The metropolitan region of the future therefore will be planned to contain a number of distinct urban communities which will be enabled to preserve their individuality by surrounding open areas. In part these will consist of parks, some formal such as Fairmount Park which today separates Philadelphia from the main-line towns, some natural parks or forest reserves such as those Boston, Chicago and other cities are acquiring. But park land alone will not be enough. So much open space is required for the proper ventilation of our cities that a considerable part of it must be devoted to productive uses that will pay its way. Cities like New York and its New Jersey neighbors, and the great congeries of cities that are growing up about San Francisco Bay, have been blessed, largely against their wills, by open water spaces that seem to some of their bustling citizens far larger than is required - just as some of our cities in the past thought some of their streets too wide, only to find to-day that they are not wide enough. It would be difficult to overestimate the economic value of the breezes from the water that blow through the streets of New York and the Bay cities.
Awakening to the advantages which nature forced upon our fortunate members, we shall provide adequately for the new kind of harbor that is coming to us with the airplane. We doubtless shall, under stress of necessity, figure carefully how small an air field may be, how high the surrounding buildings may be permitted to rise, for we wish to bring the air harbor as far in town as possible in order to minimize change in existing values. But as the railroad induced our river towns to turn their backs upon the levees, so the airplane may induce them to face in a new direction, and those towns which make the most adequate provision are likely to reap a benefit.
But air harbors like water harbors will prove inadequate to our purpose and other uses, such as truck gardening and farming, will be found for these open areas.