474 DOMAIN XII. VOLCANIC. ' 



This vale, hollowed by rains, is the only interval 

 between Mount Somma and Mount Cantaroni. 

 South of this vale are two others nearly parallel, 

 the first called Rio Cupo; the second Fossa 

 Grande y which taking a direction from east to 

 west, merges in the plain of Saint Jorio. Its 

 northern side, nearly perpendicular, rises to a 

 considerable height above the valley, and being 

 composed only of lapillo*, pumice, and other 

 substances of an inadhesive quality, is subject 

 frequently to crumble and fall in large quantities. 

 Along the whole extent of the southern side, at 

 its upper part, is seen an ancient current of lava, 

 which at first sight appears to be several strata 

 of lava imposed one on the other, but which a 

 little attention shows is but one current, in 

 which horizontal chasms have been occasioned 

 by refrigeration, and into which the wind has 

 since introduced a slight quantity of vegetable 

 earth. This lava is hard and compact ; it con- 



* " This is the denomination given to fragments of pumice, the 

 largest of which are from six to eight millimeters (a quarter to a third 

 of an inch) in thickness. It is of this lapillo, saturated with lime- 

 water and well beaten, that the floors and terraces of the houses are 

 made at Naples. It is spread in a uniform manner about five or six ' 

 inches deep, and by beating is reduced to the thickness of two to 

 two and a half inches. It then becomes a body of sufficient solidity 

 to be impervious to water, and so hard as to bear being hewn like 

 tufo." 



