If the negative after developing and fixing turns yellow it indicates that the plate was not left long enough in the fixing-bath. As explained in one of the papers on the chemistry of photography, when the negative is placed in the fixing-bath a new compound is formed of the unchanged chloride of silver and the hyposulphite of soda. They unite and form a double salts, called silver sodium hyposulphite or thisulphate. This double salt is soluble in a solution of hypo, and the fixing-bath must be strong enough not only to form this double salt, but also to dissolve it. When it is thoroughly dissolved it is quickly washed out of the film. If the fixing-bath is too weak, or if the plate is taken from the bath too soon, the plate will soon turn yellow, and in time the image will be destroyed. To prevent this the plate should be left in the fixing-bath for five minutes after the plate is cleared from the silver bromide. When a negative after drying has a whitish appearance with a rough surface, it is because the plate was not washed long enough after removing from the hypo bath. Wash plates an hour in running water, or in eight or ten changes of water, changing at intervals of five minutes. ARTHUR NILSEN asks if portraits can be made better with snap-shots than with time exposures; and if with time exposures, the length of the exposure. Snap-shots for portraits give too harsh contrasts. For a time exposure with good light simply taking off and replacing the cap quickly will be long enough; or if a hand-camera with drop shutter, open and close the shutter as rapidly as possible without making the exposure instantaneous. One must learn to regulate the exposure according to the light, and the rapidity of the lens and plate used. With a little careful practice one can learn to expose the plate correctly. D. SAYLOR WILSON asks how to tell when a plate is fully developed. Examine the plate by looking through it toward the red light. If the detail is well out, and the negative looks as if it would be dense enough for a good print, return the negative to the developer, and rock it till the image is fading rapidly, then remove and wash and fix. With some kinds of developer the image must be allowed to fade entirely, but with hydrochinon developer the plate is developed far enough when the plate looks dense when examined by looking through it toward the light. [Illustration] The Leading Chefs Use only ROYAL BAKING POWDER Absolutely Pure EARN A GOLD WATCH! [Illustration] We wish to introduce our =Teas and Baking Powder=. Sell 50 lbs. to earn a =Waltham Gold Watch and Chain=; 25 lbs for a =Silver Watch and Chain=; 10 lbs. for a =Gold Ring=; 50 lbs. for a =Decorated Dinner Set=; 75 lbs. for a =Bicycle=. Write for a Catalog and order Blank to Dept. I W. G. BAKER, Springfield Mass.