CONTENTS. 



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 Rhaetic ; by W. B. 

 Clakk 118 



XI. — 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 Medusae ? by J. W. Fewkes 166 



Obituary. — Ferdinand V. Hayden, 179. 



