﻿294 
  Scientific 
  Intelligence. 
  

  

  English 
  Dr. 
  Meyer's 
  excellent 
  " 
  Anleitung 
  zur 
  quantitativen 
  Be 
  

   stimrnung 
  der 
  organischen 
  Atomgruppen." 
  The 
  quantitative 
  side 
  

   of 
  organic 
  chemistry, 
  too 
  often 
  neglected 
  in 
  the 
  laboratory, 
  must 
  

   receive 
  a 
  new 
  impulse 
  from 
  this 
  little 
  book, 
  and 
  so 
  must 
  help 
  

   forward 
  investigation. 
  g. 
  f. 
  b. 
  

  

  5. 
  The 
  reflective 
  power 
  of 
  metals 
  and 
  metallic 
  deposits 
  on 
  glass 
  

   surfaces. 
  — 
  E. 
  Hagen 
  and 
  H. 
  Rubens 
  have 
  investigated 
  this 
  sub- 
  

   ject 
  for 
  wave 
  lengths 
  from 
  450 
  /x 
  to 
  700 
  li/x. 
  The 
  interesting 
  con- 
  

   clusion 
  is 
  drawn, 
  from 
  the 
  long 
  list 
  of 
  substances 
  examined, 
  that 
  

   the 
  reflective 
  power 
  of 
  pure 
  metals, 
  in 
  general, 
  increases 
  with 
  

   increasing 
  wave-length. 
  This 
  fact 
  appears 
  very 
  strongly 
  in 
  the 
  

   case 
  of 
  gold 
  and 
  copper. 
  Both 
  metals 
  show 
  a 
  very 
  small 
  reflec- 
  

   tive 
  power 
  for 
  violet 
  and 
  blue 
  light; 
  while 
  for 
  the 
  red 
  rays 
  of 
  

   wave-length 
  700 
  ll^x 
  the 
  reflective 
  power 
  of 
  gold 
  is 
  as 
  great 
  as 
  

   that 
  of 
  silver. 
  The 
  behavior 
  of 
  the 
  various 
  kinds 
  of 
  speculum 
  

   metal 
  was 
  also 
  considered. 
  The 
  mirrors 
  employed 
  by 
  Rosse, 
  

   Brashear 
  and 
  Schroder, 
  which 
  consist 
  essentially 
  of 
  a 
  mixture 
  of 
  

   copper 
  and 
  tin, 
  possess 
  essentially 
  the 
  same 
  reflecting 
  power, 
  vary- 
  

   ing 
  from 
  62 
  per 
  cent 
  at 
  450 
  /x 
  to 
  68 
  per 
  cent 
  at 
  700 
  ^. 
  The 
  

   admixture 
  of 
  a 
  small 
  portion 
  of 
  nickel 
  (in 
  the 
  case 
  of 
  the 
  specu- 
  

   lum 
  metal 
  of 
  Brandes 
  and 
  Schtinemann) 
  lowers 
  somewhat 
  the 
  

   reflecting 
  power. 
  The 
  metal 
  of 
  Ludwig 
  Mach, 
  consisting 
  of 
  

   aluminum 
  and 
  magnesium 
  in 
  varying 
  proportions, 
  has 
  a 
  reflecting 
  

   power 
  between 
  the 
  same 
  limits 
  of 
  wave-lengths 
  of 
  about 
  83 
  per 
  

   cent 
  to 
  83-4 
  per 
  cent. 
  Its 
  reflecting 
  power, 
  therefore, 
  appears 
  to 
  

   be 
  independent 
  of 
  length 
  of 
  waves. 
  — 
  Ann. 
  der 
  Physik, 
  No. 
  2, 
  

   1900, 
  pp. 
  352-375. 
  J. 
  T. 
  

  

  6. 
  A 
  Vacuum 
  Electroscope. 
  — 
  It 
  has 
  generally 
  been 
  assumed 
  

   that 
  a 
  vacuum 
  does 
  not 
  conduct 
  electricity, 
  and 
  that 
  electrostatic 
  

   induction 
  takes 
  place 
  in 
  a 
  highly 
  rarified 
  medium. 
  H. 
  Pflaum 
  

   seeks 
  to 
  show 
  the 
  truth 
  of 
  this 
  assumption 
  by 
  direct 
  experiment. 
  

   With 
  a 
  highly 
  exhausted 
  vessel 
  he 
  shows 
  that 
  electrostatic 
  effects 
  

   occur 
  to 
  a 
  high 
  degree, 
  and 
  that 
  no 
  luminosity 
  could 
  be 
  detected 
  

   under 
  powerful 
  inductive 
  action. 
  The 
  vacuum 
  therefore 
  appeared 
  

   to 
  act 
  like 
  a 
  perfect 
  insulator. 
  — 
  Ann. 
  der 
  Physik, 
  No. 
  2, 
  1900, 
  pp. 
  

   290-293. 
  J. 
  t. 
  

  

  7. 
  Rapid 
  spark 
  discharges. 
  — 
  An 
  investigation 
  in 
  this 
  subject 
  

   by 
  H. 
  T. 
  Simon 
  is 
  of 
  interest 
  in 
  view 
  of 
  photographs 
  of 
  lightning 
  

   which 
  show 
  successive 
  discharges 
  passing 
  over 
  parallel 
  paths. 
  

   The 
  experiments 
  were 
  made 
  with 
  the 
  Wehvelt 
  interrupter. 
  It 
  

   was 
  found 
  that 
  a 
  spark 
  follows 
  the 
  same 
  path 
  as 
  a 
  preceding 
  one 
  

   if 
  the 
  interval 
  between 
  the 
  two 
  does 
  not 
  exceed 
  0*0028 
  second. 
  

   If 
  this 
  interval 
  is 
  larger 
  the 
  spark 
  follows 
  a 
  new 
  zigzag 
  path. 
  

   This 
  time-interval 
  appears 
  to 
  be 
  independent 
  of 
  the 
  length 
  of 
  the 
  

   spark 
  gap 
  and 
  of 
  the 
  material 
  of 
  the 
  terminals. 
  — 
  Gesellsch. 
  Wiss. 
  

   Gottingen, 
  1899, 
  pp. 
  183-186. 
  J. 
  t. 
  

  

  8. 
  The 
  discharge 
  of 
  Electricity 
  through 
  Argon 
  and 
  Helium. 
  — 
  

   R. 
  J. 
  Strutt, 
  of 
  Trinity 
  College, 
  Cambridge, 
  has 
  made 
  some 
  

   interesting 
  experiments 
  on 
  this 
  subject 
  and 
  reaches 
  the 
  following 
  

   conclusions 
  : 
  

  

  