CONTEXTS. 



Page. 



Art. XLV. — Mathematical Theories of the Earth ; by R. S. 



Woodward .. 337 



XLVI. — Darkened Silver Chloride not an Oxychloride ; by 



M. Caret Lea.. 356 



XLVII. — Observations on some of the Trap Ridges of the 



East Haven-Branford Region, with a map (Plate IX) ; 



by E. O. Hovey 361 



XLVIIX— Theory of the Mica Group ; by F. W. Clarke .. 384 

 XLIX. — Probable Law of Densities of the Planetary Bodies ; 



by R. Hooke ... _ 393 



L. — Improved Standard Clark Cell with Low Temperature 



Coefficient; by H. S. Carhart 402 



LI. — Pseudomorphs of Native Copper after Azurite, from 



Grant County, New Mexico ; by W. S. Yeates 405 



LII. — Note on the Relation of Volume, Pressure and Tem- 

 perature in case of Liquids ; by C. Bartjs 407 



SCIENTIFIC INTELLIGENCE. 



Chemistry and Physics. — Colloidal Cellulose, Guignet, 408. — Watts' Dictionary 

 of Chemistry, H. F. Morle? and M. M. P. Mum, 409. — Treatise on trie Prin- 

 ciples of Chemistry, M. M. P. Mum: Definitions adopted by the International 

 Congress of Electricians, Mascart, 410. — Lightning and the Eiffel Tower : 

 Transmission of power by Electricity, Deprez : Dissipation of negative electric 

 charges by sunlight and daylight, J. Elster and H. Geitel : Photography of 

 the invisible portions of the Solar Spectrum, Ch. V. Zenger : Carbon Spectrum, 

 H. Kayser and C. Runge, 411. 



Geology. — Movement of the Upper ice of Glaciers over the Lower : Ice- Age in 

 North America, and its bearings on the Antiquity of Man, G. F. Wright, 412. 

 — Annual Report of the Geological Survey of Arkansas for 1888, J. C. Branner, 

 413. — Jurassic Plants from Kaga, Hida, and Echizen, (Japan), Matajiro 

 Yokoyama : Rivers and Valleys of Pennsylvania, W. M. Davis, 414. 



Botany and Zoology. — Die natiirlichen Pflanzenfamilien, A. Engler and K. 

 Prantl : Guide pratique pour les travaux de Micrographie, Beauregard et 

 Gallippe : Contributions to the Physiology of Growth, J. Wortmann, 415. — 

 Atlas deutscher Meeresalgen, F. Schutt, P. Kuckuck, J. Reinke, 416. — Mono- 

 graph of the Horney Sponges, R. von Lendenfeld, 417. — The Bermuda 

 Islands ; a Contribution to the Physical History and Zoology of the Somers 

 Archipelago with an examination of the structure of Coral Reefs, A. Heilprin, 

 418. 



Miscellaneous Scientific Intelligence. — British Association : Scientific Papers of Asa 

 Gray, C. S. Sargent, 419. — Popular Treatise on the Winds, W. Ferrel: 

 Sixth Annual Report of the Bureau of Ethnology to the Secretary of the 

 Smithsonian Institution, J. W. Powell : Elementary Algebra, R. Graham : 

 Numbers Universalized, an Advanced Algebra, D. M. Lensenig, 420. 



Erratum. 

 Pages 323, 324, for Sumpter, read Sumter. 



