PHOTOGRAPHY OF AQUATIC ANIMALS. 45 



of these distant objects is formed, not on the photographic plate, but in a plane 

 situated somewhere between that plate and the lens, as at / I' . After forming 

 the image at / /' these rays again diverge and strike the photographic plate. The 

 plate is thus flooded by light from distant objects that are wholly out of focus, so 

 that such rays do not form a distinct image on it. This reflected light is usually 

 brighter than the light which forms the image of the fish. It affects the plate 

 with greater intensity, so that when the plate is developed the image of the fish is 

 quite obscured by the general fog produced by the brighter light. There appears 

 in the negative only a uniform dark haze, which represents the surface of the water. 



If the ground glass is put in place and brought b\ T focusing into the plane / /', 

 then the sharp image of distant clouds and trees is seen on it, while the image of 

 the fish lies behind the ground glass and is no longer clearly visible. If the water 

 is smooth, a plate exposed under these circumstances gives a sharp negative of 

 these distant objects, but does not show the fish. 



If one looks at the fish in the water from the point C it is seen clearly, because 

 its image is focused on the retina, while the images of more distant objects mirrored 

 in the water's surface fall in front of the retina, and the objects from which they 

 come are therefore not seen. The observer neglects the glare of light from these 

 distant objects, fixes his attention on the fish, and sees it. If now, while still 

 looking toward the fish, he adjusts his eye to distant objects by relaxing the ciliary 

 muscle, these are clearly seen mirrored in the surface of the water, while the fish is 

 no longer sharply seen. Similarly, if a mirror is laid on the ground so as to reflect 

 the clouds and its image is examined by focusing in a camera, it is impossible to 

 get at the same time on the ground glass a sharp image of the clouds reflected in 

 the mirror and of the frame of the mirror or other near object. It is only when 

 the mirrored object lies near the surface of the water that its image can be focused 

 on the photographic plate or retina at the same time with that of a submerged 

 object near the surface. It nearly always happens that the light entering the 

 camera from distant objects mirrored in the surface of the water is so much more 

 intense than that from submerged objects that the images of the latter are quite 

 obliterated on the photographic plate. Sometimes, on the other hand, when the 

 camera is pointed nearly vertically into the water at an object over a light-colored 

 bottom, the emerging light is more intense than the reflected light, and there is 

 obtained a more or less fogged negative which shows submerged objects. This is 

 the more apt to be the case if the photographer has the sun at his back. (See 

 Saville-Kent, 1893.) At other times, within the limits of the reflected image (not 

 the shadow) of a dark-colored bridge or building or of dense foliage, one may obtain 

 a fogged negative, showing submerged objects. In this case also the partial success 

 is due to the fact that the reflected light is less intense than that which comes from 

 the submerged objects to be photographed. It is not often, however, that the 

 submerged objects that one wishes to photograph are found within the reflected 

 images of dark-colored backgrounds of sufficient size and far enough away. 



The above discussion is based on the assumption that the surface of the water 

 is smooth so that it acts as a single large mirror. If the water surface is disturbed 

 it is broken into numerous smaller surfaces, concave, convex, or plane, and each 

 of these acts as an independent small mirror. These form distorted images of 



