Chap. 49.] THE VARIOUS KINDS OF SILEX. 3/1 



CHAP. 48. TOPHirS. 



Among the multitude of stones which still remain unde- 

 Fcribed, there is tophus f' a material totally unsuited for build- 

 ing purposes, in consequence of its perishableness. Still, how- 

 ever, there are some localities which have no other, Carthage, 

 in Africa, for example. It is eaten away by the emanations 

 ,from the sea, crumbled to dust by the wind, and shattered by 

 the pelting of the rain : but human industry has found the 

 means of protecting walls of houses built of it, with a coating of 

 pitch, as a plaster of lime would corrode it. Hence it is, 

 that we have the well-known saying, " that the Carthaginians 

 use pitch^^ for their houses and lime^** for their wines," this 

 last being the method used by them in the preparation of their 

 must. 



In the territories of Fidense and Alba, in the vicinity of 

 Home, we find other soft kinds of stone ; and, in Umbria and 

 Venetia, there is a stone^^ which admits of being cut with the 

 teetli of a saw. These stones are easy to be worked, and are 

 capable of supporting a considerable weight, if ihej are only 

 kept sheltered from the weather, llain, however, frost, and dew, 

 split them to pieces, nor can they resist the humidity of the 

 sea-air. The stone^^ of Tibur can stand everything except 

 heat, which makes it crack. 



CHAP. 49. THE VAKIOUS KINDS OF SILEX. 



The black silex^^ is in general the best ; but in some local- 

 ities, it is the red, and occasionally the white ; as in the 

 Anician quarries at Tarquinii, near Lalie Volsinius,^^ for ex- 

 ample, and those at Statonia,^^ the stone of which is proof 

 against fire even. ''^ These stones, sculptured for monumental 



32 Identical, probably, with the Tufa of modern Mineralogy, which 

 thence derives its name, a Carbonate of lime. 



33 Thus reversing the order of things with the Romans, who put the 

 lime on their liouses, and the pitch in their Avines. See B. xiv. cc. 3, 24, 



25. 34 See B. xiv. c. 24, ^s a white tufa, Vitruvius says, B. i. c, 7. 



39 It was in reference, possibly, to tliis etone that Cicero made the re- 

 mark, mentioned in Chapter 5 of this Book ; the heat of Chios being so 

 great, perhaps, that the Tiburtine stone could not have endured it. 



3T A general name for Silica, Flint, or Quartz, and the several varieties. 



3« See B. iii. c. 8. 39 See B. ii. c. 96, B. iii. c. 9, and B. xiv. c. 8. 



*o Ajasson thinks that Travertine is meant; a tufa, or carbonate of lime, 

 which is common in Tuscany.. * 



B B 2 



