﻿Variable 
  Frequency 
  Alternating 
  Currents. 
  483 
  

  

  magnet 
  with 
  a 
  laminated 
  core 
  of 
  stalloy, 
  which 
  is 
  an 
  alloy 
  of 
  

   iron 
  much 
  used 
  in 
  electrical 
  work, 
  a 
  mercury 
  cup 
  and 
  a 
  

   platinum 
  wire 
  contact. 
  The 
  wire 
  is 
  provided 
  with 
  a 
  tension 
  

   adjuster, 
  and 
  will 
  run 
  steadily 
  at 
  frequencies 
  varying 
  from 
  

   100— 
  to 
  250— 
  

  

  The 
  frequency 
  of 
  the 
  alternating 
  output 
  is 
  quite 
  inde- 
  

   pendent 
  of 
  the 
  wire 
  frequency, 
  and 
  is 
  obtained 
  by 
  means 
  of 
  a 
  

   separate 
  circuit, 
  mercury 
  cup, 
  and 
  contact. 
  The 
  mercury 
  

   cups 
  are 
  made 
  from 
  glass 
  tube 
  4 
  mm. 
  in 
  internal 
  diameter, 
  

   and 
  these 
  are 
  enclosed 
  in 
  brass 
  tubes 
  to 
  which 
  the 
  mercury 
  

   is 
  connected 
  by 
  means 
  of 
  a 
  platinum 
  wire 
  fused 
  into 
  the 
  glass. 
  

  

  The 
  cups 
  thus 
  made 
  slip 
  into 
  brass 
  adjustable 
  carriers 
  from 
  

   which 
  they 
  can 
  readily 
  be 
  removed 
  for 
  cleaning 
  purposes, 
  

   and 
  the 
  carriers 
  admit 
  of 
  a 
  fine 
  vertical 
  adjustment. 
  

  

  Experiments 
  have 
  been 
  made 
  with 
  cups 
  of 
  varying 
  

   diameter. 
  Those 
  with 
  the 
  smallest 
  diameters 
  gave 
  the 
  best 
  

   results. 
  

  

  It 
  would 
  appear 
  that 
  the 
  mercury 
  in 
  the 
  small 
  cups 
  

   remains 
  much 
  steadier 
  under 
  the 
  action 
  of 
  the 
  vibrating 
  

   contact 
  than 
  in 
  those 
  of 
  larger 
  diameter, 
  owing 
  possibly 
  to 
  

   the 
  greater 
  surface-tension 
  effect. 
  

  

  Single 
  Action 
  Circuit. 
  — 
  Several 
  forms 
  of 
  oscillating 
  circuit 
  

   have 
  been 
  used 
  of 
  which 
  the 
  two 
  principal 
  ones 
  may 
  be 
  

   described 
  as 
  " 
  single 
  action 
  " 
  and 
  " 
  double 
  action 
  " 
  

   respectively. 
  

  

  Fig'. 
  6. 
  — 
  Single 
  Action 
  Circuit. 
  

  

  

  

  

  

  

  j. 
  

  

  

  

  ~\ 
  

  

  

  

  

  < 
  

  

  <-i 
  

  

  ^ 
  

  

  

  

  1 
  — 
  ' 
  

  

  

  

  

  * 
  

  

  k 
  

  

  -1 
  

  

  j 
  

  

  

  

  

  t= 
  zr— 
  

  

  

  

  

  

  

  WcTTST 
  — 
  * 
  

  

  oooo 
  

  

  

  

  Fig. 
  6 
  shows 
  the 
  single 
  action 
  circuit 
  and 
  also 
  the 
  wire 
  

   driving 
  circuit. 
  The 
  latter 
  requires 
  no 
  explanation. 
  The 
  

   former 
  consists 
  of 
  a 
  platinum 
  contact 
  and 
  mercury 
  cup 
  which 
  

  

  2K2 
  

  

  