45 BULLETIN OF THE BUREAU OF FISHERIES. 
in a plane vertical to that piece. When the two pieces are separated by moving the 
upper one on the hinge which connects them the rod slips through the opening in 
the block and may be firmly clamped at any point in its length by means of a 
set screw. Thus the upper piece may be held firmly at any angle to the lower 
piece from 0° to 90°, and the camera may be pointed at the water at any 
desired angle. The position in which the legs of the tripod are attached permits the 
camera to be pointed directly downward in the space between the two front legs, 
whereas if the legs were attached in the usual manner with one leg in front it would 
be impossible to bring the camera into the vertical position. Tripods of this type 
are to be found in the market or may be made from an ordinary tripod by any 
mechanic. 
When the operator has placed his camera and roughly adjusted it, he should 
set up a screen to cut off the light reflected from the surface of the water into the 
camera. Any piece of dark fabric, a blanket, shawl, or for small objects even a 
coat, may be used. It may be supported by hand or tied to poles stuck in the 
bottom. The writer carries into the field a screen made by sewing together pieces 
of black calico to form a sheet either 6 or 9 feet square. To three of the edges 
of this, at intervals of about a foot, are sewn pieces of tape each about a foot long and 
attached at its middle so as to leave 6 inches projecting on each side. One piece 
of tape should be attached to each corner of the screen. Two poles are cut of 
sufficient length to project 6 to 10 feet above the water when firmly set in the 
bottom. The poles are sharpened at one end, and beginning at the unsharpened 
end the square of calico is tied to them by the opposite edges by means of the 
tapes. The third side to which tapes are attached is the upper, between the 
unsharpened ends of the poles. The poles are now thrust mto the bottom on that 
side of the camera opposite the object to be photographed and so that they slant 
toward the camera. The screen (s s’, fig. 1) is thus stretched upward from the 
surface of the water in a slanting position, so that its upper edge is nearer the camera 
than its lower. If the two poles are pulled together by the weight of the cloth or the 
action of the wind so that the screen sags, a third pole tied between their upper 
ends will keep them apart, while the tapes on the upper edge of the screen will 
serve to attach it to the cross-pole. 
If the operator now returns to the camera he will see the screen mirrored in 
the surface of the water. The object to be photographed should fall within the 
limits of this mirrored image as seen from the camera.’ If it does not, the screen 
or the camera must be shifted until it does. The operator will see also the shadow 
of the screen. This should not fall on the object to be photographed. The screen 
should, if possible, be adjusted by slanting it or by moving one of the poles so that 
the sun strikes it nearly edgewise, but yet does not strike that face of it which is 
toward the camera. If this adjustment is properly made the shadow of the screen 
is a very narrow band, which lies beneath the screen and a little nearer the camera 
barrier reefs, but Rudaux (1908) stated the principle explicitly as applied in photographing in natural waters with a 
vertical camera objects within the reflected image of the tripod top. Neither recognized the broad application of the 
principle here described. 
