MOUNT WILSON SOLAR OBSERVATORY. 203 



Other additions to the optical equipment are a Pulfrich refractometer 

 with accessories for use with monochromatic light, a 4-inch plane grating 

 having bright spectra in the first and second orders, and a number of pieces 

 of polarizing apparatus. 



COMPUTING DIVISION. 



The Computing Division has remained throughout the year under the 

 direction of Mr. Seares. 



Miss Eda Bowman was appointed to the division on February 1, but after 

 a few weeks' service she was obliged to give up the work on account of ill 

 health. Her time was devoted to the measurement and reduction of pho- 

 tometric plates. 



During the year Miss Burwell has been engaged chiefly in work relating 

 to solar and stellar spectroscopy. She has made measures on solar mag- 

 netic field plates and has determined the wave-lengths of the standard lines 

 used in the radial-velocity determinations of stars from spectra of the sun's 

 center. She has made a careful study of the intensities of the spectrum 

 lines of Arcturus for the region A 4250 to A 6650, and has obtained the in- 

 tensity curves for Nova Geminorum from 14 spectrum plates. She has 

 further made measures with the tower polarimeter for a study of the polar- 

 ization produced by the mirrors of the 150- foot tower telescope, and has 

 examined 45 laboratory pressure plates for the determination of the char- 

 acter of the reversals of the enhanced lines. Miss Burwell is at present 

 engaged in the measurement of chromosphere plates. 



Miss Ensign has devoted the greater part of the year to the measurement 

 and reduction of 920 stellar spectrograms, she has assisted in the prepara- 

 tion of tables used for the solution of the Hartmann formula, has calculated 

 constants employed in reducing observed radial velocities to the sun, and 

 has also given assistance in copying, recording, and proof-reading. 



Miss Helen High, since her appointment to the division on June 1, has 

 measured 60 pairs of solar magnetic field plates with the parallel-plate 

 micrometer, and has assisted Mr. Fath with reductions and calculations re- 

 lating to nebulae. 



Miss Lasby has continued to devote the greater part of her time to stellar 

 spectra. She has measured and reduced 750 plates. Several weeks were 

 spent in the preparation of tables for facilitating the reduction of stellar 

 spectra, and a month was devoted to miscellaneous measures on solar mag- 

 netic field plates, laboratory pressure plates, and spectra of Nova Gemino- 

 rum. 



Up to the time of her resignation on April 1, Miss Renner was engaged 

 with the work in photographic photometry. 178 plates made for the inves- 

 tigation of the distance correction and for the determination of the magni- 

 tudes of the stars of the Polar Sequence were measured by her. She also 

 devoted much time to the extensive reductions and calculations involved in 

 the photometric investigations. 



