THE DISTORTION OF PHOTOGRAPHIC FILMS IN STELLAR WORK.—In No. i, vol. i., of the Publications of the Allegheny Observatory (Pennsylvania), Dr. Frank Schlesinger discusses the possibilities of error introduced into photographic star-measures by reason of the distortion undergone by the film during the process of development. He further describes some experiments and measures he has made in order to determine the magnitude of this error. By developing, drying, and measuring, a negative in the ordinary way, and afterwards putting it through the developing, fixing, washing, drying, and measuring processes again, he has obtained the data from which he draws his conclusions. Briefly, he finds that this error is much smaller than the error of bisection for good star images, being of the order of one one-thousandth of a millimetre for the kind of plate employed.