﻿386 
  A. 
  G. 
  Webster 
  — 
  Rapid 
  Break 
  for 
  large 
  Currents. 
  

  

  prevent 
  air 
  being 
  sucked 
  in 
  at 
  T 
  on 
  stopping 
  the 
  action. 
  The 
  

   cock 
  D 
  is 
  also 
  to 
  be 
  closed 
  at 
  the 
  same 
  time. 
  O 
  is 
  a 
  trough 
  to 
  

   catch 
  any 
  water 
  that 
  may 
  overflow 
  at 
  T. 
  The 
  flow 
  should 
  be 
  

   adjusted 
  so 
  that 
  water 
  is 
  just 
  about 
  to 
  overflow 
  at 
  T 
  ; 
  the 
  spark 
  

   is 
  then 
  well 
  under 
  water, 
  and 
  no 
  air 
  is 
  likely 
  to 
  be 
  drawn 
  into 
  

   the 
  water 
  tube 
  P. 
  The 
  tube 
  R 
  must 
  have 
  length 
  enough 
  to 
  

   hang 
  down 
  with 
  a 
  certain 
  amount 
  of 
  slack, 
  so 
  that 
  the 
  mercury 
  

   shall 
  have 
  inertia 
  enough 
  for 
  the 
  proper 
  working 
  of 
  the 
  pump. 
  

   When 
  the 
  proper 
  arrangement 
  is 
  arrived 
  at, 
  the 
  level 
  of 
  the 
  

   mercury 
  fluctuates 
  with 
  a 
  regular 
  pulsating 
  motion, 
  and 
  at 
  each 
  

   pulsation 
  the 
  water 
  is 
  momentarily 
  shut 
  off 
  in 
  Y 
  and 
  mercury 
  

   is 
  carried 
  up. 
  In 
  order 
  to 
  start 
  the 
  apparatus 
  working 
  it 
  is 
  

   only 
  necessary 
  to 
  turn 
  on 
  the 
  water 
  and 
  open 
  the 
  cock 
  D. 
  The 
  

   apparatus 
  of 
  the 
  size 
  indicated 
  in 
  the 
  figure 
  working 
  on 
  a 
  

   head 
  of 
  two 
  and 
  one-half 
  meters 
  of 
  water 
  with 
  a 
  flow 
  of 
  about 
  

   three-tenths 
  of 
  a 
  gallon 
  per 
  minute, 
  has 
  carried 
  a 
  current 
  

   of 
  twenty 
  amperes, 
  and 
  has 
  been 
  used 
  with 
  forks 
  giving 
  

   fifty 
  and 
  one 
  hundred 
  breaks 
  per 
  second. 
  I 
  know 
  of 
  no 
  other 
  

   arrangement 
  which 
  will 
  stand 
  such 
  a 
  current 
  for 
  any 
  length 
  of 
  

   time. 
  

  

  Clark 
  University, 
  Worcester, 
  Mass. 
  

  

  