( I90 



Tiieir whitenefs was fubfequently acquired, 

 and probably was caufed by the impreffions 

 of the atmofphere. 



Before I conclude thefe obfervatlons on 

 the Eolian ifles, I think it neceffary to fay 

 a few words on a fubjedl which has a re- 

 lation to the productions of Vulcano and 

 AHcuda, and on which the opinions of 

 modern naturalifts are divided ; I mean the 

 bafahiform lavas which are found within 

 the crater of the former ifland, and along 

 the fhores of the latter *, and which by 

 their conformation cannot but remind the 

 reader of the enquiries and difputes which 

 have taken place wdthin thefe few years 

 relative to the orifrin of bafaltes. To re- 



o 



peat all that has been written on the fubjed: 

 would fill a volume ; but I am far from 

 purpofing to tire either my own or the 

 reader's patience in any fuch manner. It, 

 befides, appears to me that this long agitated 

 queftion may, at prefent, be determined 



* See Chaps. XIII and XVII. 



without 



