194 Physical Notices on the Bay of Naples. 



terwards Shuckburgh took the point whence the lava of 1776 

 had flowed at 3692 = 3935 English. This lava formed a hill 

 in the middle of the crater and disappeared in 1779. In July 

 1805, Gay-Lussac found the highest point of the summit 606 

 toises = 3757 English feet above the sea, and Humboldt a 

 month after took the hill in the centre of the crater 542 toises. 

 A mean of Humboldt and Gay-Lussac gives the base of the 

 cone 370 toises and the hermitage 300. In 1817 the highest 

 summit must have been (according to the Earl of Minto*) 

 3963 feet high. In February 1822 the summit was raised 

 202 feet, giving the extreme altitude 4165 feet. Salvatore 

 the Vesuvian guide informed me, that before October 1822 

 its height was 4250 feet, (an estimation which it seems differ- 

 ed less than 100 feet from the truth), and that at the eruption 

 of that period, more than 800 feet of the summit, including of 

 course the cone lately formed, were carried away, so that the 

 height may not be estimated at much above 3400 feet about 

 the present time. The change of form will be made apparent 

 by the diagrams in Plate III. 



A represents the mountain as it was seen from Naples before 

 1822 ; B its form, December 1826. The consequence of this 

 change was evidently the enlargement of the crater ; for the 

 mountain is so completely a crust in its upper part that the 

 edge of the summit can hardly be said to be level for a yard 

 in breadth between the exterior and interior slope. A few 

 words on the modifications of the crater will find a proper 

 place here. Before the first recorded eruption (that of a. d. 79,) 

 Strabo, lib. v. informs us that the summit was a level plain 

 covered with ashes and rocks, exhibiting marks of igneous 

 action with many caverns and grottos between. In 1631, 

 after a repose of 492 years, Bracini informs us that the crater 

 was 5000 paces round and 1000 deep. In the bottom was 

 a plain where cattle grazed, and the banks were clothed 

 with abundant forests, in which wild boars took shelter ; and 

 numerous caverns of great size were found in the centre. The 

 sloping path down was about three miles long. Three little 

 Jakes also existed there, the water of one of which he describes 

 * See this Journal, No. xiii. p. 72. 



