At the first meeting of the autumn, held on the evening of October 15, sixteen persons present, Mr. Wm. H. Roever, of Washington University, presented an elaborate paper discussing in detail the subject of the establishment of the method of least squares. Professor F. E. Nipher presented two papers, entitled respectively Positive Photography, with special reference to eclipse work, and The Frictional Effects oi Railway Trains upon the Air; and Mr. C. F. Baker exhibited an interesting collection representing nearly all of the species of fleas thus far known, which he had prepared for the United States National Museum.