﻿380 
  Mr. 
  E. 
  B. 
  H. 
  Wade 
  on 
  a 
  

  

  experiment 
  was 
  tried 
  with 
  negative 
  result, 
  three 
  times 
  at 
  

   intervals 
  of 
  several 
  months. 
  The 
  final 
  series 
  of 
  readings 
  

   from 
  the 
  last 
  trial, 
  taken 
  when 
  the 
  sensibility 
  of 
  the 
  galvano- 
  

   meter 
  was 
  10 
  -10 
  , 
  is 
  given 
  below 
  : 
  — 
  

  

  Ja 
  - 
  readings. 
  Station 
  charge. 
  ™L£ 
  Average. 
  

  

  20 
  10 
  + 
  4- 
  +32 
  +3-2 
  

  

  20 
  10 
  + 
  - 
  +36 
  +3-6 
  

  

  21 
  10 
  - 
  + 
  — 
  2 
  - 
  -2 
  

  

  21 
  10 
  - 
  - 
  +17 
  +1*7 
  

  

  The 
  last 
  set 
  was 
  taken 
  within 
  30 
  minutes 
  of 
  an 
  accident 
  

   which 
  necessitated 
  the 
  soldering 
  of 
  two 
  joints 
  on 
  the 
  wheel 
  

   in 
  the 
  galvanometer 
  circuit, 
  and 
  therefore 
  cannot 
  be 
  compared 
  

   with 
  the 
  one 
  above 
  taken 
  on 
  the 
  same 
  nighty 
  If, 
  however, 
  

   we 
  average 
  these 
  readings, 
  assuming 
  that 
  the 
  direction 
  of 
  the 
  

   readings 
  should 
  reverse 
  both 
  with 
  the 
  charge 
  and 
  with 
  the 
  

   direction 
  of 
  rotation, 
  we 
  obtain 
  a 
  mean 
  of 
  *35 
  mm. 
  or 
  -175 
  mm. 
  

   in 
  each 
  direction, 
  which 
  is 
  identical 
  in 
  magnitude 
  with 
  that 
  

   obtained 
  under 
  similar 
  circumstances 
  with 
  no 
  charge. 
  

  

  Jn 
  conclusion 
  I 
  take 
  pleasure 
  in 
  acknowledging 
  my 
  obli- 
  

   gation 
  to 
  Professor 
  Rowland, 
  who 
  suggested 
  the 
  work 
  and 
  

   who 
  followed 
  its 
  progress 
  with 
  much 
  interest 
  ; 
  to 
  Professor 
  

   Ames 
  for 
  his 
  kindness 
  in 
  many 
  ways 
  ; 
  to 
  Mr. 
  Harold 
  Pender 
  

   for 
  his 
  assistance 
  in 
  obtaining 
  the 
  later 
  readings, 
  and 
  to 
  

   Professor 
  L. 
  A. 
  Bauer 
  for 
  valuable 
  criticisms 
  and 
  references. 
  

  

  Johns 
  Hopkins 
  University, 
  

   Feb. 
  1, 
  1901. 
  

  

  XLI. 
  A 
  new 
  Hygrometric 
  Method. 
  

   By 
  E. 
  B. 
  H. 
  Wade, 
  M. 
  A* 
  

  

  (1) 
  ^HE 
  object 
  of 
  this 
  note 
  is 
  to 
  describe 
  a 
  new 
  hygrometric 
  

   method, 
  in 
  which 
  a 
  thermometer 
  is 
  wetted 
  not 
  with 
  

   water 
  but 
  with 
  sulphuric 
  acid 
  of 
  suitable 
  strength. 
  

  

  (2) 
  It 
  is 
  claimed 
  that 
  the 
  method 
  is 
  (a) 
  theoretically 
  sound, 
  

   (b) 
  cheap 
  and 
  easy 
  to 
  manipulate, 
  (c) 
  specially 
  suited 
  for 
  the 
  

   study 
  of 
  ordinary 
  wet 
  bulbs, 
  (d) 
  independent 
  of 
  ventilation. 
  

  

  (3) 
  Theory 
  of 
  the 
  method. 
  — 
  Let 
  t 
  = 
  temperature 
  of 
  dry 
  bulb, 
  

   2' 
  = 
  the 
  same 
  for 
  wet 
  bulb, 
  = 
  the 
  same 
  for 
  bulb 
  wet 
  with 
  acid 
  

   (acid 
  bulb) 
  ; 
  /= 
  tension 
  of 
  vapour 
  in 
  air, 
  /' 
  = 
  maximum 
  tension 
  

   of 
  water-vapour 
  at 
  t\ 
  <£ 
  = 
  maximum 
  tension 
  for 
  acid 
  at 
  6. 
  If 
  

  

  * 
  Communicated 
  by 
  the 
  Physiqal 
  Society 
  : 
  read 
  December 
  13, 
  1901. 
  

   Published 
  by 
  permission 
  of 
  the 
  Under 
  Secretary 
  of 
  State, 
  Public 
  Works 
  

   Ministry. 
  

  

  