This is a very simple and easily made optical apparatus for copying pictures and making drawings of flat objects. Get a smooth board, or your drawing board will do; make a wood frame and fit an 8 x 10 sheet of clear glass in it and screw the frame to the middle of the board as shown in Fig. 52.

Now all you have to do is to lay a picture or a flat object, such as a leaf or a butterfly, on one side of the glass and a sheet of paper on the other side and look into the glass at a sharp slant, or acute angle would be the better term, and you will see the picture projected plainly on the paper so that you can easily draw it in with a pencil.