An ingenious solution was advanced by Mr. Charles Ingrey, C.E. He proposed to erect a central power-station and to control the sounding of two sirens, placed on opposite sides of the island, therefrom, the compressed air being led through underground piping. The plans were submitted to Messrs. Stevenson, the engineers to the Northern Lighthouse Board, who, after examining the proposal thoroughly, gave it their approval. But when it came to obtaining the sanction for the requisite expenditure from the Board of Trade, that august body, despite the fact that the project had been investigated and had received the approbation of the engineers to the Northern Lighthouse Commissioners, declined to permit public money to be expended upon an untried scheme. Such is the way in which pioneering effort and ingenuity are stifled by Government departments.
The latest ingenious device for giving both audible and visual warning automatically.]
Many another engineer would have abandoned the project after such a rebuff, but Mr. Ingrey without any delay laid down a complete installation upon the lines he contemplated on the island of Pladda, where a Holmes fog-horn was in service. With the aid of a workman whom he took from Glasgow, the light-keepers and some farm labourers, this trial installation was completed, the piping being carried round the island from the air-compressing plant to the fog-signal. The work occupied about a fortnight, and then, everything being ready to convince the sceptical Board of Trade, the inspecting engineers were treated to a comprehensive and conclusive demonstration. They were satisfied with what they saw, appreciated the reliability of the idea and gave the requisite sanction. Forthwith the Ailsa Craig Island installation was put in hand and duly completed.
This plant possesses many ingenious features. As the light is derived from gas distilled from crude oil, a small gas-making plant is installed on the island, and this is used also for driving a battery of five eight-horse-power gas-engines--four are used at a time, the fifth being in reserve--to supply the thirty-horse-power demanded to operate the fog-signal. The energy thus developed drives two sets of powerful air-compressors, the four cylinders of which have a bore of 10 inches by a stroke of 20 inches, the air being compressed to 80 pounds per square inch and stored in two large air-receivers which hold 194 cubic feet. From this reservoir pipes buried in a trench excavated from the solid rock extend to the two trumpets, placed on the north and south sides of the island respectively. The length of piping on the north side is 3,400 feet, and on the south side 2,500 feet. At places where the pipe makes a dip, owing to the configuration of the rock, facilities are provided to draw off any water which may collect. Extreme care had to be displayed in connecting the lengths of piping, so that there might be no leakage, in which event, of course, the pressure of the air would drop and thereby incapacitate the signal.