790 REPORT — 1886. 



St. Catherine's Station, wliere it had been resolved to adopt the electric arc light, 

 the De Meritens machines should be employed, and they were accordingly ordered ; 

 but, as arrangements were then being made for experiments at the South Foreland 

 for testing the relative merits of electricity, gas, and oil as lighthouse illuminants, 

 it was determined that these machines should first be sent there for the experi- 

 ments. In 1862 a practical trial was made by the Trinity House at the South 

 Foreland of the Drummond or lime light, but the results were not so satisfactory, 

 after experience with the electric arc light, as to encourage its adoption. In the 

 meantime the successful development of the electric arc light for lighthouse illumi- 

 nation very soon acted as a keen stimulus to inventors of burners for producing gas 

 and oil luminaries for the purpose ; in ISGo the attention of lighthouse authorities 

 was directed to the gas system of Mr. John R. Wigham, of Dublin, which system 

 was tried in that year by the Commissioners of Irish Lights at the Ilowth Bailey 

 Lighthouse, near Dublin, and in 1878 he introduced at the Galley Head Lighthouse, 

 county Cork, his system of superposed gas burners. At this lighthouse four of his 

 large gas burners and four tiers of first-order annular lenses, eight in each tier, were 

 adopted. By successive lowering and raising of the gas flame at the focus of each 

 tier of lenses, he had previously produced the first group flashing distinction. This 

 light shows, at periods of one minute, from ordinary annular lenses, instead of the 

 usual long flash, a group of short flashes, varying in number between six and seven. 

 The uncertainty, however, in the number of flashes contained in each group is found 

 to be an objection to the optical arrangement here adopted. In the meantime the 

 attention of the Trinity House, the Commissioners of Northern Lights, and the 

 French lighthouse authorities was being directed to the question of substituting 

 mineral oil for colza as a lighthouse illuminant. In 1861 experiments were made 

 b}" the Trinity House for the purpose of determining the efliciency and economy of 

 mineral oils in relation to colza for lighthouse illumination ; but, owing to the 

 imperfectly refined oil then obtainable and its high price, the results were not found 

 to be so satisfactory as to justify a change from colza oil, at that time generally 

 used. In 1869 the price of mineral oil, of good Ulumiuating quaUty and safe 

 flashing point, having been reduced to about one-half the price of colza, the Trinity 

 House determined to make a further series of experiments, when it was ascertained 

 that, with a few simple modifications, the existing burners were rendered very 

 efficient for the purpose, and a change from colza to mineral oil was commenced. 

 It was found, during these experiments, that the improved combustion effected in 

 the colza burners, in their adaptation for consimiing mineral oils, had the eSect of 

 increasing their mean efficiency, when burning colza, 46j per cent. A further 

 advance was made during these experiments by increasing the number of wicks of 

 the first-order burner from four to six, more than doubling the intensity of the 

 light, while effecting an improved compactness of the luminary per unit of focal 

 area of 70 per cent. 



With coal fires no distinctive characters were possible beyond the costly ones 

 of double or triple lighthouses. There are at present not less than 86 distinctive 

 characters in use throughout the lighthouses and light-vessels of the world ; and,. 

 as their numbers increase, so does the necessity for giving a more clearly distiiictive 

 character to each light over certain definite ranges of coast. This important ques- 

 tion of affording to each light complete distinctive individuality is receiving the 

 attention of lighthouse authorities at home and abroad, and it is hoped that greater 

 uniformity and consequent benefit to the mariner wUl be the result. 



During the old days of sailing vessels, when the duration of voyages was so 

 uncertain, sound signals, as aids to the mariner, were but little demanded. The 

 seaman on approaching the coast in fog trusted entirely to his lead, and, when he 

 found circumstances favourable for doing so, he anchored his vessel until the atmo- 

 sphere cleared. But, since the application of steam to navigation, with keener com- 

 petition in trade, these conditions have been entirely changed. The modern steam 

 vessel is expected to keep time with nearlj^ the same degree of precision as a railway 

 train, and it is evident that, even with the utmost care and attention on the part of 

 her commander, this requirement cannot possibly be fulfilled, and collisions and 

 strandings must occur, unless efficient sound signals for fog be carried by each 



