730 PROCEEDINGS OF THE AMERICAN ACADEMY. 



On adjournment to the Council Room, Professor J. E. Wolff 

 gave an illustrated talk on " A Geological Tour in the Moun- 

 tains of Montana and British Columbia." 



Professor Percival Lowell spoke on his recent discovery, 

 made through photographs, of the watery vapor surrounding 

 Mars. 



The following papers were presented by title : — 



" A Revision of the Atomic Weight of Arsenic. Preliminary 

 Paper: The Analysis of Silver Arsenate." By Gregory Paul 

 Baxter and Fletcher Barker Coffin. 



" Properties of Aluminium Anodes." By H. W. Morse. 

 Presented by John Trowbridge. * 



Contributions from the Harvard Mineralogical Museum 

 XIII: "Notes on the Crystallography of Leadhillite." By 

 Charles Palache. 



" Crystal Rectifiers for Electric Currents and Electric Oscil- 

 lations. Part II. Carborundum, Anatase, Brookite, Molyb- 

 denite." By George W. Pierce. 



" On the Joule-Thomson Effect in Air." By S. B. Serviss. 

 Presented by John Trowbridge. 



" The Measurement of High Hydrostatic Pressure : I. A 

 Simple Primary Gauge. II. A Secondary Mercury Resistance 

 Gauge." By P. W. Bridgman. Presented by W. C. Sabine. 



" An Experimental Determination of Certain Compressibili- 

 ties." By P. W. Bridgman. Presented by W. C. Sabine. 



Nine hundred eighty-sixth Meeting. 



January 13, 1909. — Stated Meeting. 



The President in the chair. 



There were twenty-four Fellows present. 



The Corresponding Secretary announced that letters had 

 been received from Professor William Trelease stating that he 

 attended the inauguration of President Hill at the University 

 of Missouri, as the representative of the Academy ; from the 

 Museo National of Mexico, offering the felicitations of the New 

 Year ; from Charles I. Kiralfy, announcing the Imperial Inter- 

 national Exhibition in London in 1909 ; from the Societe* des 



