ITALY. LETTER XIX. 27! 



harder and more durable. It ferves in the exterior 

 parts and walls of the buildings as the pietra fs- 

 rcna in the inner parts and decorations, which are 

 lefs expofed to the air. The fuperior beds, which 

 are ftrongly mixed with clay, go here in the quar- 

 ries under the name of pietra worta, and thi$ 

 ferves in the walls of furnaces and fire-places. 



2. Cave di pietra forte die Camp or a, two miles 

 diftant from Florence. The pieira forte is the 

 found, fine-grained, yellow-grey, or blueifh lime 

 ormarl-ftone; which is employed in the pavings 

 of Florence. It is found not only alls Camper a^ 

 but likewife at 5. Franc efco di Paolo in a wide-* 

 ftretching low ridge of hills, three miles diftant 

 from the city to the South- weft. The pietra forte 

 alle Campora is found generally in horizontal beds, 

 three or four inches thick, fuperincumbent one to 

 the other, but now and then, feparatcd by fimilar 

 beds of hardened clay, called Bardelloni. In thefe 

 Uft beds frequently offer little veins of calcareous 

 fpar, not above one or two twelfth parts of an 

 inch thick ; and the pitfra forte is throughout pe-, 

 retrated and glued by fpar, wherein it is remark- 

 ably different from the Bardelloni, which are but 

 argillaceous. The pietra forte before this fatu ra- 

 tion with fpar feems to have been but Bardellone-, 

 as Bardellone would have been changed into pietra 

 forte if the calcareous folution or glu.e had not 

 4 been 



