Chap. 49.] THE VABIOUS KINDS OF SILEX. 371 



CHAP. 48. TOPHUS. 



Among the multitude of stones which still remain unde- 

 Fcribed, there is tophus; 3 - a material totally unsuited for build- 

 ing purposes, in consequence of its pcrishableness. 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. Henoo it is, 

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

 use pitch 33 for their houses and lime 34 for their wines," this 

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

 must. 



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

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

 Venetia, there is a stone 3 * which admits of being cut with the 

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

 capable of supporting a considerable weight, if they are only 

 kept sheltered from the weather. Itain, however, frost, and dew, 

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

 sea-air. The stone 36 of Tibur can stand everything except 

 heat, which makes it crack. 



cn\i'. 49. TIIK VARIOUS KINDS OF SILKX. 



The black silex 37 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 Lake Volsiuius, 35 for ex- 

 ample, and those at Htaonia, M the stone of which is proof 

 against lire even. 40 These stones, sculptured for monumental 



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

 thence derives its mime, a Carbonate of lime. 



-* Thus reversing the order of things with the Romans, who put the 

 lime ou their houses, and the pitch in their wines. See 13. xiv. cc. 3, 24, 

 '2b. 31 Sec 13. xiv. c. 24. " A white tufa, Vitruvius says, 15. i. c. 7. 



: ' It was in reference, possibly, to this etoiu? that Cicero made the re 

 mark, mentioned in Chapter 6 of this 15ook ; the heat of Chios being so 

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



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



s< * See 15. iii. c. 8. 3<J See B. ii. c. DO, 1?. iii. c. 9, and K. xiv. c. 8. 



40 Ajashcm thinks that Travertine is uieautj a tufa, or carbonate of lime, 

 which u cwiumou in Tuscany.. 



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