CONTENTS. 



Page 



Art. XXV. — Notes on the Colorado Canyon District; by 



W. M. Davis 251 



XXVI. — Determination of Minerals in thin Rock-sections by 

 their maximum Birefringence; by L. V. Pirsson and 

 H. H. Robinson _•.__ 260 



XXVII. — Studies in Oyperaceae; by T. Holm 266 



XXVIII. — Experiments on High Electrical Resistance ; bj r 



O. N. Rood 285 



XXIX. — Occurrences .of Corundum in North Carolina ; by 



J. H. Pratt 295 



XXX. — Products of the Explosion of Acetylene, and of Mix- 

 tures of Acetylene and Nitrogen ; by W. G. Mixter .. 299 



XXXI. — Scapolite Rocks from Alaska; by J. E. Spurr 310 



XXXII. — Qualitative Separation of Nickel from Cobalt by 

 the action of Ammonium Hydroxide on the Ferricyan- 

 ides; by P. E. Browning 316 



SCIENTIFIC INTELLIGENCE. 



Physics — Radio-activity of Uranium, W. Crookes, 318. — Electrical conductivity 

 of Gases traversed by Cathode Rays. J. C. McLennax. 319. — Kleiner Leitfaden 

 der Praktischen Physit, Friedrich Kohlrausch: Photometrical Measure- 

 ments and Manual for the General Practice of Photometry, W. M. Stine, 320. 



Geology and Mineralogy — Status of the Mesozoic Floras of the United States, L. 

 F. Ward, 320.— La Flore Wealdienne de Bernissart, A. C. Seward, 323. — 

 Notes on Some Jurassic Plants in the Manchester Museum, A. C. Seward: 

 "The Maidenhair Tree/' A. C. Seward: New Minerals from Greenland. 323. 



Obituary — James Edward Keeler, 325. 



TEtf-VOUUME IJXDEX. 



An extra number, containing a full Index to volumes I to X of the Fourth 

 Series, will be ready in December. Sent only to those who specially order it. 

 Price one dollar. 



