Having discussed the general principles applicable to the arrangement and development of streets within a city, we come to the specific problem. The city of Chicago now extends for about twenty-six miles along the Lake front, and has a width of not more than seven miles. It is apparent that as population increases, the entire territory between the present western boundaries and the Des Plaines River will become thickly settled, and that as this occupation proceeds the pressure of the increased numbers to reach the business district and the Lake front will work serious congestion, unless additional thoroughfares shall be created in order to add to transit facilities inadequate even at the present time. Obviously it is idle to expect those who plat subdivisions for the mere purpose of selling land to make provision for a circulatory system sufficiently comprehensive to meet the requirements of a growing city. That task belongs to the city itself, and the only way in which it can be accomplished is by the preparation and adoption of a plan for platting all those lands adjacent to the city which are reasonably certain to be included within the enlarged boundaries. The entire territory extending westward to the Des Plaines should be laid out to meet future requirements, with the requisite area for residences, as well as wide thoroughfares for traffic, well-planned diagonals to gather and distribute the travel, and adequate park spaces. As the architects of Louis XIV. laid out streets and avenues of Paris far in advance of occupation, and as the United States government adopted a plan for the development of the entire District of Columbia in accord with the original L’Enfant plan, so the authorities of Chicago should see to it that when and as new subdivisions are platted in any portion of Cook County not now included within the city boundaries, the thoroughfares in those subdivisions shall be fitted to care for the traffic that will be imposed upon them by reason of their location in relation to the business district. [Illustration: XCIX. THEORETICAL DIAGRAM OF THE STREETS OF BERLIN. REPRODUCED FROM “LES TRANSFORMATIONS DE PARIS,” BY M. E. HÉNARD] The functions of the diagonals and circuits proposed for the area impinging upon the business district are three in number: first, to allow traffic seeking the center to reach its destination expeditiously; secondly, to divert from the center traffic not having its objective point within the central area; and, thirdly, to afford direct passage through the center in those cases where such crossing is necessary. [Illustration: C. THEORETICAL DIAGRAM OF THE STREETS OF LONDON. REPRODUCED FROM “LES TRANSFORMATIONS DE PARIS,” BY M. E. HÉNARD]