LIGHTING 73 



current enters the park, so that in case of accident, the 

 entire park will not be thrown into darkness. 



Arc and incandescent lights may be connected either in 

 multiple or series. It is possible to use both kinds of lights 

 on the same circuit. 



The multiple system of wiring is generally preferred, 

 especially when the number of lights is large, inasmuch as 

 it is safer than the series system. The voltage commonly 

 employed for multiple wiring is 110, though it may be 220 

 and even 550, as in the case of a park illuminated by a 

 trolley current. Willow Grove Park near Philadelphia is 

 an example. To determine the voltage required for an arc 

 light circuit in series, the rule is to multiply the voltage of 

 each light, which is about 80, by the number of lights. 

 Series wiring is frequently employed in small city squares. 



2. Gas. The plain jet does not give sufficient illumina- 

 tion. Lights with mantles give a bright and satisfactory 

 light. Gas can be used to advantage in districts where 

 the price is low, as in the natural-gas belt. Gas mains 

 should never be laid near trees and shrubbery. Leakage 

 of gas exerts a very harmful effect on vegetable life. 



3. Acetylene. This gives a brilliant and satisfactory 

 ulterior light, but is seldom used in park lighting by reason 

 of the expense. The acetylene gas is piped in wrought-iron 

 pipes. 



4. Gasoline. Gasoline lighting is cheap and satisfactory 

 in several respects. The great drawback lies in time con- 

 sumed in igniting the lamps. Each lamp is provided with 

 a mantle, and a torch must be used to vaporize the gasoline. 



