CONTENTS 
Page 
GEOLOGYf — The Mechanics op Intrusion ot the Black Hills (S. D.) Pre- 
CAMBSiAN Granite By Sidney Paige 113 
Anthropology.— Archaeological Explorations at Pecos, New Mexico . • . . 
By A. V.Kidder 119 
Anthropology.~Man and Metals By Walter Hough 123 
Astronomy. — On the Observed Rotations of a Planetary Nebula .... 
By W.Campbell and J. H. Moore 129 
Astronomy. — A Short Period Cepheid with Variable Spectrum 
By Harlow Shapley 132 
Astronomy. — The Spectrum of d Cephei . By Walter S, Adams and Harlow Shapley 136 
Astronomy. — Investigations in Stellar Spectroscopy. I. A Quantitative 
Method of Classifying Stellar Spectra . ... By Walter S. Adams 143 
Astronomy. — Investigations in Stellar Spectroscopy. II. A Spectroscopic 
Method of Determining Stellar Parallaxes . . . By Walter S. Adams 147 
Astronomy. — ^Investigations in Stellar Spectroscopy. III. Application of a 
Spectroscopic Method of Determining Stellar Distances to Stars of 
Measured Parallax . . . . / By Walter S. Adams 152 
Astronomy. — Investigations in Stellar Spectroscopy. IV. Spectroscopic 
Evidence for the Existence of Two Classes of M Type Stars .... 
By Walter S. Adams 157 
Anthropology. — The Failure and Revival of the Process of Pigmentation in 
the Human Skin . . . . • By A. E.fenks 164 
Geology. — Banded Glacial Slates of Permo-carboniferous Age, Showing Pos- 
sible Seasonal Variations in Deposition . . . .By Robert W. Sayles 167 
Mathematics. — An Extension of Feuerbach's Theorem . . . By P. Morley 171 
Mathematics. — Deformations of Transformations of Ribaucour .... 
By L. P. Eisenhart 173 
Geology. — Geographic History of the San Juan Mountains Since the Close 
OF THE Mesozoic Era . .By Wallace W. Ativood and Kirtley P. Mather 177 
Geology. — The Age of the Middle Atlantic Coast Upper Cretaceous Deposits 
By W. B. Clark, E. W. Berry , and J. A. Gardner 181 
Geology. — Upper Cretaceous Floras of the World . . By Edward W'. Berry 185 
Zoology. — Observations on Ameba Feeding on Infusoria, and Their Bearing 
on the Surface-Tension Theory . . . . ByS.O. Mast and P. M. Root 188 
Physics. — ^The Electromotive Force Produced by the Acceleration of Metals 
By Richard C. Tolman and T. Dale Stewart 189 
