﻿ARTICLE 
  XX. 
  

  

  Description 
  of 
  an 
  Electrical 
  Machine, 
  with 
  a 
  Plate 
  four 
  feet 
  in 
  dia- 
  

   meter, 
  so 
  constructed 
  as 
  to 
  be 
  above 
  the 
  Operator 
  : 
  also 
  of 
  a 
  Battery 
  Dis- 
  

   charger 
  employed 
  therewith 
  : 
  and 
  some 
  Observations 
  on 
  the 
  Causes 
  of 
  the 
  

   Diversity 
  in 
  the 
  Length 
  of 
  the 
  Sparks 
  erroneously 
  distinguished 
  by 
  the 
  

   terms 
  Positive 
  and 
  Negative. 
  By 
  R. 
  Hare, 
  M. 
  D., 
  4*c, 
  #c, 
  fyc. 
  

  

  The 
  opposite 
  engraving 
  represents 
  a 
  machine 
  with 
  a 
  plate 
  four 
  feet 
  

   in 
  diameter, 
  which 
  I 
  have 
  recently 
  constructed 
  so 
  as 
  to 
  be 
  permanently 
  

   affixed 
  to 
  the 
  canopy 
  over 
  the 
  hearth 
  of 
  my 
  lecture 
  room. 
  

  

  This 
  situation 
  I 
  have 
  found 
  convenient 
  even 
  beyond 
  my 
  expecta- 
  

   tions, 
  as 
  the 
  machine 
  is 
  always 
  at 
  hand, 
  yet 
  never 
  in 
  the 
  way. 
  In 
  

   lecturing, 
  with 
  the 
  aid 
  of 
  a 
  machine 
  on 
  the 
  same 
  level 
  with 
  the 
  lec- 
  

   turer, 
  one 
  of 
  two 
  inconveniences 
  is 
  inevitable. 
  Either 
  the 
  machine 
  

   will 
  occasionally 
  be 
  between 
  him 
  and 
  a 
  portion 
  of 
  the 
  audience, 
  or 
  he 
  

   must 
  be 
  between 
  a 
  portion 
  of 
  the 
  audience 
  and 
  the 
  machine. 
  Situ- 
  

   ated 
  like 
  that 
  which 
  I 
  am 
  about 
  to 
  describe, 
  a 
  machine 
  can 
  neither 
  

   hide 
  the 
  lecturer, 
  nor 
  be 
  hidden 
  by 
  him. 
  With 
  all 
  its 
  power 
  at 
  his 
  

   command, 
  while 
  kept 
  in 
  motion 
  by 
  an 
  assistant, 
  he 
  has 
  no 
  part 
  of 
  it 
  to 
  

   reach 
  or 
  to 
  handle 
  besides 
  the 
  knob 
  and 
  sliding 
  rod 
  of 
  the 
  conductor, 
  

   which 
  are 
  in 
  the 
  most 
  convenient 
  situation. 
  

  

  The 
  object 
  of 
  this 
  machine 
  being 
  to 
  obtain 
  a 
  copious 
  supply 
  of 
  

   electricity 
  for 
  experiments, 
  in 
  which 
  such 
  a 
  supply 
  is 
  requisite, 
  it 
  was 
  not 
  

   vol. 
  v. 
  — 
  4 
  s 
  

  

  