172 re;ports of investigations and projects. 



ASTRONOMY. 



Campbell, W. W., Lick Observatory, Mount Hamilton, California. Grants 

 Nos. 421 and 231. (a) Pay of assistants to take part in researches at 

 the Lick Observatory, $4,000. (h) Measurement and reduction of photo- 

 graphic plates of Eros, $3,000. (For previous reports see Year Book No. 

 2, p. xix ; Year Book No. 3, p. 86 ; Year Book No. 4, pp. 82-83, and Year 

 Book No. 5, pp. 86-88.) $7,000. 



(a) In the spectrographic determination of stellar velocities there have 



been employed, as assistants in the past year : 



Mr. Keivin Burns, October 1, 1906, to October i, 1907. 

 Dr. B. L. Newkirk, October i, 1906, to August i, 1907. 

 Miss Leah Allen, September 9, 1907, to October i, 1907. 



Mr. Burns secured 52 spectrograms with the ]\Iills spectrograph attached to 

 the 36-inch refractor, and made first measures and reductions of 40 spectro- 

 grams and definitive measures and reductions of 223 spectrograms. This 

 completed the measurement and reduction of all the spectrograms obtained 

 with the Mills spectrograph, as originally mounted, between August, 1897, 

 and July, 1903. Mr. Burns devoted three months to a study of the residuals 

 afforded by the separate spectrum lines on 750 plates selected from those 

 obtained in this 6-year period. The stars were classified in the order of their 

 spectral types, on the Harvard system (xii to xviii), but independently of 

 the Harvard assignment of types for the individual stars. The residuals 

 were tabulated in the order of the types, and the determination of the cor- 

 rections to individual lines in the various types, in order to reduce all to a 

 homogeneous system, is approaching completion. In the same connection 

 Mr. Burns is making a study of blended lines, i. e., of lines apparently single 

 with the moderate dispersion of the Mills spectrograph, which the much 

 higher dispersion of Rowland's solar spectrograms recorded as composed of 

 several separated lines. We can not safely adopt the mean of Rowland's 

 wave-length of the individual lines as the wave-length of the resulting blend. 

 The proper values must be determined with each spectrograph employed. 



Dr. Newkirk measured definitively 338 spectrograms, reduced 81 defini- 

 tively, and reduced 98 approximately. In addition he made a study of the 

 errors of the lines of titanium and iron in the comparison spectra, upon which 

 all the velocity determinations depend. Miss Allen is reducing definitively the 

 unreduced measures by Dr. Newkirk. 



Throughout the year Mr. Sanford has read the microscopes of one of the 

 two declination circles of the meridian instrument, in Professor Tucker's 

 program for determining fundamental star positions. Mr. Sanford has been 

 engaged steadily with the reduction of these observations, and has relieved 

 Professor Tucker of many routine details ; for example, by taking charge of 

 the standard clocks upon which the right ascensions of the program depend. 



