The Ansco machine makes use of an idea frequently applied in the moving picture industry. The film is carried spirally, upon two cross-arms which bisect each other at right angles, and which contain vertical pins around which the film is looped, beginning at the center and working out. After it is wound it is placed in a tub of developer, as in the G. E. M. machine. It has an advantage over this apparatus in that the shape of the tubs or tanks is square instead of round. But it is equally extravagant of space and water. This same criticism may be made of the Eastman apron apparatus for film developing. This is similar to the G. E. M. machine, but differs from it in using a perforated celluloid apron to support the film during the various operations, instead of a metal chain. The Brock developing outfit consists of a rectangular wooden frame and a three-compartment tank. The frame, which is approximately 3 by 4 feet in size, is used as a support for the 4 inch wide film, which is wound spirally around it, between guiding pins. A special support is provided, on which the frame may be rotated as the film is fed off the camera spool. The frame, with the film on it, is lowered successively into the three narrow but deep compartments of the developing tank. The first compartment holds developer, the next water, the next hypo. The amount of developing solution required is rather large (96 gallons of water in all for a strip of 100 4 × 5 inch exposures), but because of the small surface exposed to the air, it keeps for a considerable period. The chief demand for floor space with this apparatus is for feeding the film on to the frame. In the Eastman twin reel machine the film is wound on a wooden drum or reel of large diameter, to form a helix. The drum is suspended so that the bottom edge touches the developing solution, and, upon revolving the drum, every portion of the helix of film is brought into contact with the developer. By shaping the developing tank so that it closely conforms to the shape of the reels, a high economy in quantity of developing agent can be achieved. When developing action is finished, the developer is emptied out, rinse water put in; hypo follows, and then comes the final washing with water. With this apparatus the whole cycle is completed, for the 35 feet length of film above considered, with seven gallons of water. The Air Service apparatus differs from the above only in the drying method, which will be described below.