MODE XII. TUFA. /J13 



interesting, and shall be given in the words of a 

 skilful observer. 



" The Anio or Tiverone, which descends from 

 the Apennines of Vicovaro and Subiaco, to the 

 east of Rome, before reaching the plain where it 

 unites with the Tiber, crosses Tivoli ; a place 

 equally known to the learned and the artist, by 

 its ancient monuments and its beautiful views* 

 which have employed the pencils of the greatest 

 masters. All the land through which the Anio 

 passes in Tivoli, whether near the great cascade 

 or the smaller ones, is filled with masses of a 

 calcareous stone, produced by the deposition of 

 its waters. Sometimes a piece of rush or reed, or 

 other vegetable matter, is the first point to which 

 the calcareous earth begins to attach itself. It 

 generally deposes in concentric layers, and has 

 the hardness and fibrous tissue of alabaster. 

 These layers are nevertheless separated by a bed 

 of calcareous earth, friable, yellowish, and very 

 fine. At the foot of the mountain of Tivoli, 

 where the Anio enters the plain, which extends 

 to Rome, are the quarries of travertine. This 

 calcareous rock is disposed in horizontal beds : 

 its colour is yellowish white, its grain earthy, 

 fracture uneven, and its hardness far surpasses 

 that of those calcareous masses produced by the 

 Anio, in the neighbourhood of Tivoli. Cavities, 



YOL. i. 2 i. 



