THE OBSERVATORY OF TRINITY COLLEGE, DUBLIN.—The fourth part of “Astronomical Observations and Researches made at Dunsink” has just appeared under the editorship of Mr. J. L. E. Dreyer. It contains the results of about 1140 observations of 321 red stars, chiefly taken from Schjellerup's Catalogue, made with the meridian-circle of the Dunsink Observatory, the object-glass of which has an aperture of 6.38 inches, the instrument being the work of Piston and Martins of Berlin. The observations were commenced by Dr. Copeland in July, 1875, and continued by him up to the end of March, 1876. Mr. Dreyer commenced observations in September, 1878, and the series was finished in November, 1880. As far as possible, it has been the object to secure four complete observations of each star. The separate results are printed, with the corresponding dates and estimates of the magnitudes of the stars which have a particular interest from the fact of so many of the red stars being variable. The Dublin observations show this to be the case in a striking degree, and not only is there variation in the brightness of many of the objects, but it is hardly possible to doubt that they establish changes of colour from time to time in some of the stars. Thus we find No. 5 (Schjellerup) was white on November 14, 1875, and deep orange three months later. No, 143 was considered orange on February 28, 1876, but showed no colour on March 19; in March, 1880, it was again orange. No. 186 had no colour on April 30, 1880, but was deep orange on June 10 following; and there are a number of similar cases, too many, it would appear, to allow of their being attributable to varying conditions of atmosphere.