METHODS OF STUDYING VISION IN ANIMALS 



9 



ability, both oil lamps and candles constitute fairly satisfactory 

 sources, provided the intensity of light needed is not high. 



Tables i and 2 ' present data concerning the color- and inten- 

 sity-values of the sources of light which are most commonly 

 used. It is needless to state that these data are not highly 

 accurate. 



TABLE 1 



Color of Common Illuminants 

 lUiiminant Color 



Acetylene Nearly white 



Arc light (enclosed) Bluish white to violet 



Arc light (open) White 



Candle Orange yellow 



("arbon incandescent (below voltage) Orange to orange red 



Carbon incandescent (normal voltage) Yellowish white 



Gas light (open flame) Yellowish white to pale orange 



Gem metallized filament incandescent Nearly white, slightly yellowish 



Kerosene lamp Orange, slightly yellowish 



Nernst lamp White 



Mantle burner Greenish white 



Sky light Bluish white 



Sun (high in sky) White 



Sim (near horizon) Orange red 



Tantalum White 



Tungsten White 



TABLE 2 



Intensity of Light Sources in Candle Power per Square Inch of 



Illuminating Surface 



Intrinsic 



Source lirilliancy Remarks 



Opal shaded lamps (electric) ^ to 2 c. p. 



Frosted incandescent lamps 2 to 5 



Candle 3 to 4 



Gas flame 3 to 8 Varies widely 



Oil light 3 to 8 



Mantle burner 20 to 25 Prol)ably too low 



Acetylene flame 75 to 100 



Enclosed arc lamp 75 to 200 Depending on globe 



Incandescent lamps (carbon) 



Carbon 4.0 watts per candle 300 



Carbon 3.5 watts per candle 375 



Carbon 3.1 watts per cantUe 480 



Gem metallized filament incandescent, 



2.5 watts per candle 625 



Tantalum incandescent 750 



Tungsten incandescent 1 ,000 



Nernst lamp (bare) SOO to 1,000 



Open arc lamp 10,000 to 100,000 (200,000 in crater) 



Sun on horizon 2 , 000 



Sun at 30° elevation 500 ,000 



Sun at zenith . . 600 , 000 



' These tables are taken from " Data on illumination." Bulletin of the Engi- 

 neering Department "of the National Electric Lamp Association, No. 7, June 1, 1907. 



