( "3 ) 



of lavas cf this ifland, it will now be proper 

 to proceed to treat of the other volcanic 

 fubftances it contain*?. Among thefe are 

 the tufas, which are found in great abun- 

 dance in other parts of the ifland befide 

 thofe above defcribed. In general they 

 are pulverulent, light, fpungy, of an argilla- 

 ceous nature, and greedily imbibe water. 

 The places in which they are found, are the 

 only parts of the ifland which the inhabit- 

 ants can render productive by cultivation. 



It is among the tufas that we difcover 

 glafles and pumices. We will treat of thefe 

 two fubftances feparately, beginning with 

 the firft. 



I have already faid, that I had fcarc ely 

 landed in Felicuda before I difcovered feve- 

 ral pieces of volcanic glafs. In my fubfe- 

 quent refearches, I afterwards difcovered 

 that this glafs was not found among the la- 

 vas, but in the cultivated earth of the fields. 

 The peafants of thofe parts confirmed the 

 truth of this obfervation, and, finding I was 



VOL. III. I in 



