﻿214 
  Scientific 
  Intelligence. 
  

  

  pitchblende 
  showed 
  that 
  in 
  the 
  latter 
  case 
  the 
  line 
  was 
  less 
  

   refrangible 
  by 
  0-005 
  A., 
  while 
  the 
  line 
  given 
  by 
  lead 
  from 
  

   Ceylon 
  thorite 
  was 
  more 
  refrangible 
  by 
  0-0022A. 
  Thallium, 
  

   which 
  occurs 
  in 
  pitchblende 
  in 
  very 
  small 
  quantity, 
  was 
  found 
  

   to 
  give 
  a 
  line 
  more 
  refrangible 
  than 
  ordinary 
  thallium 
  by 
  

   0-005 
  5 
  A. 
  These 
  facts 
  are 
  interesting 
  in 
  giving, 
  in 
  the 
  case 
  of 
  

   lead, 
  another 
  physical 
  property, 
  besides 
  atomic 
  weight 
  and 
  spe- 
  

   cific 
  gravity, 
  in 
  which 
  the 
  metal 
  produced 
  by 
  radioactive 
  trans- 
  

   formations 
  differs 
  from 
  the 
  ordinary 
  metal. 
  — 
  Chem. 
  News, 
  119,. 
  

   281. 
  h. 
  l. 
  w. 
  

  

  5. 
  The 
  Petroleum 
  Handbook; 
  by 
  Stephen 
  O. 
  Andros, 
  

   16mo, 
  pp. 
  206. 
  Chicago, 
  1919 
  (The 
  Shaw 
  Publishing 
  Company. 
  

   Price 
  $2.00). 
  — 
  This 
  book 
  is 
  chiefly 
  a 
  compilation 
  made 
  from 
  

   many 
  sources 
  with 
  excellent 
  judgment 
  and 
  covering 
  all 
  phases 
  

   of 
  the 
  petroleum 
  industry 
  from 
  the 
  location 
  of 
  oil 
  wells 
  to 
  the 
  

   delivery 
  of 
  the 
  refined 
  products 
  to 
  consumers. 
  It 
  deals 
  with 
  the 
  

   origin 
  and 
  occurrence 
  of 
  the 
  substance, 
  exploration 
  and 
  drilling, 
  

   refining, 
  natural 
  gas, 
  the 
  shale-oil 
  industry, 
  the 
  marketing 
  of 
  the 
  

   products, 
  and 
  with 
  special 
  topics 
  in 
  connection 
  with 
  gasoline. 
  

   The 
  book 
  is 
  well 
  illustrated 
  by 
  figures, 
  and 
  it 
  contains 
  many 
  

   interesting 
  tables 
  of 
  statistics. 
  It 
  is 
  a 
  very 
  useful 
  book 
  for 
  

   those 
  who 
  desire 
  to 
  obtain 
  a 
  knowledge 
  of 
  the 
  scientific 
  and 
  

   technical 
  aspects 
  of 
  this 
  great 
  industry. 
  h. 
  l. 
  w. 
  

  

  6. 
  Secret 
  Signalling 
  by 
  Light 
  Rays. 
  — 
  Of 
  the 
  numerous 
  

   ingenious 
  applications 
  of 
  scientific 
  knowledge 
  to 
  the 
  solution 
  of 
  

   problems 
  which 
  were 
  emphasized 
  by 
  the 
  world 
  war, 
  one 
  at 
  least 
  

   is 
  of 
  sufficient 
  general 
  interest 
  to 
  merit 
  attention 
  in 
  this 
  place. 
  

   More 
  specifically, 
  reference 
  is 
  here 
  made 
  to 
  the 
  investigations 
  

   of 
  R. 
  W. 
  Wood 
  on 
  the 
  sending 
  and 
  receiving 
  of 
  signals 
  by 
  means 
  

   of 
  light 
  waves, 
  both 
  within 
  and 
  beyond 
  the 
  confines 
  of 
  the 
  visible 
  

   spectrum. 
  Ordinary 
  parabolic 
  mirrors 
  are 
  not 
  suitable 
  for 
  

   sending 
  signals 
  over 
  long 
  distances, 
  from 
  the 
  rear 
  to 
  the 
  front, 
  

   because 
  the 
  field 
  covered 
  by 
  the 
  cross-section 
  of 
  the 
  inaccurate 
  

   beam 
  is 
  so 
  large 
  as 
  to 
  incur 
  the 
  risk 
  of 
  including 
  a 
  portion 
  of 
  the 
  

   enemy's 
  trenches 
  simultaneously 
  'with 
  the 
  proper 
  receiving 
  sta- 
  

   tion. 
  This 
  prohibitive 
  characteristic 
  is 
  entirely 
  avoided 
  in 
  

   "Wood's 
  "flash 
  telescope." 
  

  

  This 
  apparatus 
  consisted 
  primarily 
  of 
  a 
  telescope 
  having 
  a 
  

   tungsten 
  lamp 
  at 
  the 
  common 
  focus 
  of 
  the 
  objective 
  and 
  ocular. 
  

   The 
  objective 
  was 
  a 
  non-cemented 
  doublet, 
  of 
  three 
  inch 
  linear 
  

   aperture, 
  corrected 
  to 
  have 
  the 
  same 
  focal 
  length 
  for 
  the 
  near 
  

   infra-red 
  and 
  for 
  a 
  certain 
  wave-length 
  in 
  the 
  ultra-violet. 
  The 
  

   tungsten 
  lamp 
  was 
  of 
  the 
  nitrogen 
  filled 
  type 
  containing 
  a 
  very 
  

   short 
  spiral 
  filament. 
  With 
  the 
  low 
  power 
  ocular 
  employed, 
  the 
  

   total 
  magnification 
  produced 
  by 
  the 
  telescope 
  was 
  about 
  four- 
  

   teen 
  fold. 
  The 
  focusing 
  was 
  effected 
  by 
  moving 
  the 
  objective 
  

   along 
  its 
  optic 
  axis, 
  the 
  position 
  of 
  the 
  lamp 
  being 
  invariable 
  

   relatively 
  to 
  the 
  telescope 
  tube, 
  etc. 
  The 
  filter 
  wheel 
  was 
  placed 
  

  

  