ON THE VOLCANIC PHENOMENA OF VESUVIUS. 339 



many places it is quite removed. Towards Torre Gavetta the ' Museum ' 

 breccia is well developed, 'being composed of very large blocks of the 

 numerous varied rocks, followed by beds of the woody pumice, woody 

 looking scoriae and scoriaceous black centred vitreous trachyte fragments 

 and pumice. Lying with very marked unconformability upon it is a 

 great thick bed of the compact yellow tuff, either derived from Cam- 

 pagnone or the neighbouring cone, a slice of which forms Misenum. In 

 this section we have splendidly exhibited many of the great geological 

 records in the history of this remarkable volcanic region. Bach of 

 these stages is defined from those above and below it by more or less long 

 periods, during which in some cases very extensive denudation had taken 

 place. At this point also I am satisfied we have products of the erup- 

 tions of the Procida and neighbouring centres interstratified with those 

 of the mainland, and in which I hope in time to work out the relative 

 chi-onology. 



The discoveries, which in so striking a manner confirm my conclusions 

 regarding the highly complex stratigraphy of this region, induced me once 

 naore to examine in detail that isolated eminence upon which once stood 

 the renowned Greek town of Cumse, founded about 1000 B.C. 



Time has favoured the geologist, for here, however much the archaeo- 

 logist may grieve, it has once more exposed to human eyes sections that 

 for many centuries were hidden by buildings, but which reveal the fact that 

 those very rocks that as geologists we look upon as very recent had 

 nearly 3,000 years ago much the same characters as now. The pumices 

 that form the uppermost yellow tuff had then already been converted 

 into a rock which those early colonists cut out and used for the construc- 

 tion of their walls. When we first visit Cumae, and our thoughts wander 

 back through historic time, we are impressed by the human associations 

 with this hill for such a long period ; but when we return with our eyes 

 and minds geologically cultured, the ancient Greek town sinks into insig- 

 nificance by the side of the physical history of the mound it stood upon, 

 when we remember that not only this mound, but the whole region is 

 post-Pliocene in age. 



The foundation of the Cnmean hill is the well-known trachyte rich in 

 inclusions of sodalite, of amphibole, and I have detected not uncommonly 

 crystals of fayalite. Were it more vesicular it would very much resemble 

 the western mass of ti'achyte of the Cumana railway tunnel at the back 

 of Naples. 



Above this come some pumice and dust beds, which are probably the 

 equivalent of the Rione Amedeo tuffs. Superposed on this we find a 

 dirty grey pipernoid tuff which shows much remaniement. The Museum 

 breccia is well represented in patches, and is overlaid by a bed of vitreous 

 trachyte produced by the resoldering of the falling masses into one solid 

 stratum, where the surface was flat, but where an incline is the fragments 

 have remained separate. The whole is capped by the compact yellow 

 tuff. There are also some minor pumice and dust beds which require 

 further working out. 



The trachyte seems to have oozed forth in a highly pasty condition, 

 breaking up its scoriaceous surface, which rolled down the sides of the 

 dome-shaped mass, and by pressure and heat from the main mass became 

 again soldered together — in fact, a sort of regelation. The brecciated struc- 

 ture is undiscernible in hand specimens or under the microscope, but is well 

 etched out by meteoric agencies. Each of the deposits mentioned above 



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