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NATIONAL RESEARCH COUNCIL 
12. Peculiarities of spectra, including the relative intensities bf lines, es- 
pecially of those of wave lengths 4216, 4455, etc. Study of lines of great and 
small wave-lengths. Intensity of light of different wave-lengths. 
13. Radial velocities of stars, including all of magnitude 6.0, and brighter, 
with a computed probable error not exceeding 3 km. Radial velocities of a 
selected list of stars like those in No. 8. 
14. Radial velocities of spectroscopic binaries. Minimum number of good 
determinations forty, with at least one in each twenty-fourth of the period. 
15. Photographic and photovisual magnitudes of a Durchmusterung of all 
stars of the ninth magnitude, and brighter, on the international scale. It may 
be best to begin with 40,000 stars, one in each square degree of about the 
ninth magnitude, or with the standard stars of No. 3. 
16. Photographic and photovisual magnitudes of selected lists of faint 
stars. 
17. Photometric, photographic, or visual determinations of the brightness 
of all variables of long period, or irregular, having a range of four magnitudes, 
or more, or three magnitudes when of the ninth magnitude, or brighter, at 
maximum. 
18. Light curve of all variables of short period. For the bright stars the 
photoelectric cell should be used. Dividing the period into twenty-four equal 
parts, a point on the curve should be determined in each of these parts with a 
probable error not exceeding =i=0.02 magn. Observations should be made 
every five years, at phases when the light is changing most rapidly, to deter- 
mine the variations in the period. In the case of globular clusters and the 
Magellanic Clouds, photographs with large reflectors are much to be desired 
to extend the work to the fainter stars. 
19. Measures hke those of No. 18 of all Algol variables. In addition, at 
least twenty points should be determined at nearly equal intervals during the 
primary, and secondary minimum, if any exists. 
20. A catalogue of all stars of the magnitude 6.5, and brighter, giving for 
each the approximate position, proper motion, radial velocity, parallax, mag- 
nitude, spectrum, color index, etc. The type to be kept standing and a new 
edition issued every three years, giving corrected values computed by experts 
who should maintain a bibliography accessible to all investigators. 
Edward C. Pickering, Chairman ^ 
W. W. Campbell, George E. Hale, 
George C. Comstock, Henry N. Russell, 
W. S. ElCHELBERGER, FrANK ScHLESINGER, 
Edwin B. Frost, Joel Stebbins. 
