196 REPORTS ON INVESTIGATIONS AND PROJECTS. 



had shown to be of most importance in their relation to the several streams. 

 Accordingly, the following groups of stars were placed on the observing 



list: 



(1) Distant A-type stars, which appear to belong to the second stream. 



(2) Certain stars having spectra designated c according to Miss Maury's 

 notation. These stars have been found by Hertzsprung to be very remote. 

 A recent determination by Kapteyn and Hertzsprung from 45 stars with 

 magnitude of 4.5 gave an average parallax of o".oo2. This is about the 

 average parallax of A-type stars of magnitude 10.7. 



(3) A-type stars, presumably members of the first and second streams, 

 which are approximately 90 distant from the corresponding vertices of the 

 streams. 



(4) A-type stars of the second stream which have fairly large coefficients 

 for the determination of the stream velocity. 



(5) All the B, A , and A x stars which appear to belong to the second 

 stream. 



(6) Stars which belong to the Ursa Major group. 



professor Barnard's observations. 



Prof. E. E. Barnard, of the Yerkes Observatory, spent the month of 

 November on Mount Wilson making photographic and visual observations 

 of the planets Mars and Saturn with the 60-inch reflector. The season 

 was not the best for such work, as bad conditions had set in with the winter 

 rains. The selection of this season, however, was conditioned by the op- 

 position of Mars, which occurred November 24, and was not therefore a 

 matter of choice. The size of the image of Mars, which is a most impor- 

 tant factor in photographing the planet, was much smaller than in 1909. 

 The maximum values were: 1909, diameter 26".o; 191 1, diameter I9".8. 



On account of the regular program of observations with the 60-inch re- 

 flector, the observations were necessarily limited to certain nights, when 

 the telescope was arranged for the work in hand. Most of the observa- 

 tions were made with the Cassegrain arrangement, giving an equivalent 

 focal length of 100 feet, because of the increased scale value of the photo- 

 graphs. On a few occasions visual observations were also made in the 

 principal focus of the telescope. The time required for the change from 

 one arrangement of the telescope to the other prohibited the use of both 

 arrangements during a single night. Some opportunities were therefore 

 lost when visual observations might have been made to advantage with the 

 shorter focal length. 



A number of exposures on Mars and Saturn were obtained with the equiv- 

 alent focal length of 100 feet, with the addition of an enlarging lens which 

 had previously been employed in photographing Mars with the 40-inch 

 Yerkes telescope in 1909. To secure increased sharpness of the enlarged 

 image, the photographs of Saturn were made through a yellow color-screen 



