﻿370 
  

  

  be 
  sufficient 
  projectile 
  and 
  penetrative 
  power 
  to 
  break 
  through 
  the 
  air, 
  

   and 
  thus 
  open 
  a 
  passage 
  for 
  the 
  whole 
  of 
  the 
  quantity 
  attracted 
  by 
  the 
  

   small 
  negatively 
  excited 
  globe. 
  

  

  When, 
  by 
  the 
  process 
  last 
  described, 
  the 
  fluid 
  is 
  made 
  to 
  leap 
  through 
  

   a 
  comparatively 
  small 
  interval, 
  by 
  the 
  concentrated 
  attraction 
  exercised 
  

   by 
  a 
  small 
  negative 
  ball 
  upon 
  the 
  expanded 
  surface 
  of 
  electric 
  matter 
  

   diffused 
  through 
  a 
  large 
  globe, 
  the 
  air 
  does 
  not 
  become 
  sufficiently 
  

   condensed 
  to 
  resist 
  it 
  before 
  it 
  reaches 
  its 
  destination, 
  and, 
  of 
  course, 
  it 
  

   cannot 
  assume 
  the 
  erratic 
  form 
  which 
  would 
  arise 
  from 
  repeated 
  

   changes 
  in 
  its 
  course, 
  as 
  in 
  the 
  instance 
  of 
  the 
  long 
  spark. 
  

  

  OF 
  THE 
  ELECTRICAL 
  BRUSH. 
  

  

  When 
  the 
  machine 
  is 
  in 
  active 
  operation, 
  and 
  the 
  prime 
  conductor 
  

   insulated 
  ; 
  from 
  a 
  small 
  knob 
  attached 
  to 
  it, 
  as 
  at 
  B, 
  in 
  the 
  figure, 
  the 
  

   electricity 
  will 
  be 
  so 
  sent 
  off, 
  as 
  by 
  the 
  concomitant 
  light 
  to 
  exhibit 
  

   the 
  form 
  of 
  a 
  luminous 
  brush, 
  as 
  represented 
  in 
  this 
  figure 
  at 
  B. 
  For 
  

   the 
  production 
  of 
  this 
  phenomenon, 
  it 
  is 
  necessary 
  that 
  the 
  electric 
  

   fluid 
  shall 
  be 
  condensed 
  into 
  a 
  small 
  prominent 
  mass, 
  so 
  as, 
  agreeably 
  

   to 
  the 
  preceding 
  explanation, 
  to 
  have 
  great 
  penetrating 
  power. 
  This 
  

   it 
  cannot 
  possess, 
  when, 
  with 
  the 
  same 
  intensity 
  in 
  the 
  generating 
  

   power, 
  a 
  large 
  ball 
  is 
  positively 
  electrified. 
  In 
  that 
  case, 
  the 
  electric 
  

   column 
  presents 
  a 
  front 
  too 
  broad 
  to 
  procure 
  a 
  passage 
  through 
  the 
  

   surrounding 
  non-conducting 
  air. 
  A 
  small 
  ball, 
  negatively 
  electrified, 
  

   can 
  only 
  be 
  productive 
  of 
  a 
  diffuse 
  attraction 
  for 
  the 
  electricity 
  in 
  the 
  

   atmospheric 
  medium 
  around 
  it; 
  so 
  that 
  it 
  has 
  less 
  ability 
  to 
  create 
  any 
  

   penetrating 
  power, 
  than 
  when 
  acting 
  upon 
  the 
  electricity 
  in 
  a 
  compa- 
  

   ratively 
  large 
  globular 
  conductor, 
  as 
  in 
  the 
  preceding 
  illustration. 
  

   Hence, 
  when 
  the 
  knob 
  is 
  on 
  the 
  negative 
  pole, 
  it 
  may 
  be 
  productive 
  

  

  