It is ten years and over, now, since that line divided New York's population evenly. To-day three-fourths of its people live in the tenements, and the nineteenth century drift of the population to the cities is sending ever-increasing multitudes to crowd them. The fifteen thousand tenant houses that were the despair of the sanitarian in the past generation have swelled into thirty-seven thousand, and more than twelve hundred thousand persons call them home. The one way out he saw--rapid transit to the suburbs--has brought no relief. We know now that there is no way out; that the "system" that was the evil offspring of public neglect and private greed has come to stay, a storm-centre forever of our civilization. Nothing is left but to make the best of a bad bargain. What the tenements are and how they grow to what they are, we shall see hereafter. The story is dark enough, drawn from the plain public records, to send a chill to any heart. If it shall appear that the sufferings and the sins of the "other half," and the evil they breed, are but as a just punishment upon the community that gave it no other choice, it will be because that is the truth. The boundary line lies there because, while the forces for good on one side vastly outweigh the bad--it were not well otherwise--in the tenements all the influences make for evil; because they are the hot-beds of the epidemics that carry death to rich and poor alike; the nurseries of pauperism and crime that fill our jails and police courts; that throw off a scum of forty thousand human wrecks to the island asylums and workhouses year by year; that turned out in the last eight years a round half million beggars to prey upon our charities; that maintain a standing army of ten thousand tramps with all that that implies; because, above all, they touch the family life with deadly moral contagion. This is their worst crime, inseparable from the system. That we have to own it the child of our own wrong does not excuse it, even though it gives it claim upon our utmost patience and tenderest charity.