y LIGHTHOUSE CHARACTERISTICS. 409 



snow, the fixed light is much safer than a one- 

 minute revolving light of much greater absolute 

 brilliancy ; as several successive flashes of the 

 revolving light may be lost through passing 

 showers, while the fixed light loses no chance of 

 being seen in intervals between the showers. On 

 the other hand, in hazy or foggy weather of toler- 

 ably steady character, a revolving light can be seen 

 efficiently at a greater distance than the same 

 absolute quantity of light, given out uniformly as a 

 fixed light. 



In the question of economy, the great first cost 

 of the optical apparatus, special to the revolving 

 light, must be set against the greater consumption 

 of oil, or gas, or fuel to obtain in a fixed light, 

 whether it be an oil or gas lamp, or an electric light, 

 the same brilliancy. In many cases, indeed, the 

 interest of the money spent on prisms, and lenses, 

 and mechanism in the revolving light, and in some 

 of the most beautiful and perfect of the appliances 

 for the azimuthal condensation of fixed lights, 

 would supply the oil required to give the same, or 

 nearly the same, brilliancy all round the horizon. 



