Meantime British engineers had not been idle. In 1871 Messrs. Stevenson, the engineers-in-chief to the Commissioners of Northern Lighthouses, advocated strongly the establishment of an electric light upon the Scottish coast; but it was not until 1883 that the Board of Trade sanctioned the sum necessary to complete such an enterprise, and suggested that the innovation should be made at the Isle of May lighthouse, as being the most important on the East Scottish coast. This is one of the historic light-stations of Scotland. Lying in the Firth of Forth, five miles off the Fifeshire shore, the islet obstructs a busy marine thoroughfare. For 276 years a light has gleamed from its summit, the change from the coal fire to Argand lamps with reflectors having been made by Thomas Smith, the first engineer to the Commissioners of Northern Lighthouses, when this body assumed its control in 1816. Twenty years later it was converted to the dioptric system, with a first-order fixed light apparatus having a four-wick burner. This arrangement was in service for half a century, when it was converted to electricity in conjunction with a dioptric condensing apparatus. The electric installation was designed throughout by Messrs. Stevenson, and it possesses many ingenious and novel features to this day, while it was the pioneer of modern electric lighting systems as applied to lighthouse engineering. Although marked improvements have been effected in electrical engineering and science since its completion, it still ranks as one of, if not the, most powerful electric lighthouses in the world. The beacon is a prominent edifice on the summit of the island. The building is somewhat pretentious, rather resembling a battlemented castle than a warning for the mariner, the optical apparatus being housed in a square turret rising above the main part of the building. When electric illumination was adopted, the existing accommodation for three keepers was found insufficient, while a generating-station was necessary. Instead of extending the old building to accommodate the additional facilities, a second station was built at a low-lying point near the sea-level. This contains the engine and generating house, together with quarters for three more keepers and their families. This decision was made because at this point, 810 feet away and 175 feet below the lighthouse, there is a small fresh-water loch whence water is available for the boilers and condensers, while a marked saving in the cost of handling fuel as well as of the haulage of the building materials and machinery was feasible. The current is led from the power-house to the lighthouse by means of overhead copper conductors.