﻿168 
  Scientific 
  Intelligence. 
  

  

  tions 
  in 
  question. 
  The 
  vacuum 
  spectrometers 
  perfected 
  by 
  Sieg- 
  

   babn 
  and 
  others 
  are 
  illustrated 
  and 
  explained 
  in 
  detail. 
  This 
  is 
  

   followed 
  by 
  a 
  discussion 
  of 
  the 
  relations 
  between 
  the 
  speeds 
  of 
  

   the 
  exciting 
  cathode 
  rays 
  and 
  the 
  excited 
  characteristic 
  .X-rays. 
  

   The 
  rest 
  of 
  the 
  article 
  is 
  devoted 
  mainly 
  to 
  the 
  relatively 
  accu- 
  

   rate 
  wave-lengths 
  determined 
  experimentally 
  by 
  Siegbahn 
  and 
  

   his 
  co-workers, 
  full 
  credit 
  being 
  also 
  given 
  to 
  the 
  more 
  explora- 
  

   tory 
  and 
  less 
  accurate 
  work 
  of 
  their 
  predecessors. 
  

  

  In 
  the 
  case 
  of 
  the 
  JT-group 
  the 
  wave-lengths 
  cover 
  the 
  interval 
  

   from 
  A0*292, 
  for 
  neodymium, 
  to 
  A 
  1P951 
  for 
  sodium. 
  Eight 
  

   series 
  of 
  lines 
  have 
  been 
  traced 
  for 
  the 
  .ZT-group. 
  The 
  wave- 
  

   lengths 
  belonging 
  to 
  the 
  X-group 
  fall 
  into 
  14 
  series 
  extending 
  

   from 
  A 
  0'596 
  for 
  uranium 
  to 
  A 
  12*346 
  for 
  zinc. 
  For 
  the 
  elements 
  

   of 
  high 
  atomic 
  numbers, 
  — 
  gold 
  to 
  uranium, 
  — 
  the 
  author 
  has 
  dis- 
  

   covered 
  a 
  third 
  group 
  of 
  lines 
  which 
  he 
  calls 
  the 
  37-series. 
  The 
  

   paper 
  closes 
  with 
  a 
  very 
  useful 
  table 
  containing 
  all 
  the 
  accurately 
  

   known 
  wave-lengths, 
  the 
  number 
  of 
  which 
  is 
  1729.— 
  Jahrbuch 
  d. 
  

   RadioaJctivitat 
  it. 
  Elektronik, 
  vol. 
  xiii, 
  pp. 
  296-341, 
  Sept., 
  1916. 
  

  

  h. 
  s. 
  TJ. 
  

  

  6. 
  General 
  Physics 
  ; 
  by 
  William 
  S. 
  Franklin 
  and 
  Barry 
  

   MacNutt. 
  Pp. 
  viii, 
  604 
  ; 
  479 
  figures. 
  New 
  York, 
  1916 
  

   (McGraw-Hill 
  Book 
  Co.). 
  — 
  This 
  book 
  has 
  the 
  sub-title 
  " 
  An 
  

   Elementary 
  Treatise 
  on 
  Natural 
  Philosophy" 
  and 
  it 
  is 
  designed 
  

   as 
  a 
  text-book 
  for 
  colleges 
  and 
  technical 
  schools. 
  The 
  field 
  cov- 
  

   ered 
  is 
  divided 
  into 
  five 
  parts: 
  I 
  Mechanics 
  (pages 
  5-104), 
  II 
  

   Theory 
  of 
  Heat 
  (107-177), 
  III 
  Electricity 
  and 
  Magnetism 
  (181- 
  

   343), 
  IV 
  Theory 
  of 
  Light 
  (347-484), 
  and 
  V 
  Theory 
  of 
  Sound 
  

   (487-528). 
  Each 
  part 
  is 
  preceded 
  by 
  a 
  list 
  of 
  titles 
  of 
  selected 
  

   reference-books 
  together 
  with 
  comments 
  on 
  their 
  nature 
  and 
  

   scope. 
  But 
  little 
  space 
  is 
  devoted 
  to 
  statics 
  and 
  elasticity 
  since 
  

   these 
  subjects 
  have 
  been 
  presented 
  at 
  some 
  length 
  in 
  two 
  earlier 
  

   volumes 
  by 
  the 
  same 
  authors. 
  A 
  list 
  of 
  409 
  problems, 
  for 
  solu- 
  

   tion 
  by 
  the 
  student, 
  constitutes 
  Appendix 
  A. 
  

  

  The 
  spirit 
  and 
  method 
  of 
  the 
  calculus 
  pervade 
  the 
  entire 
  text. 
  

   In 
  this 
  connection 
  the 
  authors 
  say: 
  " 
  The 
  method 
  of 
  differential 
  

   calculus 
  is 
  used 
  quite 
  freely 
  in 
  this 
  elementary 
  treatise 
  on 
  physics, 
  

   but 
  the 
  authors 
  believe 
  that 
  the 
  use 
  of 
  this 
  text 
  does 
  not 
  depend 
  

   upon 
  the 
  previous 
  study 
  of 
  calculus 
  by 
  the 
  student. 
  Indeed 
  the 
  

   authors 
  are 
  convinced 
  that 
  the 
  use 
  of 
  this 
  book 
  or 
  its 
  equivalent 
  

   is 
  a 
  necessary 
  preparation 
  for 
  the 
  study 
  of 
  calculus; 
  and 
  the 
  

   authors 
  suggest 
  that 
  the 
  student 
  be 
  required 
  to 
  turn 
  again 
  and 
  

   again 
  to 
  the 
  brief 
  discussion 
  of 
  the 
  methods 
  of 
  differential 
  and 
  

   integral 
  calculus 
  in 
  Appendix 
  B 
  ". 
  As 
  a 
  matter 
  of 
  fact, 
  formal 
  

   proofs 
  depending 
  upon 
  theorems 
  of 
  the 
  calculus 
  are 
  presented 
  in 
  

   small 
  type 
  and 
  in 
  such 
  places 
  as 
  not 
  to 
  interfere, 
  in 
  the 
  least, 
  with 
  

   the 
  continuity 
  of 
  the 
  main 
  body 
  of 
  the 
  text. 
  

  

  The 
  authors' 
  style 
  is 
  lucid 
  and 
  straightforward. 
  Clearness 
  of 
  

   conception 
  is 
  facilitated 
  in 
  other 
  branches 
  of 
  the 
  subject 
  by 
  

   numerous 
  mechanical 
  analogies, 
  presented 
  both 
  graphically 
  and 
  

   by 
  the 
  use 
  of 
  corresponding 
  sentences 
  in 
  parallel 
  columns. 
  The 
  

   definitions 
  of 
  units 
  and 
  the 
  statements 
  of 
  fundamental 
  laws 
  are 
  

  

  