50 



In one point, these gentlemen are entirely agreed ; tliat is, 

 in their account of the Volvic lava, Avhich Mr. Desmarest 

 allows to be quite different from his basaltic lava, in its 

 neighbourhood, but perfectly resembling the Vesuvian lava, 

 full of poi'es, and breaking in all directions, (casse en tout 

 sens;) while his own prismatic lava was quite compact, and 

 so refractory, in the hands of masons, that the natives, who 

 had a name of their own for it, pierre d'emgne, and were 

 well acquainted with its inutility, instantly forsook a quarry, 

 when they found the stone of this species. 



Thus, by Mr. Desmarest's account, tlie volcanos of Au- 

 A'ergne produced two sorts of lava, quite different from each 

 other. The first, exactly like the lavas of all other volcanos; 

 the second, totally different: in' texture, as being quite com- 

 pact ; in form, as being shaped into pillars and prisms ; and 

 in fracture, as disobedient to the tool of the workman. 



Mr. Guetafd's account is more simple. He tells us, the 

 volcanos of Auvergne produced but one species of lava, and 

 that exactly like all other lavas. 



Should the reader be emban-assed by the contradictions of 

 these gentlemen; the testimony of an author, Avho lived, at 



the 



that of Vesuvius, half a mile. Sir William thinks, that the craters of extin- 

 guished volcanos increase in size; and, accordingly, Bracini found, before the 

 eruption of 1531, after an interval of rest of 493 years, that the circumference 

 of the crater of Vesuvius was then five miles. 



Sir William adds, that the craters of the extinguished volcanos, of Astruni 

 and Monte Ga.uro, were six miles; while the smallest crater he mentions, is 

 that of Monte Nuovo, which was but a quarter of a mile. This mountain, 

 however, was thrown up in one night. 



