332 Applicability of the Electric Light to Lighthouses. 



required for obtaining it may be turned to good account in 

 bell-ringing, and the production of other sounds much louder, 

 and therefore audible to a much greater distance, than those 

 which are possible with the means at present employed. 



It is only in intermediate states of the atmosphere that the 

 electric light has advantages over the ordinary light. At other 

 times, its intensity is considered by the French engineers, even 

 as a disadvantage, since it causes the eye to be dazzled, and 

 therefore renders it incapable of seeing distinctly. Com- 

 parisons have been made between it and a first-class oil light, 

 in hazy states of the atmosphere ; and it has been found that 

 its advantage rapidly diminishes as the state of fog is ap- 

 proached. But, with the electric light, the greatest power of 

 the rays may be directed a little below the horizon, so as to 

 give more intensity to the plunging rays ; which is impossible, 

 with the ordinary light, without reducing the distance at which 

 it will be visible. And the necessity for having a duplicate 

 steam-engine makes it easy, without much additional expense, 

 to double the power of the apparatus, which increases the 

 penetrative capability of the light. Thus, when an electric 

 light, of a given power, in a given state of the atmosphere, will 

 be visible for the distance of not quite sixteen kilometres, a 

 light of double the power will be visible, in the same state of 

 the atmosphere, for more than seventeen kilometres. The light 

 of a first-class oil apparatus, in the same circumstances, would 

 be visible only for the distance of about thirteen kilometres. 



The optical apparatus required by the electric light is less 

 expensive than that which must be used with a light of the 

 ordinary kind. The optical apparatus must, in every case, bear 

 a relation to the light in its focus ; and the oil light is far 

 larger than the electric. With the ordinary optical apparatus, 

 the electric light would not have sufficient divergence ; and 

 the rays would be thrown into the form of a ring, either whole or 

 broken. When an oil light requires an optical apparatus 1*84 

 met. in diameter, one 0*30 met. in diameter will be large 

 enough for the electric light. If, therefore, a new lighthouse 

 is to be erected, there will be, with the electric light, a great 

 saving in the item of optical apparatus ; but, if the electric 

 light is to be substituted for the ordinary oil light, . the aug- 

 mentation of expense, attendant on its use, will be considerable. 



The cost of the electric light, both in its application and 

 maintenance, is very serious; though not sufficiently so to 

 justify its rejection, should it be found, in other respects, 

 advantageous. The Elder Brethren of the Trinity House state 

 that the cost of the apparatus which it requires, and even the 

 maintenance of the light, far exceed those of an ordinary 

 dioptric light of the first order. The apparatus at Dungeness 



