The paper says: “Daguerreotype images of the star Vega were obtained at the observatory of Harvard College on July 17, 1850, and subsequently impressions were taken from the double star Castor, exhibiting an elongated disc, but no separation of its two components. “These were the first, and until very recently, the only known instances of the application of photography to the delineation of fixed stars. A serious difficulty was interposed to further progress by the want of suitable apparatus for communicating uniform sidereal motion to the telescope. “This has been supplied by replacing the original clock of the great equatorial of the observatory by a new one, operating on the principle of the spring-governor. Immediately upon its completion, a new series of experiments was commenced. These have been successful in transferring to the plate by the collodian process, images of fixed stars to the fifth magnitude, inclusive, with singular and unexpected precision. The most remarkable instances of success are the simultaneous impressions of the group of stars composed of Mizar of the second magnitude, its companion of the fourth and Alcor of the fifth magnitude. The following measurements of the angular distance of the companion from Mizar were taken from the plates.” [Illustration: THE GOLD MEDAL; REVERSE SHOWING SIR WILLIAM HERSCHEL’S 40-FOOT TELESCOPE.] A tabulated statement follows in the paper, giving dates from April 27 to May 8, with measurements from 13 photographic negatives produced on the respective dates. The mean for distance is 14.49 seconds, and for angle of position, 147°.80. For the same stars observed in the usual way, Struve’s mean of six observations is, for distance, 14.40 seconds; for positions, 147°.40. Mr. Bond’s comments are: “The photographic method has thus in its first efforts attained the limit of accuracy, beyond which it is not expected the other can ever be sensibly advanced. “Should photographic impressions be obtained from stars between the sixth and eleventh magnitudes as has already been done for those between the first and fifth, the extension given to our present means of observation would be an advance in the science of stellar astronomy of which it would scarcely be possible to exaggerate the importance.”