MODE XII. TUFA, 517 



Romans have employed this stone in the most 

 noble structures, they have but followed the ex^ 

 amples of other people before them. The tem- 

 ples of Pestum, the most ancient monuments 

 that are known after the pyramids of Egypt, 

 were built with a travertine, formed by the de- 

 position of waters which still exist in that dis- 

 trict. This stone, when long exposed to the 

 air, acquires a considerable degree of hardness ; 

 its colour assumes a reddish tinge, pleasing to 

 the eye, and which in no small degree contri- 

 butes to bestow on monuments of antiquity that 

 majestic character which is so striking. Buch 

 justly observes, c that the temples of ancient, 

 the churches and palaces of modern, Rome, 

 would infinitely have lost of their grandeur and 

 majesty, if the bold genius which erected them 

 had not met with such a material as travertine. 

 They would have lost much of their solidity, if 

 the formation of tufa had not given rise to the 

 discovery of puzzolana.' The chance which 

 collects in its vicinity the materials most fit for 

 architecture, travertine, and puzzolana, was not 

 a little happy for Rome. The mortar or cement, 

 which results from a mixture in just proportion 

 of that ferruginous volcanic earth with lime, so 

 much surpasses in hardness all other known 



