Ch. XXV. J 



STRUCTURE OF THE CONE OF VESUVIUS. 



621 





8 



fe OX 

 LYAS ' 



atAu 



of the 



ater of 

 p from 

 minor 

 w and 

 was a 

 id sco- 

 mds of 

 totally 



■lit ex- 

 broke 



leave 

 rhat 



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o 



iev 



when 



of it' 

 rsof a 



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it 



V 



oi * 



diminished daily by the dilapidation and falling in of its sides. 

 It measured, at first, according to the account of some au- 

 thors, 2,000 feet in depth from the extreme part of the exist- 

 ing summit ; * but Mr. Scrope, when he saw it, soon after 

 the eruption, estimated its depth at less than half that 

 amount. More than 800 feet of the cone was carried awav 



mountain 



hy the explosions, so that the 

 height from about 4,200 to 3,400 feet.f 



reduced in 



mass 



rangement. 



of loose materials — a mere heap of rubbish, thrown together 

 without the slightest order ; but on arriving at the brim of 

 the crater, and obtaining a view of the interior, we are agree- 

 ably surprised to discover that the conformation of the whole 

 displays in every part the most perfect symmetry and ar- 



The materials are disposed in regular strata, 

 slightly undulating, appearing, when viewed in front, to be 

 disposed in horizontal planes. But, as we make the circuit 

 of the edge of the crater, and observe the cliffs by which it is 

 encircled projecting or receding in salient or retiring angles, 

 we behold transverse sections of the currents of lava and 

 beds of sand and scoriae, and recognise their true dip. We 

 then discover that they incline outwards from the axis of the 

 cone, at angles varying from 25° to 40°. The whole cone, in 



1 



act, is composed of a number of concentric coatings of alter- 



sand, and scoriae. Every shower of ashes 



nating lavas, 



which has fallen from above, and every stream of lava de- 

 scending from the lips of the crater, have conformed to the 

 outward surface of the hill, so that one conical envelope may 

 be said to have been successively folded round another, until 

 the aggregation of the whole mountain was completed. The 

 marked separation into distinct beds results from the differ- 

 ent colours and degrees of coarseness in the sands, scoriae, 

 and lava, and the alternation of these with each other. The 

 greatest difficulty, on the first view, is to conceive how so 

 much regularity can be produced, notwithstanding the un- 

 equal distribution of sand and scoriae, driven by prevailing 



* Mr. Forbes, Account of Mount Ve- p. 195. Oct, 1828 

 s'Jvms, Edin. Journ. of Sci. No. xviii. f Ibid. p. 195. 



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