80 Mr Forbes's Physical Notices of the Bay of Naples. 



a mile high. * Of all writers of the last century Lalande f 

 formed the most moderate estimate, by putting it at two or 

 three hundred French feet ; but an eminent Italian mineralo- 

 gist, Piiii, has lately set the question at rest by determining its 

 height very accurately by the barometer, as well as that of 

 many other remarkable elevations in the south of Italy. \ He 

 found the height of the summit of the Monte Nuovo to be 

 41f3.0 Paris feet above the level of the bay, = 440.2 English. 



The form of the hill is that of a truncated cone. Its base 

 may be considered as about 8000 feet in circumference, or 

 nearly a mile and a half ; § and the truncation, which is esti- 

 mated at a quarter of a mile in circumference, is, in fact, the 

 edge of a crater of very great size proportioned to the magni- 

 tude of the hill ; a circumstance confirmatory of a general 

 fact we once took occasion to observe in the description of 

 Vesuvius, that the magnitude of craters is almost universally 

 in the inverse ratio of the size of the volcano. Hamilton ob- 

 served that the crater of the Monte Nuovo is as deep as the 

 hill is high, and this singular fact is substantially confirmed by 

 the measurements of Pini. He found its depth from the sum- 

 mit to be 395.2 French feet, = 421.2 English. The bottom 

 is therefore only 19 feet above the level of the sea. 



The geological structure of the hill requires but little ex- 

 planation. We have already remarked that it consists entirely 

 of ejected fragments loosely aggregated, and without any ap- 

 pearance of the ejection of lava. From the quantity of water 

 produced by the eruption, it is highly probable that the basis 

 of the hill consists of Tufa, || and, in fact, from its extreme 

 proximity to the sea, its appearance may be considered nearly 

 in the light of a submarine eruption ; and perhaps it was under 

 very similar circumstances that Monte Barbaro and some of 

 the neighbouring cones were formed, which have little appear- 

 ance of that actual attrition of superincumbent water which 



• Capaccio. 



t Voyage en If die, vii. S-'jS. 



X Memorie delta Societa Italiana, vol. ix. 



§ Daubcny on Fokano.s, p. 165. 



II Sir William Hamilton actually mentions such a tufa of a yellowish 

 colour, and less aggregated than that of Pausilipo. Owi. PIdeg. Exp. PI. 

 xxrii. 



