﻿Disks 
  and 
  Rings 
  of 
  Metal. 
  275 
  

  

  diminution 
  of 
  this 
  weight 
  in 
  each 
  successive 
  experiment. 
  

   After 
  each 
  experiment 
  with 
  the 
  ring 
  on 
  the 
  salt 
  solution 
  it 
  was 
  

   placed 
  in 
  distilled 
  water, 
  vigorously 
  agitated 
  therein 
  for 
  a 
  

   minute 
  or 
  two, 
  then 
  placed 
  in 
  fresh 
  distilled 
  water 
  for 
  several 
  

   minutes, 
  wiped 
  dry 
  and 
  allowed 
  to 
  remain 
  for 
  about 
  fifteen 
  

   minutes 
  before 
  another 
  experiment 
  was 
  made. 
  The 
  following 
  

   table 
  gives 
  the 
  result 
  of 
  six 
  experiments. 
  

  

  AY 
  

   2-543 
  

   2-430 
  

   2-425 
  

   2-424 
  

   2-411 
  

   2-407 
  

  

  It 
  was 
  found 
  that, 
  if 
  the 
  ring 
  after 
  having 
  been 
  thoroughly 
  

   freed 
  of 
  the 
  salt 
  solution 
  was 
  allowed 
  to 
  rest 
  for 
  a 
  day, 
  it 
  

   recovered 
  its 
  primitive 
  breaking 
  weight. 
  Thus 
  an 
  interval 
  of 
  

   a 
  day 
  existed 
  between 
  the 
  following 
  experiments. 
  

  

  W 
  

   2-543 
  

   2-541 
  

   2-530 
  

  

  2-538 
  = 
  mean. 
  

  

  A 
  similar 
  diminution 
  of 
  W 
  in 
  each 
  successive 
  experiment, 
  

   but 
  of 
  greater 
  extent, 
  was 
  observed 
  in 
  six 
  successive 
  experi- 
  

   ments 
  on 
  the 
  salt 
  solution 
  with 
  a 
  tinned 
  iron 
  ring. 
  

  

  The 
  only 
  explanation 
  of 
  the 
  phenomenon 
  that 
  has 
  occurred 
  

   to 
  me 
  is 
  that 
  the 
  salt 
  solution 
  in 
  each 
  successive 
  experiment 
  

   takes 
  off 
  a 
  portion 
  of 
  the 
  air 
  condensed 
  on 
  the 
  surface 
  of 
  the 
  

   ring 
  and 
  gradually 
  brings 
  it 
  towards 
  that 
  condition 
  of 
  the 
  ring 
  

   when 
  it 
  is 
  freed 
  of 
  air, 
  as 
  by 
  heat, 
  and 
  does 
  not 
  float 
  at 
  all. 
  

   But 
  why 
  it 
  takes 
  twenty-four 
  hours 
  to 
  recover 
  its 
  primitive 
  sur- 
  

   face, 
  whereas, 
  after 
  having 
  been 
  heated 
  to 
  redness 
  it 
  recovers 
  

   it 
  in 
  a 
  half 
  -hour, 
  I 
  cannot 
  explain. 
  

  

  Uses 
  of 
  the 
  platinum 
  ring 
  in 
  measures 
  of 
  the 
  degree 
  of 
  contamina- 
  

   tion 
  of 
  the 
  surface 
  of 
  -water 
  ', 
  and 
  in 
  experiments 
  on 
  con- 
  

   taminated 
  toater 
  contained 
  in 
  the 
  trough 
  of 
  Miss 
  Pockets. 
  

  

  If 
  the 
  platinum 
  ring 
  be 
  loaded 
  to, 
  say, 
  one-tenth 
  of 
  the 
  

   weight 
  required 
  to 
  make 
  it 
  sink 
  and 
  then 
  floated 
  on 
  freshly 
  dis- 
  

   tilled 
  water, 
  it 
  will 
  sink 
  when, 
  from 
  any 
  cause, 
  the 
  surface 
  ten- 
  

   sion 
  of 
  the 
  water 
  has 
  been 
  lessened 
  ten 
  per 
  cent. 
  The 
  duration 
  

   of 
  flotation 
  of 
  the 
  ring 
  is 
  variable. 
  On 
  one 
  day 
  it 
  floated 
  

   during 
  only 
  two 
  hours 
  ; 
  on 
  another 
  day 
  it 
  floated 
  for 
  9 
  hours 
  ; 
  

  

  