OF ARTS AND SCIENCES. 633 



The Academy then visited tlie Laboratory rooms and wit- 

 nessed several experiments, among which were the passage of 

 electrical discharges over water in preference to a path through 

 it, and other experiments illustrating the good conducting power 

 of air under powerful electro-motive force. Electrical discharges 

 six feet in length in ordinary air were shown, and it was made 

 evident that in order to submit atmospheric air to a pressure of 

 three million volts the apparatus would have to be raised to a 

 considerable height above the earth, and be removed from all 

 surrounding objects. The various investigations now being 

 pursued in the Laboratory were exjilained, and the apparatus 

 shown. Among these investigations were three which are being 

 carried on under the aid of the Kumford Committee : one on 

 Heat Conductivity, by B. O. Peirce and R. W. Willson ; one 

 also on Heat Conductivity, by Edwin H. Hall, who explained 

 his apparatus ; and one on the measurement of very short waves 

 of light. In this latter subject Theodore Lyman and E. H. 

 Colpitts have succeeded in obtaining the shortest wave lengths 

 of metals hitherto measured. 



Harold Edwards explained his investigation on measurements 

 with an improved air thermometer. H. H. Brown exhibited 

 his apparatus for the measurement of dielectrics, and a new 

 method of measuring electric waves in air was described and 

 exhibited. 



John E. Wolff presented the following papers by title : — 



A Comparative Study of Etch-figures : the Amphiboles and 

 Pyroxenes. By R. A. Daly. 



On the Optical Characters of the Vertical Zone of Amphiboles 

 and Pyroxenes : and on a new ]\Iethod of determining the 

 Extinction-Angles of these Minerals by Means of Cleavage- 

 Pieces. By R. A. Daly. 



Nine hundred and fourth Meeting. 



January 11, 1899. — Stated Meeting. 



Vice-President Hyatt in the chair. 



The Corresponding Secretary read letters from the Inter- 

 national Geographical Congress, announcing its seventh meet- 



