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828 HANDBOOK OF PROJECTION FOR
has higher temperature than any light source yet used for motion picture projection.
Well, suppose the claim is true. What of it? The reflector arc lamp has been in use in this country in considerable numbers during the past two years. They have been in very general use in European countries during that period of time, and in considerable use for an even longer period. In fact this type of lamp has virtually superceded all other light sources for motion picture projection in some countries of Europe, and up to date we have heard of no greater percentage of fires, either in this country, Canada or elsewhere, since they have come into use.
As a matter of fact, with any light source acceptable for the projection of motion pictures under modern practice, the time required to lire the film, once it has become stationary over the projector aperture, and thus exposed to the light, is so very short that any added heat the reflector arc might produce would merely shorten it by a small fraction of a second. That this is exactly the real condition, every one familiar with motion picture projection knows. We submit that the addition or subtraction of the fraction of a second could not and would not make any real practical difference in the item of fire hazard, insofar as has to do with actual practice.
Modern professional motion picture projectors are so constructed that if they be kept in order, and if the projectionist be and remain beside them when they are working, there is little if any danger of an aperture fire getting away from the aperture. The danger of the fire getting into a magazine comes largely through the projectionist being elsewhere than in his rightful place beside the projector when, through some mishap the film, or some particle torn from it, becomes stationary over the aperture.
WE MAKE THE UNQUALIFIED ASSERTION THAT THE TIME FOR FIRING THE FILM WHEN USING A LIGHT SOURCE GIVING THE MINIMUM AMOUNT OF HEAT AT THE SPOT IS, IN PRACTICE, SO VERY SHORT THAT ANY ADDED HEAT BELOW THE TEMPERATURE WHICH WILL WARP THE PROJECTOR MECHANISM FRAME, OR MAKE THE METAL ITSELF DANGEROUSLY HOT, DOES NOT AND CANNOT POSSIBLY ADD APPRECIABLY TO THE ELEMENT OF FIRE FIAZARD.
ABUSE OF MIRROR.— It is necessary to the successful operation of reflecting arc lamps that (A) the rated amperage