IV CONTENTS. 



Number 206. 



Page 



Art. VIII. — Seismoscopes and Seismological Investigations; 



by T. C. Mendenhall 97 



IX. — Petrographical Microscope of American Manufacture ; 



by G. H. Williams . 114 



X. — New Ammonite which throws additional light upon the 



geological position of the Alpine Rhtetic ; by W. B. 



Clark 118 



XL — Three Formations of the Middle Atlantic Slope ; by 



W. J. McGee. (With Plate II) 120 



XII. — Experiments with the Capillary Electrometer of Lipp- 



mann ; by J. H. Pratt, Jr. 143 



XIII.— Period of the Rotation of the Sun as determined by 



the Spectroscope; by Henry Crew . .. 151 



XIV.— Theory of the Bolometer; by H. F. Reid 160 



XV.— Are there Deep-Sea Medusas ? by J. W. Fewkes 166 



Obituary. — Ferdinand V. Hayden, 179. 



Number 207. 



Page 



Art. XVI.— Asa Gray; by J. D. Dana 181 



XVII. — Calibration of an Electrometer ; by D. W. Shea . . . 204 

 XVIII. — On the so-called Xorthford, Maine, Meteorite ; by 



F. C. Robinson 212 



XIX. — History of the Changes in the Mt. Loa Craters ; by 



James D. Dana 213 



XX. — The Taconic System of Emmons, and the use of the 



name Taconic in Geologic nomenclature ; by Chas. D. 



Walcott, of the U. S. Geological Survey 229 



XXI. — On the crystalline form of Polianite ; by Edward S. 



Dana and Samuel L. Penfield 243 



SCIENTIFIC INTELLIGENCE. 



Chemistry and Physics — Stalagmometer and its use in quantitative analysis, 

 Traube, 248. — Apantlesis, a Separation of the Constituents of a Solution by- 

 Rise of Temperature, Mallet : Properties of Fluorine, Moissan, 249. — Oxygen 

 Carriers, - Lothar Meyer: Atomic Weight of Zinc, Reynolds, and Ramsay, 

 250. — Text-book of Inorganic Chemistry, Victor yon Richter, Edgar F. 

 Sjjith: Manual of Analytical Chemistry, John Muter: New instrument for 

 measuring heat, Weber, 251. — Velocity of Sound, A. W. Rucker: Transmis- 

 sion of power by alternating electrical currents, T. H. Blakesley : Measurement 

 of Electromotive Forces, William Thomson: Influence of Magnetism on the 

 Thermo-electric behavior of Bismuth, Giovann[ Pietro Grimaldi: Coincidences 

 between lines of different Spectra, 252 — Influence of thickness and luminosity 

 of light-producing layers, upon the character of Spectra, Ebert: Measurement 

 of force of gravitation, M. Deffor&es : Influence of temperature on Magnetiza- 

 tion, 253. 



