STRUCTURE AND ACTION OF VOLCANOS. 365 



of which, the bottom of the crater, which had continued unin- 

 terruptedly accessible from the year 1811, is now nearly 800 

 feet below the northern and 213 feet below the southern 

 margin of the volcano. The varying form and relative posi- 

 tion of the cones of eruption, the apertures of which must not, 

 as they sometimes are, be confounded with the crater of the 

 volcano, give to Vesuvius at different epochs a peculiar 

 physiognomy; so much so, that the historiographer of this 

 volcano, by a mere inspection of Hackert's landscapes in the 

 Palace of Portici, might guess the exact year in which the 

 artist had made his sketch, by the outline of the summit 

 of the mountain, according as the northern or southern side is 

 represented in respect to height. 



Twenty-four hours after the fall of the cone of scoriae, which 

 was 426 feet high, and when the small but numerous streams 

 of lava had flowed off, on the night between the 23rd and 

 24th of October, there began a fiery eruption of ashes and 

 rapilli, which continued uninterruptedly for twelve days, but 

 was most violent during the first four days. During this 

 period the explosions in the interior of the volcano were so loud 

 that the mere vibrations of the air caused the ceilings to crack 

 in the Palace of Portici, although no shocks of an earthquake 

 were then or had previously been experienced. A remarkable 

 phenomenon was observed in the neighbouring villages of 

 Eesina, Torre del Greco, Torre del' Annunziata, and Bosche 

 Tre Case. Here the atmosphere was so completely saturated 

 with ashes that the whole region was enveloped in complete 

 darkness during many hours in the middle of the day. The 

 inhabitants were obliged to carry lanterns with them through 

 the streets, as is often done in Quito during the eruptions of 

 Pichincha. Never had the flight of the inhabitants been more 

 general, for lava streams are less dreaded even than an erup- 

 tion of ashes, a phenomenon unknown here in any degree of 

 intensity, and one which fills the imaginations of men with 

 images of terror from the vague tradition of the manner 



