﻿22 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  1 
  

  

  be 
  outstanding 
  characteristic 
  differences 
  between 
  results 
  obtained 
  at 
  the 
  

   same 
  station 
  with 
  two 
  or 
  more 
  needles. 
  These 
  are 
  probably 
  due 
  to 
  irregu- 
  

   larity 
  of 
  general 
  form 
  of 
  pivot 
  and 
  are 
  eliminated 
  by 
  applying 
  corrections 
  

   derived 
  from 
  least 
  square 
  reductions 
  where 
  data 
  are 
  available, 
  or 
  from 
  em- 
  

   pirical 
  graphs 
  otherwise. 
  

  

  Occasionally 
  a 
  needle 
  will 
  give 
  a 
  result 
  differing 
  widely 
  from 
  the 
  mean 
  of 
  

   the 
  others 
  used 
  at 
  the 
  same 
  station, 
  and 
  a 
  critical 
  study 
  of 
  several 
  cases 
  of 
  

   this 
  kind 
  derived 
  from 
  results 
  of 
  field 
  work 
  in 
  widely 
  separated 
  regions, 
  

   shows 
  that 
  when 
  not 
  purely 
  accidental, 
  these 
  differences 
  vary 
  with 
  the 
  varying 
  

   dip 
  as 
  they 
  would 
  if 
  they 
  were 
  caused 
  by 
  a 
  small 
  particle 
  adhering 
  to 
  the 
  

   pivot 
  of 
  the 
  needle. 
  A 
  method 
  was 
  presented 
  of 
  analyzing 
  the 
  results 
  de- 
  

   rived 
  from 
  a 
  series 
  of 
  stations 
  at 
  each 
  of 
  which 
  the 
  dip 
  had 
  been 
  obtained 
  by 
  

   use 
  of 
  four 
  needles, 
  so 
  that 
  such 
  deviations 
  from 
  the 
  normal 
  value 
  could 
  be 
  

   readily 
  recognized. 
  Cases 
  illustrating 
  the 
  results 
  of 
  such 
  analysis 
  were 
  

   presented. 
  

  

  Theory 
  was 
  developed 
  by 
  which 
  it 
  was 
  shown 
  that 
  the 
  occasional 
  differ- 
  

   ences 
  under 
  investigation 
  could 
  be 
  produced 
  by 
  a 
  very 
  minute 
  particle 
  of 
  

   rust, 
  and 
  an 
  equation 
  was 
  given 
  by 
  which 
  the 
  diameter 
  and 
  thickness 
  of 
  

   the 
  particle 
  could 
  be 
  determined. 
  By 
  this 
  method 
  it 
  was 
  found 
  that 
  a 
  minute 
  

   patch 
  of 
  rust 
  0.02 
  millimeter 
  in 
  diameter 
  and 
  6 
  X 
  10~^ 
  millimeters 
  thick, 
  

   on 
  the 
  pivot 
  of 
  an 
  ordinary 
  Dover 
  dip 
  needle, 
  would 
  produce 
  an 
  error 
  of 
  

   6 
  minutes 
  in 
  arc 
  in 
  the 
  determination 
  of 
  dip 
  at 
  a 
  place 
  where 
  the 
  total 
  mag- 
  

   netic 
  force 
  is 
  0.55. 
  

  

  An 
  example 
  was 
  given 
  to 
  show 
  that 
  the 
  rust 
  particle 
  might 
  later 
  become 
  

   detached 
  so 
  that 
  the 
  needle 
  would 
  behave 
  normally 
  at 
  the 
  value 
  of 
  dip. 
  

   Also 
  it 
  was 
  shown 
  that 
  particles 
  of 
  this 
  kind 
  develop 
  very 
  quickly. 
  From 
  

   these 
  examples 
  it 
  is 
  concluded 
  that 
  the 
  correction 
  for 
  a 
  dip 
  needle 
  cannot 
  

   be 
  relied 
  upon 
  permanently 
  at 
  any 
  one 
  place 
  nor 
  be 
  safely 
  transferred 
  to 
  a 
  

   place 
  where 
  the 
  field 
  has 
  a 
  different 
  direction 
  or 
  intensity 
  without 
  a 
  comparison 
  

   with 
  such 
  a 
  reliable 
  standard 
  as 
  is 
  afforded 
  by 
  the 
  latest 
  type 
  of 
  portable 
  

   earth 
  inductor. 
  In 
  case 
  a 
  dip 
  circle 
  must 
  be 
  used, 
  not 
  less 
  than 
  four 
  needles 
  

   should 
  be 
  employed 
  in 
  order 
  to 
  furnish 
  an 
  improved 
  mean, 
  and 
  to 
  better 
  

   detect 
  such 
  errors 
  as 
  arise 
  from 
  minute 
  pivot 
  defects. 
  (Author's 
  abstract.) 
  

  

  The 
  second 
  paper 
  on 
  The 
  latitude 
  of 
  Ukiah 
  and 
  the 
  motion 
  of 
  the 
  Pole 
  was 
  

   presented 
  by 
  Mr. 
  Walter 
  D. 
  Lambert 
  and 
  was 
  illustrated. 
  It 
  was 
  dis- 
  

   cussed 
  by 
  Messrs. 
  I,. 
  H. 
  Adams 
  and 
  L. 
  A. 
  Bauer. 
  

  

  Prof. 
  A. 
  C. 
  lyawson 
  in 
  support 
  of 
  his 
  explanation 
  of 
  certain 
  earth 
  move- 
  

   ments 
  in 
  California 
  brings 
  forward 
  the 
  evidence 
  afforded 
  by 
  the 
  astronomic 
  

   latitudes 
  at 
  Ukiah, 
  California, 
  one 
  of 
  the 
  stations 
  of 
  the 
  International 
  Latitude 
  

   Service. 
  These 
  latitudes 
  show 
  an 
  apparent 
  increase 
  of 
  about 
  0.01 
  a 
  year, 
  

   which 
  is 
  explained 
  as 
  an 
  actual 
  shifting 
  northward 
  of 
  the 
  crust 
  at 
  Ukiah 
  

   relative 
  to 
  its 
  substratum. 
  Ukiah 
  is 
  somewhat 
  outside 
  of 
  the 
  region 
  in 
  which 
  

   the 
  existence 
  of 
  large 
  earth 
  movements 
  has 
  been 
  proved 
  by 
  the 
  evidence 
  of 
  

   triangulation 
  executed 
  at 
  different 
  dates. 
  The 
  attempt 
  is 
  made 
  in 
  this 
  

   paper 
  to 
  see 
  whether 
  the 
  astronomical 
  evidence 
  at 
  Ukiah 
  may 
  properly 
  be 
  

   interpreted 
  otherwise 
  than 
  as 
  indicating 
  a 
  creep 
  of 
  the 
  surface 
  strata. 
  

  

  It 
  is 
  found 
  that 
  the 
  other 
  stations 
  of 
  the 
  International 
  Latitude 
  Service 
  

   show 
  increases 
  or 
  decreases 
  of 
  the 
  same 
  order 
  of 
  magnitude 
  as 
  that 
  of 
  Ukiah, 
  

   the 
  general 
  tendency 
  being 
  toward 
  an 
  increase, 
  a 
  feature 
  especially 
  noticeable 
  

   toward 
  the 
  end 
  of 
  the 
  period 
  of 
  observation. 
  At 
  Gaithersburg, 
  Maryland, 
  

   the 
  rate 
  of 
  increase 
  even 
  exceeds 
  that 
  at 
  Ukiah. 
  The 
  universality 
  of 
  these 
  

  

  