The “Seven Hills” of Rome have really become eight, as the city has extended. Not one of these is lofty, but they give a diversity to the city that prevents the great masses of blank walls and of ungainly tenement houses lining most of the streets from becoming too ugly, and they secure light and air to many quarters that are grievously congested. These hills can be thus catalogued: 1. _Capitoline_, about 150 feet above sea level.[3] 2. _Palatine_ (S. E. of Capitoline), about 166 feet high. 3. _Aventine_ (South of Palatine), about 146 feet high. 4. _Cœlian_ (East of Palatine), about 158 feet high. 5. _Esquiline_ (North of Cælian), about 204 feet high. 6. _Viminal_ (North of Esquiline), about 160 feet high. 7. _Quirinal_ (N. E. of Capitoline), about 170 feet high. To the familiar “seven” ought to be added the hill of the great northern suburb. 8. _Pincian_, or “Hill of the Gardens” (North of Quirinal), about 204 feet high. Highest of all rises the _Janiculum_ beyond the Tiber, 297 feet high; commanding a noble prospect over the city and the whole Campagna beyond. It formed, therefore, in the olden days, a very proper place for the fort with its watch-tower and its sentinel, when Rome dreaded an Etruscan raid from the north, and when the citizens dropped their tools to seize their weapons the minute the “flag on Janiculum” was struck as signal that the foe was at hand. =8. Building Materials Used in Rome.=--The most cursory view of the city gives an overwhelming impression of the _enormous quantities of building material_, as well as of the expenditure of human labor which has gone into the creation of Rome. Strabo the geographer[4] has wisely observed that it is lucky that the city can get a constant supply of stone, timber, etc., on account of “the ceaseless building which is rendered needful by the pulling down of houses and on account of the great fires and constant sales of [house] property,” everybody being incessantly scrapping old buildings, erecting new ones, and speculating generally in real estate. Of course, the great public buildings are erected with extremely durable materials which will defy the assaults of time, but the vast districts of ugly tenement houses are often thrown together in as flimsy a manner as those in the least elegant quarters of American cities of another age. However, there are almost no wooden houses in Rome; and for the better structures there is provided most excellent building stone. The standard masonry is of _tufa_, a soft red or black stone needing a stucco to protect it from the weather; for superior work there is dark brown _peperino_, golden _travertine_, and last but not least, for the finest buildings, white and many colored _marble_. The marble trade, as will be explained, is, in fact, one of the greatest commercial activities of the city.