Mabch 9, 1S83.] 



SCIENCE. 



135 



were of special interest ; earthquakes were re- 

 ported in New Hampshire and California on 

 the 19th, and in Maine on the 31st. 



HISTORY OF THE APPLICATION OF THE 

 ELECTRIC LIGHT TO LIGHTING THE 

 COASTS OF FRANCE. 



I. 



The value to navigation of thoronghlj- light- 

 ing our coasts is too evident to require anj' 

 argument in its favor; and, in view of the 

 immense interests at stalie, there is no ques- 

 tion but that improved methods of lighting 

 should be adopted, almost regardless of ex- 

 pense, providing that the advantages gained 

 are in anj' wajr commensurate with the cost. 



France has long appreciated this ; and it is 

 to her that the world owes the Fresnel lens 

 and manj' improved lamps burning successive- 

 ly whale, vegetable, and mineral oils. She 

 has finallj' led the way, as usual, in the use of 

 the electric light, which has been definite!}- 

 adopted for the lighting of her coasts, after 

 manj- expensive and conclusive experiments ; 

 and, when the plan has been fnll}^ carried out, 

 France can boast of having the best and most 

 sj-stematic method of coast-lighting of any 

 countrj' in the world. 



The United States has followed France. 

 Our optical apparatus has been almost exclu- 

 sivelj' imported from that countrj'. We use 

 lamps made after French patterns, and now 

 we are making experiments to determine its 

 value for our lighthouses. This is deemed 

 sufflcieut excuse for giving full details of the 

 French sj'stem. The information has naturall}' 

 been mostly obtained from French sources. 



It was in 1863 that the electric light was 

 for the first time used in lighthouses. The ex- 

 periment was made with an Alliance machine 

 in the first-order lighthouse of la Heve, near 

 Havre ; and the results were so satisfactory' 

 that doubtless all the lighthouses would have 

 been immediately furnished with electric lights, 

 had it not been for the great expense attend- 

 ing a general alteration. It was proved that 

 the electric light was seen about eight kilo- 

 metres farther than the oil-light, and that, in 

 time of fog, the range of the former light was 

 more than double that of the latter. 



M. Quinette de Eochemont, ing(^nieur des 

 ponts et chauss^es, published in 1870 a report 

 upon the lighthouses at la Heve. Below are 

 some extracts : — 



" The electric light having been installed for six 

 years at la Hfeve, enough time has elapsed to allow 

 us to form an exact idea of the value of this means 



of producing light for the lighting of coasts. Sailors 

 take pleasure in recognizing the good services ren- 

 dered them by the electric light. The advantages of 

 the system have been highly appreciated : the increase 

 of the range of the light is very apparent; and, 

 above all, in slightly foggy weather, many ships can 

 continue their voyage, and enter the port at night, 

 which they could not do when oil was used. The 

 light, which at first was rather tmsteady, gradually 

 acquired a remarltable fixity, — thanks to the im- 

 provement of the apparatus and to the experience 

 gained by the keepers. The fears which were at first 

 entertained regarding the delicacy of certain parts of 

 the apparatus are not realized in practice. The acci- 

 dents have been rare, the extinctions short and very 

 few, — two only during this period of six years hav- 

 ing had a notable duration : one, of an hour, was due 

 to an accident to the steam-engine ; the other, of four 

 hours, should, it appears, be attributed to malevo- 

 lence. Under these circumstances it seems hardly 

 worth while to worry about possible accidents." 



Since 1863 experience has onlj' confirmed 

 the favorable views of M. Quinette. The 

 lighthouses of Gris-Nez, France ; Cape Liz- 

 ard, England ; Odessa, Russia ; and Port Said, 

 Egypt, — have been provided with electric ap- 

 paratus ; and there is a question of placing it 

 in the lighthouses of Planier and Palmyre, 

 France, and in several lighthouses in other 

 foreign countries. 



The following information was furnished by 

 MM. Sautler and Lemonnier : — 



"When the light is to be fixed, the optical part of 

 the apparatus is composed of a lenticular drum of 

 proper form, which renders the rays horizontal in 

 the vertical plane while allowing them to diverge in 

 the horizontal plane. The dimensions of this drum 

 vary from a diameter of half a metre for a fourth- 

 order light to one metre in a first-order light. This 

 increase in diameter of the apparatus is sensibly 

 proportional to the increase in diameter of the carbon- 

 pencils between which the voltaic arc is produced, 

 and which determines very nearly the dimensions of 

 the electric light. It follows from this, that the ver- 

 tical divergence remains the same in the different 

 types of apparatus. When the light is to be revolv- 

 ing, the fixed lens is surrounded by a movable drum 

 formed of straight vertical lenses of which the form 

 varies according to the characteristics desired to be 

 given to the light." 



Revolving electric lights have this great ad- 

 vantage over revolving oil-lights : the flashes 

 can be given a duration equal to that of the 

 eclipses. In oil-lights, when the light is con- 

 centrated in the form of flashes, there are two 

 ends in view: 1°, to augment the intensity, 

 and consecjuentlj' the range, of the light ; 2°, 

 to create an appearance different from that of 

 a fixed light. The first can only be obtained 

 by giving the flash a duration much shorter 

 than that of tlie eclipse ; or, in other terms, 

 by making the angle of the luminous beam a 

 small part of the angle subtended by the lens. 

 Moreover, this angle depends on the dimensions 



