228 STRUCTURE AND MODE OF ACTION 



remarkable cone, which it had become customary in Naples 

 to regard as the true summit of the mountain, fell in, with a 

 dreadful noise, in the last eruption, on the night of the 

 22d of October (1822) : so that the floor of the crater, 

 which had been constantly accessible since 1811, is now 

 750 (almost 800 English) feet lower than the northern, and 

 200 (213 English) feet lower than the southern edge of the 

 volcano. Yariations in the form and relative position of 

 the cones of eruption, the openings of which ought not to 

 be confounded, as the}' often are, with the crater of the vol- 

 cano itself, 1 give to Vesuvius at different epochs a different 

 appearance, which would enable a person well acquainted 

 with the history of the volcano, on a mere inspection of 

 Hackert's paintings in the palace of Portici, to tell from 

 the outlines of the summit, according as the northern or the 

 southern side of the mountain is represented as the highest, 

 in what year the artist had taken the sketch from which the 

 picture was made. 



In the last eruption, in the night of the 23d to the 24th 

 of October, twenty-four hours after the falling in of the 

 great cone of scoriae which has been mentioned, and when 

 the small but numerous currents of lava had already flowed 

 off, the fiery eruption of ashes and rapilli commenced : it 

 continued without intermission for twelve days, but was 

 greatest in the first four days. During this period the 

 detonations in the interior of the volcano were so violent 

 that the mere concussion of the air, (for no earthquake 

 movement was perceived), rent the ceilings of the rooms 

 in the palace of Portici; In the neighbouring villages of 



