TKANSACTIONS OF SECTION G. 791 



vessel, and powerful signals of this class be provided at lighthouse and light- 

 vessel stations. 



These circumstances have led to a rapid development of fog signals, both ashore 

 and afloat, there being now about 700 of these signals, of various descriptions, on 

 the coasts of the world. We therefore find, as might naturally have been expected, 

 that coast fog signals have been made, by lighthouse authoiities, the subject of 

 careful experiment and scientific research ; but, unfortunately, the practical results 

 thus far have not been so satisfactory as coidd be desired, owing, 1st, to the very 

 short range of the most powerful of these signals under occasional unfavourable 

 conditions of the atmosphere during fog, and, 2nd, to the present want of a reliable test 

 for enabling the mariner to determine at any time how far the atmospheric condi- 

 tions are against him in listening for the anxiously expected signal. In 1854 some 

 experiments on diflerent means of producing sounds for coast fog signals were made 

 by the engineers of the French hghthouse department, and in 1861-62 MM. Le 

 Gros and Saint Ange Allard, of the Corps des Fonts et Chaussees, conducted a 

 series of experiments upon the sound of bells and the various methods of striking 

 them. 



In 1863-64 a Committee of the Elder Brethren of the Trinity House made 

 some experiments at Dungeness upon various fog signals. In June 1863 a Com- 

 mittee of the British Association memorialised the then President of the Board of 

 Trade, with the view of inducing him to institute a series of experiments upon fog 

 signals. The memorial, after briefly setting forth a statement of the nature and 

 importance of the subject, described what was then known respecting it, and 

 several suggestions were made as to the nature of the experiments recommended. 

 The proposal dees not appear to havebeenfavourably entertained by the authorities 

 to whom it was referred, and the experiments were not carried out. 



In 1864 a series of experiments was undertaken by a Commission appointed by 

 the Lighthouse Board of the United States, to determine the relative powers of 

 Tarious fog signals which were brought to the notice of the Board. 



In 1872 a Committee of the Trinity House visited the United States and 

 Canada, with the object of ascertaining the actual efficiency of various fog 

 signals then in operation on the North American continent, about which very 

 favourable reports had reached this country. Among other instruments, they 

 witnessed the performance of a siren apparatus, patented by Messrs. A. & F. Brown, 

 of New York. One of these instruments was, in 1873, very kindly sent to the 

 Trinity House by the United States authorities, and tested with other instruments 

 in the experimental trials at the South Foreland in 1873-74. This investigation 

 was carried out at the South Foreland by the Trinity House, with the object of 

 obtaining some definite knowledge as to the relative merits of diiferent sound-pro- 

 ducing instruments, and also of ascertaining how the propagation of sound was 

 aifected by meteorological phenomena. These experiments were extended over 

 a lengthened period, in all conditions of weather, and the well-known scientific 

 and practical results obtained, together with the ascertained relative merits of 

 sound-producing instruments for the service of the mariner, are of the highest 

 scientific interest and practical importance. 



The investigation at the South Foreland was followed up by the Trinity House 

 by further experiments, in which they were assisted by the authorities at Wool- 

 wich, with guns of various forms, weight of charges, and descriptions of gun- 

 powder. The powders tested were (1) fine grain, (2) larger grain, (3) rifle 

 large grain, and (4) pebble. The result placed the powders exactly in the order 

 above stated ; the fine grain, or most rapidly burning powder, gave indisputably 

 the loudest sound, while the report of the slowly-burning pebble powder was 

 the weakest of all. Experiments were also made with the object of ascer- 

 taining the relative value of the sound produced by the explosion of varying 

 quantities of gun-cotton. Here again the greater value of increased rapidity of 

 combustion in producing sound was clearly demonstrated. It was found that 

 charges of gun cotton yielded reports louder at all ranges than equal charges of 

 gunpowder, and further experiments proved that the explosion of half-a-pound of gun- 

 cotton gave a result at least equal to that produced by 3 lbs. of the best gunpowder. 



