In arranging for the picture it is more convenient to fix on some line or small object which shall come in the centre of the plate when the exposure is made. The subject to be photographed should stand at least nine or ten inches one side of this central point, for if the drapery of the dress overlaps, the picture will show a blur. In making the exposure great care must be taken not to move the camera, as if it is moved even the very least bit, a blurred line will appear in the picture showing just where the two exposures join. The focus must not be changed unless a plain background is used. In making the exposures for the two pictures the time of both must be equal. This is more necessary for an exposure made out-of-doors than for one made in the house. If the exposures are unequal in time the negative will be unequal in development, and, as a consequence, half of it will be lighter than the other. Many interesting and amusing pictures may be made by the means of double photographing. A person may be taken playing checkers or chess with himself, reading to himself, taking his own picture, offering himself something to eat, etc. An amusing picture might be made of a person begging of himself, the first picture being taken in his ordinary walking dress, and the second dressed in ragged clothes and holding out his hat for alms. [Illustration: AT WAR WITH HIMSELF.] In the accompanying picture the subject is fighting a duel with himself. SIR KNIGHT FREDERICK CLAPP sends a print, and asks the reason of the spots on the negative from which it is made, and when the next photographic competition is to be conducted. The spots on the negatives which make the print imperfect are caused either by bits of film or dirt in the developer settling on the film, or by air-bubbles forming on the surface of the plate when it is covered with the developer. In either case the developer is prevented from acting on the film, and causes spots which have the effect of halation. Small round holes in the negatives are caused by dust on the plate. The time of the photographic contest has not yet been decided. It will be announced in this column as soon as arrangements are completed. SIR KNIGHT CALVIN FARRAR sends a print of the interior of the log cabin built for the recent celebration in Cleveland. Please accept thanks for same. SIR KNIGHT RICHARD C. LORD asks for a formula for developer for snap-shots and for time exposures. See answer to Sir Charles Lusenkamp for formula in No. 886. The J. C. tabloids make a fine developer for instantaneous exposures. "QUAD," Pittsburg, Pa., sends a print from a film, and asks what gives it its mottled appearance. As far as one can judge from the blue print, the mottling is due to imperfect fixing, or the film was left too long in the developer without rocking. There is no remedy for the film.