The growth of the city has been rapid, as a few statistics will show. In 1656 the population amounted to 1,000, in 1664 to 1,500, in 1700 to 5,000, in 1750 to 13,500, in 1774 to 22,750, in 1800 to 60,489, in 1820 to 123,706, in 1830 to 202,589, in 1840 to 312,932, in 1850 to 515,547, and in 1860 to 813,669. In consequence of the high prices occasioned by the, war, and the disorganized condition of the various industrial pursuits, the census of 1865 showed a decrease in the population, which amounted to 726,386. The census returns of 1870 place the population of the island at 942,252. It is probable that the population of the island will eventually reach a million and a half, and perhaps even more. Many portions of the city have long since been deserted by the better classes of society, but their departure has been speedily followed by a much denser packing of the localities thus deserted. In 1800 the fashionable part of the city was in Wall and Pine streets, and between Broadway and Pearl. It has gradually moved northward, lingering in our day long around Union Square, which has at last been deserted, and it is difficult deciding where the matter will end. When the plan for the erection of the City Hall was made, about seventy years ago, it was urged that the city would never extend above Chambers street; hence the rear wall of the edifice was made of sandstone, and not of marble like the rest, because it was said it would never be seen. To fill the entire island and suburbs, would produce an immensely smaller change than has already occurred since that time. There are now about sixty-five thousand buildings on the island, many of which cover several lots, and not a few twenty or thirty each; and as fully one thousand acres are covered by the parks and reservoirs, there is not as much vacant land remaining as many writers have supposed. The vicinity of Central Park is now considered the most eligible part of the city; but who can tell but even this may yet become a grand commercial theatre, as many places already have which were once held sacred by a generation long since departed? Some sections in the lower wards are now packed with a population amounting to the appalling figure of two hundred and ninety-thousand to the square mile. If this should become general, the island would contain over six millions. Hundreds of residences are annually rising on the upper parts of the island, but an equally large number farther down are being converted into places of business; and this, we opine, will continue until the entire island is one vast centre of commerce, manufacture, and storage. Thirty years will probably entirely drive the elite from the island. The bridges and tunnels now in immediate prospect will hasten this result, make the surrounding country for miles the real suburbs of the metropolis, and fill it with wealth and palatial splendor. Already many thousands doing business here daily, reside in other places, not a few thirty, and some fifty miles up the Hudson. It has been estimated that two hundred thousand persons daily cross the East river, while not many less cross on the other side to New Jersey, Staten Island, or depart on the railroads running north. The construction of a railroad on the west side of the Hudson, and a bridge across the East river, at Blackwell''s Island, will open eligible sections for suburban residences hitherto inaccessible to the business public of Manhattan. These enterprises cannot long be delayed.