﻿ARTICLE 
  XXII. 
  

  

  Description 
  of 
  an 
  Mr 
  Pump 
  of 
  a 
  new 
  construction, 
  which 
  acts 
  either 
  

   as 
  an 
  Air 
  Tump, 
  or 
  a 
  Condenser, 
  or 
  as 
  both 
  ; 
  enabling 
  the 
  operator 
  to 
  

   exhaust, 
  to 
  condense, 
  to 
  transfer 
  a 
  Gas 
  from 
  one 
  cavity 
  to 
  another, 
  

   or 
  to 
  pass 
  it 
  through 
  a 
  Liquid. 
  By 
  B. 
  Hare, 
  M. 
  D., 
  fyc, 
  fyc, 
  fyc. 
  

  

  This 
  pump 
  has 
  one 
  iron 
  chamber,* 
  one 
  piston, 
  and 
  four 
  valves. 
  

   When 
  in 
  operation, 
  it 
  is 
  always 
  simultaneously 
  exhausting 
  and 
  condens- 
  

   ing; 
  and, 
  of 
  course, 
  accomplishes 
  as 
  much, 
  in 
  a 
  given 
  time, 
  as 
  two 
  

   chambers 
  of 
  the 
  usual 
  construction, 
  of 
  the 
  same 
  calibre 
  and 
  stroke. 
  

   A 
  suction 
  valve 
  is 
  placed 
  at 
  each 
  end 
  of 
  a 
  steel 
  rod, 
  which 
  slides 
  through 
  

   the 
  packing 
  of 
  the 
  piston,f 
  so 
  as 
  to 
  be 
  air 
  tight, 
  and 
  to 
  be 
  pressed 
  in 
  

   opposite 
  directions 
  alternately. 
  It 
  is 
  of 
  such 
  a 
  length, 
  that 
  while 
  it 
  

   forces 
  one 
  valve, 
  towards 
  which 
  the 
  piston 
  moves, 
  against 
  its 
  seat, 
  clos- 
  

   ing 
  a 
  corresponding 
  aperture, 
  it 
  withdraws 
  the 
  other 
  valve 
  from 
  its 
  

   seat, 
  and, 
  consequently, 
  opens 
  the 
  aperture 
  with 
  which 
  this 
  valve 
  cor- 
  

   responds. 
  Hence, 
  with 
  every 
  reversal 
  of 
  the 
  motion, 
  the 
  aperture 
  

   previously 
  opened 
  will 
  be 
  shut, 
  while 
  that 
  previously 
  shut 
  will 
  be 
  

  

  * 
  The 
  diameter 
  of 
  the 
  chamber 
  in 
  the 
  instrument 
  represented 
  in 
  the 
  figure 
  is 
  three 
  

   inches 
  ; 
  the 
  length 
  is 
  ten 
  and 
  a 
  half 
  inches, 
  allowing 
  a 
  stroke 
  of 
  about 
  eight 
  inches, 
  taking 
  off 
  

   the 
  thickness 
  of 
  the 
  piston. 
  In 
  order 
  to 
  render 
  this 
  instrument 
  insusceptible 
  of 
  injury 
  from 
  

   mercury, 
  it 
  was 
  constructed 
  altogether 
  of 
  iron 
  or 
  cast 
  steel. 
  

  

  t 
  This 
  contrivance 
  was 
  suggested 
  to 
  me 
  by 
  an 
  excellent 
  pump 
  with 
  glass 
  chambers, 
  ob- 
  

   tained 
  many 
  years 
  ago 
  from 
  Pixii. 
  In 
  that 
  pump 
  a 
  steel 
  rod 
  is 
  made 
  to 
  open 
  and 
  shut 
  one 
  valve 
  : 
  

   in 
  mine 
  the 
  same 
  rod 
  opens 
  and 
  shuts 
  two 
  valves. 
  

   VOL. 
  V. 
  4 
  X 
  

  

  