﻿70 
  Scientific 
  Intelligence. 
  

  

  necessarily 
  the 
  cheapest 
  source 
  of 
  light. 
  In 
  order 
  to 
  estimate 
  the 
  

   cheapness 
  of 
  a 
  light 
  account 
  must 
  be 
  taken 
  of 
  the 
  entire 
  trans- 
  

   formation 
  of 
  the 
  energy 
  of 
  the 
  light 
  in 
  the 
  process 
  of 
  vision." 
  — 
  

   Beiblatter 
  zu 
  den 
  Aunalen 
  der 
  Physik, 
  No. 
  4, 
  189 
  1 
  , 
  p. 
  281. 
  j. 
  t. 
  

  

  9. 
  Reflection 
  and 
  Refraction 
  of 
  light 
  by 
  thin 
  surface 
  layers. 
  — 
  

   P. 
  Dkude 
  examines 
  mathematically 
  the 
  conditions 
  which 
  must 
  

   hold 
  for 
  the 
  reflection 
  and 
  refraction 
  of 
  light 
  by 
  thin 
  layers 
  of 
  

   metals 
  such 
  as 
  Professor 
  Kundt 
  has 
  experimented 
  with 
  in 
  obtain- 
  

   ing 
  indices 
  of 
  refraction 
  of 
  metals. 
  The 
  paper 
  is 
  long 
  and 
  ex- 
  

   haustive 
  ; 
  but 
  is 
  not 
  supported 
  by 
  experimental 
  results. 
  The 
  

   author 
  hopes 
  to 
  obtain 
  suitable 
  surfaces 
  to 
  verify 
  his 
  theoretical 
  

   conclusions. 
  These 
  are 
  as 
  follows 
  : 
  

  

  (1.) 
  In 
  the 
  expression 
  for 
  the 
  absolute 
  amplitude, 
  ratios 
  and 
  dif- 
  

   ference 
  of 
  phase 
  of 
  the 
  reflected 
  and 
  the 
  transmitted 
  light 
  — 
  three 
  

   constants 
  depending 
  upon 
  the 
  nature 
  of 
  the 
  layer 
  enter. 
  In 
  

   Cauchy's 
  formula 
  but 
  one 
  constant 
  depending 
  upon 
  the 
  boundary 
  

   enters. 
  

  

  (2.) 
  For 
  refraction 
  and 
  ordinary 
  reflection 
  the 
  formulas 
  are 
  

   identical 
  with 
  those 
  of 
  Cauehy. 
  

  

  (3.) 
  A 
  lower 
  limit 
  for 
  the 
  thickness 
  of 
  the 
  layer 
  transmitting 
  

   light 
  is 
  given 
  by 
  elliptical 
  polarization. 
  

  

  (4.) 
  No 
  ellipticity 
  is 
  shown 
  if 
  the 
  layer 
  is 
  contained 
  between 
  

   the 
  media 
  of 
  the 
  same 
  index 
  of 
  refraction. 
  If 
  the 
  plate 
  is 
  wedge- 
  

   shaped 
  of 
  small 
  angle; 
  in 
  reflected 
  light 
  the 
  bright 
  bands 
  have 
  

   the 
  normal 
  polarization 
  angle. 
  The 
  dark 
  bands 
  deviate 
  from 
  

   this, 
  and 
  a 
  conclusion 
  can 
  thus 
  be 
  drawn 
  in 
  regard 
  to 
  the 
  index 
  

   of 
  refraction 
  of 
  the 
  layer 
  in 
  case 
  the 
  layer 
  is 
  homogeneous. 
  

  

  (5.) 
  In 
  the 
  dark 
  band 
  the 
  reflected 
  light 
  is 
  linear 
  polarized 
  — 
  

   the 
  transmitted 
  light 
  elliptically 
  polarized. 
  In 
  the 
  bright 
  bands 
  

   the 
  reflected 
  as 
  well 
  as 
  the 
  transmitted 
  light 
  is 
  elliptically 
  polar- 
  

   ized. 
  

  

  (6.) 
  From 
  observation 
  upon 
  the 
  light 
  transmitted 
  by 
  thin 
  

   metallic 
  layers 
  and 
  on 
  light 
  reflected 
  the 
  true 
  optical 
  constants 
  of 
  

   the 
  metals 
  can 
  be 
  computed. 
  — 
  An?i. 
  der 
  Physik 
  and 
  Ghe?nie, 
  No. 
  

   5, 
  1891, 
  pp. 
  126-157. 
  J. 
  t. 
  

  

  II. 
  Geology 
  and 
  Mineralogy. 
  

  

  I. 
  Annual 
  Report 
  of 
  the 
  State 
  Geologist 
  of 
  JVeto 
  Jersey 
  for 
  

   the 
  year 
  1890. 
  305 
  pp. 
  8vo. 
  1891.— 
  Since 
  the 
  death 
  of 
  Prof. 
  

   Cook, 
  Prof. 
  G. 
  C. 
  Smock 
  has 
  been 
  appointed 
  the 
  State 
  Geologist 
  

   of 
  New 
  Jersey 
  with 
  F. 
  L. 
  Nason 
  and 
  C. 
  W. 
  Coman 
  as 
  assistant 
  

   geologists. 
  This 
  report 
  contains 
  an 
  article 
  on 
  the 
  age 
  of 
  the 
  

   Sussex 
  Co. 
  crystalline 
  limestones 
  by 
  Mr. 
  Nason 
  ; 
  an 
  account 
  of 
  

   geological 
  work 
  in 
  the 
  southern 
  part 
  of 
  the 
  State 
  by 
  C. 
  W. 
  

   Coman, 
  treating 
  especially 
  of 
  the 
  strata 
  overlying 
  the 
  upper 
  marl 
  

   bed, 
  and 
  a 
  report 
  on 
  the 
  water-power 
  and 
  water-supply 
  of 
  the 
  

   State 
  by 
  C. 
  C. 
  Vermeule. 
  

  

  Mr. 
  Nason's 
  paper 
  contains 
  the 
  important 
  announcement 
  that 
  

   the 
  bluish, 
  semi-crystalline 
  limestone 
  of 
  Sussex 
  Co. 
  and 
  the 
  asso- 
  

  

  