Hopwood's Living pictures; their history, photo-production, and practical working (1915)

i 7 8 LIVING PICTURES they offer with respect to cleanliness. The expense of such drums would, however, be somewhat heavy, and it is doubtful if the advantages would be sufficiently great. Two other forms of apparatus are of interest. In Marey's apparatus (Fig. 171), two drums, P, P, are used, the film F, wound in spiral, passing from one to the other. The drums do not themselves enter the liquid, but the film is carried down and under a roller, G, immersed in the trough D. The film might also be passed as an endless band through a long trough, A (Fig. 172), by means of a rotated roller, B. For drying the film, the most common method is to 1% / £^r\ ri^jj \ \ s— ^h FIG. 171. ' "; " " / FIG. 172. wind the film on a large rotated drum, such as B in Fig. I7OA, the drum being rotated by a motor in a room which is kept at a uniform temperature of 80° C. An alternative method is to hang the film by hand in a zig- zag path from a series of hooks in the ceiling. Continuous Processes. —With such frames the necessary winding from one frame to another, though very con- venient for comparatively short lengths of film, such as a topical film, is not the most scientific method for large quantities of film. The use of glass drums, as previously described, suggests a method that might be adopted— namely, joining several lengths of film, and running the film on to the drum at one end, and off at the other end,