172 MARVELS OF FISH LIFE 



sion upon it. Therefore, when using the camera above 

 the surface of the water it is necessary to use some 

 form of apparatus which cuts off the light from above. 

 With this object I use three different contrivances : 

 (1) A light wooden frame, six feet by four, over which 

 is stretched a sheet of dark-coloured canvas ; (2) a 

 large golf umbrella ; and (3) a special apparatus on 

 the principle of a sea telescope. The method of 

 using the frame is to fix it at an angle to the sur- 

 face of the water, facing the sun. Thus the light is 

 cut off from above, and if the shield points directly 

 towards the sun, only a narrow shadow is thrown at 

 its base. The sunlight, penetrating the water at an 

 angle, illuminates every pebble. In this manner a 

 photograph of a swimming fish can be taken at an 

 exposure of ^th of a second below three feet of 

 water. 



When it is desired to take a photograph looking 

 directly down on a fish, the second method is avail- 

 able. In this case the light from above is cut off by 

 holding a large umbrella above the head of the photo- 

 grapher. The illustration of a young thornback ray, 

 facing page 44, was obtained in this manner. 



These two devices, however, can only be employed 

 when the surface of the water is unbroken. When that 

 condition prevails resort is made to my third device, 

 which is illustrated on the plate facing this page. This 

 apparatus was constructed with the two-fold object of 

 cutting off the light from above and of getting below 



