﻿Intelligence 
  and 
  Miscellaneous 
  Articles, 
  359 
  

  

  Chapter 
  III. 
  deals 
  with 
  the 
  measurement 
  of 
  current. 
  The 
  

   author 
  passes 
  in 
  review 
  the 
  electrolytic 
  and 
  absolute 
  methods 
  of 
  

   measurement, 
  giving 
  full 
  directions 
  and 
  useful 
  hints 
  in 
  connexion 
  

   with 
  each 
  method. 
  On 
  p. 
  342 
  there 
  is 
  an 
  obvious 
  erratum, 
  the 
  

   electrochemical 
  equivalent 
  of 
  silver 
  being 
  given 
  once 
  as 
  0-001132, 
  

   and 
  again 
  as 
  0-001193, 
  instead 
  of 
  -0011182 
  and 
  -0011193 
  

   respectively. 
  This 
  chapter 
  also 
  contains 
  an 
  account 
  of 
  wave-form 
  

   measurements, 
  frequency- 
  and 
  phase-meters. 
  

  

  Electromotive-force 
  measurements 
  form 
  the 
  subject 
  of 
  Chapter 
  IV. 
  

   The 
  use 
  of 
  a 
  Kelvin 
  balance 
  in 
  this 
  connexion 
  is 
  carefully 
  ex- 
  

   plained, 
  and 
  is 
  followed 
  by 
  an 
  account 
  of 
  potentiometer 
  methods, 
  

   several 
  forms 
  of 
  this 
  instrument 
  being 
  described 
  in 
  detail. 
  The 
  

   calibration 
  of 
  a 
  high-tension 
  voltmeter 
  is 
  next 
  dealt 
  with, 
  and 
  

   descriptions 
  are 
  given 
  of 
  some 
  standard 
  forms 
  of 
  laboratory 
  and 
  

   switchboard 
  voltmeters. 
  

  

  The 
  concluding 
  Chapter 
  V. 
  deals 
  with 
  the 
  important 
  subject 
  of 
  

   power 
  measurement. 
  We 
  are 
  probably 
  not 
  far 
  wrong 
  in 
  asserting 
  

   that 
  the 
  wattmeter 
  is 
  an 
  instrument 
  of 
  which 
  more 
  utterly 
  useless 
  

   specimens 
  have 
  been 
  offered 
  to 
  a 
  confiding 
  electrical 
  public 
  than 
  

   of 
  any 
  other 
  instrument. 
  The 
  author 
  gives 
  a 
  thorough 
  discussion 
  

   of 
  the 
  precautious 
  which 
  must 
  be 
  observed 
  in 
  constructing 
  and 
  

   using 
  this 
  important 
  instrument. 
  

  

  The 
  value 
  of 
  the 
  work 
  under 
  review 
  is 
  largely 
  increased 
  by 
  the 
  

   numerous 
  references 
  to 
  original 
  sources 
  of 
  information. 
  We 
  hope 
  

   that 
  the 
  author 
  will 
  soon 
  be 
  able 
  to 
  bring 
  out 
  Vol. 
  II., 
  and 
  thus 
  

   complete 
  a 
  work 
  which 
  will 
  earn 
  him 
  the 
  gratitude 
  of 
  all 
  interested 
  

   in 
  electrical 
  engineering 
  measurements. 
  

  

  Annuaire 
  du 
  Bureau 
  els 
  Longitudes. 
  Avec 
  des 
  Notices 
  Scienti- 
  

   tiques. 
  Paris: 
  Gauthier-Villars, 
  1902, 
  Pp. 
  iv 
  + 
  850. 
  Prix 
  

   1 
  fr. 
  50 
  c. 
  

  

  This 
  well-known 
  and 
  handy 
  little 
  annual 
  contains, 
  as 
  umal, 
  a 
  

   mass 
  of 
  useful 
  information 
  for 
  the 
  physicist, 
  chemist, 
  astronomer, 
  

   and 
  engineer. 
  Among 
  the 
  articles 
  specially 
  contributed 
  for 
  this 
  

   year 
  must 
  be 
  mentioned 
  the 
  following 
  : 
  — 
  Polyphase 
  Currents, 
  by 
  

   M. 
  A. 
  Cornu 
  ; 
  Wireless 
  Telegraphy, 
  by 
  M. 
  H. 
  Poineare 
  ; 
  and 
  

   The 
  Decimal 
  Division 
  of 
  the 
  Circumference, 
  by 
  M 
  . 
  GriiyOu. 
  

  

  XXXIX.- 
  Intelligence 
  and 
  Miscellaneous 
  Articles. 
  

  

  ON 
  THE 
  FLUORESCENCE 
  AND 
  ABSORPTION- 
  SPECTRUM 
  OF 
  SODIUM 
  

   VAPOUR. 
  BY 
  R. 
  W. 
  WOOD, 
  PROFESSOR 
  OF 
  EXPERIMENTAL 
  

   PHYSICS, 
  JOHNS 
  HOPKINS 
  UNIVERSITY. 
  

  

  1 
  N 
  my 
  paper 
  on 
  the 
  anomalous 
  dispersion 
  of 
  sodium 
  vapour, 
  

   -"■■ 
  which 
  was 
  communicated 
  to 
  the 
  lioyal 
  Societv 
  ia^t 
  June, 
  and 
  

   which 
  appeared 
  in 
  the 
  January 
  number 
  of 
  the 
  Philosophical 
  

   Magazine 
  as 
  well 
  as 
  in 
  the 
  Society's 
  Proceedings, 
  I 
  mentioned 
  having 
  

   observed 
  an 
  emission 
  of 
  light 
  by 
  sodium 
  vapour 
  illuminated 
  by 
  a 
  

  

  