DOMAIN XII. VOLCANIC. 



NOME V. PUMICE. . 



Former rocks. This substance deserves to be ranged among 

 the rocks, as in the isle of Lipari, whence it is 

 chiefly brought into commerce, it appears in the 

 form of large currents*. Pumice also abounds 

 at the smaller volcanoes of the isles of Santarin 

 and Vulcano: and, according to Troil, Hecla 

 presents vast quantities of brown and black 

 pumice. The volcanoes of Ternate, and other 

 Molucca isles, also eject such prodigious quan- 

 tities of this substance that the ocean appears 

 covered for many leagues. 



Chiefly felspar. Different lavas may become pumice by some 

 peculiar modification of the volcanic agents. 

 Felspar in particular has been detected passing 

 into pumice: and according to the degrees of 

 heat and other circumstances, it may be more or 

 less porous and lightf. That which only pre* 

 sents small cavities may be termed porous; 

 while the more lax may be styled vesicular. 



* Patrin, v. 28Q, from Dolomieu's Lipari. 



f Ferrara, p. 304, mentions a large specimen ejected by Etna i: 

 1802, of which one half was lava, or melted siderite, the other 

 pumice or melted felspar. See also his account of the pumices of 

 Lipari, p. 215. 



