English: Drawing of a Leyden jar, sectioned longitudinally through the axis to show the construction. It consists of a glass jar (C), coated on the outside (A) and inside (B) with conducting metal foil. An area around the mouth of the jar is left free of foil to prevent the charge from arcing between the foils. A metal electrode in contact with the inner foil sticks up out of the jar, so it can be charged with electricity. Alterations: removed caption.