A further promoting cause is found in the opening of the Brooklyn Elevated Railway in 1885. We must, therefore, assume the average annual gain for the past eight years (of 25,237) to be greater than the average gain of the three or four years following 1880. If so, it is obvious that the gains for the present year and for the years immediately preceding must have been greater than 25,000. That the two causes suggested contributed to change the rate of growth is not likely to be questioned by any one. But they are only the accompaniments of a broader and more persistent cause, which is the fundamental reason of the existence of the bridge and of our present system of rapid transit. This larger cause is a general change in the relation between New York and Brooklyn, gradually manifesting itself as a necessary result of the development of the whole metropolitan community surrounding the port of New York. The first two causes, therefore, though permanent, were auxiliary and specific. The last is a general, continuous condition, whose force seems unlikely to decline, but more likely to augment from year to year. The first two causes, also, may be said to have a fixed or, at all events, an ascertainable maximum influence, based upon their respective capacity to transport passengers. They are merely methods of transit. Their capacity may in time be exhausted. In such case they may be supplemented; new bridges can be built, and doubtless will be; newer elevated railroads have been built and opened for business since the construction of the one already mentioned. More elevated railroads are to be built. In addition to the Brooklyn Elevated Railroad Company, already named, now operating six and three-fourths miles of railroad, the Kings County Elevated Railroad Company is operating five and one-half miles of railroad, and the Union Elevated Railroad Company is operating four and three-fifths miles, forming together a system of nearly seventeen miles, which promises to increase its capacity as well as its mileage. Construction is still progressing upon these lines, and it is reported that at the close of the year 1889, or earlier, there will be twenty-five miles of elevated railroad in operation in the city. These features of the city's condition call attention to the fact that we have reached a period of development, at which it is our duty to provide clearly and understandingly for the needs of a far greater population than that now included within our limits.