CONTENTS 
PACK 
Newton's Method in General Analysis By Albert A. Bennett 592 
A Set of Independent Postulates for Cyclic Order, By Edward V. Huntington 630 
Certain General Properties of Functions By Henry Blumberg 646 
ASTRONOMY 
PAGi: 
A Possible Origin for Some Spiral Nebulae By George F. Becker 1 
Studies of Magnitudes in Star Clusters, I. On the Absorption of Light in 
Space By Harlow Shapley 12 
Studies of Magnitudes in Star Clusters, II. On the Sequence of Spectral 
Types in Stellar Evolution By Harlow Shapley 15 
On the Albedo of the Planets and Their Satellites By Henry N orris Russell 74 
The Minute Structure of the Solar Atmosphere 
By George E. Hale and F^dinand Ellerman 102 
Monochromatic Photography of Jupiter and Saturn By R. W. Wood 109 
On the Observed Rotations of a Planetary Nebula 
By W. W. Campbell and J. H. Moore 129 
A Short Period Cepheid with Variable Spectrum By Harlow Shapley 132 
The Spectrum of 5 Cephei By Walter S. Adams and Harlow Shapley 136 
Investigations in Stellar Spectroscopy, I. A Quantitative Method of Classi- 
fying Stella Spectra By Walter S. Adams 143 
Investigations in Stellar Spectroscopy, II. A Spectroscopic Method of De- 
termining Stellar Parallaxes By Walter S. Adams 147 
Investigations in Stellar Spectroscopy, III. Application of a Spectroscopic 
Method of Determining Stellar Distances to Stars of Measured Parallax 
By Walter S. Adams 152 
Investigations in Stellar Spectroscopy, IV. Spectroscopic Evidence for the 
Existence of Two Classes of M Type Stars By Walter S. Adams 157 
Discovery of Eight Variable Stellar Spectra By Harlow Shapley 208 
Systematic Motion Among Stars of the Helium Type By Benjamin Boss 214 
The Situation in Regard to Rowland's Preliminary Table of Solar Spectrum 
Wave-Lengths By Charles E. St. John 226 
Changes in the Form of the Nebula N. G. C. 2261 By Edwin P. Hubble 230 
On Some Relations Between the Proper Motions, Radial Velocities, and Mag- 
nitudes OF Stars of Classes B and A By C. D. Perrine 289 
Asymmetry in the Proper Motions and Radial Velocities of Stars of Class B 
AND Their Possible Relation to a Motion of Rotation. . . .By C. D. Perrine 292 
The Pyranometer: An Instrument for Measuring Sky Radiation 
By C. G. Abbot and L. B. Aldrich 333 
The Work of the American Meteor Society in 1914 and 1915 
By Charles P. Olivier 372 
An Apparent Dependence of the Apex and Velocity of Solar Motion, as De- 
termined from Radial Velocities, Upon Proper Motion. .By C. D. Perrine 376 
Preliminary Evidence of Internal Motion in the Spiral Nebula Messier 101 
By A . van Maanen 386 
On the Suggested Mutual Repulsion of Fraunhofer Lines 
By Charles E. St. John 458 
The Rotation and Radial Velocity of the Spiral Nebula N. G. C. 4594 
By Francis G. Pease 517 
A Simple Method For Determining the Colors of the Stars 
By Frederick H. Seares 521 
Studies of Magnitudes in Star Clusters, III. The Colors of the Brighter 
Stars in Four Globular Systems By Harlow Shapley 525 
