ETNA 383 



crater during the period of our visit, but an excursion to the top in the 

 early morning of July 23 made by the guides alone revealed several 

 bright cracks, both within the well and to the eastward of it. 



The second conspicuous opening is a cone filling the eastern half of 

 the crater floor and perhaps 100 meters high. The present appearance 

 of this cone indicates an explosive origin. This opening is exactly oppo- 

 site the outside crater and immediately suggests a connection between the 

 two. We did iiot, however, during the limited period of our observations, 

 discover any connection between the occasional explosions emanating 

 from iliis coiu> ;iiul tlio activiiy of ilir outer crater. The explosions from 

 this inner cone were ofteji vioIiMii and yielded treniciidous volumes of 

 smoke, wliicli emerged in the usual cauliflower form, very black and 

 heavily dust-laden (plate 17). On one excursion to the summit during 

 the evening of July 16 a considerable outburst was seen coming from this 

 opening, accompanied by a flash of light and a dense cauliflower cloud, 

 but with no sound of explosion nor of falling rocks following the flash. 

 No incandescent matter was visible at that time. On another occasion 

 (July 23) loud explosions were frequent, accompanied by the usual caidi- 

 flower clouds, but no flashes. 



In appearance this inner cone is jagged and irregular, though roughly 

 square in form, with very steep, smooth inner walls closing together to a 

 narrow black throat in which all detail was lost in smoke, even on the 

 most favorable days. The outer surface of the inner cone is concealed 

 under fresh ash. Surface slides are frequent and appear to indicate that 

 the ash is dry and has the maximum steepness of slope at which such 

 material can come to rest. 



The bottom of the crater Avas over 450 meters deep, according to meas- 

 urements with a plummet-line in the hands of our guides, A. Barbagallo 

 and D. Caruso, who returned to the crater after our departure for that 

 purpose. The line did not quite reach the bottom. 



The new outer **bocca," or crater, on the northeast slope of the cone is 

 about 80 meters below the summit. It is shown in plate 19. When first 

 formed it was roughly triangular and about 100 meters across. It is now 

 approximately circular and about 200 meters in diameter. Owing to falls 

 of the sides, especially on the side toward the main crater, it is cutting 

 rapidly into the cone and its southwest edge is now less than 100 meters 

 from the crater rim. So far as could be seen through the clouds of smoke 

 which filled it, the sides are vertical, but not even a glimpse of the bottom 

 was to be had and no estimate of its depth was possible. No glow or flash 

 could be seen in this crater during any of our visits, day or night. 



There was a constant emission of clouds of a dense, dark gray smoke, 

 which came in huge puffs at irregular intervals, sometimes welling slowly 



XXX- Rfi-r- r,For.. Soc. Am.. Vor,. iR, 1014 



