CONTENTS. 



Page 

 Aet. XLVIII. — Determination of the Molecular Weight of 

 Radium Emanation by the Comparison of its Kate of 

 Diffusion with that of Mercury Vapor ; by P. B. Per- 

 kins ". 461 



XLIX. — Paleozoic Formations in Trans-Pecos, Texas ; by G. 



B. Richardson _ _ 474 



L. — Rectification Effect in a Vacuum Tube ; by H. A. Per- 

 kins 485 



LI. — Life of Radium ; by B. B. Boltwood ... 493 



LII. — New Occurrence of Proustite and Argentite ; by F. R. 



Van Horn 507 



LIII. — Occurrence of Gedrite in Canada ; by N. N. Evans 



and J. A. Bancroft 509 



LIV. — Iodometric Determination of Arsenic and Antimony 



Associated with Copper ; by F. H. Heath.. 513 



SCIENTIFIC INTELLIGENCE. 



Chemistry and Physics — Crystallized Chlorophyl, Willstatter and Benz : 

 Mercury Peroxide, Von Antropoff, 520. — Supposed New Element in 

 Thorianite, C. de B. Evans : Stereochemistry, A. W. Stewart, 521. — 

 Condensation of Water Vapor in the Presence of Eadium Emanation, Mme. 

 Curie : Anode Pays, Gehrcke and Reichenheim : Hand'buch der Spectro- 

 scopic, H. Katser, 522. — Refrigeration, J. W. Anderson : Introduction 

 to Metallography, P. Goerens, 524. — Lehrbuch der theoretischen Elektro- 

 chemie auf thermodynamischer Grundlage, J. J. van Laar : Compara- 

 tive Electro-Physiology, J. C. Bose, 525. 



Geology— -New Zealand Geological Survey, 526. — Geological Survey of 

 Western Australia: Geological Survey of Canada, 527. — The Ankylo- 

 sauridfe, B. Brown : Revision of the American Eocene Horses, W. 

 Granger: Ideas on the Origin of Flight, Dr. B. F. Nopcsa, 528. — Traite 

 de Geologie I, Les Pkenomenes geologiques, E. Hatjg : Key for the Deter- 

 mination of the Rock-formino; Minerals in Thin Sections, A. Johannsen, 

 529. 



Miscellaneous .Scientific Intelligence — Monograph of the British Annelids, 

 W. C. McIntosh, 530 — Selectionsprinzip und Probleme der Artbildung, 

 Dr. L. Plate : Annals of the Astrophysical Observatory of the Smithso- 

 nian Institution, C. G. Abbot, 531. — Bulletin of the Mount Weather 

 Observatory, W. L. Moore : Field Columbian Museum, O. C. Farring- 

 ton, 532. — Museum of the Brooklyn Institute of Arts and Sciences : Uni- 

 versity of California Publications in American Archaeology and Ethnol- 

 ogy : Medico-Physical Works of John Mayow, 533. — Graphic Algebra. A. 

 Schultze : Ostwald's Klassiker der Exakten Wissenschaften: Decapod 

 Crustacea of the Bermudas, Part 1, A. E. Verrill, 534. 



313 



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