﻿342 
  Scientific 
  Intelligence. 
  

  

  spirals 
  filled 
  with 
  mercury. 
  These 
  spirals 
  were 
  placed 
  in 
  a 
  

   Wheatstone's 
  bridge 
  in 
  order 
  to 
  control 
  the 
  ratio 
  of 
  the 
  resist- 
  

   ance 
  during 
  the 
  flowing 
  of 
  the 
  current 
  and 
  to 
  keep 
  it 
  constant.-^ 
  

   Wiener 
  Berichte, 
  April 
  9, 
  1891. 
  j. 
  t. 
  

  

  1. 
  Optical 
  relation 
  of 
  Organic 
  Dyes. 
  — 
  E. 
  Vogel 
  discusses 
  

   the 
  sensitizing 
  power 
  of 
  the 
  various 
  compounds 
  of 
  eosine 
  and 
  

   gives 
  charts 
  of 
  the 
  sensitizing 
  power. 
  He 
  recommends 
  for 
  ortho- 
  

   chromatic 
  photography 
  that 
  ordinary 
  dry 
  plates 
  containing 
  a 
  

   weak 
  amount 
  of 
  iodide 
  of 
  silver 
  should 
  be 
  bathed 
  in 
  the 
  follow- 
  

   ing 
  : 
  25 
  ccm 
  solution 
  of 
  the 
  coloring 
  matter, 
  erythrosine, 
  in 
  water, 
  

   (1:1000); 
  0-5 
  ccm 
  solution 
  nitrate 
  of 
  silver 
  (1:20 
  water): 
  2 
  ccra 
  

   ammonia, 
  spec. 
  grav. 
  0'94; 
  75 
  ccm 
  distilled 
  water. 
  The 
  author 
  

   finds 
  that 
  the 
  eosine 
  dyes 
  which 
  are 
  the 
  most 
  strongly 
  fluorescent 
  

   are 
  the 
  poorest 
  sensitizers. 
  Among 
  the 
  other 
  conclusions 
  of 
  the 
  

   writer 
  we 
  find 
  the 
  following 
  : 
  The 
  sensitizing 
  power 
  of 
  the 
  eosine 
  

   dyes 
  depends: 
  1. 
  On 
  the 
  sensitiveness 
  to 
  light 
  of 
  the 
  dye. 
  2. 
  On 
  

   the 
  proportion 
  of 
  light 
  rays 
  that 
  is 
  absorbed 
  in 
  other 
  than 
  chem- 
  

   ical 
  work. 
  The 
  more 
  energy 
  of 
  the 
  latter 
  that 
  is 
  consumed 
  in 
  

   other 
  than 
  chemical 
  work 
  the 
  smaller 
  the 
  chemical 
  action. 
  — 
  Ann. 
  

   der 
  PhysiJc 
  and 
  Chemie, 
  No. 
  vii, 
  1891, 
  pp. 
  449-472. 
  j. 
  t. 
  

  

  8. 
  Maxim's 
  Plying 
  Machine. 
  — 
  It 
  is 
  stated 
  that 
  Mr. 
  Maxim 
  is 
  

   now 
  constructing 
  a 
  flying 
  machine 
  at 
  Crayford, 
  which 
  is 
  nearly 
  

   ready 
  for 
  launching. 
  " 
  It 
  will 
  be 
  propelled 
  by 
  a 
  light 
  screw 
  

   making 
  2500 
  revolutions 
  per 
  minute. 
  The 
  motive 
  power 
  is 
  said 
  

   to 
  be 
  a 
  petroleum 
  condensing 
  engine 
  weighing 
  eighteen 
  hundred 
  

   pounds, 
  and 
  capable 
  of 
  raising 
  a 
  forty 
  thousand 
  pound 
  load. 
  

   The 
  real 
  suspending 
  power 
  will 
  lie 
  in 
  an 
  enormous 
  kite 
  measuring 
  

   110 
  feet 
  long 
  and 
  40 
  feet 
  wide."— 
  Nature, 
  July 
  30, 
  1891. 
  j. 
  t. 
  

  

  9. 
  Small 
  Electrometers. 
  — 
  At 
  a 
  meeting 
  of 
  the 
  Physical 
  Society 
  

   held 
  in 
  London, 
  June 
  26, 
  Professor 
  Boys 
  described 
  small 
  portable 
  

   electrometers 
  of 
  his 
  design. 
  In 
  one 
  of 
  these 
  the 
  needle 
  was 
  

   cross-shaped 
  and 
  made 
  of 
  zinc 
  and 
  platinum, 
  and 
  reliance 
  was 
  

   placed 
  upon 
  contact 
  electricity 
  to 
  keep 
  the 
  needle 
  at 
  different 
  

   potentials. 
  The 
  instrument 
  was 
  very 
  sensitive. 
  — 
  Nature, 
  July 
  

   16, 
  1891. 
  J. 
  t. 
  

  

  10. 
  Influence 
  of 
  brightness 
  upon 
  phenomena 
  of 
  interference 
  of 
  

   light. 
  — 
  According 
  to 
  Michelson 
  and 
  Morley 
  the 
  red 
  hydrogen 
  line 
  

   is 
  a 
  close 
  double. 
  They 
  found 
  that 
  if 
  the 
  light 
  of 
  this 
  line 
  was 
  

   employed 
  to 
  obtain 
  interference 
  bands, 
  that 
  these 
  bands 
  disap- 
  

   peared 
  with 
  a 
  difference 
  of 
  path 
  of 
  15,000 
  wave-lengths, 
  and 
  also 
  

   with 
  a 
  difference 
  of 
  path 
  of 
  45,000 
  wave-lengths, 
  and 
  from 
  a 
  

   similar 
  phenomena 
  produced 
  by 
  the 
  double 
  sodium 
  line 
  it 
  was 
  

   concluded 
  that 
  the 
  hydrogen 
  line 
  H 
  a 
  consisted 
  of 
  two 
  compo- 
  

   nents 
  at 
  a 
  distance 
  apart 
  of 
  -g 
  1 
  ^ 
  of 
  that 
  of 
  the 
  sodium 
  lines. 
  

   Ebert 
  concludes 
  from 
  his 
  investigation 
  of 
  this 
  subject 
  that 
  this 
  

   difference 
  in 
  the 
  position 
  of 
  minima 
  is 
  not 
  connected 
  with 
  du- 
  

   plicity 
  of 
  the 
  line 
  but 
  depends 
  upon 
  particular 
  conditions 
  of 
  the 
  

   source 
  of 
  light 
  ; 
  and 
  believes 
  that 
  peculiarities 
  in 
  the 
  appearances 
  

   of 
  the 
  hydrogen 
  line 
  in 
  stars 
  of 
  certain 
  types 
  depends 
  also 
  upon 
  

   character 
  of 
  emission 
  of 
  the 
  light. 
  The 
  method 
  of 
  high 
  interfer- 
  

  

  