﻿442 
  Mr. 
  A. 
  P. 
  Wills 
  on 
  the 
  Susceptibility 
  of 
  

  

  Results. 
  

  

  The 
  tabular 
  results 
  are, 
  in 
  general, 
  arranged 
  in 
  groups 
  

   which 
  give 
  the 
  substances 
  experimented 
  upon 
  and 
  the 
  data 
  

   obtained 
  in 
  a 
  given 
  series 
  of 
  experiments. 
  

  

  A 
  table 
  of 
  abbreviations, 
  which 
  will 
  be 
  found 
  convenient 
  in 
  

   referring 
  to 
  the 
  tables 
  of 
  data, 
  is 
  given 
  below 
  : 
  — 
  

  

  H. 
  Unit 
  tubes 
  of 
  force 
  per 
  square 
  centimetre 
  at 
  bottom 
  

  

  surface 
  of 
  slab. 
  

   pi. 
  Balance 
  reading 
  in 
  grams, 
  field 
  on 
  and 
  slab 
  in 
  position. 
  

   p 
  . 
  Balance 
  reading 
  in 
  grains, 
  field 
  off 
  and 
  slab 
  in 
  position. 
  

   pi. 
  Balance 
  reading 
  in 
  grams, 
  field 
  on, 
  plaster 
  slab 
  in 
  

  

  position, 
  and 
  current 
  through 
  conductor. 
  

   Pq. 
  Balance 
  reading 
  in 
  grams, 
  field 
  on, 
  and 
  plaster 
  slab 
  in 
  

   position, 
  but 
  no 
  current 
  through 
  conductor. 
  

   P. 
  Mechanical 
  force, 
  in 
  grams, 
  upon 
  the 
  slab. 
  

   F. 
  Mechanical 
  force, 
  in. 
  grains, 
  upon 
  conductor 
  in 
  field 
  

  

  when 
  current 
  is 
  on. 
  

   I. 
  Current 
  in 
  amperes 
  through 
  conductor 
  when 
  field 
  is 
  

  

  being 
  measured. 
  

   e. 
  Correction 
  necessary 
  on 
  account 
  of 
  magnetic 
  attraction 
  

  

  upon 
  suspension 
  apparatus 
  without 
  slab. 
  

   8. 
  Correction 
  necessary 
  on 
  account 
  of 
  extension 
  in 
  wires 
  

  

  iv 
  and 
  w' 
  when 
  current 
  is 
  sent 
  through 
  them. 
  

   I. 
  Length, 
  in 
  centimetres, 
  of 
  conductor 
  used 
  in 
  measuring 
  

  

  field. 
  

   w. 
  Mean 
  width, 
  in 
  centimetres, 
  of 
  experimental 
  slab. 
  

   t. 
  Mean 
  thickness, 
  in 
  centimetres, 
  of 
  experimental 
  slab. 
  

   k. 
  Coefficient 
  of 
  magnetic 
  susceptibility. 
  

   In 
  the 
  first 
  series 
  of 
  experiments, 
  determinations 
  of 
  k 
  were 
  

   made 
  for 
  five 
  samples 
  of 
  marble. 
  In 
  the 
  first 
  column 
  of 
  the 
  

   table 
  are 
  found 
  the 
  names 
  of 
  the 
  different 
  varieties 
  of 
  marble 
  

   experimented 
  upon. 
  The 
  second 
  column 
  gives 
  pi, 
  two 
  values 
  

   being 
  given 
  for 
  each 
  substance, 
  since 
  each 
  slab 
  is 
  reversed 
  in 
  

   each 
  experiment, 
  the 
  top 
  being 
  put 
  for 
  the 
  bottom 
  ; 
  and 
  the 
  

   third 
  column 
  gives 
  the 
  mean 
  of 
  these 
  tw 
  T 
  o 
  values. 
  The 
  fourth 
  

   column 
  gives 
  p 
  , 
  the 
  reading 
  of 
  the 
  balance 
  when 
  slab 
  is 
  in 
  

   position, 
  but 
  no 
  field 
  on. 
  In 
  the 
  fifth 
  column 
  are 
  the 
  values 
  

   of 
  P=/?o 
  — 
  Fi 
  + 
  € 
  « 
  J- 
  11 
  the 
  next 
  two 
  columns 
  are 
  found 
  w 
  and 
  

   t, 
  the 
  factors 
  of 
  A, 
  the 
  area 
  of 
  the 
  slab. 
  The 
  last 
  column 
  

   gives 
  the 
  values 
  of 
  k 
  multiplied 
  by 
  10 
  to 
  the 
  sixth 
  power, 
  

   which 
  values 
  are 
  calculated 
  from 
  the 
  data 
  found 
  in 
  the 
  columns 
  

   and 
  below. 
  Below 
  the 
  columns 
  are 
  found 
  the 
  corrections 
  e 
  

   and 
  S, 
  the 
  necessary 
  data 
  for 
  the 
  calculation 
  of 
  H, 
  and 
  the 
  

   calculated 
  value 
  of 
  H. 
  The 
  same 
  value 
  of 
  H 
  was 
  used 
  through- 
  

   out 
  a 
  given 
  series 
  of 
  experiments. 
  The 
  same 
  arrangement 
  of 
  

   data 
  and 
  results 
  is 
  followed 
  in 
  all 
  of 
  the 
  tables 
  given. 
  

  

  