ijji/fr PROCEEDINGS 



OF THE 



American Philosophical Society 



HELD AT PHILA^t/EI^MiA 



FOR PROMOTING USEFUL KNOWLEDGE 

 Vol. LVIII. 1919. No. 2. 



CONTENTS 



PAGE 



Alternating-current Planevector Potentiometer Measurements at Telephonic 



Frequencies. By A. E. Kennelly and Edy Velander . 97 



Some Scientific Aspects of the Meteoi'ological Work of the United States 



Army. By Robert A. Millikan . . . . . • 133 



Detecting Ocean Currents by Observing their Hydrogen-ion Concentra- 

 tion. By Alfred Goldsborough Mayor .... 150 



PHILADELPHIA 



THE AMERICAN PHILOSOPHICAL SOCIETY 



104 South Fifth Street 



1919 



