334 DOMAIN XII. VOLCANIC, 



greatest being, as far as I was able to observe, 

 about eighteen feet, and the least six. Its 

 course is down the west side of the mountain ; 

 and, like the other lava which flowed in July 

 1787 5 it issued immediately from the great cratef 

 of Etna. The whole number of the eruptions of 

 this mountain of which we have any record, 

 before and after the Christian aera, is thirty-one; 

 Eruptions from and ten only, as we are informed by Gioeni, in- 

 cluding that of which he has given an account, 

 have issued immediately from the highest crater* 

 That which I observed may be the eleventh, 

 unless it should rather be considered as the same 

 with that described by the Sicilian naturalist, 

 since the interval between August and October 

 is a very short intermission of rest for a volcano. 

 The cause of the rarity of the eruptions which 

 issue immediately from the crater, compared 

 with those which disgorge from the sides, seems 

 easily to be assigned. The centre of this vol- 

 cano is probably at a great depth, and perhaps 

 on a level with the sea. It is therefore much 

 more easy for the matter liquified by the fire, 

 put in effervescence by the elastic fluids, and 

 impelled on every side from the centre to the 

 circumference, to force its way through one of 

 the sides of the mountain where it finds least 

 resistance, and there form a current; than to be 



