CONTENTS XXIX 



815. Spectroscopic eclipsing binaries 629 



816. Periods of known binary stars within 10 parsecs of the sun [Luyten, 



1930] 630 



817. Masses and absolute magnitudes of binary stars [Pitman, 1929] . 631 



818. Mass luminosity data 631 



819. Stellar radiation measurements (Pettit, Nicholson, 1928) .... 632 



820. Spectrum classes and temperatures 632 



821. Visual and radiometric magnitudes and total radiations 632 



822. Stellar radiation measurements : Energy spectra (Abbot, 1929) . . 633 



823. " " " Temperatures, radiation, diameters. 633 



Variable Stars 



824. Variable stars, general characteristics; classification 634 



825. The Cepheid period-luminosity curve 635 



826. Novae 635 



827. Observed maxima of spectrum lines in the giant sequence .... 635 



828. High-density stars. White dwarfs 636 



829. Low-density stars. Giants 636 



830. High-temperature stars. High-luminosity stars 636 



Star Clusters 



831. Properties and classification of star clusters 637 



832. Distribution of open star clusters 637 



833. Globular star clusters 638 



834. Galactic star clusters 638 



Nebulae 



835. Classification of nebulae 639 



836(a). Galactic nebulae 639 



836(b). Data on six planetary nebulae 639 



837. Diffuse galactic nebulae, dimensions 640 



838. Nongalactic nebulae 640 



839. The Magellanic clouds and N.G.C 6822, dimensions 640 



840. Magnitudes, radial velocities and distances of external galaxies . . 641 



841. Extra-galactic nebulae, high velocities 642 



842. Rotation of stars 642 



843. The galaxy, its center and rotation 643 



844. Transmission of light across space; theoretical 643 



845. " " " " " observed estimates 643 



846. Amount of matter in interstellar space 644 



847. Radii of curvature of space 644 



