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Any discussion on the state of the art on such a broad subject as capacitors must by necessity Ibe somewhat sketchy. As many writers have pointed out, a capacitor is a relatively simple device; and because of its simplicity, its purpose can be achieved in many ways and with many materials. In this discussion I shall limit myself primarily to those constructions and materials which are now in production and which are be!.ng used in sufficient quantities to make their inclusion in any survey of economic importance. Some of the types are used only in Europe, while some types are used only in this country. The chronological comparisons that will be made will go back about forty years, Many of the capacitors used today were used at that time. No attemot will be made to determine just when during this period any of thesle capacitors came into existence. Also, only general characteristics will be given, since the number of various types is so great that it would require much more time than is alloted to me to discuss them. This discussion will attempt to cover two aspects of the art. One is based on materials and processes. The second is based on the evolution of the capacitor as indicated by the development of military specifications.