A USEFUL DRAWING CAMERA 



315 



keeping it free from wrinkles was attached to the reflecting box. 

 This consisted of three parts. The roll (w) was made of wood 

 and provided with a slit like a kodak film roll. It was attached 

 by brackets just above the glass plate. The roll (r) consisted 

 of a brass rod provided with a small crank at one end and cov- 

 ered for a length equal to the width of the glass plate with a 

 piece of soft thick walled rubber tubing. This roll was so fas- 

 tened to the frame that the tubing was compressed against the 

 glass plate near its upper edge. The strip (s) of springy brass 

 plate was bent into a flat curve and fastened by two screws at 

 the left of the glass plate and near its lower edge. Over the 

 strip several short pieces of soft rubber tubing were drawn. A 



Fig. 2. Reflecting box as seen from above, showing arrangement for holding 

 the parchment paper. Explanation in the text. 



metal tongue attached to the frame at the right made it possible 

 to hold the brass strip against the glass plate. 



In use the parchment paper cut in strips of proper width and 

 wound on the roll (w) was passed between the roll (r) and the 

 glass plate. The end of the paper was then fastened at the lower 

 end of the plate by means of the strip (s). A few backward 

 turns of the roll (r) stretched the paper smoothly over the glass. 



The whole apparatus rested upon wooden strips mounted on 

 a laboratory stand the height of which could be adjusted by a 

 crank. By sliding the camera along the strips it was possible 

 to focus the image without changing the distance between the 

 lens and the drawing surface. Thus a constant magnification 

 could be maintained throughout a series. 



