S50 On the Bmldin^ Materials used by the Romans, 



This continued to be used, not only during the regal govern- 

 ment, but almost to the fall of the republic. The Career Mamer- 

 tinum constructed by Ancus Marcius ; Cloaca Maxima, the 

 work of the Tarquins ; parts of the Wall of Servius, under the 

 Quirinal ; the sepulchre of the Scipios, and many other ancient 

 monuments, are built of this stone. When Tibur was subdued, 

 A. M., 417, they began to introduce Travertino, which was ever 

 afterwards promiscuously used with the lapis albanus. As it is 

 harder and more compact than peperino, it was particularly used 

 for ornaments, arches, and architraves. Thus, the Doric capi- 

 tals and architrave of the tabularium, the insulated columns of 

 the temple of Fortuna Virilis, and the arch of Dolabella on the 

 Mons Coelius, are composed of this stone. As far as we can . 

 perceive from the remains of antiquity, square masses of stone 

 were used during the kings and the republic. But on its de- 

 cline, they introduced that sort of construction which Vitruvius 

 calls Opus Incertum, and which must not be confounded with 

 diat formed of large polygons, which we see at Cora, Prasneste, 

 and other ancient cities of Latium. Vitruvius, indeed, tells us, 

 and we can perceive it from the ruins, that this opus incertum 

 consisted of small stones mixed with mortar. There is an ex- 

 ample of it in Rome in the temple of Romulus, under the Pala- 

 tine ; at Tivoli, in the temple of Vesta ; at Praeneste, i^ the tem- 

 ple of Fortune, and in many other ruins scattered through the 

 country. On the contrary, the vi^alls of the above mentioned 

 places are built of massive polygons of three, four, and five feet 

 in length, and without mortar. The opus incertum is only an 

 outward facing of the wall, and is supported behind by a mass 

 of every sort of material. ' 



The opus incertum, was soon succeeded by the opus reticular 

 turn, which is mentioned, by Vitruvius, as the fashionable archi- 

 tecture ^f his age, andwhich continued to be, more or less, used 

 down to the reign of Caracalla. This reticulated construction 

 derived its name from its resemblance to net-work, and was 

 formed of stones found in the neighbourhood, which were cut 

 into the form of coves. At Rome the stone is tuffa ; at Prae- 

 neste, calcareous limestone ; at Tivoli, travertino ; and at Tus- 

 culum, a kind of peperino, which the Itahans call Piatra Tus- 

 culana. As this particular sort of construction could not be 



