﻿Disks 
  and 
  Rings 
  of 
  Metal. 
  

  

  265 
  

  

  and 
  the 
  wire 
  appears 
  hung 
  in 
  an 
  annular 
  envelope 
  of 
  water 
  

   supported 
  by 
  the 
  two 
  curved 
  water 
  surfaces. 
  As 
  the 
  wire 
  

   descends 
  in 
  the 
  water 
  these 
  water 
  surfaces 
  always 
  meet 
  the 
  

   wire 
  as 
  surfaces 
  convex 
  upward. 
  When 
  the 
  two 
  water-surfaces 
  

   have 
  approached 
  it 
  T 
  L- 
  mm 
  as 
  shown 
  in 
  tig. 
  5, 
  the 
  angle 
  made 
  by 
  

   a 
  water-surface 
  with 
  the 
  vertical 
  where 
  it 
  meets 
  the 
  wire 
  at 
  

   that 
  point 
  is 
  2|°. 
  

  

  The 
  contour 
  of 
  the 
  depressed 
  surface 
  of 
  the 
  water, 
  as 
  I 
  have 
  

   drawn 
  it, 
  was 
  obtained 
  as 
  follows 
  : 
  In 
  a 
  tank, 
  fig. 
  6, 
  with 
  sides 
  

  

  Fig. 
  6. 
  

  

  

  vv 
  

  

  1 
  

  

  

  . 
  s 
  II 
  

  

  

  

  M 
  

  

  c 
  

  

  made 
  of 
  flat 
  glass, 
  a 
  wire 
  W, 
  of 
  l 
  mra 
  in 
  diameter, 
  bent 
  twice 
  at 
  

   right 
  angles, 
  is 
  brought 
  down 
  into 
  the 
  water 
  by 
  means 
  of 
  the 
  

   slide 
  and 
  micrometer 
  screw 
  already 
  described. 
  It 
  was 
  found 
  

   that 
  this 
  wire 
  went 
  to 
  the 
  same 
  depth, 
  *503 
  Gm 
  , 
  before 
  it 
  broke 
  

   through 
  the 
  depressed 
  water 
  as 
  did 
  a 
  ring 
  made 
  of 
  wire 
  of 
  the 
  

   same 
  diameter. 
  A 
  microscope, 
  M, 
  with 
  a 
  low-power 
  objective, 
  

   magnifying 
  11J 
  diameters, 
  is 
  focussed 
  on 
  the 
  wire 
  at 
  S. 
  The 
  

   leg, 
  W, 
  of 
  the 
  wire 
  ^acts 
  only 
  as 
  a 
  kind 
  of 
  diaphragm 
  to 
  the 
  

   objective 
  and 
  does 
  not 
  prevent 
  one 
  from 
  having 
  a 
  sharp 
  image 
  

   of 
  the 
  depressed 
  water-surface 
  at 
  S, 
  though 
  this 
  point 
  is 
  

   directly 
  behind 
  the 
  wire, 
  W. 
  Undoubtedly 
  there 
  must 
  be 
  

   some 
  distortion 
  in 
  this 
  image, 
  caused 
  by 
  the 
  refraction 
  of 
  the 
  

   depressed 
  meniscus 
  of 
  the 
  water; 
  but 
  this 
  method, 
  used 
  to 
  

   obtain 
  the 
  approximately 
  correct 
  contour 
  of 
  the 
  surfaces 
  of 
  the 
  

   depression, 
  is 
  the 
  only 
  one 
  I 
  have 
  been 
  able 
  to 
  devise. 
  With 
  

   the 
  camera 
  lucida 
  at 
  C, 
  several 
  drawings 
  were 
  made 
  of 
  the 
  

   contour 
  of 
  the 
  surfaces. 
  The 
  one 
  given 
  in 
  fi.g. 
  5 
  is 
  formed 
  by 
  

   combining 
  these 
  drawiDgs 
  in 
  an 
  average 
  curve. 
  

  

  The 
  upper 
  horizontal 
  line 
  shows 
  the 
  general 
  level 
  of 
  the 
  sur- 
  

   face 
  of 
  the 
  water. 
  The 
  bottom 
  of 
  the 
  wire 
  is 
  -503 
  cm 
  below 
  this 
  

   level. 
  The 
  figure 
  represents 
  the 
  phenomenon 
  magnified 
  14 
  

   diameters. 
  On 
  this 
  scale 
  the 
  depressed 
  surfaces 
  would 
  meet 
  

   the 
  general 
  level 
  of 
  the 
  water 
  at 
  21 
  cm 
  on 
  either 
  side 
  of 
  the 
  

   centre 
  of 
  the 
  figure. 
  If 
  the 
  radius 
  of 
  curvature 
  of 
  the 
  portion 
  

  

  