanos. At all events, it appears strikingly probable, 

 that the substance which covered Herculaneum was ejected in 

 the form of liquid mud, being an accumulation of earthy, 

 pumiceous, and bituminous substances combined, and carried 

 along by the force of water and steam, probably at a red heat 

 "^hen issuing from the pressure it experienced in the bowels 

 of the mountain, which may probably have given rise, as I 

 have before hinted, to the description of the " latissimse 

 flammae," mentioned by Pliny ; since we know that no true lava 



* Naples, Folio, 1776, Vol. ii. Plates xlii. and xlv. — It would be of the 

 highest interest to examine the nature of these fossil remains in the scale 

 of organization ; whether the oyster-shells approach nearer to the present 

 existing or fossil species, and if the vegetable remains are monocotyledonous 

 or dicotyledonous. To establish the relative antiquity of these tufas to 

 the other strata would be an acquisition of extraordinary interest in geo- 

 logy. 



t Edin. Encyc, Art. Physical Geography, Vol. xvi. p. 487. 



