﻿248 
  Scientific 
  Intelligence, 
  

  

  the 
  earth 
  at 
  the 
  instant 
  when 
  the 
  light 
  strikes 
  the 
  observer's 
  eye, 
  

   the 
  star 
  will 
  appear 
  to 
  be 
  displaced 
  from 
  its 
  true 
  position 
  on 
  the 
  

   celestial 
  sphere 
  for 
  the 
  reason 
  that 
  in 
  passing 
  through 
  the 
  sun's 
  

   gravitational 
  field 
  the 
  ray 
  will 
  be 
  bent 
  out 
  of 
  the 
  line 
  in 
  which 
  it 
  

   had 
  previously 
  been 
  moving. 
  The 
  theoretical 
  angular 
  displace- 
  

   ment 
  only 
  amounts 
  to 
  //# 
  83 
  which 
  is 
  probably, 
  too 
  small 
  to 
  be 
  

   observed. 
  

  

  A 
  second 
  special 
  case 
  relates 
  to 
  the 
  solar 
  spectrum. 
  As 
  a 
  con- 
  

   sequence 
  of 
  the 
  fact 
  that 
  the 
  rates 
  at 
  which 
  synchronous 
  clocks 
  

   will 
  run 
  depends 
  upon 
  the 
  potential 
  of 
  the 
  gravitational 
  field 
  in 
  

   which 
  they 
  are 
  immersed, 
  it 
  follows 
  that 
  solar 
  spectral 
  lines 
  

   should 
  appear 
  to 
  an 
  observer 
  on 
  the 
  earth 
  to 
  be 
  displaced 
  toward 
  

   longer 
  wave-lengths. 
  The 
  magnitude 
  of 
  the 
  shift 
  is 
  given 
  by 
  

   the 
  approximate 
  equation 
  (v 
  — 
  v)/v 
  a 
  — 
  2 
  X 
  10 
  _G 
  where 
  v 
  denotes 
  

   the 
  frequency 
  of 
  the 
  light 
  vibrations 
  on 
  leaving 
  the 
  sun, 
  and 
  v 
  

   stands 
  for 
  the 
  frequency 
  on 
  reaching 
  the 
  earth. 
  Displacements 
  

   of 
  this 
  magnitude 
  and 
  direction 
  have 
  been 
  observed 
  by 
  L. 
  E. 
  

   Jewell 
  and 
  others, 
  but, 
  unfortunately 
  for 
  the 
  present 
  theory, 
  it 
  

   has 
  not 
  been 
  possible 
  to 
  eliminate 
  other 
  causes 
  which 
  might 
  have 
  

   produced 
  the 
  effects 
  observed 
  ; 
  increase 
  of 
  pressure, 
  for 
  example. 
  

  

  The 
  only 
  quantity 
  of 
  appreciable 
  size 
  for 
  which 
  the 
  theory 
  

   seems 
  to 
  account 
  perfectly 
  is 
  the 
  secular 
  motion 
  of 
  Mercury's 
  

   perihelion. 
  If 
  this 
  be 
  true, 
  and 
  not 
  a 
  coincidence, 
  then 
  Einstein 
  

   has 
  overcome 
  a 
  difficulty 
  which 
  has 
  completely 
  baffled 
  all 
  astrono- 
  

   mers. 
  A 
  certain 
  angle 
  associated 
  with 
  the 
  orbit 
  of 
  Mercury 
  has 
  

   the 
  values 
  +118 
  //# 
  00 
  and 
  +118 
  //, 
  58 
  according 
  to 
  observation 
  and 
  

   to 
  Einstein's 
  theory, 
  respectively. 
  The 
  agreement 
  is 
  perfectly 
  

   satisfactory 
  since 
  the 
  probable 
  error 
  of 
  the 
  experimental 
  datum 
  is 
  

   ±0 
  /;, 
  43. 
  On 
  the 
  other 
  hand, 
  according 
  to 
  Newcomb, 
  the 
  differ- 
  

   ence 
  between 
  observation 
  and 
  theory 
  amounts 
  to 
  as 
  much 
  as 
  

   + 
  8 
  //# 
  48 
  (instead 
  of 
  — 
  O'^S 
  ± 
  //# 
  43) 
  when 
  the 
  computations 
  are 
  

   based 
  on 
  the 
  laws 
  of 
  Newtonian 
  mechanics. 
  h. 
  s. 
  u. 
  

  

  6. 
  Ball 
  Lightning. 
  — 
  The 
  absolute 
  reliability 
  of 
  the 
  following 
  

   interesting 
  observations 
  is 
  vouched 
  for 
  by 
  M. 
  E. 
  Mathias 
  in 
  a 
  

   short 
  article 
  on 
  the 
  subject. 
  On 
  the 
  fifteenth 
  of 
  last 
  April, 
  at 
  

   about 
  18 
  h 
  20 
  m 
  , 
  a 
  flash 
  of 
  lightning 
  burned 
  out 
  the 
  telegraphic 
  

   apparatus 
  associated 
  with 
  the 
  observatory 
  on 
  the 
  Puy 
  de 
  Dome. 
  

   One 
  observer, 
  who 
  happened 
  to 
  be 
  looking 
  toward 
  the 
  south, 
  

   noticed 
  that 
  the 
  discharge 
  first 
  assumed 
  the 
  form 
  of 
  a 
  ball 
  of 
  fire 
  

   with 
  a 
  soft, 
  delicate 
  outline, 
  then 
  became 
  spheroidal 
  with 
  the 
  

   greatest 
  diameter 
  horizontal, 
  and 
  finally 
  exploded, 
  throwing 
  out 
  

   tongues 
  of 
  fire 
  in 
  all 
  directions. 
  At 
  18 
  h 
  30 
  m 
  and 
  18 
  h 
  50 
  m 
  two 
  

   similar 
  electrical 
  discharges, 
  which 
  behaved 
  in 
  precisely 
  the 
  same 
  

   manner 
  as 
  the 
  first, 
  w 
  T 
  ere 
  seen 
  by 
  all 
  of 
  the 
  people 
  at 
  the 
  signal 
  

   station. 
  The 
  balls 
  of 
  fire 
  made 
  their 
  appearance 
  suddenly 
  in 
  the 
  

   fog 
  and 
  at 
  the 
  same 
  point 
  in 
  the 
  air. 
  They 
  seemed 
  to 
  be 
  very 
  

   close, 
  in 
  fact, 
  at 
  the 
  level 
  of 
  the 
  second 
  story 
  of 
  the 
  dwelling 
  

   house 
  near 
  the 
  ruins 
  of 
  the 
  temple 
  of 
  Mercury. 
  The 
  balls 
  

   appeared 
  to 
  remain 
  sensibly 
  stationary 
  for 
  two 
  or 
  three 
  seconds 
  

   before 
  bursting. 
  Their 
  color 
  was 
  primarily 
  white 
  with 
  a 
  slight 
  

  

  