It is possible to take twelve different pictures of various subjects on one 5-in. by 4-in. plate, one lens only being used. A repeating back to the camera is needed for such work. But where more than one row of pictures is taken, the back must have a vertical sliding movement as well as a horizontal one. The reversing back is made in two frames: the first or back frame fastens to the camera back frame or into the reversing back catches; the second consists of two rails A A, between which runs a sliding board B with opening C of the desired size, say 1 in. square. Across from A to A run the slide rails D, with a catch in the top and three cuts in the slide to engage with the catch. For the first exposure the slide is put in as shown in the sketch, and is moved forward for each successive one. After three exposures have been made, the sliding board is then lowered to the next point and the slide pulled back to the first position again. By lowering the board and pulling back the slide twice more in this way, twelve exposures, each about 1 in. square, may be made on a 5-in. by 4-in. plate, as has been stated.

Double Repeating Back for Camera.