TRANSACTIONS OF THE SECTIONS. 15 



revert to my former proposal of leading electricity through wires for the illuinina- 

 tiou of beacons and buoys at sea. 



For such a piu-pose neither Holmes' nor Wilde's light could be employed, as they 

 are produced by the rapid consumption of carbon?, and require the employment of 

 lamp machinery, v/liich, though to a large extent automatic, involves the constant 

 presence of a lightkeeper in the lantern. I therefore resolved on employing the 

 simple electric spark, eitlier by itself or in vacuum tubes. After consulting with 

 my friend Professor Sv,'an, who suggested the combination of tlie Leyden jar with 

 the induction-coil, experiments were made, and in an interim communication to 

 the Scot. Soc. Arts on loth January 186G, I was able to report that, " by means of 

 four Bunsen cells, an induction-coil, and a Ley den jar, I liad succeeded with a 

 simple unaided sparlc placed in the focus of liglithouse apparatus, to produce an 

 effect at the distance of about half a mile, which was in all respects satisfactory." 

 Tlie light might have been seen much furth.er but for the intervention of obstructious 

 to the view. 



The Commissioners of Northern Lights, on the recommendation of Messrs. Ste- 

 venson, in their report of 1st February 1866, procured, with the sanction of the 

 Board of Trade, a submarine cable from Messrs. Siemens of London, but as the 

 cable was not suitable for this kind of apparatus, the current could not be passed 

 imder the water. Messrs. Stevenson then reported to the Board that, as ]Mi\ 

 Siemens had thought of a difierent form of apparatus, he shoidd be employed to 

 furnish one. This beautifid arrangement is now exhibited, and Mr. Siemens has 

 kindly sent me a description of its difierent parts, which I shall afterwards read. 



While Mr. Siemens was engaged with this instrument, I received many impor- 

 tant suggestions as to the induction-spark apparatus. Mr. Brebner, C.E., sug- 

 gested that the induction-coU shoidd be placed on the beacon, while the break and 

 ■ batteries should be on the shore. Dr. S. Wright recommended that, instead of one 

 large coil, several coils of small intensity should be used ; and Mr. Hart, who con- 

 ducted all the experiments, and to whose untiring zeal is mainly due whatever 

 amount of efficiency the induction-spark apparatus may possess, added a new con- 

 tact breaker with two magnets and a double break. 



By means of these improvements the light was Icept in action during a week at 

 the expense of about 2 shillkigs for 16 hours, with a current passing through a wire 

 800 feet long. The light so produced, as viewed from the .sea and elsewhere, was 

 perfectly suflicieut for tlie purpose required. It may be ailded, that of all the 

 metals which I have tried a wire of bismutli produced the brightest spark. The 

 effect might, perhaps, be also increased without using additional cells, if the same 

 cuiTents could be again utilized so as to generate a second spark in the focus. 



There can be no doubt that a sufRcient light can be obtained either from the 

 induction-spark or from the arrangement of Mr. Siemens, to be afterwards described. 

 Beacon lights, which are needed for pointing out local dangers, do not, of course, 

 require to be of tlie gi-eat power wliicli is needed in lighthouses for illuminating 

 the ocean. In determining which of Ihe two kinds of "apparatus should be pre- 

 ferred, the point turns upon wliich is likely to be tlie most certain in its exhibition. 

 Each method has its own peculiar advantages and disadvantages. In the induc- 

 tion-spark apparatus the contact brealvcr is on the shore and under control, but, on 

 the other hand, the coils may periiaps not last long. In Mr. Siemens's apparatus the 

 products of combustion may perhaps afl'ect the efficiency of the optical apparatus, 

 and the moving parts are at sea and beyond control. 'Nothing but a continuous 

 tri.al for some leugtli of time can determine which is the preferable. It is to be 

 hoped that one or other may prove suitable, for the conveyance of electricity from 

 the shore to outlying rocks promises to form a new and most important" era in 

 maritime illumination. Tlie time, indeed, mav not be far distant wlien such a 

 navigation as the entrance to Liverpool ^^^ll be as clearlv defined at night as in the 

 daytime, by the illumination of its beacons and buoys I'lv electricitv. 



Mr. Siemens's apparatus was worked by twenty cells, wliile the iuductiou-sparii: 

 had only six, but when fully equipped, it' will be' ^^•orkcd by eighteen cells. Each 

 apparatus was shown in the focus of a Ilolophote, the former producing the most 

 powerful flash. 



