﻿Chemistry 
  and 
  Physics. 
  247 
  

  

  albuminous 
  matter. 
  The 
  saving 
  in 
  yeast 
  is 
  evidently 
  due 
  to 
  the 
  

   increased 
  growth 
  under 
  the 
  influence 
  of 
  a 
  suitable 
  food. 
  — 
  Jour. 
  

   Ind. 
  and 
  En 
  g. 
  Chem., 
  ix, 
  148. 
  h. 
  l. 
  w. 
  

  

  4. 
  General 
  Chemistry 
  • 
  by 
  Hamilton 
  P. 
  Cady. 
  12mo, 
  pp. 
  

   522. 
  New 
  York, 
  1916 
  (McGraw-Hill 
  Book 
  Company, 
  Inc.).— 
  

   This 
  is 
  one 
  of 
  the 
  " 
  International 
  Chemical 
  Series." 
  It 
  is 
  b*ased 
  

   upon 
  the 
  author's 
  earlier 
  "Inorganic 
  Chemistry," 
  being 
  " 
  some- 
  

   thing 
  of 
  an 
  abridgement 
  and 
  much 
  of 
  a 
  simplification 
  " 
  of 
  the 
  

   latter. 
  It 
  gives 
  a 
  very 
  satisfactory 
  presentation 
  of 
  chemical 
  facts 
  

   with 
  a 
  suitable 
  amount 
  of 
  theory 
  introduced 
  in 
  such 
  a 
  manner 
  as 
  

   to 
  explain 
  the 
  facts 
  as 
  they 
  are 
  brought 
  forward. 
  Comparatively 
  

   little 
  attention 
  is 
  paid 
  to 
  the 
  details 
  of 
  chemical 
  experiments, 
  so 
  

   that 
  it 
  is 
  to 
  be 
  presumed 
  that 
  the 
  book 
  is 
  expected 
  to 
  be 
  used 
  in 
  

   connection 
  with 
  another 
  book, 
  a 
  guide 
  to 
  laboratory 
  work. 
  

  

  h. 
  l. 
  w. 
  

  

  5. 
  Generalized 
  Relativity 
  and 
  Gravitation 
  Theory. 
  — 
  In 
  a 
  

   number 
  of 
  papers 
  published 
  in 
  several 
  scientific 
  journals 
  during 
  

   the 
  past 
  few 
  years 
  Einstein 
  has 
  developed 
  a 
  generalization 
  of 
  the 
  

   original 
  principle 
  of 
  relativity 
  and 
  has 
  deduced 
  certain 
  results 
  

   which 
  seem 
  to 
  be 
  of 
  great 
  importance. 
  Since 
  the 
  mathematical 
  

   analysis 
  pertains 
  to 
  four-dimensional 
  "space" 
  and 
  is 
  extremely 
  

   complex 
  it 
  will 
  only 
  be 
  possible 
  to 
  give 
  in 
  this 
  place 
  a 
  slight 
  sug- 
  

   gestion 
  of 
  these 
  very 
  original 
  investigations. 
  

  

  The 
  fundamental 
  assumption 
  consists 
  in 
  the 
  " 
  hypothesis 
  of 
  

   equivalence." 
  Some 
  idea 
  of 
  this 
  conception 
  may 
  be 
  obtained 
  

   from 
  the 
  following 
  considerations. 
  Suppose 
  an 
  observer 
  at 
  rest 
  

   in 
  a 
  gravitational 
  field 
  notices 
  that 
  all 
  bodies 
  fall 
  with 
  the 
  same, 
  

   constant 
  acceleration. 
  According 
  to 
  the 
  non-generalized 
  theory 
  

   this 
  state 
  of 
  affairs 
  will 
  be 
  equivalent 
  to 
  the 
  case 
  where 
  there 
  is 
  

   no 
  gravitational 
  field 
  with 
  the 
  system 
  of 
  bodies 
  at 
  rest 
  but 
  with 
  

   the 
  observer 
  moving 
  in 
  such 
  a 
  manner 
  as 
  to 
  cause 
  the 
  bodies 
  to 
  

   appear 
  to 
  him 
  to 
  possess 
  the 
  same 
  acceleration 
  as 
  they 
  seemed 
  to 
  

   have 
  when 
  accelerated 
  in 
  the 
  gravitational 
  field. 
  Because 
  of 
  the 
  

   changes 
  in 
  the 
  units 
  of 
  time 
  and 
  length 
  in 
  the 
  two 
  cases, 
  the 
  

   acceleration 
  of 
  the 
  observer 
  relative 
  to 
  the 
  bodies 
  in 
  the 
  second 
  

   set 
  of 
  circumstances 
  will 
  not 
  necessarily 
  be 
  equal 
  numerically 
  to 
  

   the 
  acceleration 
  of 
  the 
  bodies 
  in 
  the 
  first 
  or 
  gravitational 
  field. 
  

   Einstein's 
  equivalence 
  hypothesis 
  consists 
  in 
  assuming 
  that 
  the 
  

   two 
  cases 
  are 
  not 
  only 
  equivalent 
  for 
  purely 
  mechanical 
  phe- 
  

   nomena 
  but 
  that 
  they 
  are 
  absolutely 
  equivalent 
  in 
  all 
  respects, 
  — 
  

   electrodynamically, 
  etc. 
  Another 
  noteworthy 
  feature 
  of 
  Ein- 
  

   stein's 
  theory 
  is 
  that 
  it 
  involves 
  only 
  the 
  Gaussian 
  constant 
  and 
  

   the 
  velocity 
  of 
  light 
  in 
  the 
  free 
  ether. 
  No 
  other 
  quantities 
  having 
  

   physical 
  dimensions 
  are 
  introduced. 
  

  

  Attention 
  may 
  now 
  be 
  directed 
  to 
  certain 
  practical 
  deductions 
  

   from 
  the 
  general 
  theory. 
  In 
  the 
  first 
  place, 
  it 
  can 
  be 
  shown 
  that 
  

   a 
  ray 
  of 
  light 
  will 
  be 
  deflected 
  by 
  a 
  large 
  mass 
  just 
  as 
  if 
  the 
  

   luminiferous 
  vibrations 
  were 
  endowed 
  with 
  ordinary 
  momentum. 
  

   Accordingly, 
  when 
  light 
  from 
  a 
  star 
  passes 
  close 
  to 
  the 
  sun 
  and 
  

   then 
  proceeds 
  in 
  such 
  a 
  manner 
  as 
  to 
  be 
  aimed 
  at 
  the 
  center 
  of 
  

  

  