I. The art of man is able to construct monuments far more permanent than the narrow span of his own existence; yet these monuments, like himself, are perishable and frail; and in the boundless annals of time his life and his labors must equally be measured as a fleeting moment. Of a simple and solid edifice it is not easy, however, to circumscribe the duration. As the wonder of ancient days, the Pyramids attracted the curiosity of the ancients: a hundred generations, the leaves of autumn, have dropt into the grave; and after the fall of the Pharaohs and Ptolemies, the Caesars and caliphs, the same Pyramids stand erect and unshaken above the floods of the Nile. A complex figure of various and minute parts is more accessible to injury and decay; and the silent lapse of time is often accelerated by hurricanes and earthquakes, by fires and inundations. The air and earth have doubtless been shaken, and the lofty turrets of Rome have tottered from their foundations, but the seven hills do not appear to be placed on the great cavities of the globe; nor has the city in any age been exposed to the convulsions of nature which in the climate of Antioch, Lisbon, or Lima, have crumbled in a few moments the works of ages in the dust. Fire is the most powerful agent of life and death.... From her situation, Rome is exposed to the danger of frequent inundations. Without excepting the Tiber, the rivers that descend from either side of the Apennine have a short and irregular course; a shallow stream in the summer heats; an impetuous torrent when it is swelled in the spring or winter by the fall of rain and the melting of the snows. When the current is repelled from the sea by adverse winds, when the ordinary bed is inadequate to the weight of waters, they rise above the banks and overspread without limits or control the plains and cities of the adjacent country. Soon after the triumph of the first Punic war, the Tiber was increased by unusual rains; and the inundation, surpassing all former measure of time and place, destroyed all the buildings that were situate below the hills of Rome. According to the variety of ground, the same mischief was produced by different means; and the edifices were either swept away by the sudden impulse, or dissolved and undermined by the long continuance of the flood. Under the reign of Augustus the same calamity was renewed: the lawless river overturned the palaces and temples on its banks; and after the labors of the Emperor in cleansing and widening the bed that was incumbered with ruins, the vigilance of his successors was exercised by similar dangers and designs. The project of diverting into new channels the Tiber itself, or some of the dependent streams, was long opposed by superstition and local interests; nor did the use compensate the toil and costs of the tardy and imperfect execution. The servitude of rivers is the noblest and most important victory which man has obtained over the licentiousness of nature; and if such