ITALY. LETTER XI. " 37 



compofed, I. Of grey afhes mixed with pumice- 

 ftones. 2. Of grey blueifh lava fprinkled with 

 thin and black Iherl-flakes. 3. Of black lava 

 mixed with white garnet-like polygone fherl-cryf- 

 tallizations. They are fuperincumbent one to an- 

 other, without any order, except that the cineri- 

 cious or afh-ftrata are more frequent than the lava 

 beds. Perhaps each lava bed may be confidered 

 as a monument of as many eruptions. Through 

 thefe horizontal beds fink vertical or nearly verti- 

 cal veins, about three feet large, filled up either 

 with grey blueilh lava, which is porous and honey- 

 combed towards the middle, and contains now and 

 then black Iherl-flakes; or with black greyifh 

 lava, which contains white farinaceous decayed 

 garnet-like fnerl-cryflallizations. Thefe perpendi- 

 cular veins may be confidered as fiftures, caufed 

 by earthquakes and by following eruptions filled 

 with lava. 



I have mentioned already feveral productions of 

 Vefuvius ; but I give you now a defcnption of all 

 their fpecies. Every eruption produces new varie- 

 ties ; but upon the whole they agree. Therefore 

 I (hall notice them without regarding, whether 

 they are owing to old or new eruptions , and I 

 lhall defcribe as many varieties as I have happened 

 to fee, either in different collections, efpecially in 

 Abbate Bofti's, which was the compleateft of that 



kind, 



