﻿Smithsonian 
  Report 
  1922. 
  — 
  Humphreys. 
  

  

  Plate 
  17. 
  

  

  I. 
  Mammato-cumulus. 
  

  

  (L. 
  C. 
  Twyford, 
  pholo. 
  ) 
  

  

  2. 
  Lenticular 
  Cloud 
  (Alto-stratus 
  Lenticularis), 
  Seen 
  from 
  Mount 
  

  

  Wilson, 
  Calif. 
  

  

  (F. 
  Ellerman, 
  photo. 
  I 
  

  

  