Starting with a geological discussion of the soil on which the city is built, we are introduced to the original materials for building in Rome and its immediate neighborhood. There is abundant evidence of volcanic action in the tufaceous rock which is characteristic of the region; and this is associated with the depositions of water--both salt and fresh--and in some cases has been manifestly modified by their action. Indeed, there is proof that the valleys between the famous hills were marshes, frequently flooded by the Tiber, down into the early period of Roman history. There are two sorts of tufa, one more granular, and so lighter than the other, as well as a fair portion of a limestone rock, named travertine, harder than either of the tufas; besides these there is capital clay for bricks, and matter which makes the best mortar in the world. We are not surprised, therefore, to find that not only during the Republic, but in later times, when, under the emperors, the wealth and luxury of the Romans was boundless, the main substance even of the most magnificent of their buildings was brick; and marble 'facings,' columns, and pavements came in to give finish and beauty to their solid brickwork. Indeed, to this fact we owe it that so much is still left to us. The barbarous rapacity of the Middle Ages, which ruthlessly appropriated these enrichments, would no doubt have taken all, had all been marble. Our author regards the myths which connect the early Romans with the Greeks, and with the Trojans under Æneas, as belonging rather to the domain of poetry than history, and confining himself to the facts as illustrated by these ruins, begins with the Palatine, as the hill originally occupied by the first fathers of the Romans; and he gives us, in chronological order, as far as possible, notices of all ruins now uncovered there. He then passes on to the Capitoline, as having been occupied next in point of time, dealing with it in the same manner; after this we return southward to the Aventine; thence, turning east, we cross the valley of the Circus Maximus to the Cælian Hill, and then proceed northward to the Esquiline, the Viminal, Quirinal, and Pincian, in succession. On all these we are introduced to the remains of ancient buildings; their chronology, their identity, their extent, their present condition, and their associations with such historic matter as has come down to us, are all set before us with great accuracy of detail. Then we cross the Tiber, and visit Janiculum and the Vatican Hill; recrossing into the valleys among the hills, we visit the Circus Maximus, the Campus Martius (now occupied by the modern city), and the Via Lata. The 'Forum' (Romanum) is discussed in the earlier part of the work, and with it the Fora of the emperors, which were meant to supersede it and its associations, and did so. The line of the walls of Servius, built mainly of the tufa already mentioned, in large rectangular blocks, is traced