iv 
CONTENTS 
PAGE 
Relation of Color to Intrinsic Luminosity in Stars of the Same Spectral Type 
By Frederick H. Scares 232 
The Motions in Space of Some Stars of High Radial Velocity 
By W. S. Adams and A. H. Joy 239 
Deviations of the Sun's General Magnetic Field from That of a Uniformly 
Magnetized Sphere By F.H. Scares, A. van Maanen, and F. Ellerman 242 
Studies of Magnitudes in Star Clusters, IX. The Distances and Distribution 
OF Seventy Open Clusters By Harlow Shapley 344 
On the Distribution of the Aphelia of the Secondary Bodies of the Solar 
System By C. D. Perrine 371 
Recent Simultaneous Measurements of the Solar Constant of Radiation at # 
Mount Wilson, California, and Calama, Chile By C. G. Abbot 383 
Some Problems of Sidereal Astronomy By Henry N arris Russell 391 
On the Spectral Lines of a Pulsating Star By Harlow Shapley and Seth B. Nicholson 417 
Studies of Magnitudes in Star Clusters, X. Spectral Type B and the Local 
Stellar System By Harlow Shapley 443 
PHYSICS 
Note on a Contact Lever, Using Achromatic Displacement Fringes By Carl Barus 39 
Interferential Contact Lever Experiments Relating to the Elastics of Small '0, 
Bodies By Carl Barus 44 
Note on the Self-Ad justing Interferometer in Relation to the Achromatic 
Fringes By Carl Barus] 53 
An Adjustment in Relation to the Fresnel Coefficient By Carl Barusjl20 
Superposed or Duplicated Spectrum Fringes By Carl Barus 149 
An Approximate Law of Energy Distribution in the General X-Ray Spectrum P 
By David L. Webster 163 
A Complete Apparatus for Absolute Acoustical Measurements 
By Arthur Gordon Webster 173 
The Thermo-Electric Equation P = TdVjdT Once More By Edwin H. Hall 197 
On the X-Ray Absorption Wave-Lengths of Lead Isotopes 
By William Duane and Takco Shimizu 198 
An Electrodynamometer Using the Vibration Telescope By Carl Barus 211 
A New Instrument for Measuring Pressures in a Gun 
By A,G. Webster and L. T. E. Thompson 259 
On the Angle of Repose of Wet Sand By A. G. Webster 263 
The Elongation Due to Magnetization By C. Barus 267 
Acoustical Impedance and the Theory of Horns and of the Phonograph 
By Arthur Gorgon Webster 21 S 
On the Possible Form of the Equation of State of Powder Gases By A.G. Webster 286 
The Relative Adsorption of Mixtures of Oxygen and Nitrogen in Cocoanut 
Shell Charcoal By Harvey B. Lemon and Kathryn Blodgett 289 
Variations, Due to Heat Treatment, in the Rate of Adsorption of Air by 
Cocoanut Shell Charcoal By Harvey B. Lemon 291 
The Interferometry of Rapid Vibrations Chiefly in Relation to Telephone 
Currents By C. Barus 331 
On the Pressure Variation of Specific Heat of Liquids By C. Barus 340 
A Comparison of Certain Electrical Properties of Ordinary and Uranium Lead 
By P. W. Bridgman 351 
Radiation from a Moving Magneton By H. Bateman 367 
Rotating Projectiles from Smooth-Bore Guns By C. G.Abbot 386 
