﻿Notices 
  respecting 
  JSew 
  Boohs. 
  255 
  

  

  1882-3. 
  The 
  results 
  are 
  shown 
  graphically 
  in 
  Plates 
  n., 
  yni., 
  

   ix., 
  & 
  x. 
  

  

  The 
  remainder 
  of 
  the 
  volume 
  is 
  mainly 
  devoted 
  to 
  a 
  description 
  

   or 
  experiments 
  made 
  with 
  cathode 
  rays 
  and 
  magnetic 
  fields 
  in 
  high 
  

   vacua, 
  to 
  a 
  discussion 
  of 
  recent 
  physical 
  work 
  by 
  Goldstein, 
  J. 
  J. 
  

   Thomson 
  and 
  others, 
  and 
  to 
  the 
  enunciation 
  of 
  Birkeland's 
  own 
  

   theory 
  of 
  the 
  proximate 
  cause 
  of 
  magnetic 
  storms 
  aud 
  aurora- 
  

   He 
  believes 
  in 
  the 
  emission 
  from 
  the 
  sun 
  — 
  notably 
  at 
  times 
  of 
  

   maximum 
  sun-spot 
  frequency 
  — 
  of 
  cathode 
  rays. 
  When 
  these 
  

   reach 
  the 
  earth's 
  rarefied 
  atmosphere 
  they 
  come 
  under 
  the 
  in- 
  

   fluence 
  of 
  the 
  earth's 
  magnetic 
  field, 
  and 
  tend 
  to 
  coincide 
  with 
  the 
  

   direction 
  of 
  the 
  lines 
  of 
  magnetic 
  force. 
  For 
  aurora 
  the 
  primary 
  

   requisite 
  is 
  local 
  intensity 
  of 
  current 
  ; 
  for 
  big 
  magnetic 
  disturbance 
  

   a 
  large 
  total 
  current 
  is 
  required, 
  but 
  it 
  need 
  not 
  always 
  be 
  suffi- 
  

   ciently 
  concentrated 
  to 
  occasion 
  much 
  aurora. 
  

  

  The 
  laboratory 
  experiments 
  consist 
  mainly 
  in 
  the 
  production 
  of 
  

   phenomena 
  resembling 
  aurora. 
  Judging 
  by 
  the 
  descriptions, 
  by 
  

   fig. 
  6 
  p. 
  57, 
  and 
  by 
  Plates 
  xi. 
  and 
  xn., 
  the 
  resemblance 
  between 
  

   the 
  laboratory 
  phenomena 
  and 
  auroral 
  bands, 
  ribbons, 
  aud 
  " 
  merry 
  

   dancers 
  " 
  must 
  be 
  striking. 
  

  

  That 
  aurora 
  is 
  an 
  electrical 
  manifestation, 
  and 
  that 
  it 
  is 
  usually 
  

   concurrent 
  with 
  magnetic 
  storms 
  and 
  earth 
  currents, 
  is 
  now 
  

   generally 
  believed 
  ; 
  but 
  it 
  would 
  be 
  prudent 
  as 
  yet 
  to 
  regard 
  with 
  

   reserve 
  any 
  of 
  the 
  theoretical 
  speculations 
  advanced 
  to 
  account 
  for 
  

   the 
  interconnection. 
  A 
  theory 
  may 
  be 
  in 
  general 
  accord 
  with 
  a 
  

   number 
  of 
  facts 
  discussed 
  by 
  its 
  founder, 
  and 
  yet 
  be 
  found 
  wanting 
  

   when 
  tested 
  over 
  another 
  range 
  of 
  phenomena 
  by 
  independent 
  

   critics. 
  This 
  may 
  be 
  the 
  fate 
  in 
  store 
  for 
  Prof. 
  Birkeland's 
  theory 
  ; 
  

   but 
  in 
  any 
  case 
  it 
  should 
  serve 
  a 
  useful 
  purpose 
  in 
  suggesting 
  

   lines 
  of 
  research 
  and 
  focussing 
  attention 
  on 
  crucial 
  points. 
  

  

  By 
  the 
  older 
  type 
  of 
  magnetic 
  observer, 
  the 
  physicist, 
  with 
  his 
  

   laboratory 
  experiments 
  and 
  proclivities 
  to 
  theory, 
  is 
  apt 
  to 
  be 
  

   regarded 
  as 
  a 
  relative 
  of 
  the 
  chamber 
  philosopher, 
  who 
  aims 
  at 
  the 
  

   immediate 
  regeneration 
  of 
  Society. 
  There 
  is 
  sometimes 
  a 
  good 
  

   deal 
  to 
  be 
  said 
  for 
  this 
  view 
  ; 
  but 
  at 
  the 
  present 
  time 
  another 
  side 
  

   of 
  the 
  picture 
  may 
  be 
  more 
  profitably 
  regarded, 
  at 
  least 
  in 
  this 
  

   country. 
  We 
  have 
  in 
  England 
  various 
  magnetic 
  observatories, 
  

   some 
  of 
  which 
  devote 
  a 
  good 
  deal 
  of 
  time 
  to 
  recording 
  magnetic 
  

   results 
  and 
  dealing 
  with 
  them 
  in 
  a 
  routine 
  way 
  ; 
  but 
  there 
  is 
  no- 
  

   adequate 
  provision 
  for 
  securing 
  the 
  existence 
  on 
  their 
  staffs 
  or 
  the 
  

   co-operation 
  of 
  men 
  possessing 
  wide 
  theoretical 
  knowledge, 
  with 
  

   the 
  brain-power 
  and 
  the 
  leisure 
  necessary 
  to 
  secure 
  the 
  best 
  

   results. 
  The 
  volume 
  before 
  us 
  seems 
  evidence 
  that 
  the 
  Norwegian 
  

   Government 
  and 
  People 
  take 
  a 
  sympathetic 
  view 
  in 
  such 
  matters.. 
  

   and 
  it 
  is 
  to 
  be 
  hoped 
  that 
  they 
  have 
  in 
  contemplation 
  the 
  con- 
  

   tinuance 
  of 
  the 
  Haldde 
  observations 
  during 
  the 
  forthcoming 
  

   ''Antarctic 
  Year." 
  

  

  0. 
  Chkee. 
  

  

  