stitutes a battery of Leyden jars, which has the same effect as a much larger single jar. Instead of being in the form of a round jar, this device is sometimes made in a flat form; that is, the glass and, consequently, the sheets of foil are flat.
When the terminals of a Leyden jar are connected to a source of electrical energy, it will receive and retain a
Fig. 4.—Types of Leyden Jars.
charge equal in electrical pressure to that of the source of energy. If, after receiving a charge, its terminals be brought near one another, a sudden discharge takes place in the form of an electric spark which, while appearing to be single and momentary, has been found by experiment to consist of a series of alternating flashes in rapid succession, each flash lasting less than one hundred thousandth part of a second. The frequency of these oscillations is regulated by the capacity, or size,
