NOME V. PUMICE. 431 



examine the pumices most suitable to this pur- 

 pose, and to make further experiments on them 

 after my return to Pavia ; which practice I like- 

 wise observed with respect to the other volcanic 

 products. 

 '" Campo Bianco is a mountain that rises al- Mountain of 



pumice. 



most perpendicularly from the sea, and which 

 seen at a distance appears to be about a quarter 

 of a mile in height, and above half a mile in 

 breadth. No plants grow on it, except a few 

 which bear no fruit, and likewise grow on the 

 tops of the Alps. Its sides are streaked with a 

 great number of furrows, that grow deeper and 

 wider as they approach the bottom, and have 

 been formed by the rains, which easily corrode 

 and excavate a substance so soft and yielding as 

 pumice. The sea at the foot of it has likewise 

 occasioned great devastations, by means of 

 which we discovered a large vein of horizontal 

 lava, on which the last waves die away when 

 the sea becomes calm. The formation of this 

 lava was, therefore, prior to the vast accumula- 

 tion of pumices which rest upon it. 



" On attentively viewing this prodigious mass in beds, 

 of pumice, we soon perceive that it is not one 

 solid whole, and forming only one solid single 

 piece; but that it is an aggregation of numerous 

 beds or strata of pumices, successively placed on 



