﻿650 
  

  

  'r. 
  J. 
  Patterson 
  on 
  the 
  Change 
  of 
  the 
  Electrical 
  

  

  In 
  these 
  observations 
  the 
  bridge 
  was 
  balanced 
  by 
  placing 
  

   B 
  (fig. 
  2) 
  in 
  multiple 
  arc 
  with 
  the 
  variable 
  resistance 
  ; 
  then, 
  in 
  

   order 
  that 
  the 
  relation 
  Acr 
  = 
  CD 
  may 
  hold 
  when 
  A 
  is 
  

   increased, 
  a 
  must 
  be 
  decreased. 
  Hence 
  the 
  increase 
  in 
  A 
  

   appears 
  in 
  the 
  table 
  as 
  a 
  decrease 
  in 
  a. 
  

  

  The 
  average 
  of 
  all 
  the 
  results 
  given 
  in 
  Tables 
  I., 
  II., 
  and 
  

   III. 
  are 
  plotted 
  in 
  fig. 
  3, 
  where 
  the 
  abscissre 
  represent 
  the 
  

   field 
  and 
  the 
  ordinates 
  the 
  change 
  of 
  resistance. 
  

  

  

  

  

  

  

  

  

  

  Fig 
  

  

  .3. 
  

  

  

  

  

  

  

  

  

  

  * 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  2XK) 
  4 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  " 
  ^ 
  

  

  

  

  1-5.0* 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  K 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  to* 
  

  

  

  

  

  

  

  

  

  

  x* 
  — 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  l/M£S 
  

  

  pes 
  y<? 
  cm 
  

  

  

  

  

  

  

  

  24 
  25 
  85 
  & 
  

  

  If 
  the 
  change 
  of 
  resistance 
  due 
  to 
  the 
  magnetic 
  field 
  

   varied 
  as 
  the 
  square 
  of 
  the 
  resistance, 
  then 
  — 
  ^ 
  sn 
  °rdd 
  be 
  a 
  

  

  constant. 
  The 
  values 
  obtained 
  for 
  

  

  

  would 
  indicate 
  

  

  that 
  this 
  is 
  so. 
  

  

  Experiments 
  were 
  also 
  made 
  with 
  " 
  Eureka 
  "' 
  wire, 
  which 
  

   contains 
  iron 
  and 
  has 
  practically 
  no 
  temperature-coefficient. 
  

   The 
  spiral 
  had 
  a 
  resistance 
  of 
  94*87 
  ohms, 
  and 
  the 
  other 
  three 
  

   resistances, 
  also 
  of 
  " 
  Eureka" 
  wire, 
  were 
  each 
  of 
  about 
  95'21 
  

   ohms. 
  In 
  this 
  case 
  a 
  decrease 
  of 
  resistance 
  of 
  0*75 
  in 
  10,0f 
  

   for 
  a 
  transverse 
  field 
  of 
  26,900 
  lines 
  was 
  obtained. 
  As 
  the 
  

   composition 
  of 
  the 
  wire 
  was 
  not 
  known, 
  these 
  experiments 
  

   were 
  not 
  pursued 
  further. 
  They 
  are 
  of 
  interest, 
  however, 
  

   in 
  that 
  they 
  show 
  that 
  iron 
  in 
  its 
  alloys 
  still 
  retains 
  the 
  

   property 
  of 
  decreasing 
  its 
  resistance 
  when 
  placed 
  in 
  a 
  transverse 
  

   magnetic 
  field. 
  

  

  To 
  measure 
  the 
  change 
  of 
  resistance 
  in 
  mercury, 
  a 
  spiral 
  

   was 
  made 
  of 
  capillary 
  glass 
  tubing 
  and 
  filled 
  with 
  mercury. 
  

  

  The 
  resistance 
  was 
  about 
  2*39 
  ohms. 
  In 
  this 
  case 
  the 
  

   deflexions 
  of 
  the 
  galvanometer 
  were 
  observed, 
  and 
  the 
  change 
  

   calculated 
  from 
  the 
  formulae 
  

  

  E 
  

  

  E 
  

  

  = 
  aha 
  

  

  E 
  

  

  A' 
  

  

  