134 Physical Notices of the Bay of Naples. 



one or two remarks connected with that work which maybe con- 

 sidered as a postscript to my last paper. The extreme N. W. , 

 point of the crater, which received the name of " Rocca Del 

 Palo," from a post which stood upon it, remained, it would 

 seem, unaffected by the internal action of the mountain, at least 

 from 1773 to 1822. This Humboldt points out as an interest- 

 ing proof that some positions of considerable stability may be 

 found even in a volcano whose aspect is apparently so change- 

 ful as Vesuvius. Saussure's measurement in 1773, which I 

 gave in last Number, p. 193, was nearly the same as all suc- 

 ceeding ones ; but the same observer remarked that the N. W. 

 and S. E. edges of the crater were precisely equal in that year, 

 but in the eruption of 1794 the latter was lowered 75 toises. 

 What the changes of this discrepancy may be is doubtful ; 

 for we have in this instance an example of a general haste 

 and want of attention, which is rather conspicuous in this little 

 essay of Humboldt's, and which gives us room to doubt his accu- 

 racy on the measurements of the crater, which are much smal- 

 ler than those I have given in my paper. He says, the bottom 

 of the crater after the eruption of 1822 was 750 feet below 

 the northern, and 200 below the southern edge. This leaves 

 550 feet for the difference. Yet he tells us, " d'apres mes der- 

 nieres observations le bord du S. E. que en 1794 etait de 400 

 pieds plus bas que le precedent (le N. W.) a eprouve un dimi- 

 nution de 10 toises." Hence for the difference we would have 

 400 feet +10 toises = 460 feet instead of 550. I point this 

 out as one of the inconsistencies which occur in this paper. 

 No one I should conceive, who has seen the crater in its present 

 state, could take it on any man's word, that the bottom of the 

 crater is only half as deep below its lowest edge as that is be- 

 low the highest : and I can more distinctly express my con- 

 viction, as in 1826 I descended two-thirds of the depth to the 

 bottom from the lowest edge. Besides, the numbers I have 

 given in my last paper, chiefly derived from information on 

 the spot from my most intelligent guide, have been corroborat- 

 ed from very different quarters ; the general dimensions, by 

 Ferrar?s " Guida di Napoli,^'' and a statement which appeared' 

 in the Edin. Phil. Journ, vol. x. : the total height, by Lord 

 Minto's measurements ; and the difference which I heard ex- 



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