That the education comes slowly need excite no surprise. The forces on the other side are ever active. The faculty of the tenement for appropriating to itself every foul thing that comes within its reach, and piling up and intensifying its corruption until out of all proportion to the beginning, is something marvellous. Drop a case of scarlet fever, of measles, or of diphtheria into one of these barracks, and, unless it is caught at the very start and stamped out, the contagion of the one case will sweep block after block, and half people a graveyard. Let the police break up a vile dive, goaded by the angry protests of the neighborhood--forthwith the outcasts set in circulation by the raid betake themselves to the tenements, where in their hired rooms, safe from interference, they set up as many independent centres of contagion, infinitely more destructive, each and every one, than was the known dive before. I am not willing to affirm that this is the police reason for letting so many of the dives alone; but it might well be. They are perfectly familiar with the process, and entirely helpless to prevent it. This faculty, as inherent in the problem itself--the prodigious increase of the tenement-house population that goes on without cessation, and its consequent greater crowding--is the chief obstacle to its solution. In 1869 there were 14,872 tenements in New York, with a population of 468,492 persons. In 1879 the number of the tenements was estimated at 21,000, and their tenants had passed the half-million mark. At the end of the year 1888, when a regular census was made for the first time since 1869, the showing was: 32,390 tenements, with a population of 1,093,701 souls. To-day we have 37,316 tenements, including 2,630 rear houses, and their population is over 1,250,000. A large share of this added population, especially of that which came to us from abroad, crowds in below Fourteenth Street, where the population is already packed beyond reason, and confounds all attempts to make matters better there. At the same time new slums are constantly growing up uptown, and have to be kept down with a firm hand. This drift of the population to the great cities has to be taken into account as a steady factor. It will probably increase rather than decrease for many years to come. At the beginning of the century the percentage of our population that lived in cities was as one in twenty-five. In 1880 it was one in four and one-half, and in 1890 the census will in all probability show it to be one in four. Against such tendencies, in the absence of suburban outlets for the crowding masses, all remedial measures must prove more or less ineffective. The "confident belief" expressed by the Board of Health in 1874, that rapid transit would solve the problem, is now known to have been a vain hope.