C () N T E N T S. 



Aet. XXI. — Ionization by Collision in Gases and Vapors ; 



by \Y. A. Baess 229 



XXII. — Geology of Arisaig-Antigonish District, Nova 

 Scotia ; by M. Y. Williams - 242 



XXIII. — Jackson on the Phylogeny of the Echini; A 



synopsis by C. Sciiucheet _ 251 



XXIV. — The Belt and Pelona Series ; by O. H. Heeshey .. 263 



XXV. — Absorption and Thickness of thin Films ; by C. C. 



IIUTCHINS 2 74 



XXVI. — The Mazon Creek, Illinois, Shales and their Amphib- 

 ian Fauna ; by R. L. Moodi k 277 



XXVII. — An American Jurassic Frog; by R. L. Moodie 286 



XXVIII.— On the Hydrolysis of Metallic Alky] Sulphates ; 



by G. A. Linhaet . 289 



XXIX. — On the Hydrolysis of Esters of Substituted Aliphatic 



Acids ; by \V.' A. Deushel and E. W. Dean 293 



XXX.— An Electromagnetic Effect ; by S. R. Williams.. . 297 



IC 



SCIENTIFIC INTELLIGENCE. 



Physics — Growth of Air Bubbles at the Walls of a Beaker containing a 

 Liquid, when the Gas at the free Surface is not air, C. Barus, 304. 



Geology and Miueraloqy — First Annual Report of the Director of the Bureau 

 of Mines, J. A. Holmes. 305. — Platinum and Platiniferous Deposits of the 

 Ural, L. Duparc : Gabbros and Associated Rock at Preston, Connecticut, 

 G. F. Loughlin, 306. — Dana's Manual of Mineralogy ; for the Student of 

 Elemental'}' Mineralog}'. the Mining Engineer, the Geologist, the Prospec- 

 tor, the Collector, etc., W. E. Ford, 307. 



Miscellaneous Scientific Intelligence — On a Period of 33'33 in the Earth's 

 Climate, and its connection with Sun Spots, J. Zilius : The Elements of 

 Statistical Method, W. I. King : Archiv fur Zellforschung, 308. 



