ITALY. LETTER XIX. 2J 



tiful and great Carthufian Monaftery, three miles 

 diftant from Florence. But I have fome very 

 good reafons to fuppofe this Gabbro, near Impru- 

 9teta t to be fuperincumbent on limeftone ; for beyond 

 this monaftery arife found limeftone-hills, which 

 you afcend, till within a mile from Impruneta you 

 reach the Gabbro, on which you afcend further 

 up to Impruneta. On the hill where this place 

 is fituated, behind and fideways of it, they have 

 occafionally funk a pit in the Gabbro, and found 

 under it a grey compact limeftone with pyritical 

 nodules. Not far off, in another pit, they have dif- 

 covered a remarkably large ftratum of clay of a 

 blueifh-grey or yellowifh, which dips between forty- 

 five and feventy-five degrees, and furnifhes the 

 potters at Impruneta with the materials for their 

 pottery; which confifts of great vafes, and gets 

 reddifh in the fire. The fingular fituation of this 

 clay in and between the Gabbro, together with 

 its different mixtures, caufe feveral opinions on its 

 origin. It is fomewhat mixed with lime , accord- 

 ingly it is of the marl-kind, and it is acted upon 

 by acids. This is probably owing to the inferior 

 lime. The reddiih colour, when baked, may be 

 afcribed to a mixture of iron particles of the py- 

 ritical nodules in the limeftone. The fmall pieces 

 of felenite offering in this clay may have been 

 T 2 produced 



