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  A. 
  M. 
  Mayer 
  — 
  On 
  the 
  Flotation 
  of 
  

  

  of 
  the 
  water-surface 
  near 
  the 
  wire 
  were 
  at 
  R, 
  in 
  the 
  horizontal 
  

   plane 
  through 
  S, 
  then 
  the 
  curved 
  surface 
  where 
  it 
  meets 
  the 
  

   wire 
  at 
  S 
  would 
  be 
  tangent 
  to 
  a 
  vertical 
  at 
  that 
  point. 
  But 
  

   the 
  radius 
  of 
  curvature 
  of 
  this 
  portion 
  of 
  the 
  curved 
  surface 
  is 
  

   at 
  R 
  1 
  , 
  making 
  EsE 
  1 
  equal 
  to 
  2J° 
  and 
  showing 
  that 
  the 
  verti- 
  

   cal 
  to 
  S 
  makes 
  an 
  angle 
  of 
  2J° 
  with 
  the 
  tangent 
  to 
  the 
  curve 
  

   at 
  that 
  point. 
  

  

  To 
  determine 
  the 
  lateral 
  extent 
  of 
  the 
  depression 
  of 
  the 
  

   water 
  on 
  either 
  side 
  of 
  the 
  wire 
  of 
  l 
  mm 
  in 
  diameter, 
  when 
  it 
  is 
  

   just 
  on 
  the 
  point 
  of 
  breaking 
  through 
  the 
  water, 
  the 
  following 
  

   method 
  was 
  used 
  : 
  On 
  the 
  top 
  of 
  a 
  cylindrical 
  vessel, 
  holding 
  

   water 
  to 
  within 
  about 
  3 
  mm 
  of 
  its 
  top, 
  was 
  placed 
  a 
  millimeter, 
  

   scale, 
  S, 
  fig. 
  7, 
  8 
  mtn 
  wide. 
  On 
  the 
  upper 
  surface 
  of 
  this 
  scale 
  

  

  Fig. 
  7. 
  

  

  Fig. 
  8 
  

  

  \ 
  

  

  was 
  cemented 
  a 
  slip 
  of 
  thin 
  mirror 
  glass 
  with 
  its 
  plane 
  inclined 
  

   to 
  the 
  horizontal 
  scale 
  S, 
  as 
  shown 
  in 
  fig. 
  8. 
  The 
  top 
  of 
  the 
  

   glass 
  vessel 
  was 
  carefully 
  levelled 
  so 
  that 
  its 
  plane 
  was 
  

   parallel 
  to 
  that 
  of 
  the 
  water. 
  On 
  looking 
  at 
  the 
  scale 
  

   with 
  the 
  line 
  of 
  sight 
  at 
  the 
  proper 
  angle 
  of 
  incidence 
  

   we 
  see 
  the 
  scale 
  directly, 
  and 
  in 
  front 
  of 
  it 
  the 
  image 
  

   of 
  its 
  lower 
  surface 
  reflected 
  from 
  the 
  water. 
  The 
  off 
  edge 
  of 
  

   this 
  dark 
  reflected 
  image 
  of 
  the 
  scale 
  is 
  made 
  nearly 
  to 
  coin- 
  

   cide 
  with 
  the 
  near 
  edge 
  of 
  the 
  scale, 
  so 
  that 
  a 
  narrow, 
  bright 
  

   line 
  is 
  seen 
  between 
  the 
  off 
  edge 
  of 
  the 
  reflection 
  and 
  the 
  near 
  

   edge 
  of 
  the 
  scale, 
  as 
  shown 
  in 
  fig. 
  7. 
  On 
  now 
  depressing 
  the 
  

   wire 
  in 
  the 
  water, 
  the 
  surface 
  of 
  the 
  latter 
  is 
  curved, 
  and 
  this 
  

   surface 
  curves 
  the 
  reflection 
  of 
  the 
  edge 
  of 
  the 
  scale. 
  By 
  

   sighting 
  along 
  the 
  scale 
  so 
  that 
  the 
  pupil 
  of 
  the 
  eye 
  is 
  seen 
  

   reflected 
  from 
  the 
  slip 
  of 
  mirror, 
  at 
  the 
  point 
  where 
  the 
  curved 
  

  

  