28^ Baron Humboldt on the Structure and Action of 



the bottom of the crater, which, since 1811, was always acces- 

 sible, is now 750 feet lower than the northern edge of the vol- 

 cano, and 200 feet lower than the southern. The variable 

 form and relative position of the cones of eruption, whose aper- 

 ture ought not, as is too often done, to be confounded with the 

 crater of the volcano, give a particular aspect to Vesuvius at 

 different periods, and the historiographer of this volcano might, 

 from the contours of the summit, and from the simple inspection 

 of the landscapes painted by Hackert, which are at Portici, ac- 

 cording as the northern or southern side of the mountain is re- 

 presented higher or lower, guess the year in which the artist 

 made the drawing from which he composed his picture. 



A day after the cone of scoriae, 400 feet high, had fallen in, 

 when already small but numerous torrents of lava had flowed, 

 in the night of the 23d October, commenced the luminous erup- 

 tion of ashes and rapilli. It lasted twelve days without inter- 

 ruption ; but it was more intense during the first four. All this 

 time, the detonations in the interior of the volcano were so vio- 

 lent, that the mere concussion of the air (for no commotion was 

 observed in the earth), cracked the ceilings of the apartments in 

 the palace of Portici. The villages of Resina, Torre-del-Greco, 

 Torre del Anunziata, and Bosche-Tre-Case, which are close up- 

 on the mountain, witnessed a remarkable phenomenon. The 

 atmosphere was so filled with ashes, that the whole district was 

 for several hours in the middle of the day enveloped in profound 

 darkness. People used lanterns in the streets, as often hap- 

 pens at Quito, during the eruptions of Pichincha. The inhabi- 

 tants never fled in such numbers. The torrents of lava were 

 much less dreaded than an eruption of ashes, — a phenomenon 

 which had not before been known to such a degree, and which, 

 from the obscure tradition of the manner in which Hercula- 

 neum, Pompeii and Stabiae were destroyed, filled the imagination 

 of men with terrifying images. 



The watery and hot vapour which shot up from the crater 

 during the eruption, and diff'used itself in the atmosphere, form- 

 ed, on cooling, a thick cloud round the column of ashes and 

 flame which rose to the height of 9000 feet. So rapid a con- 

 densation of the vapours, and, as M. Gay Lussac has shewn, the 

 very for^nation p( the cloud, augmented the electrical intensity. 



