on the Materials used in the city of Rome. 33 ' 



near the same place, very improbably called the prisons of Ma- 

 rius ; also in the ancient wall at the Forum of Nerva in Rome. 

 Afterwards, though for buildings of very great solidity like the 

 Colisseum, quadrilateral blocks were used, a minute covering 

 to the wall called " opus incertum" was introduced towards 

 the end of the republic. It was merely a covering for the in- 

 terior mass of the wall, and was composed of small irregular 

 polygons, as represented at Fig. 7. We have a beautiful ex- 

 ample in the temple of Vesta at Tivoli, in the church of St 

 Theodore in the forum, and at Preneste ; likewise in the north 

 of Italy, in a temple disinterred last season at Brescia, and in 

 the villa of Catullus on the Lago di Guarda. * After a short 

 time, two other styles of building succeeded the " opus incer- 

 tum? viz. the " opus reticulatum et lateritium" These con- 

 tinued in extensive use for two centuries between Augustus and 

 Caracalla. The specimens we have of them are innumerable. 

 The former was an exterior facing to the wall like the " incer- 

 tum? but the pieces were perfectly rectangular, and set lozenge- 

 wise, as shown at Fig. 8 ; the pieces being small, were made of 

 any stone most easily attainable ; at Rome, of tufa, — at Tivoli, 

 travertino, — at Preneste, limestone, &c. As it could not be em- 

 ployed for the corners of buildings, these were generally made 

 of large flat bricks. Of this workmanship we have examples 

 in the gardens of Sallust and baths of Titus at Rome, and at 

 the villas of Mecaenas and Adrian at Tivoli, besides many beau- 

 tiful specimens in southern Italy, as at Cicero's Formian Villa, 

 the Tomb of Virgil, and the buildings on the Bay of Baiae, 

 whose remarkable appearance is mentioned in the first note of 

 this paper. The common brickwork, or " opus lateritium? 

 was yet more generally employed. In the Augustan age, the 

 bricks were little more than an inch in thickness, and triangu- 

 lar, and always of red clay. Under Tiberius, the clay was mix- 



* This villa of Catullus affords an excellent example of the practical use 

 of a knowledge of the different styles of building. It is quite evident that 

 on the Sirmian promontory are two sets of building totally unconnected, a 

 confusion between which has much puzzled antiquaries. The one next the 

 lake is almost Saracenic building, while that on the top of the hill, a little 

 way off, presents exactly the opus incertum of Vitruvius, which, as it seems 

 not to have been long employed, fixes the date so exactly to that of Catul- 

 lus, (first century, B. C.) as to leave little doubt as to its authenticity. 



VOL. IX. NO. I. JULY 1828, c 



