Henry Adams's use of jarring image of dynamo and Virgin provides an excellent starting point for the study of medieval technology. The first great technological revolution of the Middle Ages took place in the development of labor-saving devices for farming. Closely related to developments in agriculture was the invention of labor-saving power technologies. Economically, the most important direction in which the energy generated by wind and water would flow was toward the manufacture of cloth. The risk and reality of worker, and peasant uprisings, coupled with the normal course of dynastic and territorial conflict and the fear of invasion, contributed to continuously escalating military needs on the part of kings and noblemen. Medieval improvements in ship design made sea trade faster, safer, and far more profitable. The construction of a cathedral represents a cross section of the technological achievements of the late Middle Ages and demonstrates both indigenous talent and the absorption of foreign innovations.