l6o COMPARATIVE ARCHITECTURE. No. 6i, some of the arch voussoirs of the internjediate tier projected to carry the temporary centering. Other aqueducts exist at Tarragona and Segovia, Spalato and elsewhere. BRIDGES. The chief characteristics of Roman bridges were solidity and simplicity, with a view to their withstanding the ravages of time and the elements. The roadway was generally kept le^el throughout. The Bridge at Rimini is the best preserved in Italy and has five arches. There are examples of two types of Roman bridges in Spain which are equally impressive, (a.) The many-arched type, as exemplified in the extreme length of the bridges at Cordova and Alcantara. (/;.) The single-arched type, of which the romantic sweep of the bridge at Toledo, spanning the rocky 'alley of the Tagus, is the best example. PALACES. Of the Roman palaces the ruins only remain, but there is enough to show their enormous extent and imposing character. The Palaces of the Roman Emperors. — The principal approach was from the Forum Romanum, by a road which branched off from the Via Sacra, on the west side of the Arch of Titus (No. 47). Excavations on the Palatine Hill, commenced by Napoleon III. in 1863, and afterwards continued by the Italian Government, have revealed remains of a group of magnificent palaces. These, commenced by Augustus (a.d. 3), and having additions by Tiberius, Caligula, Nero and Domitian, were remodelled by Septimius Severus, and the giant remains attributed to him will probably impress the student of architecture most when visiting the site. The chief apartments in these palaces were : — The Tablinum or Throne-room; the Basilica, or hall for administering justice; the Peristylium, a square garden surrounded by a colonnade ; the Triclinium, or banqueting hall ; the Lararium, or apartment for statues of the household gods ; and the Nymphasum. Besides these there were many minor chambers of service, whose uses cannot now be ascertained. The disposition of the buildings was governed by axial lines producing magnificent vistas. Irregular spaces, caused by additions being made from time to time, were rendered sym- metrical by the use of hemicycles and other devices, disguising the
