PROCEEDINGS 



OF THE 



American Philosophical Society 



HELD AT PHILADELPHIA 



FOR PROMOTING USEFUL KNOWLEDGE 



Vol. LIV. May- July, 19 15. No. 217, 



CONTENTS 



Additions to the Fauna of the Lower PHocene Snake Creek Beds (Re- 

 sults of the Princeton University 1914 Expedition to Nebraska). 

 By William J. Sinclair - - - - - - - 73 



Explorations Over the Vibrating Surfaces of Telephonic Diaphragms 

 Under Simple Impressed Tones. By A. E. Kennelly and 

 H. O. Taylor - - - - - - - - - 96 



The Ruling and Performance of a Ten Inch Diffraction Grating. By 



A. A. MiCHELSON - - -- 137 



The Constitution of the Hereditary Material. By T. H. Morgan - 143 



Spontaneous Generation of Heat in Recently Hardened Steel. By 



Charles F. Brush -------- 154 



Relationships of the White Oaks of Eastern North America. With an 

 Introductory Sketch of their Phylogenetic History. (Plates 

 IV-VI.) By Margaret V. Cobb - - - - - - 165 



A New Form of Nephelometer. By J. T. W. Marshall and H. W. 



Banks, 3D- - -.- - - - -- - 176 



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