Almost every modern city has several histories of its recent development, and the current magazines contain a great deal of general information about particular cities. The list of typical works on the modern city might be extended indefinitely, but the numerous bibliographies already available make this task unnecessary. There are published bibliographies of some of the more important European and American cities. Books on London, for instance, are so numerous that there exists in the city of London a library devoted exclusively to works on that city. A similar volume of literature is available about Paris, Rome, and other centers of culture around which there has grown up an historical tradition which gives to the locality a world-wide human interest. There are a number of books on such cities as Moscow, the city of churches, which emphasize the fact that this metropolis has occupied a position of dominance in Russian life because of its spiritual leadership, which expresses itself institutionally in its magnificent cathedrals. There are other Meccas of this sort, the literature on which would occupy many pages. The inclusion of such books as Augustus Hare’s _Paris_ and von Ende’s _New York_ in this list might well raise the question as to why these two rather unimportant works were included and others of a similar nature excluded. Their pertinence in this connection was thought to lie in the fact that they are typical of books on many cities which are intended as guides to tourists or represent accounts of travelers, which are not included in this bibliography, but which might prove of interest to the student dealing with the individualities and eccentricities of individual cities. There has grown up in recent years a renewed interest in the variety and diversity of American cities. Many such books have appeared, often in series including several cities, which give more than a traveler’s account, and actually succeed in entering into the spirit of the city. Grace King’s volume on New Orleans is perhaps the best, if not the most representative, of these American volumes. III. TYPES OF CITIES Each city, like every other object in nature, is, in a sense, unique. A scientific study of the city presupposes, however, that a study of a number of cities will reveal certain classes or types, the members of which have certain common characteristics which mark them off from other types. There are, obviously, many criteria, on the basis of any one of which cities might be classified and distinguished from each other. Certain fundamental types appear in the literature of the subject of which the sociologist may profitably take note.