CONTENTS. 



Page. 

 I. Vision and the Technique of Art. By A. Ames, Jr., C. A. 



Proctor and Blanche Ames 1 



II. The Boundary Problems and Developments Associated with a 

 System of Ordinary Linear Differential Equations of the First 

 Order. By George D. Birkhoff and Rudolph E. Langer . 49 



III. Lichenes in Insula Trinidad a Prof essoreR. Thaxter Collecti. By 



Edward A. Vainio 129 



IV. The Effect of Pressure on the Electrical Resistance of Cobalt, Alumi- 



num, Nickel, Uranium and Caesium. By P. W. Bridgman . 149 



V. The Compressibility of Thirty Metals as a Function of Pressure 



and Temperature. By P. W. Bridgman 163 



VI. A Revision of the Atomic Weight of Silicon. The Analysis of Sili- 

 con Tetrachloride and Tetrabromide. By Gregory P. Baxter, 

 Philip F. Weatherill and Edward W. Scripture, Jr. . 243 



VII. The Chilean Species of Metzgeria. By Alexander W. Evans . 269 



VIII. Some New Fossil Parasitic H ymenoptera from Baltic Amber. By 



Charles T. Brues 325 



IX. Text of the Charter of the Academie Royale de Bslgique, Translated 

 from the Original in the Archives of the Academie at Brussels. 

 By A. E. Kennelly 347 



X. On Double Polyadics, with Application to the Linear Matrix Equa- 

 tion. By Frank L. Hitchcock 353 



XI. Identities Satisfied by Algebraic Point Functions in N-Space. By 



Frank L. Hitchcock 397 



XII. The Minimum Audible Intensity of Sound. By Clifford M. 



Swan . . 423 



XIII. The Salamanders of the Family Hynobiidae. By Emmett Reid 



Dunn 443 



XIV. An Example in Potential Theory. By O. D. Kellogg . . . 525 



XV. The Typical Shape of Polyhedral Cells in Vegetable Parenchyma 

 and the Restoration of that Shape following Cell Division. By 

 Frederic T. Lewis 535 



XVI. The Effect of Pressure upon Optical Absorption. By Frances 



G. Wick 555 



