Business, in a wider sense, has done more than all other agencies together to wipe out the worst tenements. It has been New York's real Napoleon III., from whose decree there was no appeal. In ten years I have seen plague-spots disappear before its onward march, with which health officers, police, and sanitary science had struggled vainly since such struggling began as a serious business. And the process goes on still. Unfortunately, the crowding in some of the most densely packed quarters down town has made the property there so valuable, that relief from this source is less confidently to be expected, at all events in the near future. Still, their time may come also. It comes so quickly sometimes as to fairly take one's breath away. More than once I have returned, after a few brief weeks, to some specimen rookery in which I was interested, to find it gone and an army of workmen delving twenty feet underground to lay the foundation of a mighty warehouse. That was the case with the "Big Flat" in Mott Street. I had not had occasion to visit it for several months last winter, and when I went there, entirely unprepared for a change, I could not find it. It had always been conspicuous enough in the landscape before, and I marvelled much at my own stupidity until, by examining the number of the house, I found out that I had gone right. It was the "flat" that had disappeared. In its place towered a six-story carriage factory with business going on on every floor, as if it had been there for years and years. This same "Big Flat" furnished a good illustration of why some well-meant efforts in tenement building have failed. Like Gotham Court, it was originally built as a model tenement, but speedily came to rival the Court in foulness. It became a regular hot-bed of thieves and peace-breakers, and made no end of trouble for the police. The immediate reason, outside of the lack of proper supervision, was that it had open access to two streets in a neighborhood where thieves and "toughs" abounded. These took advantage of an arrangement that had been supposed by the builders to be a real advantage as a means of ventilation, and their occupancy drove honest folk away. Murderers' Alley, of which I have spoken elsewhere, and the sanitary inspector's experiment with building a brick wall athwart it to shut off travel through the block, is a parallel case.