NOME II. VESICULAR LAVA. 349 



the liquid lava of Etna, either at the time when 

 Baron Riedesel visited the crater, or when I 

 observed it in a state of slight commotion within 

 the gulf, it must immediately have swelled in 

 every part, beating violently against the sides of 

 the caverns in which it was imprisoned, thun- 

 dered among the deep cavities, and, bursting 

 forth through the sides, have poured out a river 

 of fire; or should its violence have been there 

 resisted, it would have rushed up within the 

 crater, until it overflowed its brink, and deluged 

 the sides of the mountain with its torrents. 



" Sir William Hamilton, on the 26th of Octo- Hamilton, 

 ber, 1769, arrived at the summit of Etna with 

 great difficulty, on account of the snows he met 

 with in his way, the severity of the atmosphere, 

 the sulphureous vapours, and the violence of the 

 wind. He was unable to view distinctly the 

 lower parts of the crater, being prevented by 

 the great quantity of smoke which issued from 

 it; though when this smoke was sometimes dri- 

 ven away by the wind, he could discover that 

 the crater was shaped like a funnel, diminishing 

 until it ended in a point ; and that this funnel 

 was incrusted over with salt and sulphur. The 

 crater was two miles and a half in circumference. 



" From the time therefore of the journey of 

 Baron Riedesel to that of Sir William Hamilton, 



