Mr. A. A. Merrill, lecturer on aeronautics for the Boston. Y. M. C. A., will deliver a stereopticon lecture on "The Principles of Mechanical Flight" in the Lecture Room of the Fogg Museum this evening at 7.30 o'clock. This will take the place of the motion picture exhibit which was advertised for this date.

Mr. W. H. Aitken, who has charge of the aeronautical exhibit at the "Boston 1915" exposition, will fly a model Bleriot aeroplane. Announcement as to the library, lecture courses, and gliding sections will be made by officers of the society. J. V. Martin Sp., director of the society, will speak about the flying exhibit to be given in the spring.

Admission will be free and the lecture will be open to the University and the Massachusetts Institute of Technology, where Mr. Merrill gave a course of lectures on aeronautical subjects.