The United Charities Building, at the corner of Fourth Avenue and 22d Street, was erected and presented Jointly to the Charity Organization Society, the Children Aid Society, the Association for Improving the Condition of the Poor, and the New-York City Mission and Tract Society, by the munificence of John S. Kennedy, and with the expectation that many other charities of the city will be gathered under its roof, and that their efficiency and economy will be promoted thereby. It is a magnificent