the discussion, Professor Fox stated that he had seen Ha and He bright on the night of the 23rd. Slides of spectra taken at the Yerkes Observatory were also shown. F. Henroteau, "A region of the sky rich in variable stars." Reynold K. Young "The stationary calcium lines H and K in B-type stars"; and "The orbit of H. R. 8800." W. Carl Rufus, "The radial velocities of ten 0e5 stars." W. S. Adams and A. H. Joy, "The spectra of some variable stars"; and "Note on the spectrum of T Pyxidis." S. I. Bailey, "Periods of variable stars in the globular cluster, Messier 22." Harold L. Alden, "Observations of variable stars at the McCormick Observatory." Joel Stebbins, "Progress in photo-electric photometry, with a new lightcurve of Algol." The new curve of variability of Algol measured with the photo-electric cell shows only slight divergences from that measured earlier with the selenium cell. E. S. King, "Velocity curves for spectroscopic binaries." Sets of curves were exhibited from which the elements of the observational curve could be readily inferred. Leon Campbell, "Notes on long-period variables." Star Positions and Proper Motions.-Henry Norris Russell, "Radiation pressure and celestial motions"; and, "On the value of parallaxes derived from the proper motions of small groups of stars." S. A. Mitchell, "Systematic errors in stellar parallaxes determined by photography at the McCormick Observatory. H. L. Alden and S. A. Mitchell, "Parallax determinations of bright stars." Oliver J. Lee and George Van Biesbroeck, "Parallax results obtained at the Yerkes Observatory." Frank B. Littell, "Photographic zenith tube: Accuracy of observations for variation of latitude: Constant of aberration from four years' observation." The mean value for the four years was 20 454, corresponding to the parallax 8" 807. Arthur J. Roy, "A solution of R minus D observations." Philip Fox, "Stellar parallax determinations at Dearborn Observatory." instruments and Mechanical Devices.-Alice H. Farnsworth, "The photometric fields of three Yerkes telescopes." Robert W. Willson, "A new method of observing the position of the centre of the sun." By using a cone of glass or multiple prism arrangement the usual image of the sun is converted into an image with accurately defined centre on which settings may be made. Louis Bell, "Ghosts and oculars." The reflections and multiple reflections of many lenses and combinations of lenses were considered and the arrangements most free from them were pointed out. George E. Hale, "Some recent photographs taken with the 100-inch telescope." The lantern slides shown at the conversazione were greatly admired, and a congratulatory message was sent by the society to Dr. Hale and his staff. The sharpness of fine details in the moon pictures was perfect in the great enlargements. The photographs of nebulæ, star clusters, and Jupiter were splendid, and the comparisons with the 60-inch reflector illustrated the advantages of the larger. (Recent tests of the two reflectors-simultaneous 2-minute exposures on Seed 30 plates, average seeing, the same development-show limiting magnitudes of about 18 and 17— a gain of about a magnitude for the larger instrument). R. M. Stewart, "Temperature compensation of chronometers." Miscellaneous.-Sebastian Albrecht, "Personality in the estimation of tenths." Frequent familiarization with known' tenth settings and also the use of scale markings two-tenths wide lessen the preference for certain tenths which most individuals possess. F. Henroteau, "A curious effect of superposition of two photographic plates"; and, "A graphical construction for obtaining the period of a phenomenon." Frank E. Ross, "Mensurational properties of the photographic plate." Depending on the developer used, the parts of the film affected and unaffected by light, dry at different rates and produce shrinkages at the edges of images of such a nature that the measurements of the separations of adjacent star-images or spectrum lines may be seriously affected. George Henry Peters, "Absorption of the photographic rays by the atmospheric water content." E. C. Bower, "On telegraphing the position of a celestial object." Louis A. Bauer, "Concerning results of observed gravitational light deflections." L. Silberstein, "The astronomical aspects of aether theory versus relativity." The possibility of explaining the three Einstein effects on the assumption of a condensation of the aether about the sun, was discussed. C. C. Kiess, "New lines in the spectrum of oxygen." R. M. Stewart, "Canadian transcontinental longitudes"; and, "Arlington time signals." H. T. Stetson, "The investigation of the plate errors in photographic photometry." H. N. Russell, "The probable diameters of the stars." Seven methods were discussed and comparisons made of results obtained by the various methods. As usual, the meeting was most interesting. The annual meeting usually attracts members from even the greatest distances, and this year Townley came from California, Gallo from Mexico, and Douglas, with perrennial enthusiasm, from Arizona. There are no astronomical meetings in Canada just like it as our Society holds its meetings at the local centres. A large annual meeting might be arranged during the summer when the centres do not hold meetings, but the same purpose would be served if many more members of our Society would become members of the American Astronomical Society (which includes members from both American continents), and attend its meetings. The two Canadian observatories contributed fourteen papers to the meeting, and four members attended from the Dominion Observatory, whose Director, Dr. Klotz, was honoured by election to a Vice-Presidency. The next meeting of the Society will be held in connection with the large meeting of the American Association for the Advancement of Science to be held in Chicago in December, 1920. The place of the annual meeting next summer has not yet been decided upon. BY F. HENROTEAU The following observations were made by the author at the Observatoire Royal de Belgique in 1911. Their object was to determine the photographic light-curve of RS Orions and see how it compared with the visual. Not very many observations had been obtained; however, it was thoght advisable not to leave them unpublished any longer. The photographic light-curve was determined by means thirteen plates, using the focal method. The diameters of the star images were measured with a microscope, five times in a horizontal direction and five times in a vertical direction. The following stars were taken as comparison stars on each plate: B.D. 14°. 1249. B.D. +14°. 1248. B.D. +14°. 1262. whose magnitudes given in the B.D. catalogue are respectively 8m. 5, 9m. 0, 8m. 4, and 9m. 1. In the different columns of the following table we designated: 1o. By the letter L or I the plates that have been used. L are the very rapid Lumiére plates (violet label) and I the Imperial plates (made in London). 2o. To obtain the magnitudes from the measures we used the formula m = a - n√D Where a and n have been determined separately for each plate, using a least squares solution. The first comparison star was not used, however, since the results furnished by the measures of the diameters of its images showed that its photographic magnitude was very different from its visual. Nevertheless. it seems to confirm that the three other comparison stars have photographic magnitudes not very different from their visual. Adopting the period given by Münch who determined the visual light-curve of RS Orions1 we have the following table of observations: 1A. N. 182, 1909, p. 129. |