On the 8th December, 1858, at the South Foreland High Lighthouse, and with the direct current magneto machines of Holmes, the first important application of the electric arc light, as a rival to oil and gas for coast lighting, was carried out by the Trinity House, under the advice of Faraday. The carbons then used, and for several years afterwards, were sawn from the residuum carbon of gas retorts; they were square in section, 6¼ × 6¼ mm., and the mean intensity of the arc, measured in the horizonal plane, was 670 candle units, being 17 candle units nearly per square millimetre of cross sectional area of the carbon. The crater formed at the point of the upper carbon of the “Holmes” lamp was so small that no appreciable loss of light was found to occur, and the arc proved to be very perfect in affording an exceptionally large vertical angle of radiant light for application with the optical apparatus as shown, one-third full size, in the sketch (Plate 6).