MODE III. BASALTIC. 



cano suddenly burst out in the vale of Jorullo, 

 1759; when, according to Humboldt, who saw 

 it in 1803, a basaltic cone appeared above 

 ground, of 1400 feet in height: but this cone 

 seems rather to have been developed than ele- 

 vated by the new volcano, as it could scarcely 

 be formed from fluid lava, which would be con- 

 tradictory to the common laws of hydrostatics. 

 The accounts of the volcanoes in the Andes are 

 far from being complete ; but there seems to be 

 little or no mention of basalt, and no hint of ba- 

 saltic columns ; which, if they were volcanic, 

 would be truly surprising in a chain which ex- 

 tends more than three thousand miles, and con- 

 tains about a hundred active volcanoes. 



But as the presence of iron seems necessary 

 to volcanic inflammation, and the same metal 

 forms the ruling ingredient of basalt, it is no 

 wonder that this coincidence should have occa- 

 sioned a confusion of ideas. Around the grand 

 volcano of the isle of Bourbon, there are basaltic 

 rocks ; and where the basaltin contains sulphur, 

 it may be presumed to be a compact lava ; but 

 here are no ranges of those grand basaltic co- 

 lumns which distinguish Faroe, or Staffa. Jf we 

 return to Europe, the grand volcano of Etna has 

 probably been in a state of conflagration for 

 2500 years, and the circumference is computed 



