PHOTOGRAPHY OF AQUATIC ANIMALS. 49 



distant objects which would otherwise be reflected into the camera from the surface 

 of the water are cut off. If the sunlight is permitted to fall on that face of the 

 screen which is toward the camera, it is reflected from the screen to the surface of 

 the water and thence into the camera. A picture taken under these conditions 

 may show, besides the object under the water, also the screen itself, although this 

 image of the screen is usually so faint that it does not interfere with the use of the 

 picture for scientific purposes. 



When the screen has been properly set the operator has merely to adjust the 

 camera and make the exposure in the customary way. If the subjects are fish they 

 will usually have been frightened away, but if the fish are engaged in nest building 

 or in some other occupation that attracts them to a particular spot, they will, in 

 most cases, return after a tune varying from five minutes to an hour. The operator 

 has merely to remain quiet until this happens. The photographer may focus his 

 camera on the spot to which the fish is likely to return and then withdraw and 

 operate the camera from a distance by pulling a string or pressing a bulb when 

 the fish returns. The method is of most use in securing photographs of the nests 

 and habitats of fish in shallow water, yet the writer has succeeded by means of it 

 in making some satisfactory photographs of fish on the nest. 



The result of using the screen is shown in figure 1 of plate ni, which is a photo- 

 graph of the nest of a small-mouthed black bass. The screen in this case was stretched 

 on a frame and was held by hand. Within the limits of the reflection of the screen 

 in the water's surface the bottom may be seen clearly. At the center are the larger 

 stones which form the bottom of the nest, and these show sharply the details of 

 then" markings. Outside the limits of the reflection of the screen the bottom is not 

 clearly visible; its image has been obscured on the sensitir'e plate by the bright 

 light reflected from the surface of the water. The sun struck the back of the screen 

 from the left, as is shown by the shadow which lies close to the screen. Within 

 the limits of this shadow the plate was underexposed and details of the bottom 

 are not visible. With a longer exposure as good a negative could have been made 

 of what lay in the shadow. 



If the surface of the water is not smooth it may be made so by a water glass, 

 which may be constructed as follows (fig. 1, pi. iv): A square frame is made of 

 heavy galvanized iron, and measures 3$ inches deep and 12 inches on each side 

 within. One of its edges (the top) is turned outward three-fourths of an inch and 

 then downward one-half inch to form a lip. This stiffens the frame and tends to pre- 

 vent water from slopping into it. The lower edge of the frame is turned outward 

 about half an inch to form a flat surface, against which the glass, 13 inches square, is 

 bedded in aquarium cement. After the glass is in position four trough-shaped pieces 

 are soldered to the sides of the frame and to one another in the manner shown in the 

 figure. The free edges of these pieces project inward beneath the lower surface of 

 the glass and support it. Before the pieces are soldered into place cement is placed 

 between them and the lower face of the glass. The whole border of the glass is thus 

 bedded in cement on both surfaces and at the edge. To protect the glass when not in 

 use a flat cover is provided, which fits against its lower face. Such a water glass may 



B. B. F. 19074 



