﻿204 
  Mr. 
  J. 
  Patterson 
  on 
  a 
  

  

  recording 
  mechanism 
  is 
  shown 
  in 
  Plate 
  VI. 
  fig. 
  3. 
  Just 
  

   below 
  the 
  boom 
  H 
  is 
  an 
  inked 
  thread 
  or 
  carbon 
  paper 
  

   parallel 
  to 
  the 
  axis 
  of 
  the 
  paper 
  roller 
  L. 
  The 
  bar 
  J 
  which 
  

   is 
  operated 
  by 
  a 
  cam 
  attached 
  to 
  the 
  driving 
  mechanism 
  is 
  

   allowed 
  to 
  drop 
  once 
  every 
  two 
  minutes, 
  and 
  in 
  doing 
  so 
  

   depresses 
  the 
  boom 
  H, 
  causing 
  the 
  inked 
  thread 
  to 
  strike 
  the 
  

   recording 
  paper 
  just 
  below 
  the 
  boom, 
  giving 
  a 
  dot 
  which 
  

   shows 
  the 
  deflexion 
  of 
  the 
  needle 
  at 
  the 
  instant 
  of 
  marking. 
  

   The 
  boom 
  being 
  pivoted 
  as 
  already 
  described 
  does 
  not 
  disturb 
  

   the 
  needle 
  or 
  bend 
  the 
  suspension. 
  

  

  The 
  inked 
  thread 
  gives 
  a 
  short 
  dash 
  instead 
  of 
  a 
  dot 
  on 
  

   the 
  recording 
  paper, 
  and 
  this 
  is 
  not 
  as 
  satisfactory 
  as 
  it 
  

   might 
  be 
  when 
  the 
  potential 
  is 
  constantly 
  changing. 
  To 
  

   obtain 
  a 
  dot 
  instead 
  of 
  a 
  dash, 
  a 
  narrow 
  ribbon 
  of 
  ordinary 
  

   carbon 
  paper 
  was 
  employed 
  for 
  a 
  time, 
  and 
  a 
  slotted 
  bar 
  

   with 
  a 
  rod 
  1/16 
  in. 
  diameter 
  resting 
  in 
  the 
  slot 
  had 
  to 
  be 
  sub- 
  

   stituted 
  for 
  the 
  roller 
  L 
  ; 
  when 
  the 
  boom 
  was 
  depressed 
  it 
  

   hit 
  the 
  carbon 
  paper 
  just 
  above 
  the 
  rod, 
  and 
  left 
  a 
  small 
  dot. 
  

   This 
  arrangement 
  was 
  very 
  good 
  so 
  long 
  as 
  the 
  room 
  was 
  

   dr}% 
  but 
  if 
  it 
  got 
  damp 
  the 
  boom 
  was 
  very 
  liable 
  to 
  stick 
  on 
  

   the 
  paper. 
  The 
  difficulties 
  were 
  finally 
  overcome 
  by 
  taking, 
  

   a 
  couple 
  of 
  threads 
  out 
  of 
  a 
  typewriter 
  ribbon, 
  twining 
  them 
  

   together 
  and 
  then 
  doubling. 
  This 
  was 
  used 
  in 
  the 
  same 
  way 
  

   as 
  the 
  inked 
  thread, 
  and 
  gave 
  good 
  results. 
  It 
  is 
  a 
  very 
  

   simple 
  matter 
  to 
  make 
  in 
  a 
  few 
  minutes 
  sufficient 
  thread 
  to- 
  

   last 
  for 
  several 
  months 
  without 
  requiring 
  attention. 
  The 
  

   thread 
  was 
  stored 
  on 
  a 
  spool, 
  and 
  was 
  wound 
  off 
  at 
  the 
  rate 
  

   of 
  1^ 
  in. 
  per 
  day 
  on 
  to 
  another 
  spool 
  attached 
  to 
  the 
  axis 
  of 
  

   the 
  drum 
  Q. 
  

  

  Clocks. 
  — 
  There 
  are 
  two 
  separate 
  clocks 
  in 
  the 
  clock-case, 
  

   the 
  drum 
  clock 
  and 
  slave 
  clock. 
  The 
  drum 
  clock 
  drives 
  the 
  

   paper 
  at 
  a 
  definite 
  speed 
  of 
  14 
  mm. 
  per 
  hour 
  or 
  168 
  mm. 
  

   per 
  hour, 
  according 
  to 
  whichever 
  speed 
  is 
  required; 
  generally 
  

   the 
  slower 
  speed 
  is 
  used. 
  The 
  slave 
  clock 
  drives 
  the 
  cam 
  

   wheel 
  which 
  operates 
  the 
  depressor 
  bar 
  at 
  intervals 
  of 
  two' 
  

   minutes. 
  

  

  Charts. 
  — 
  A 
  continuous 
  paper 
  movement. 
  is 
  provided. 
  The 
  

   paper 
  is 
  stored 
  on 
  the 
  drum 
  P 
  (PI. 
  VI. 
  fig. 
  3), 
  and 
  passes 
  up 
  

   at 
  the 
  back 
  of 
  the 
  drum 
  Q, 
  over 
  roller 
  L, 
  down 
  in 
  front 
  of 
  

   drum 
  Q, 
  between 
  friction 
  rollers 
  not 
  shown, 
  on 
  to 
  the 
  storage- 
  

   drum 
  S, 
  where 
  it 
  can 
  be 
  fixed 
  by 
  inserting 
  the 
  end 
  of 
  the 
  

   paper 
  in 
  a 
  slot 
  provided 
  for 
  it. 
  The 
  spindle 
  of 
  8 
  is 
  provided 
  

   with 
  a 
  cord 
  the 
  end 
  of 
  which 
  can 
  be 
  fixed 
  in 
  any 
  convenient 
  

   position 
  under 
  the 
  case. 
  A 
  weight 
  and 
  pulley 
  not 
  shown 
  

   are 
  then 
  suspended 
  on 
  this 
  cord, 
  thus 
  exerting 
  a 
  turning 
  

   movement 
  to 
  the 
  drum 
  and 
  keeping 
  the 
  paper 
  taut 
  while 
  

  

  