114 



INTERIOR OF CRATERS. 



explains what frequently takes place in volcanoes, and, for exam- 

 ple, at Vesuvius (fig. 199), where domes have been raised which 

 remained for a long time, and were subsequently broken, giving 

 passage to lavas, and finally sank into abysses left beneath them. 

 Certain craters, having a widely extended bottom, often contain 

 hills of considerable height, which have had an origin such as we 

 have described; either the lava is arrested at a certain height, in 



Fig. 199. Adventitious Crater, in the middle of Vesuvius, in 1829. 



form of a cap, or swelled up at different points, or elevations took 

 place in different matters which had filled the cavity. 



28. Sometimes, in place of lava, there is found at the bottom of 

 craters boiling sulphur, as was seen at Vulcano, and, on a larger 

 scale, at the volcan of Taal, in the island of Luzon, and at that of 

 Azufra., to tne north of Quito, in the Andes ; hills, and even 

 domes of sulphur, are also mentioned, as M. Boussingault observed 

 at the volcan of Pasto. 



A crater now often mentioned by voyagers is that of Kirauea, on the island 

 of Hawaii, one of the Sandwich group. This vast cavity is three and a 

 naif miles long 1 and two and a half wide, and over a thousand feet deep : 

 Uaplain Wilkes, in his narrative of the United States Exploring Expedition, 

 r-tate? that "the city of New York might be placed within it, and when at 

 Us bottom would be hardly noticed. A black ledge surrounds it at the depth 

 f 660 feet, and thence to the bottom is 384 feet. The bottom looks in the 



26. Is anything found at the bottom of craters besides lava? 



