42 IOWA ACADEMY OF SCIENCES. 



through A. See Fig. 2. M, M are the sides of the fixed 

 portion of the pillar. I, I are the sides of the movable 

 parts. The bolts X, X are screwed into a hexagonal ring 

 or collar, and pass through holes in M and vertical slots in 

 I. The clamping screw A is attached to the same collar. 

 Tightening the thumb-nut A clamps I, I firmly against 

 M, M. 



On the top of this triangular pillar is a device for further 

 adjusting the camera by revolving it about the axis of the 

 lens. This is effected by placing the camera K (see Fig. 1) 

 on a base CB whose curved supports Y (one at each end 

 of the camera base) slide upon a sub-base, fixed on top of 

 the pillar and having end pieces Z curved to receive Y. 

 Cleats on Z prevent Y from displacement forward and 

 backward. The center of curvature of Z and Y is in the 

 axis of the lens. When tlit adjustment of the camera 

 about its axis has been made, the base CB is clamped 

 by the screw H, which engages a slotted plate of metal of 

 the same curvature as Y. 



The object to be photographed is mounted on the rack 

 or holder shown in Fig. 3. It consists of two uprights F 

 standing on a base 20 by 33 inches which rests upon the 

 rails R, and slides on them the same way as the camera 

 stand already described. If a drawing is to be copied, it 

 is pinned on a board 22 by 20 inches which rests in grooves 

 in the uprights F and is held up by the support P which 

 can be clamped at any height by the clamping device BO. 

 The construction of this clamp is shown in cross section 

 in Fig. 4. The rod BO, by pressure of the thumb nut B 

 causes the hinged plates at the ends to grasp the uprights 

 FF on the outside. The top of the support forms a shelf 

 OJJ on which small objects may be placed while being 

 photographed. The board P, which forms part of the 

 adjustable support, slides up and down in the grooves J of 

 the uprights. 



This whole rack or holder may be clamped to the table 

 by the clamp G, which slides with it in the longitudinal 

 slot. Besides being a clamp this contrivance, when the 



