Note 13 — II

It is true that many scholars estimate a high-water mark for the Roman population in excess of two millions; and one daring authority, by throwing out suburbs ad libitum into the Campagna, suburbs of which no trace remains, has raised the two to ten. The Colosseum could, no doubt, seat over 80,000 spectators; the circuit of the bench frontage of the Circus Maximus was very nearly a mile in length, and the Romans of Imperial times certainly used ten times as much water as the modern Romans. But, on the other hand, habits change, and Rome as it is defined by lines drawn at the times of its greatest ascendancy—the city, that is, enclosed by the walls of Aurelian and including all the regiones of Augustus, an enclosure from which there could have been no reason for excluding half or more of its population—could have scarcely contained a million. It would have packed very comfortably within the circle of the Grands Boulevards of Paris—the Paris, that is, of Louis XIV., with a population of 560,000; and the Rome of to-day, were the houses that spread so densely over the once vacant Campus Martius distributed in the now deserted spaces in the south and east, and the Vatican suburb replaced within the ancient walls, would quite fill the ancient limits, in spite of the fact that the population is under 500,000. But these are incidental doubts on a very authoritative opinion, and, whatever their value, they do not greatly affect the significance of these new great cities, which have arisen all over the world, as if by the operation of a natural law, as the railways have developed.