iv 
CONTENTS 
The PROBABI.B Error of the Vitai. Index of a Popui^ation. .By J. R. Miner 106 
On the Measurement of a Physicai^ Quantity Whose Magnitude is In- 
Fi^uENCED BY Primary Causes beyond the Controi^ of the Observer 
and on the Method of Determining the Rei^ation between Two Such 
Quantities By W. A. Shewhart 248 
A Further Note on the Age Index of a Population 
By R. Pearl and T. J. LeBlanc 300 
The Stability of the Normal Age Distribution By Alfred J. Lotka 339 
A Further Note on the Mathematical Theory of Population Growth 
By Raymond Pearl and Lowell J. Reed 365 
PHYSICS 
The Frequency-Sensitivity of Normal Ears. .By H. Fletcher and R. L. Wegel 5 
Experiments with the Vacuum Gravitation Needle By C. Barus 13 
Absorption of Short X-R ays by Aluminium and Copper 
By W. Duane and K. C. Mazumder 45 
The Grating Space of Mica and the Intensities of the Spectral Orders. . . . 
By Bergen Davis and H. M. Terrill 59 
Ionization and Radiation Potentials and the Size of the Atom 
By Bergen Davis 61 
Periods and Logarithmic Decrement of the Gravitation Needle under 
High Exhaustion By C. Barus 63 
Plane Reflection of Sound, as Exhibited by the Pinhole Resonator 
By C. Barus 66 
Note on X-Ray Spectra By W. Duane and R. A . Patterson 85 
A New Method of Using X-Rays in Crystal Analysis 
By G. L. Clark and W. Duane 90 
Acoustic Topography Varying with the Position of the Organ Pipe 
By C. Barus 96 
On Steering an Automobile around a Corner By A. G. Webster 100 
Cylindrical Distribution of Nodal Strength around the Pipe Normal 
By C. Barus 119 
Ionization and Absorption Effects in the Electric Furnace . .By A,S. King 123 
The Physical Examination of Hearing and Binaural Aids for the Deaf .... 
By R. L. Wegel 155 
The Production of an E. M. F. on Closed Circuit by a Light Effect on 
Argentite By H. H. Sheldon and P. H. Geiger 161 
Positive and Negative Pinhole Resonators By C. Barus 163 
The Evaluation of Quantum Integrals By P. S. Epstein 166 
The Spectral Energy Distribution and Opacity of Wire Explosion Vapors 
By J. A. Anderson 231 
Electronic Bombardment of Nickel By H. E. Farnsworth 251 
The Crystal Structure of Potassium ByL.W. McKeehan 254 
Preliminary Report on the Ionization of Potassium Vapor by Light 
By R. C. Williamson 255 
The Absorption of Light by Sodium and Potassium Vapors . .By G. R. Harrison 260 
The Energy Losses Accompanying Ionization and Resonance in Mercury 
Vapor By John A. Eldridge 268 
The Crystal Structure of Beryllium and of Beryllium Oxide 
By L. W. McKeehan 270 
Some Cases of Nerve-Deafness and Their Bearing on Resonance Theories 
OF Audition By John P. Minton 274 
