﻿Chemistry 
  and 
  Physics. 
  511 
  

  

  5. 
  Chapters 
  on 
  Electricity 
  : 
  An 
  introductory 
  text-book 
  for 
  

   students 
  in 
  College; 
  by 
  Samuel 
  Sheldon, 
  pp. 
  351-452. 
  New 
  

   York, 
  1891. 
  (Charles 
  Collins 
  and 
  the 
  Baker 
  & 
  Taylor 
  Co.).— 
  

   These 
  chapters 
  on 
  Electricity 
  are 
  reprinted 
  from 
  the 
  new 
  (fourth) 
  

   revised 
  edition 
  of 
  Olmsted's 
  Natural 
  Philosophy. 
  They 
  give 
  a 
  

   concise 
  and 
  systematic 
  statement 
  of 
  the 
  most 
  essential 
  principles 
  

   and 
  phenomena 
  in 
  the 
  subjects 
  of 
  Electricity 
  and 
  Magnetism 
  as 
  

   now 
  understood. 
  The 
  treatment 
  is 
  of 
  necessity 
  very 
  brief 
  but 
  if 
  

   supplemented 
  by 
  the 
  illustrations 
  and 
  explanations 
  of 
  the 
  class- 
  

   room, 
  the 
  book 
  should 
  give 
  the 
  average 
  student 
  a 
  satisfactory 
  

   elementary 
  knowledge 
  of 
  his 
  subject. 
  

  

  6. 
  Apparent 
  change 
  in 
  electrochemical 
  equivalent 
  of 
  copper. 
  — 
  

   Certain 
  observers 
  have 
  maintained 
  that 
  the 
  electrochemical 
  

   equivalent 
  of 
  copper 
  changes 
  with 
  the 
  density 
  of 
  the 
  current 
  

   per 
  square 
  millimeter 
  of 
  the 
  surface 
  of 
  the 
  electrodes. 
  • 
  J. 
  Vanni 
  

   shows 
  that 
  the 
  conditions 
  of 
  acidity 
  of 
  the 
  bath 
  produce 
  the 
  dis- 
  

   cordant 
  results 
  obtained 
  by 
  previous 
  observers. 
  When 
  sulphuric 
  

   acid 
  is 
  present 
  in 
  excess, 
  the 
  electrodes 
  are 
  attacked. 
  By 
  making 
  

   a 
  normal 
  solution 
  with 
  a 
  definite 
  proportion 
  of 
  free 
  sulphuric 
  

   acid, 
  concordant 
  results 
  can 
  be 
  obtained 
  with 
  a 
  copper 
  voltameter. 
  

   The 
  author 
  gives 
  results 
  of 
  his 
  experiments 
  and 
  shows 
  that 
  the 
  

   deposition 
  of 
  copper 
  can 
  be 
  employed 
  with 
  great 
  exactness 
  to 
  

   measure 
  electrical 
  currents 
  if 
  the 
  proper 
  care 
  is 
  taken 
  in 
  forming 
  

   a 
  normal 
  solution- 
  without 
  too 
  much 
  acidity. 
  — 
  Ann. 
  der 
  PhysiJc 
  

   und 
  Chemie, 
  No. 
  10, 
  1891, 
  p. 
  214, 
  221. 
  J. 
  t. 
  

  

  7. 
  Electrolytic 
  generation 
  of 
  Gas 
  in 
  a 
  closed 
  space. 
  — 
  M. 
  

   Chabry 
  of 
  the 
  Societe 
  de 
  Biologie 
  has 
  succeeded 
  in 
  obtaining 
  by 
  

   this 
  means 
  a 
  pressure 
  of 
  1200 
  atmospheres. 
  The 
  electrolyzed 
  

   liquid 
  was 
  a 
  25 
  per 
  cent 
  soda 
  solution. 
  The 
  current 
  had 
  a 
  

   strength 
  of 
  1-^ 
  amperes 
  and 
  was 
  very 
  constant 
  during 
  the 
  experi- 
  

   ment. 
  — 
  Nature, 
  Oct. 
  15, 
  1891. 
  j. 
  t. 
  

  

  8. 
  Upon 
  the 
  damping 
  of 
  electrical 
  oscillations. 
  — 
  An 
  important 
  

   paper 
  on 
  this 
  subject 
  has 
  been 
  written 
  by 
  V. 
  Bjerknes. 
  The 
  

   author 
  discusses 
  the 
  mathematical 
  theory 
  and 
  shows 
  that 
  the 
  

   multiple 
  resonance 
  discovered 
  by 
  Sarasin 
  and 
  de 
  la 
  Rive 
  can 
  be 
  

   explained 
  by 
  the 
  phenomena 
  of 
  damping. 
  Their 
  results 
  are 
  

   therefore 
  in 
  accord 
  with 
  the 
  experiments 
  of 
  Hertz. 
  r 
  The 
  author 
  

   expresses 
  his 
  obligations 
  to 
  the 
  work 
  of 
  Poincare 
  (Electricite 
  et 
  

   Optique, 
  II, 
  Paris, 
  1891). 
  — 
  Ann. 
  der 
  Physik 
  und 
  Chemie, 
  No. 
  9, 
  

   1891, 
  pp. 
  74-101. 
  j. 
  t. 
  

  

  9. 
  Velocity 
  of 
  Electrical 
  loaves 
  in 
  solid 
  insulators. 
  — 
  Avons 
  

   and 
  Rubens 
  in 
  a 
  previous 
  article 
  (Wied. 
  Ann., 
  vol. 
  xlii, 
  p. 
  582, 
  

   1891), 
  described 
  a 
  method 
  of 
  measuring 
  electrical 
  waves 
  in 
  die- 
  

   lectrics, 
  which 
  was 
  an 
  extension 
  of 
  Hertz's 
  method. 
  Its 
  pecu- 
  

   liarity 
  consisted 
  in 
  the 
  employment 
  of 
  a 
  bolometer 
  instead 
  of 
  an 
  

   electric 
  spark 
  for 
  the 
  observation 
  of 
  maxima 
  and 
  minima 
  of 
  

   oscillations. 
  They 
  have 
  extended 
  their 
  work 
  to 
  an 
  investigation 
  

   of 
  Maxwell's 
  law 
  connecting 
  the 
  dielectric 
  constant 
  with 
  the 
  

   index 
  of 
  refraction 
  of 
  the 
  dielectric, 
  and 
  find 
  a 
  very 
  satisfactory 
  

   agreement 
  between 
  his 
  theory 
  and 
  their 
  experiments. 
  Maxwell's 
  

  

  