WHAT THE FISH SEES 



surface, showed the image on the ground glass was 

 always blurred, because the lens was made for the 

 refraction between glass and air and not for that 

 between glass and water, which differs by about 

 one-third. A lens could be made for this purpose, 

 but it would take much time and expense, so the 

 usual method of looking through a glass plate into 

 the water was adopted. The plate was set in the 

 end of the tank holding the water, at an angle of 

 forty-eight and one-half degrees, and the camera 

 placed at right angles to the surface of the plate. 

 In this way the light from the water to the camera 

 passes through the glass exactly at right angles 

 and will not be bent or distorted, and a true image 

 of what the fish sees in the water or on the surface 

 is obtained. As the effects of light, due to the mo- 

 tion of the fly, were of most interest, I soon saw 

 that the ordinary camera would not succeed in 

 catching just the things I wished to show, so I 

 decided to use a moving-picture camera and make 

 "cut-outs" from the film, which would give more 

 convincing illustrations of what was seen. Mr. 

 James L. Clark, who makes the wonderful Akeley 

 Camera, kindly volunteered to take this difficult 

 subject. It was very hard to do because of the 

 small size of the flies and the reduction of the light 



[ 45 ] 



