﻿CORRECTION 
  TO 
  BAROMETER 
  FOR 
  FORCE 
  OF 
  WIND. 
  

  

  379 
  

  

  that 
  every 
  gust 
  of 
  wind 
  was 
  indicated 
  by 
  a 
  corresponding 
  depression 
  of 
  the 
  baro- 
  

   meter, 
  whilst 
  the 
  barometer 
  on 
  the 
  open 
  ground 
  remained 
  stationary 
  during 
  all 
  

   the 
  changes 
  in 
  the 
  amount 
  of 
  pressures 
  of 
  the 
  wind, 
  whether 
  arising 
  from 
  the 
  in- 
  

   creased 
  force 
  of 
  the 
  gale, 
  or 
  from 
  the 
  intermittent 
  gusts. 
  

  

  It 
  was, 
  therefore, 
  obvious 
  that 
  the 
  cause 
  of 
  the 
  depressions 
  of 
  the 
  barometer 
  

   was 
  owing 
  solely 
  to 
  the 
  screened 
  position 
  of 
  the 
  instrument 
  in 
  the 
  cottage 
  and 
  in 
  

   the 
  summer-house 
  ; 
  and 
  that 
  all 
  barometers 
  in 
  detached 
  houses, 
  or 
  observatories 
  in 
  

   exposed 
  situations, 
  must 
  be 
  similarly 
  affected 
  ; 
  and 
  that 
  a 
  ship's 
  barometer, 
  which 
  

   is 
  always 
  hung 
  in 
  the 
  cabin, 
  and 
  therefore 
  also 
  in 
  a 
  screened 
  position, 
  must 
  be 
  

   affected 
  in 
  a 
  like 
  manner. 
  

  

  The 
  cause 
  of 
  this 
  phenomenon 
  may 
  be 
  explained 
  by 
  the 
  pneumatic 
  experiments 
  

   made 
  by 
  Hawkesbee 
  and 
  Leslie, 
  and 
  by 
  the 
  hydrodynamic 
  experiments 
  of 
  Ber- 
  

   noulli 
  and 
  Venturi, 
  though 
  the 
  former 
  were 
  made 
  to 
  illustrate 
  a 
  different 
  sub- 
  

   ject 
  from 
  that 
  which 
  is 
  now 
  under 
  investigation.* 
  

  

  " 
  Dr 
  H 
  alley 
  sought 
  to 
  account 
  for 
  the 
  depression 
  of 
  the 
  barometer 
  before 
  a 
  

   storm, 
  to 
  the 
  withdrawing 
  of 
  the 
  vertical 
  pressure 
  of 
  the 
  atmosphere, 
  when 
  borne 
  

   swiftly 
  along 
  the 
  surface 
  of 
  the 
  globe 
  by 
  a 
  horizontal 
  motion." 
  — 
  Encyc. 
  Brit. 
  

  

  The 
  experiment 
  of 
  Hawkesbee 
  was 
  made 
  with 
  the 
  view 
  of 
  illustrating 
  and 
  

   supporting 
  the 
  above 
  hypothesis, 
  whilst 
  the 
  experiment 
  of 
  Leslie 
  was 
  made 
  with 
  

   the 
  view 
  of 
  refuting 
  it 
  ; 
  but 
  they 
  each 
  serve 
  admirably 
  to 
  explain 
  the 
  cause 
  of 
  

   the 
  depressions 
  of 
  the 
  barometer 
  in 
  a 
  screened 
  position 
  during 
  a 
  gale 
  of 
  wind. 
  

  

  In 
  Hawkesbee's 
  experiment, 
  two 
  barometers 
  are 
  enclosed 
  in 
  boxes 
  which 
  are 
  

  

  Fig. 
  2. 
  

  

  connected 
  by 
  a 
  pipe, 
  as 
  shewn 
  in 
  the 
  wood-cut. 
  A 
  globe 
  of 
  compressed 
  air 
  is 
  

   screwed 
  to 
  a 
  tube 
  leading 
  horizontally 
  into 
  the 
  upper 
  part 
  of 
  one 
  of 
  the 
  boxes, 
  

   whilst 
  a 
  larger 
  tube 
  is 
  placed 
  opposite 
  to 
  it, 
  for 
  the 
  escape 
  of 
  the 
  air. 
  When 
  the 
  

  

  * 
  I 
  am 
  indebted 
  to 
  my 
  friends 
  Professor 
  Kelland 
  and 
  Professor 
  Piazzi 
  Smyth, 
  for 
  drawing 
  

   my 
  attention 
  to 
  these 
  experiments. 
  

  

  