378 VIEWS, &C. VOLCANOS. 



differs very considerably from that assumed in our barome- 

 trical formulae, the amount of correspondence between the 

 various results will appeal- sufficiently satisfactory. 



My measurements of 1822, at the time of the Congress of 

 Verona, when I accompanied the late King to Naples, were 

 conducted with more care and under more favourable circum- 

 stances than those of 1805. Differences of elevations are 

 moreover always preferable to absolute elevations. These 

 differences show, that since 1794, the relative condition 

 of the margins of the Rocca del Palo and of that towards 

 Bosche Tre Case had remained almost the same. I found, in 

 1805, for the height, 441, and in 1822, nearly 524 feet. A 

 distinguished geologist, Mr. Poulett Scrope, obtained 473 feet, 

 although his absolute heights for these two margins of the 

 crater appear somewhat too low. So inconsiderable a varia- 

 tion in a period of twenty-eight years, and during violent 

 disturbances in the interior of the mountain, is undoubtedly 

 a remarkable phenomenon. 



The height to which the cones of scorioe rise from the 

 bottom of the crater at Vesuvius also deserves special atten- 

 tion. Shuckburgh found in 1776 a cone of this nature to be 

 3932 feet above the level of the Mediterranean; and, accord- 

 ing to Lord Minto a remarkably exact observer the cone of 

 scoria? which fell in on the 22nd of October, 1822, was even 

 4156 feet high. On both occasions therefore the cone of scoria) 

 in the crater exceeded the highest point of the margin of the 

 crater. On comparing the measurements of Rocca del Palo 

 from 1773 to 1822, one is almost involuntarily led to hazard 

 the bold conjecture that the northern margin of the crater has 

 been gradually upheaved by subterranean forces. The cor- 

 respondence of the three measurements made between 1773 

 and 1805 is almost as striking as in those between 1816 and 

 1822. No doubt can be entertained as to the height being 

 from 3970 to 4021 feet during the latter period. Ought 

 less confidence to be attached to the measurements made 

 thirty or forty years previously, and which only gave from 

 3875 to 3894 feet? After a longer lapse of time the ques- 

 tion may be decided, as to how much is attributable to 

 errors of measurement, and how much to the upheaval of 

 the margin of the crater. There is here no accumulation of 

 loose masses from above; if therefore the solid trachytic lava 



