100 TRAVELS THROUGH 



the proprietors of the ground fell by the pound. 

 Even the ftreets are in many places, and efpecially 

 before St. Peter's church, paved with fepentino 

 antico, porphyry, and antique marbles. So are 

 the floors of the churches and palaces. I 

 will now fpeak to you only of the pietra daftica, 

 in the palace Borghefe. It confifts of feveral 

 flabs or tables of a white antique marble, which 

 are faid to have been cut from a cornice- block 

 belonging to an old building. Thefe tables are 

 about four palmi Romani in length, one palm in 

 breadth, and two inches thick. One of thele pieces 

 is defigned to be fhewn to {hangers, the others 

 are fet up as fide-boards. This table, being 

 put with the larger end on the ground and making 

 it, gives on both fides an alternating belly, but 

 fprings by an elaflic motion and with a cracking 

 found into its former form. It is a white antique 

 marble, affected by aqua fortis, and compofed, as 

 appearing under the microfcope, of tranfparent 

 cryftalline grains. Its flexibility is undoubtedly 

 owing to an imperfect connection of its grains. 

 This was loft, perhaps, by the action of the air, 

 or by a foft calcination of fire, which deftroyed 4 

 part of its natural cement : fo that, the plate being 

 bent, thefe particles are forced to roll or fhift, 

 which produces the crackling found. Its friabi- 

 iity, which is fuch that even the nail of a finger 



makes 



