As mentioned above, the station is controlled electrically from a point on shore. In deciding the latter, it was necessary to discover the most favourable landing-place for the submarine cable in relation to its route, and Doyle Fort was selected as meeting all requirements in this direction. Here a two-floor dwelling has been erected for the keepers, together with an adjoining engine-house, which measures 32 feet in length by 20 feet wide. The tower being a mile distant, the designers had to meet the possibility of the machinery therein breaking down. Accordingly, at the shore station there is an auxiliary fog-siren and air-compressing plant, which is brought into use when the sea apparatus is deranged. [Illustration: _By courtesy of Messrs. D. and C. Stevenson._ AN UNATTENDED BEACON LIGHT PLACED UPON A WILD PART OF THE SCOTTISH COAST. These lights will run for several months without any human attention, and, by means of ingenious mechanism, light and extinguish themselves automatically.] The machinery includes two oil-engines which drive three-phase alternators, and an air-compressor for working the land siren when required. One of the greatest difficulties arose in connection with the submarine cable which connects the land-station with the sea-tower. Owing to the broken, rocky nature of the sea-bed, the viciousness of the currents, and the heavy seas, the cable had to be of exceptional strength; indeed, it had to be made specially for the purpose. It is a double-sheathed, steel-armoured cable of the heaviest “rock” type, being 11 inches in circumference, and weighing 45 tons per nautical mile. As the current used is three-phase, there are three conductors, which weigh 1,100 pounds per mile, protected by a thick layer of gutta-percha averaging 450 pounds per mile. In the centre of the core are two other wires for switching and telephone purposes respectively. The laying of the cable was a peculiar and exacting task in itself; 6,504 feet had to be paid out. But by waiting for a very calm day and slack water this task was achieved without mishap. In the tower there is a simple switch operated by an electro-magnet, whereby the motor-driven air-compressors are thrown in and out of action. The two compressors are used alternately, so as to keep them in thorough working order; and as they have to be left sometimes for months without being examined, special attention has been devoted to their lubrication.