﻿Chemistry 
  and 
  Physics. 
  471 
  

  

  with 
  the 
  12 
  gauges 
  which 
  were 
  first 
  tried. 
  In 
  general 
  air 
  

   electrified 
  negatively 
  by 
  bubbling 
  through 
  water 
  and 
  caused 
  to 
  

   pass 
  through 
  a 
  metallic 
  wire 
  gauge 
  strainer 
  — 
  gives 
  up 
  some, 
  but 
  

   not 
  a 
  large 
  proportion 
  of 
  its 
  electricity 
  to 
  the 
  metal. 
  — 
  Proceedings 
  

   Poyal 
  Society, 
  March 
  21, 
  1895 
  ; 
  Nature, 
  April 
  11, 
  1895. 
  j. 
  t. 
  

  

  11. 
  Beitraege 
  zur 
  Kenntniss 
  des 
  Wesens 
  der 
  Saecular 
  Variation 
  

   des 
  Erdmagnetismus 
  y 
  by 
  L. 
  A. 
  Bauer. 
  Inaugural 
  Dissertation 
  

   University 
  of 
  Berlin. 
  Large 
  8vo, 
  56 
  pp. 
  and 
  2 
  plates. 
  1895. 
  

   Abstract 
  prepared 
  by 
  the 
  author. 
  — 
  If 
  we 
  suppose 
  a 
  magnetic 
  

   needle 
  so 
  suspended 
  that 
  it 
  is 
  free 
  to 
  move 
  in 
  every 
  possible 
  direc- 
  

   tion, 
  it 
  will, 
  under 
  the 
  influence 
  of 
  terrestrial 
  magnetism, 
  assume 
  

   at 
  any 
  particular 
  time 
  a 
  definite 
  direction. 
  This 
  direction 
  is 
  a 
  

   tano-ent 
  to 
  the 
  o;eoina2metic 
  lines 
  of 
  force. 
  As 
  is 
  well 
  known 
  

   these 
  lines 
  are 
  constantly 
  shifting. 
  They 
  are 
  subject 
  to 
  diurnal, 
  

   seasonal, 
  annual, 
  11^-year, 
  etc., 
  variations, 
  also 
  to 
  non-periodic 
  

   fluctuations. 
  The 
  most 
  striking 
  one 
  of 
  all 
  the 
  changes, 
  however, 
  

   is 
  that 
  due 
  to 
  the 
  so-called 
  secular 
  variation 
  whereby 
  the 
  direc- 
  

   tion 
  of 
  the 
  needle 
  suffers 
  in 
  the 
  lapse 
  of 
  time 
  most 
  remarkable 
  

   changes. 
  This 
  variation 
  has 
  been 
  known 
  now 
  for 
  over 
  two 
  and 
  a 
  

   half 
  centuries; 
  it 
  has 
  been 
  the 
  subject 
  for 
  speculation 
  by 
  some 
  of 
  

   the 
  most 
  brilliant 
  minds. 
  The 
  great 
  riddle, 
  however, 
  is 
  still 
  

   unsolved. 
  

  

  This 
  phenomenon 
  owing 
  chiefly 
  to 
  the 
  asymmetrical 
  distribu- 
  

   tion 
  of 
  geomagnetism 
  is 
  a 
  most 
  complex 
  one. 
  But 
  the 
  method 
  

   of 
  treatment 
  heretofore 
  employed, 
  has 
  done 
  its 
  share, 
  also, 
  to 
  

   deepen 
  the 
  mystery. 
  Namely, 
  it 
  has 
  been 
  customary 
  to 
  treat 
  

   separately 
  the 
  secular 
  variation 
  of 
  the 
  different 
  magnetic 
  elements, 
  

   declination, 
  inclination, 
  or 
  intensity, 
  as 
  the 
  case 
  may 
  be, 
  as 
  

   though 
  these 
  were 
  different 
  effects 
  of 
  operative 
  forces, 
  instead 
  of 
  

   component 
  ones. 
  The 
  consequence 
  has 
  been 
  that 
  not 
  a 
  single 
  

   law 
  governing 
  the 
  secular 
  variation 
  as 
  applying 
  to 
  all 
  parts 
  of 
  

   the 
  earth 
  could 
  be 
  established. 
  

  

  At 
  the 
  meeting 
  of 
  the 
  A. 
  A. 
  A. 
  S. 
  in 
  Aug., 
  1892, 
  the 
  writer 
  

   presented 
  a 
  preliminary 
  paper 
  " 
  On 
  the 
  Secular 
  Motion 
  of 
  a 
  Free 
  

   Magnetic 
  Xeedle." 
  This 
  paper 
  had 
  for 
  its 
  object 
  to 
  investigate 
  

   the 
  total 
  change 
  suffered 
  by 
  the 
  needle 
  by 
  drawing 
  the 
  actual 
  

   curve 
  described 
  in 
  space 
  by 
  the 
  north 
  end 
  of 
  a 
  free 
  magnetic 
  

   needle 
  in 
  the 
  course 
  of 
  centuries. 
  That 
  is, 
  both 
  the 
  declination 
  

   and 
  the 
  inclination 
  changes 
  were 
  considered. 
  The 
  intensity 
  

   changes 
  are 
  not 
  taken 
  into 
  account 
  as 
  the 
  purpose 
  was 
  to 
  investi- 
  

   gate 
  solely 
  the 
  total 
  change 
  in 
  direction 
  of 
  terrestrial 
  magnetic 
  

   lines 
  of 
  force. 
  This 
  paper 
  announced 
  some 
  novel 
  conclusions, 
  

   chief 
  of 
  which 
  being 
  number 
  one 
  stated 
  below. 
  The 
  present 
  

   paper 
  is 
  a 
  continuation 
  and 
  amplification 
  of 
  the 
  A. 
  A. 
  A. 
  S. 
  com- 
  

   munication. 
  The 
  writer 
  enjoyed 
  theaise 
  of 
  the 
  Washington 
  and 
  

   the 
  Berlin 
  libraries. 
  

  

  Chapter 
  I 
  deals 
  with 
  the 
  secular 
  motion 
  of 
  a 
  free 
  magnetic 
  

   needle. 
  The 
  observation 
  data 
  for 
  twenty-four 
  stations 
  distributed 
  

   over 
  the 
  earth 
  have 
  been 
  carefully 
  collected 
  and 
  discussed. 
  The 
  

   curves 
  described 
  by 
  the 
  north 
  end 
  of 
  the 
  free 
  magnetic 
  needle 
  

  

  