CONTENTS. 



Number 231, 



Page 



Art. XXII. — Sedgwick and Murohison : Cambrian and 



Silurian: by James I). Dana 107 



XXIII. — Cretaoeous of the British Columbian Region. — 

 The Nanaimo Group; by George M. Dawson 180 



XXIV. — Celestite from Mineral County, West Virginia ; by 



George H. Williams _ 183 



XXV. — Method for the Determination of Iodine in Haloid 



Salts; by F. A. Goocn and P. E. Browning 188 



XXVI. — Mineral Locality at Branchville, Connecticut: Fifth 

 Paper ; by George J. Brush and Edward S. Dana. 

 With analyses of several manganesian phosphates ; by 

 Horace L. Wells . 201 



XXVII. — Simple Interference Experiment ; by Albert A. 



MlCHELSON 216 



XXVIII. — Improved Wave Apparatus ; by John T. Stod- 



DARD 218 



XX IX. — Recent Rock-Flexure ; by Frank Cramer. 220 



XXX. — Origin of the Rock Pressure of the Natural Gas of 

 the Trenton Limestone of Ohio and Indiana ; by Edward 

 Orton ... _ 225 



SCIENTIFIC INTELLIGENCE. 



Chemistry and Physics — Lowering of the Freezing point of Metals by the addition 

 of other Metals, Heycock and Neville, 230. — Chlorides of Selenium, Chabrie, 

 231. — Production of Sodium carbonate by the Electrolysis of the Chloride, 

 Hempel: Barium cobaltite, Rousseau, 232. — Constitution of Dextrose, Skraup: 

 Electrical Undulations, Edouard Sarasin and Lucten de la Rive: Experi- 

 ments with Hertz's Vibrations, G. F. Fitzgerald, 233. — Absolute Viscosity 

 of Solids. Liquids and Gases. C. Barus, 234. — Absolute Measurements in 

 Electricity and Magnetism by Andrew Gray : Elementary Lessons in Elec- 

 tricity and Magnetism, Silvanus P. Thompson, 235. 



Geology and Mineralogy — Sedgwick and Murchison : Calciferous Formation in the 

 Champlain Valley, E. Brainerd and H. M. Seely, 235. — Geological Survey of 

 Canada, Annual Report for the year 1887-88, A. R. C. Selwyn, 238. — Manual 

 of Palaeontology, for the use of students, with a general Introduction on the 

 principles of Palaeontology, H. A. Nicholson and R. Lyddeker, 239. — Elemente 

 der Palaontologie, G. Steinmann and L. Doderlein, 240. 



Botany and Zoology — Manual of the Botany of the Northern United States, 

 including the district east of the Mississippi and north of North Carolina and 

 Tennessee, A. Gray. 240. — Roots of Saprophytes, F. Johow: Genesis of the 

 Arietidae, A. Hyatt, 243. 



Astronomy — Transactions of the Astronomical Observatory of Yale University, 

 Mass of Saturn : The Algol System, Vogel, 245. — Rotation of Mercury, 

 Schiaparelli, 245. 



Obituary — Chester Smith Lyman. 245: John Huntington Crane Coffin, 

 Stephen J. Perry, 24'i. 



