The wheel made the road, and moved produce faster from fields to settlements. Acceleration created larger and larger centers more and more specialism, and more intense incentive, aggregates, and aggressions. So it is that the wheeled vehicle makes its appearance at once as a war chariot, just as the urban center, created by the wheel, makes its appearance as an aggressive stronghold No further motivation than the compounding and consolidating of specialist skills by acceleration of the wheel is needed to explain the mounting degree of human creativity and destructiveness. Lewis Mumford calls this urbanization "implosion," but it was really an explosion. Cities were made by the fragmenting of pastoral modes. The wheel and the road expressed and advanced this explosion by a radiational or center-margin pattern. Centralism depends on margins that are accessible by road and wheel. Maritime power does not assume this center-margin structure, and neither do desert and steppe cultures. Today with jet arid electricity, urban centralism and specialism reverse into decentralism and interplay of social functions in ever more nonspecialist forms. The wheel and the road are centralizers because they accelerate up to a point that ships cannot. But acceleration beyond a certain point, when it occurs by means of the automobile and the plane, creates decentralism in the midst of the older central ism. This is the origin of the urban chaos of our time The wheel, pushed beyond a certain intensity of movement, no longer centralizes. All electric forms whatsoever have a decentralizing effect, cutting across the older mechanical patterns like a bagpipe in a symphony. It is too bad that Mr. Mumford has chosen the term "implosion" for the urban specialist explosion "Implosion" belongs to the electronic age. as it belonged to the prehistoric cultures. All primitive societies are implosive, like the spoken word. Rut "technology is explicitness." as Lyman Bryson has said; and explicitness, or specialist extension of functions, is