﻿VOL. 
  XLVIL 
  

  

  JANUARY, 
  1919. 
  

  

  Established 
  by 
  BENJAMIN 
  SILLIMAN 
  in 
  1818. 
  

  

  THE 
  

  

  AMERICAN 
  

  

  JOURNAL 
  OF 
  SCIENCE 
  

  

  Editor; 
  EDWARD 
  S. 
  DANA. 
  

  

  ASSOCIATE 
  EDITORS 
  

  

  Professors 
  GEORGE 
  L. 
  GOODALE, 
  JOHN 
  TROWBRIDGE, 
  

   W. 
  G. 
  FARLOW 
  and 
  WM. 
  M. 
  DAVIS, 
  of 
  Cambridge, 
  

  

  Professors 
  A. 
  E. 
  VEKKILL, 
  HORACE 
  L. 
  WELLS, 
  CHARLES 
  

  

  SCHUCHERT, 
  L. 
  V. 
  PIKSSON, 
  H. 
  E. 
  GREGORY, 
  

  

  and 
  HORACE 
  S. 
  UHLER, 
  of 
  New 
  Haven, 
  

  

  Professor 
  JOSEPH 
  S. 
  AMES, 
  of 
  Baltimore, 
  

   Mr. 
  J. 
  S. 
  DILLER, 
  of 
  Washington. 
  

  

  FOURTH 
  SERIES 
  

   VOL. 
  XLVII— 
  [WHOLE 
  NUMBER, 
  CXCVII]. 
  

  

  No. 
  277— 
  JANUARY, 
  1919. 
  

  

  NEW 
  HAVEN, 
  CONNECTICUT. 
  

  

  1919. 
  

  

  THE 
  TUTTLE, 
  MOREHOUSE 
  & 
  TAYLOR 
  CO., 
  PRINTERS, 
  123 
  TEMPLE 
  STREET. 
  

  

  Published 
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  under 
  th 
  

   of 
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  3, 
  1879. 
  

  

  