secondary shutter E, placed across the lens system of the project- 

 ion lamp, can be manipulated by hand to produce variable and 

 irregular flickeringo The pulley P is driven by a 1750 RPM, J-HP 

 motor through a series of reducing pulleys and V-belts not shown 

 in the diagramo In front of the shutter Sj behind window Wj a 

 Masonite light block M and 3 Kodak light filters A^, B^ and C are 

 mounted in such a way that each can be easily pushed into the 

 path of the light beamo 



The three Kodak filters are listed as "Series VII Wratten 

 filter A, ffl^) B., i58j and 05, j^7s" respectively„ Their trans- 

 mission characteristics were examined with a Beckman Model B 

 spectrophotometer with the results shown in figure 16, The fflS 

 red filter transmits a band of light with wave lengths between 

 about ^90 and 700 mju j the $xl blue filter between about 36C and 

 and 530 m/( , with maximum transmission at 14+0 m^ , and the #58 

 green filter between about l|.70 and 6l5 m/U j with maximum trans- 

 mission at 525 myu „5/ 



The intensity of illumination was controlled by use of the 

 powerstat when using the lantern, or by changing electric bulbs 

 from one wattage to anotner by methods to be described belowo 

 As lights of different ftrequencies have different intensity and 

 different penetrating power through water the intensity was 

 measured in situ by means of a photoelectric cell and an attached 

 microammeter;r The microariimeter was calibrated under standard 

 conditions 2! in terms of foot-candles and the calibration curve 

 was used in determining the intensities of the different lights 

 used as stimuli » 



A piece of heavy canvas was dr-aped over the instrument box 

 E to protect the apparatus against the weather and to serve as a 

 blind for the experimenter. An opening about 2 inches square was 

 cut in the canvas as an observation "peek hole," 



To contrast the -effect of a single beam of light with that of 

 night lights used in certain commercial fisheries^ incandescent 

 electric light bulbs were adapted for submergence under water and 

 for carrying a frame for glass filters of different colors » To 

 produce different quantities of light for stimulation,, UO-^, 60-j 

 IOO-5 and 200-watt bulbs were used, while to produce intermittent 

 light a practically noiseless mercury switch was introduced into 

 the line. Commercial colored electric bulbs (similar to those 



V The Kodak catalog lists this filter as transmitting two portions 



from the spectral bands a major portion between UBO and 6L1.O ma 



and a minor one between 670 and ?00 m/ui , with maximum transmis- 

 sion at 520 m/U 



zJ It is a pleasure to thank Mr. R.. Oberdorfer of the Physics Depart- 

 ment for his help in the calibrationo 



i;0 



