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 (8) 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 
