In the early seventies an American investigator, Mr. C. L. Daboll, contrived an entirely new system, which developed into the foundation of one of the most successful fog-signalling devices for lighthouses which has been discovered--the siren. The Daboll invention was a huge trumpet, recalling a mammoth phonograph horn. It was 17 feet in length, and its mouth was 38 inches in diameter. In the lower end of this trumpet--the throat--was placed a tongue of steel measuring 10 inches in length and secured at one end to form a reed. It was blown by air compressed in a reservoir to the desired degree, and then permitted to escape through the trumpet. The mad rush of the expanding air through the constricted passage set the reed vibrating violently, causing the emission of a penetrating, discordant bellow. When Daboll commenced his experiments, he suffered from the lack of a suitable mechanical means for compressing the air, and made shift with a donkey for this purpose until the hot-air engine was improved, when the latter was substituted. Trinity House adopted the idea and found it serviceable; but the Canadian authorities, after four years’ experiment, dissented from this view, remarking that the trumpet was expensive to maintain, unreliable in working, and liable to break down when most urgently needed. In fact, they characterized the Daboll trumpets which they had installed as “sources of danger instead of aids to navigation.” From the trumpet to the siren was not a very big step. The history of the latter’s invention is somewhat obscure, but it was brought before the United States Government in a primitive form. The American engineers, recognizing its latent possibilities, took it up, and endeavoured to improve it to such a degree as to render it suitable for lighthouse work. Their efforts were only partially successful. The solution of the many difficulties attending its perfection was effected in Great Britain by Professor Frederick Hale Holmes, whose magneto-electric machine brought electricity within reach of the lighthouse as an illuminant, and it was due to the efforts of this scientist that the siren became one of the most efficient sound-producing instruments which have been discovered for this class of work.