﻿472 
  Scientific 
  Intelligence. 
  

  

  have 
  been 
  constructed 
  and 
  plotted 
  on 
  Plate 
  I. 
  They 
  correspond 
  

   to 
  a 
  length 
  of 
  needle 
  of 
  40 
  cra 
  (15*8 
  inches). 
  The 
  main 
  conclu- 
  

   sions 
  drawn 
  are 
  : 
  

  

  I. 
  In 
  consequence 
  of 
  the 
  secular 
  variation 
  of 
  geomagnetism, 
  

   the 
  north 
  end 
  of 
  a 
  freely 
  suspended 
  magnetic 
  needle 
  viewed 
  from 
  

   the 
  center 
  of 
  suspension 
  of 
  the 
  needle 
  moves 
  on 
  the 
  whole 
  earth 
  in 
  

   the 
  direction 
  of 
  the 
  hands 
  of 
  a 
  watch. 
  

  

  II. 
  The 
  secular 
  variation 
  period 
  (if 
  there 
  be 
  such) 
  is 
  different 
  

   for 
  various 
  portions 
  of 
  the 
  earth 
  or 
  the 
  secular 
  curve 
  is 
  not 
  a 
  

   single 
  closed 
  curve, 
  but 
  consists 
  of 
  loops. 
  

  

  No. 
  I 
  has 
  been 
  tested 
  at 
  more 
  than 
  100 
  stations 
  scattered 
  over 
  

   the 
  face 
  of 
  the 
  earth 
  with 
  the 
  result 
  that 
  the 
  writer 
  believes 
  it 
  

   can 
  be 
  considered 
  as 
  a 
  safely 
  established 
  result. 
  It 
  virtually 
  

   embraces 
  two 
  laws, 
  first, 
  the 
  clockwise 
  motion, 
  secondly, 
  the 
  uni- 
  

   formity 
  of 
  this 
  motion 
  in 
  both 
  magnetic 
  hemispheres. 
  This 
  law 
  

   is 
  playing 
  an 
  important 
  role 
  in 
  the 
  differentiation 
  of 
  the 
  operat- 
  

   ing 
  causes. 
  

  

  Chapter 
  II 
  is 
  devoted 
  to 
  a 
  comparison 
  of 
  the 
  phenomena 
  of 
  

   the 
  secular 
  variation 
  with 
  those 
  due 
  to 
  the 
  actual 
  distribution 
  of 
  

   terrestrial 
  magnetism. 
  It 
  was 
  noted 
  in 
  this 
  chapter 
  that 
  the 
  

   incomplete 
  secular 
  variation 
  curve 
  at 
  any 
  particular 
  station 
  could 
  

   be 
  apparently 
  completed 
  by 
  a 
  consideration 
  of 
  the 
  parts 
  of 
  curves 
  

   described 
  at 
  the 
  stations 
  passed 
  in 
  making 
  an 
  easterly 
  circuit 
  of 
  

   the 
  earth. 
  This 
  led 
  to 
  the 
  following 
  conclusions 
  : 
  

  

  III. 
  The 
  north 
  end 
  of 
  a 
  free 
  magnetic 
  needle 
  viewed 
  from 
  the 
  

   ■ 
  center 
  of 
  suspension 
  of 
  the 
  needle 
  moves 
  clockwise 
  in 
  making 
  an 
  

  

  instantaneous 
  circuit 
  of 
  the 
  earth 
  along 
  a 
  parallel 
  of 
  latitude-, 
  or, 
  

   as 
  I 
  have 
  put 
  it 
  later 
  : 
  

  

  The 
  north 
  end 
  of 
  a 
  free 
  magnetic 
  needle 
  whose 
  center 
  of 
  sus- 
  

   pension 
  is 
  fixed 
  in 
  space 
  close 
  to 
  the 
  earth? 
  s 
  surface 
  will 
  describe 
  

   a 
  curve* 
  as 
  the 
  earth 
  rotates 
  under 
  it 
  which 
  as 
  vieioed 
  from 
  the 
  

   center 
  of 
  suspension 
  of 
  the 
  needle 
  moves 
  anti-clockwise. 
  

  

  IV. 
  The 
  secular 
  variation 
  and 
  the 
  prevailing 
  distribution 
  of 
  

   geomagnetism 
  appear 
  to 
  be 
  closely 
  related, 
  i. 
  e. 
  seem 
  to 
  be 
  subject 
  

   to 
  similar 
  laws. 
  

  

  The 
  five 
  subsequent 
  chapters 
  contain 
  preliminary 
  announce- 
  

   ments 
  of 
  additional 
  investigations 
  of 
  the 
  secular 
  variation. 
  The 
  

   paper 
  will 
  be 
  found 
  fully 
  abstracted, 
  as 
  also 
  the 
  curves 
  given, 
  in 
  

   the 
  Physical 
  Review, 
  May, 
  '95, 
  and 
  subsequent 
  number. 
  

  

  L. 
  A. 
  B. 
  

  

  12. 
  A 
  Text 
  Book 
  of 
  the 
  Principles 
  of 
  Physics 
  ; 
  by 
  Alfred 
  

   Daniell. 
  Third 
  edition 
  (sixth 
  thousand), 
  782 
  pp., 
  8vo, 
  1894. 
  

   New 
  York 
  and 
  London 
  (Macmillan 
  & 
  Co.) 
  — 
  Daniell's 
  Text 
  Book 
  

   of 
  Physics 
  has 
  become 
  so 
  widely 
  known 
  as 
  a 
  work 
  of 
  high 
  scien- 
  

   tific 
  grade, 
  carefully 
  developed 
  throughout 
  on 
  a 
  uniform 
  and 
  con- 
  

   sistent 
  plan, 
  that 
  it 
  hardly 
  needs 
  now 
  to 
  be 
  commended 
  anew. 
  

   The 
  present 
  third 
  edition, 
  a 
  few 
  advance 
  copies 
  of 
  which 
  have 
  

  

  * 
  The 
  curves 
  resulting 
  thus 
  are 
  termed 
  the 
  " 
  instantaneous 
  curves 
  " 
  and 
  have 
  

   been 
  laid 
  down 
  on 
  Plate 
  IE 
  for 
  the 
  epochs 
  1780, 
  1829 
  and 
  J 
  885 
  and 
  for 
  the 
  paral- 
  

   lels 
  of 
  latitude 
  40° 
  north, 
  equator 
  and 
  40° 
  south. 
  

  

  