﻿150 
  Scientific 
  Intelligence. 
  

  

  index 
  of 
  the 
  liquid, 
  JV, 
  in 
  terms 
  of 
  the 
  predetermined 
  index 
  

   of 
  the 
  calibrated 
  prism, 
  n, 
  and 
  of 
  sin 
  D. 
  By 
  substituting 
  in 
  

   the 
  power 
  series 
  the 
  value 
  of 
  D, 
  obtained 
  from 
  interpolation, 
  the 
  

   value 
  of 
  JV 
  common 
  to 
  the 
  liquid 
  and 
  the 
  lens 
  may 
  be 
  readily 
  

   computed. 
  

  

  The 
  rest 
  of 
  the 
  article 
  deals 
  with 
  the 
  determination 
  to 
  the 
  

   fifth 
  decimal 
  place 
  of 
  the 
  indices 
  of 
  refraction 
  of 
  specimens 
  of 
  

   prismatic 
  and 
  of 
  completely 
  irregular 
  shapes, 
  with 
  unpolished 
  

   surfaces, 
  etc. 
  "With 
  due 
  regard 
  to 
  the 
  fact 
  that, 
  in 
  general, 
  

   it 
  takes 
  time 
  to 
  attain 
  a 
  very 
  high 
  degree 
  of 
  precision, 
  the 
  new 
  

   adaptation 
  of 
  the 
  method 
  of 
  immersion 
  seems 
  to 
  be 
  the 
  most 
  

   promising 
  one 
  as 
  yet 
  proposed. 
  — 
  Jour, 
  de 
  Phys., 
  9, 
  11, 
  1919. 
  

  

  h. 
  s. 
  u. 
  

  

  6. 
  Problems 
  of 
  Cosmogony 
  and 
  Stellar 
  Dynamics; 
  by 
  J. 
  H. 
  

   Jeans. 
  Pp. 
  ix, 
  293 
  ; 
  with 
  45 
  figures 
  and 
  5 
  plates. 
  Cambridge, 
  

   1919 
  (University 
  Press). 
  — 
  The 
  subject 
  of 
  the 
  Adams 
  Prize 
  of 
  

   the 
  University 
  of 
  Cambridge, 
  for 
  the 
  year 
  1917, 
  was: 
  "The 
  

   course 
  of 
  evolution 
  of 
  the 
  configurations 
  possible 
  for 
  a 
  rotating 
  

   and 
  gravitating 
  fluid 
  mass, 
  including 
  the 
  discussion 
  of 
  the 
  stabil- 
  

   ities 
  of 
  the 
  various 
  forms." 
  This 
  prize 
  was 
  awarded 
  to 
  the 
  

   author 
  for 
  the 
  essay 
  which 
  he 
  wrote 
  and 
  subsequently 
  elaborated 
  

   in 
  the 
  form 
  of 
  the 
  present 
  volume. 
  

  

  "The 
  main 
  object 
  of 
  the 
  essay 
  is 
  to 
  build 
  a 
  framework 
  of 
  abso- 
  

   lute 
  mathematical 
  truth; 
  the 
  backbone 
  of 
  the 
  structure 
  is 
  the 
  

   theoretical 
  investigation 
  into 
  the 
  behaviour 
  of 
  rotating 
  masses." 
  

   Six 
  chapters 
  (II 
  to 
  VII) 
  are 
  devoted 
  to 
  abstract 
  theory. 
  The 
  

   analysis 
  therein 
  contained 
  centers 
  around 
  three 
  fundamental 
  

   problems, 
  namely, 
  the 
  tidal, 
  the 
  rotational, 
  and 
  the 
  double-star 
  

   problem. 
  It 
  is 
  shown 
  that 
  in 
  all 
  three 
  problems 
  there 
  are 
  no 
  

   figures 
  of 
  stable 
  equilibrium 
  except 
  ellipsoids 
  and 
  spheroids. 
  In 
  

   the 
  course 
  of 
  the 
  analysis 
  the 
  author 
  has 
  made 
  several 
  important 
  

   contributions 
  to 
  the 
  subject. 
  Two 
  examples 
  may 
  be 
  cited 
  to 
  

   illustrate 
  this 
  statement. 
  In 
  the 
  chapter 
  on 
  the 
  gravitational 
  

   potential 
  of 
  a 
  distorted 
  ellipsoid 
  it 
  is 
  pointed 
  out 
  that 
  Poincare 
  's 
  

   method 
  of 
  development 
  as 
  far 
  as 
  terms 
  of 
  the 
  second 
  order 
  does 
  

   not 
  lend 
  itself 
  readily, 
  if 
  at 
  all, 
  to 
  extension 
  to 
  the 
  third 
  order, 
  

   consequently 
  Jeans 
  has 
  developed 
  a 
  plan 
  of 
  attack 
  that 
  enables 
  

   him 
  to 
  carry 
  the 
  analysis 
  to 
  the 
  required 
  degree 
  of 
  accuracy, 
  

   that 
  is, 
  through 
  terms 
  of 
  the 
  third 
  order. 
  Again, 
  in 
  the 
  discus- 
  

   sion 
  of 
  the 
  stability 
  of 
  pear-shaped 
  figures, 
  an 
  explanation 
  is 
  

   found 
  for 
  the 
  conflicting 
  results 
  obtained 
  by 
  Sir 
  G. 
  Darwin 
  and 
  

   by 
  Liapounoff. 
  The 
  slip 
  was 
  made 
  by 
  the 
  investigator 
  first 
  

   named 
  who 
  announced 
  the 
  configurations 
  to 
  be 
  stable, 
  whereas 
  

   instability 
  has 
  been 
  claimed 
  by 
  the 
  second 
  analyst 
  and 
  rigorously 
  

   demonstrated 
  by 
  Jeans. 
  Of 
  the 
  six 
  chapters 
  referred 
  to 
  above, 
  

   the 
  first 
  five 
  pertain 
  to 
  the 
  behavior 
  of 
  perfectly 
  homogeneous 
  

   and 
  incompressible 
  matter, 
  while 
  the 
  sixth 
  is 
  devoted 
  to 
  the 
  gen- 
  

   eral 
  theory 
  of 
  the 
  motion 
  of 
  compressible 
  and 
  non-homogeneous 
  

  

  