CONTEXTS. 



Page 



Art. I. — The Change of Heat Conductivity on passing Iso- 



theriually from Solid to Liquid ; bj C. Bartts 1 



II. — Polybasite and Tennantite from the Mollie Gibson 



Mine in Aspen, Col.; by S. L. Penfield and S. H. 



Peaece 15 



III. — Post-Laramie Deposits of Colorado ; by W. Cross 19 



IV.— Alkali-Metal Pentahalides ; by H. L. Wells and H. 



L. Wheeler. With their Crystallography; by S. L. 



Peistfield. 42 



V. — Fossils in the " Archaean " rocks of Central Piedmont 



Virginia; by N. H. Darton 50 



VI. — Notes on the Cambrian Rocks of Virginia and the 



Southern Appalachians ; by C. D. Walcott.. 52 



VII. — Synthesis of the minerals Crocoite and Phoenico- 



chroite ; by C. Ludekhstg 5 7 



VIII. — A Hint with respect to the Origin of Terraces in 



Glaciated Regions ; by R. S. Tarr 59 



IX. — Occurrence of a Quartz Bowlder in the Sharon Coal of 



Xortheastern Ohio ; by E. Orton 62 



X. — A Method of Increasing the Range of the Capillary 



Electrometer; by J. Whitmore. 64 



SCIENTIFIC INTELLIGENCE. 



Chemistry and Physics. — Luminosity of Coal Gas Flames, Lewes, 70. — Measure- 

 ment of Osmotic Pressure, Tammann, 71. — Coefficient of Molecular Depression 

 of Phenol, Jttillard and Curchod: Determination of Yapor Density under 

 Diminished Pressure, Schall: Jahrbuch der Chemie, R. Meyer, 72. — Chemical 

 Calculations with explanatory notes, problems and answers. R. L. AVhiteley : 

 Contributions to the knowledge of the discharge of the RuhmkorfE coil, Tom 

 Moll, 73. — Photography in Colors, G. Lippm^nn, 75. — Dispersion of the 

 Ultra Red Rays, Dr. Rubens: Electrical Resistance of the Human Body, M. 

 yon Frey, 76. 



Geology and Mineralogy. — History of Volcanic Action in the Area of the British 

 Isles, A. Geikie, 76. — New Jersey Geological Report for 1891, J. C. Sjiock, 

 77. — Progress of the Kentucky Geological Survey, J. R. Procter: Kentucky 

 Geological Survey: Report on Petroleum Natural Gas and Asphah Rock of 

 Western Kentucky. E. Orton: Geological Survey of Alabama, Smith: Manning- 

 ton Oil-field and the history of its development, I. C. White, 78. — New Lower 

 Silurian Lamellibranchiata, chiefly from Minnesota rocks, E. 0. Ulrich : Der 

 Peloponnes. Yersuch einer Landeskunde auf geologischer Grundlage, nach 

 Ergebnissen einiger Reisen, A. Philippson : Chiastolite in fossiliferous meta- 

 morphic slates of Portugal, J. F. N. Delgado: Striated Garnet from Backtield. 

 Maine, W. S. Bayley, 79. — Blowpipe Analysis, J. Landauer, 80. 



Miscellaneous Scientific Intelligence. — The Great Earthquake of Japan, 1891, J. 

 Milne and W. K. Burton, 80. — Congress of Mathematicians and Astronomers : 

 American Association, 81. 



Obituary. — Lewis Morris Rutherfurd, 82. 



