Foreigners are apt to complain, not only, as they justly may, of the bad pavements of New-York, but, somewhat unreasonably, of the obstructions in the street, caused by incessant building, laying pipes, &c. They say, "Will the city never be finished?" Not very soon, we think. It is difficult to do in fifty years the work of five hundred, without a good deal of bustle and inconvenience. Rapid growth in population and wealth necessitates continual improvement in accommodation. We may, indeed, be allowed to fret a little, when the street is for weeks or months encumbered by the building materials of a merchant, who sees fit to pull down a very good house in order to erect one that shall cost a quarter of a million, merely because his neighbor has contrived to outshine him in that particular. But when sewers and gas, and Croton water, are in question, we must not grumble. These great public blessings are spreading into every quarter, carrying health and decency with them. The great sewers are arched canals of hard brick, from three to nine feet in diameter, and laid in mortar in the most durable manner. Above them are the gas-pipes, an immense net-work; and nearly on a level with these last are the huge veins and arteries, by means of which the Croton supplies life and health to the inhabitants, once half-poisoned by water which shared every salt that enters into the subsoil of a great city. Analysis shows the Croton water to be of great purity--holding in solution the salts of lime and magnesia in proportions hardly appreciable, only about two and eight-tenths of a grain to the gallon. The river springs from granitic hills, and flows through a clear upland region, free from marsh, and covered with grazing farms. When the Aqueduct was undertaken, New-York numbered but two hundred and eighty thousand inhabitants, so that the supply provided was a magnificent gift to the future. The work was completed within five years, years of great commercial difficulty; and what is more remarkable, the whole cost came _within_ the estimate of the chief engineer. The abundance of water may be guessed from the fact that two of the city fountains throw away more water than would suffice for the consumption of a large city. The solidity of the structure is such that none but slight repair can be needed for centuries to come.[10]