No. VII. — Islands of Procida and Ischia. 337 



hills, and carries it quite round to the noble cone of Vesuvius, 

 relieved by the fine blue chain of the distant Apennines. Add 

 to this the charming foreground which the spectator from 

 Epomeo enjoys. Undoubtedly one of the most striking parts 

 of the scene is the perfectly map-like configuration in which 

 the beautiful island of Ischia lies stretched below him, as seen 

 from this insulated point. The irregular Irendings of its 

 shores, the profusion of villages with which it is studded, and 

 the rich mass of foliage which encompasses most of them, pre- 

 sents a picture both novel and delightful, and though situated 

 at the extremity of the Bay, Epomeo undoubtedly affords one 

 of its most admirable points of view. 



Returning to the varieties of mineralogical structure which 

 this great mass of tufa envelopes, the most important is the 

 true or stony lava. Of this streams occur in various parts of 

 the island, and several volcanic cones are formed of modifica- 

 tions of it. We have already described the stream which 

 flowed from the Campo del Arso, and the others are almost 

 equally sterile; they contain generally more felspars, which 

 are grouped in masses containing crystals, sometimes two or 

 three inches in length. Of the origin of these, mineralogists 

 have much puzzled themselves, but we are obviously as yet 

 quite ignorant of the causes of changes observed to be induced 

 in many minerals under the action of heat. Much might be 

 learned from what goes on frequently in our furnaces, and concre- 

 tionary separations of component parts may be observed both in 

 volcanic and trap rocks. The lavas of Ischia show no disposi- 

 tion to prismatic forms, and are entirely amorphous. Their 

 mineralogical characters have been examined with minuteness 

 by Spallanzani, * but are so much alike, that they need not 

 long detain us. They are frequently porous, and abound in 

 felspar, which appears to be in one form or other the most im- 

 portant component of the island ; in some rarer cases the fel- 

 spar is tinged red by oxide of iron, but more commonly the 

 oxide is yellow, and confers its tint on a great part of the 

 lavas. There can be no doubt that this substance is derived 

 from magnetic iron ore imbedded in the solid mass, and which, 



• Travels, i. 146, &c. 



