The population of these 1,222 places is 38,758,584, considerably less than half that of the entire United States. Their book possessions, on the other hand, are nine times as great as those in the rest of the country; the circulation of the books nearly twelve times in volume. Closer analysis of these figures enforces still more strongly the actual concentration of the available book supply. The hundred largest cities of the United States, varying in size from a minimum of 53,684 to a maximum of 4,766,883, possess in the aggregate more books than all the rest of the country together, and represent the bulk of the trained professional service rendered. The great majority of the 3,000 graduates whom the library schools have sent into service since the first class was organized in 1887, are in these libraries and in the university libraries. Forty per cent of the books circulated are issued to the dwellers in these one hundred cities, and in fifteen of them the stupendous total of 30,000,834 issues for home reading was recorded last year. Without such analysis as this, the statistical totals would be misleading. The concentration of resources and of trained service in large centers of population, comparatively few in number, makes evident the underlying cause for the modern trend of library development. A further study of conditions in these human hives justifies the specialized forms of service which have become a marked factor in library extension within a decade. With increased resources, with vastly improved internal machinery, with enlarged conception of opportunity for useful service, have come greater liberality of rules and ever widening circles of activity, until today no individual and no group of individuals, remains outside the radius of library influence. If this awakened zeal has spurred to efforts that seem outside the legitimate sphere of library work, no undue concern need be felt. Neither the genius or enthusiasm of the individual nor the enterprise of a group of individuals will ever be permitted to go too rapidly or too far: the world's natural conservatism and inherited unbelief stand ever ready to retard or prevent. V