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Rh pretender Michael VII., but was compelled after a defeat to resign the empire and retire to the island of Prote, where he soon died in great misery. It was during this reign that, by the surrender of Bari (1071), the Byzantine empire lost its last hold upon Italy.

 ROME (Roma), the capital of the modern kingdom of Italy, in the province of Rome, on the river Tiber, 17 miles N.E. from its mouth on the Mediterranean. As formerly the centre of the ancient Roman republic and of the Roman empire, and the headquarters of the Christian Church, Rome is unique among historical cities, and its antiquarian interest far surpasses that of any other locality in the world. In the following account the general subject of Rome is treated broadly under two aspects, themselves subdivided. These are:—(1) the topography and growth of the city of Rome, the evolution of which is traced from the earliest times to the present, and (2) Roman history, i.e. the political and social history of the Roman republic, empire and medieval commune.

The nine or ten hills and ridges on which the city stands are formed of masses of tufa or conglomerated sand and ashes thrown out by neighbouring volcanoes now extinct, but active down to a very recent period. One group of these volcanoes is that around Lago Bracciano, while another, still nearer to Rome, composes the Alban Hills. That some at least of these craters have been in a state of activity at no very distant period has been shown by the discovery at many places of broken pottery and bronze implements below the strata of tufa or other volcanic deposits. Traces of human life have even been found below that great flood of lava which, issuing from the Alban Hills, flowed towards the site of Rome, only stopping about 13 miles short, by the tomb of Cecilia Metella.

The superficial strata on which Rome is built are of three main kinds: (1) the plains and valleys on the left bank of the Tiber are covered, as it were, by a sea of alluvial deposits, in the midst of which (2) the hills of volcanic origin rise like so many islands; and (3) on the right bank of the Tiber, around the Janiculan and Vatican Hills, are extensive remains of an ancient sea-beach, conspicuous in parts by its fine golden sand and its deposits of greyish white potter’s clay. From its yellow sand the Janiculan has been sometimes known as the Golden Hill, a name which survives in the church on its summit called S. Pietro in Montorio (Monte d'Oro). In addition to these three chief deposits, at a few places, especially in the Aventine and Pincian Hills, under-strata of travertine crop out—a hard limestone rock, once in solution in running water, and deposited gradually as the water lost its carbonic-acid solvent, a process still rapidly going on at Terni, Tivoli and other places in the neighbourhood. The conditions under which the tufa hills were formed have been very various, as is clearly seen by an examination of the rock at different places. The volcanic ashes and sand of which the tufa is composed appear in parts to lie just as they were showered down from the crater; in that case it shows but little sign of stratification, and consists wholly of igneous products. In parts time and pressure have bound together these scoriae into a soft and friable rock; in other places they still lie in loose sandy beds and can be dug out with the spade. Other masses of tufa again show signs either of having been deposited in water, or else washed away from their first resting-place and redeposited with visible stratifications; this is shown by the water-worn pebbles and chips of limestone rock, which form a conglomerate bound together by the volcanic ashes into a sort of natural cement. A third variety is that which exists on the Palatine Hill. Here the shower of red-hot ashes has evidently fallen on a thickly growing forest, and the burning wood, partly smothered by the ashes, has been converted into charcoal, large masses of which are embedded in the tufa rock. In some places charred branches of trees, their form well preserved, can be easily distinguished. The so-called “wall of Romulus” is built of this conglomerate of tufa and charred wood; a very

perfect section of the branch of a tree is visible on one of the blocks by the Scalae Caci.

So great have been the physical changes in the site of Rome since the first dawn of the historic period that it is difficult now to realize what its aspect once was. The Forum Romanum, the Velabrum, the great Campus Martius (now the most crowded part of modern Rome), and other valleys were once almost impassable marshes or pools of water (Ov. Fasti, vi. 401; Dionys. ii. 50). The draining of these valleys was effected by means of the great cloacae, which were among the earliest important architectural works of Rome (Varro, Ling. Lat. iv. 149); Again, the various hills and ridges were once more numerous and very much more, abrupt than they are now. At an early period, when each hill was crowned by a separate village fort, the great object of the inhabitants was to increase the steepness of its cliffs and render access difficult. At a later time, when Rome was united under one government, the very physical peculiarities which had originally made its hills so populous, through their natural adaptability for defence, became extremely inconvenient in a united city, where architectural symmetry and splendour were above all things aimed at. Hence the most gigantic engineering works were undertaken: tops of hills were levelled, whole ridges cut away, and gentle slopes formed in the place of abrupt cliffs. The levelling of the Velia and the excavation of the site for Trajan’s forum are instances of this. The same works were continued in the middle ages, as when in the 14th century an access was made to the Capitoline Arx from the side of the Campus Martius; up to that time a steep cliff had prevented all approach except from the side of the Forum.

Finally, after Rome had become the capital of united Italy, in the last quarter of the 19th century, an extensive government plan (piano regulatore) was gradually carried out, with the object of reducing hills and valley to a uniform level and constructing wide boulevards on the chessboard method of a modern American city. The constant fires which have at times devastated Rome have been a powerful agent in obliterating the natural contour of the ground; and the accumulated rubbish from this and other causes has in some places overlaid the ground to a depth of 40 ft., notably in the valleys.

The chief building materials used in ancient Rome may be enumerated as follows: (1) Tufa, the “ruber et niger tophus” of Vitruvius (ii. 7), varying in colour from warm brown to yellow or greyish green (called capellaccio). The Aventine, Palatine and Capitoline Hills contained quarries of the tufa, much worked at an early period (see Liv. xxvi. 27, xxxix. 44, and Varro, L.L. iv. 151). It is a very bad “weather-stone,” but stands well if protected with stucco (Plin. H.N. xxxvi. 166). (2) Lapis Albanus, from Alba Longa, of volcanic origin, a conglomerate of ashes, gravel and fragments of stone; its quarries are still worked at Albano and Marino. This is now called peperino, from the black scoriae, like peppercorns, with which the brown conglomerate mass is studded. (3) Lapis Gabinus, from Gabii, very similar to the last, but harder and a better weather-stone; it contains large lumps of broken lava, products of an earlier eruption, and small pieces of limestone. According to Tacitus (Ann. xv. 43), it is fire-proof, and this is also the case with the Alban stone. Lapis Gabinus is now called sperone. (4) Silex (mod. selce), a lava from the now extinct volcanoes in the Hills, used for paving roads; when broken into small pieces and mixed with lime and pozzolana it formed an immensely durable concrete. It is dark grey, very hard and breaks with a slightly conchoidal fracture (Plin. H.N. xxxvi. 135; Vitr. ii. 7), but does not resemble what is now called silex or flint. (5) Lapis Tiburtinus (travertine), the chief quarries of which are at Tibur (Tivoli) and other places along the river Anio; a hard pure carbonate of lime, of a creamy white colour, deposited from running or dripping water in a highly