252 On the Building Materials used hy the Romans. 



to Diocletian there are few remains, and even of these we are 

 unable to fix the exact period when they were erected. 



It is curious to observe, that they now began to be economi- 

 cal in the use of bricks, and that they introduced a mixture of 

 tuffa, as is evident from the restoration of the tomb of the Sci- 

 pios, the circus of Caracalla, and the ruins adjacent to the cir- 

 cus. The numerous churches and basilicos, which were erected 

 by the Christians in the fourth, fifth, and sixth centuries, such 

 as St Croce a Gerusalemme, St Geovanni e Paolo, St Paolo, St 

 Pietro in Vincoli, &c. and the walls which surround Rome on 

 the left bank of the Tiber, and which are of the age of Hono- 

 rius, exhibit the same poverty of materials ; they have bricks of 

 all sizes, with a great quantity of cement, which is of inferior 

 quality to that used in earlier times. On the fall of the Roman 

 empire, they even neglected the selection of proper materials to 

 form their bricks, and even employed those which they took 

 from more ancient buildings. At last they invented a method 

 of cutting the softer stones, tuffa and peperinos, into small rect- 

 angular masses, and discarded entirely the use of bricks. The 

 Italians call this Opera Saracinesca, because it was introduced 

 when the Saracens occupied Italy. The walls of the Vatican, 

 built by Leo IV. in the ninth century, are the first specimens 

 which we have of it in Rome. This sort of construction con- 

 tinued to be used during the barbarous ages till the fourteenth 

 century ; the castle of Capo de Bove, near the sepulchre of Me- 

 tella, built by Pope Boniface VIII., is a beautiful specimen of 

 it. They sometimes cut marble in this rectangular shape, as 

 may be seen in Sorre de'' Conti, a work of Innocent III. of the 

 thirteenth century. 



To conclude this part of our subject, we may remark, that 

 the Romans during the kings, and the time of the republic, em- 

 ployed in the public edifices square masses of stone ; on the de- 

 cline of the republic, they introduced opus incertum ; under Au- 

 gustus opus reticulatum and lateritium were promiscuously 

 used; the opus reticulatum ceased under the Antonines, but 

 the brick-work continued to the seventh century, and was suc- 

 ceeded by the opera Saracinesca. 



We must reserve the observations we have to make on an- 

 cient marbles, granites, porphyries, and alabaster, till another op- 

 portunity. 



