310 BULLETIN OF THE BUREAU OF FISHERIES. 
on the outside. The canvas (c) can then be placed under this frame, and hav- 
ing suitable eyelets (d) in its edge, can be stretched tightly upon the frame by 
a lacing (e) which is passed through the eyelets (d) in the canvas (c) and the 
hooks or pins (6) on the frame. In order that the radiographs of objects along 
the sides may be complete and properly made, and be not intercepted by this 
frame (a), another frame (f), of wood or other material which will allow the 
rays to pass through, is placed between the canvas and the first frame (a) and 
secured to the latter by means of screws (g). The frame } projects suffi- 
ciently inside of the frame a to hold the materials that are being examined at 
such a distance that the rays (h) pass through the very outside of the material, 
clear of the frame a, and will produce the desired effect upon the sensitized 
medium (z) underneath the tray. 
Upon the tray and preferably upon the second frame (f), or upon the canvas, 
is placed a number, letter, or some other device by which to distinguish the trays 
from each other. ‘This sign (k) is here shown as a number (23), cut out of metal, 
Fic, 3.—Conveyer to substitute for tray of figures 1 and 2, 
which is impervious to the ray, and properly secured to the frame f or the 
canvas. 
The invention may be modified, as, for instance, by substitution of a con- 
veyer in place of the tray. One form of conveyer is shown in figure 3. Here 
the canvas (c) is an endless strip passing over rollers (/J). The frame (a) is 
shown as raised above the canvas a sufficient height to allow the objects placed 
upon the canvas to be moved under it. The canvas is in divisions equal in 
size to the frame, and each division is provided with a distinguishing mark (k), 
-as already described. In operation of this modification, the objects are placed 
within the frame and upon one division of the conveyer. ‘The sensitized 
medium (2) is placed under it as shown, and the radiograph is then taken. The 
conveyer is then moved by turning one or both of the rollers, so that the objects 
will have passed to one side and an uncovered portion of the conveyer is exposed. 
More objects are placed upon this within the frame, and a second radiograph is 
taken. This will be repeated, the first radiographs being developed while others 
