of the Environs of Naples. 127 



Pumice- Tuf, 



2. Leaving out of our cx)nsideration the volcanic hills, the 

 Campania of Naples, and the islands connected with it, consist 

 of a tufF, composed of the debris of the trachyte of the first 

 period : its elements are almost entirely fragments of pumice, of 

 different sizes. In some circumstances^ the fragments are pretty 

 large, but generally, they are so comminuted as to render the 

 tuff* argillaceous, and to give it an almost homogeneous aspect. 

 The characters of the tuff, everywhere the same, prove that it 

 owes its origin always to the same cause. 



3. This tuff is disposed in thin regular beds, even when they 

 are contorted (Cape of Miceno, Island of Procida, &c.) 



It contains fossil shells (Monte Epomeo, Pausilippo, Somma, 

 &c.), and also bones of large animals, viz. of whales, hippopo- 

 tami, the mammoth, &c. (environs of Rome, coast of Sorrento. 

 Amalfi). This double circumstance proves incontestibly, that 

 this tuff*, notwithstanding the height at which it occurs on Monte 

 Epomeo and the Somma, has been deposited under a certain 

 depth of water, in the same manner as the other sedimentary 

 formations. 



4. The line of direction of the different hills of the Phle- 

 graean Fields, and the general direction of the " accidens" pre- 

 sented by the stratification of the tuff^, both from W. 20° S. to 

 E. 20° N., correspond with the direction of the upraising of 

 the principal chain of the Alps, and this coincidence makes us 

 suppose that the pumice-tufF is contemporaneous, or little pos. 

 terior to the sub-apennine formations. The nature of the fos- 

 sils (bund in this tufF at Monte Epomeo and Pausilippo, con- 

 firms the comparison deduced from the study of the directions. 



6. The greater number of the minerals which have been coU 

 lected on the sides of Vesuvius, and which are generally sup- 

 posed to have been ejected by that volcano, belong to the pu- 

 mice-tuff. They are contained in the cavities of blocks of 

 saccharoid limestone, or of micaceous rocks having a primitive 

 aspect, which form true pebbles in the midst of this formation. 

 The surface of some of these blocks is covered by Serpulop, a 

 circumstance which proves that they remained a certain time in 

 the sea- before they formed part of the pumice-tufF. Beside^ 



