wars. The pressure of the new war technology gradually developed classes and an economic system that could provide numerous cavaliers in heavy armor. By about the year 1000 A.D. the old word miles had changed from "soldier" to "knight." Lynn White has much to say, also, about horseshoes and horse-collars as revolutionary technology that increased the power and extended the range and speed of human action in the early Middle Ages. He is sensitive to the psychic and social implications of each technological extension of man, showing how the heavy wheel-plow brought about a new order in the field system, as well as in the diet of that age. "The Middle Ages were literally full of beans." To come more directly to our subject of the wheel, Lynn White explains how the evolution of the wheel in the Middle Ages was related to the development of the horsecollar and the harness. The greater speed and endurance of the horse was not available for cartage until the discovery of the collar. But once evolved, this horse-harness led to the development of wagons with pivoted front axles and brakes. The four-wheel wagon capable of hauling heavy loads was a common feature by the middle of the thirteenth century. The effects on town life were extraordinary. Peasants began to live in cities while going each day to their fields, almost in the manner of motorized Saskatchewan farmers. These latter live mainly in the city, having no housing in the country beyond sheds for their tractors and equipment. With the coming of the horse-drawn bus and streetcar, American towns developed housing that was no longer within sight of shop or factory. The railroad next took over the development of the suburbs, with housing kept within walking distance of the railroad stop. Shops and hotels around the railroad gave some concentration and form to the suburb. The automobile, followed by the airplane, dissolved this grouping and ended the pedestrian, or human, scale of the suburb. Lewis Mumford contends