In the history of New York the significance of the name Harlem has changed from Dutch to Irish to Jewish to Negro. Of these changes the last has come most swiftly. Throughout colored America, from Massachusetts to Mississippi and across the continent to Los Angeles and Seattle, its name, which as late as fifteen years ago has scarcely been heard, now stands for the Negro metropolis. Harlem is, indeed, the great Mecca for the sight-seer, the pleasure-seeker, the curious, the adventurous, the enterprising, the ambitious, and the talented of the Negro world; for the lure of it has reached down to every island of the Carib Sea and has penetrated even into Africa.[4] It is important to know what are the forces which tend to break up the tensions, interests, and sentiments which give neighborhoods their individual character. In general these may be said to be anything and everything that tends to render the population unstable, to divide and concentrate attentions upon widely separated objects of interest. What part of the population is floating? Of what elements, i.e., races, classes, etc., is this population composed? How many people live in hotels, apartments, and tenements? How many people own their own homes? What proportion of the population consists of nomads, hobos, gypsies? On the other hand, certain urban neighborhoods suffer from isolation. Efforts have been made at different times to reconstruct and quicken the life of city neighborhoods and to bring them in touch with the larger interests of the community. Such is, in part, the purpose of the social settlements. These organizations and others which are attempting to reconstruct city life have developed certain methods and a technique for stimulating and controlling local communities. We should study, in connection with the investigation of these agencies, these methods and this technique, since it is just the method by which objects are practically controlled that reveals their essential nature, that is to say, their predictable character (_Gesetzmässigkeit_).[5] In many of the European cities, and to some extent in this country, reconstruction of city life has gone to the length of building garden suburbs, or replacing unhealthful and run-down tenements with model buildings owned and controlled by the municipality. In American cities the attempt has been made to renovate evil neighborhoods by the construction of playgrounds and the introduction of supervised sports of various kinds, including municipal dances in municipal dance halls. These and other devices which are intended primarily to elevate the moral tone of the segregated populations of great cities should be studied in connection with the investigation of the neighborhood in general. They should be studied, in short, not merely for their own sake, but for what they can reveal to us of human behavior and human nature generally.