SCIOPTICON MANUAL. G7 and forefinger, without being visible upon the screen, as is sometimes the case with the square slide. Then again, it is easier to place in its proper position (right side up), having only one chance of error instead of three. A DRY PLATE PROCESS FOR LANTERN SLIDES. TA1TNO-GALLIC PRESERVATIVE.* In considering the dry process, it is hut proper to say that a large number of different formules have been published; in fact, scarcely half a dozen photographers think alike on thi3 subject. It is, therefore, impossible to give a formula that will give universal satisfaction. In preparing this paper for publication, it must be dis¬ tinctly understood that nothing new in the way of pre¬ servative or development is claimed; it is simply one of the many methods for preparing dry plates that has given reliable results. The dry-plate photographer must be prepared for many and great failures, and bo possessed of the greatest amount of patience and nicety of manipulation, for other¬ wise time is wasted, and the best process voted a failure. Commence with reliable chemicals, and follow up the process with a lavish expenditure of water when wash¬ ing is mentioned, not only on the collodion plate, but thoroughly rinse the various glasses and dishes, and particularly the fingers, between each operation. Uso as little light as possible when making or developing dry plates, and he careful that the light is yellow. Probably more dry plates are ruined, and the par¬ ticular process used condemned as worthless; by the use * I am greatly indebted to my triend, Mr. E. Wallace, Jr., for bis kindness in furnishing me with the formula, and showing, by his own experiments, the valuable results to be obtainod from this process. J. C. Browne.