286 ON LIGHTHOUSE ILLUMINATION — THE ELECTRIC LIGHT. 



divergence. If we wish, to increase the effect of brightness, we cannot 



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properly do it by enlarging the lamp flame ; for though lamps are made 

 for the dioptric arrangement of Fresnel, which have as many as four wicks, 

 flames 3^ inches wide, and burn like intense furnaces, yet if one be put 

 into the lamp place of the reflector referred to, its effect would chiefly be 

 to give a beam of wider divergence ; and if to correct this, the reflector 

 were made with a greater focal distance, then it must be altogether of a 

 much larger size. The same general result occurs with the dioptric 

 apparatus ; and here, where the four-wicked lamps are used, they are 

 placed at times nearly 40 inches distant from the lens, occasioning the 

 necessity of a very large, though very fine, glass apparatus. 



On the other hand, if the light could be compressed, the necessity for 

 such large apparatus would cease, and it might be reduced from the size of 

 a room to the size of a hat : and here it is that we seek in the electric spark, 

 and such-like concentrated sources of light, for aid in illumination. It is 

 very true, that by adding lamp to lamp, each with its reflector, upon one 

 face or direction, power can be gained ; and in some of the revolving lights, 

 ten lamps and reflectors unite to give the required flash. But then not 

 more than three of these faces can be placed in the whole circle ; and if a 

 fixed light be required in all directions round the lighthouse, nothing 

 better has been yet established than the four-wicked Fresnel lamp in the 

 centre of its dioptric and catadioptric apparatus. Now the electric light can 

 be raised up easily to an equality with the oil lamp, and if then substi- 

 tuted for it. will give all the effect of the latter ; or by expenditure of 

 money it can be raised to a five or tenfold power, or more, and will then 

 give five or tenfold effect. This can be done, not merely without increase 

 of the volume of the light, but whilst the bight shall have a volume 

 scarcely the 2000th part of that of the oil flame. Hence the extraordinary 

 assistance we may expect to obtain of diminishing the size of the optical 

 apparatus and perfecting that part of the apparatus. 



Many compressed intense lights have been submitted to the Trinity- 

 house ; and that corporation has shown its great desire to advance all such 

 objects and improve the lighting of the coast, by spending, upon various 

 occasions, much money and much time for this end. It is manifest that 

 the use of a lighthouse must be never-failing, its service ever sure ; and 

 that the latter cannot be interfered with by the introduction of any plan, 

 or proposition, or apparatus, which has not been developed to the fullest 

 possible extent, as to the amount of light produced, — the expense of such 

 light, — the wear and tear of the apparatus employed, — the steadiness of 

 the light for 16 hours, — its liability to extinction, — the amount of neces- 

 sary night care, — the number of attendants, — the nature of probable 

 accidents, — its fitness for secluded places, and other contingent circum- 

 stances, which can as well be ascertained out of a lighthouse as in it. The 

 electric spark which has been placed in the South Foreland High Light, by 

 Professor Holmes, to do duty for the six winter months, had to go through 



