﻿168 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  cease. 
  Scientific 
  investigation 
  forms 
  the 
  most 
  important 
  feature 
  

   of 
  aviation, 
  and 
  it 
  can 
  be 
  conducted 
  only 
  by 
  trained 
  students. 
  The 
  

   best 
  pilot 
  in 
  the 
  world 
  may 
  know 
  very 
  little 
  about 
  the 
  scientific 
  

   principles 
  underlying 
  flight, 
  and 
  he 
  would 
  therefore 
  be 
  unable 
  to 
  

   make 
  any 
  marked 
  improvements 
  in 
  his 
  machine. 
  Aeronautics 
  is 
  

   in 
  no 
  sense 
  a 
  function 
  of 
  an 
  engineer 
  or 
  constructor 
  or 
  aviator, 
  it 
  is 
  

   a 
  branch 
  of 
  pure 
  science. 
  Those 
  countries 
  have 
  developed 
  the 
  best 
  

   airships 
  and 
  airplanes 
  which 
  have 
  devoted 
  the 
  most 
  thought, 
  time 
  

   and 
  money 
  to 
  the 
  underlying 
  scientific 
  studies. 
  When 
  the 
  physical 
  

   facts 
  are 
  known, 
  the 
  engineer 
  can 
  design 
  his 
  aircraft, 
  the 
  constructor 
  

   can 
  make 
  it, 
  and 
  the 
  trained 
  man 
  can 
  fly 
  it 
  ; 
  but 
  the 
  foundation 
  stone 
  

   is 
  the 
  store 
  of 
  knowledge 
  obtained 
  by 
  the 
  scientist. 
  

  

  Fig. 
  1. 
  — 
  Combination 
  of 
  source 
  and 
  sink. 
  

  

  Before 
  describing 
  the 
  types 
  of 
  investigations 
  in 
  progress 
  in 
  aero- 
  

   nautics 
  and 
  the 
  methods 
  pursued, 
  it 
  may 
  be 
  interesting 
  to 
  see 
  some 
  

   illustrations 
  of 
  the 
  two 
  types 
  of 
  aircraft 
  now 
  in 
  use 
  — 
  the 
  airship 
  

   and 
  the 
  airplane. 
  If 
  I 
  had 
  time, 
  I 
  would 
  like 
  very 
  much 
  to 
  say 
  

   something 
  about 
  the 
  helicopter, 
  a 
  type 
  of 
  aircraft 
  to 
  which 
  we 
  have 
  

   given 
  a 
  name 
  before 
  constructing 
  one. 
  Up 
  to 
  the 
  present 
  no 
  such 
  

   machine, 
  worthy 
  of 
  the 
  name, 
  has 
  been 
  made; 
  but 
  beyond 
  a 
  doubt 
  

   one 
  will 
  be 
  constructed, 
  and 
  in 
  the 
  near 
  future. 
  

  

  An 
  airship 
  owes 
  its 
  flying 
  power 
  to 
  the 
  fact 
  that 
  it 
  is 
  made 
  

   " 
  lighter 
  than 
  air 
  " 
  by 
  being 
  filled 
  with 
  a 
  gas 
  lighter 
  than 
  air. 
  

   Hydrogen 
  is 
  the 
  gas 
  always 
  used, 
  although 
  helium 
  may 
  be. 
  The 
  

   lifting 
  power 
  of 
  the 
  latter 
  gas 
  is 
  about 
  four-fifths 
  of 
  that 
  of 
  

   hydrogen. 
  As 
  the 
  airship 
  moves 
  through 
  the 
  air, 
  it 
  meets 
  with 
  

  

  