﻿1875.] 
  

  

  Theory 
  of 
  Ventilation. 
  

  

  193 
  

  

  0*8432, 
  the 
  range 
  for 
  probable 
  error 
  of 
  result 
  being 
  between 
  0*8640 
  and 
  

   0*8224. 
  

  

  We 
  may 
  say 
  that 
  ventilation 
  is 
  very 
  bad 
  when 
  : 
  — 
  

   Vapour 
  reaches 
  5 
  grains 
  per 
  cubic 
  foot. 
  

  

  Carbonic 
  acid 
  in 
  excess 
  over 
  outer 
  air 
  reaches 
  0*8000 
  per 
  1000 
  volumes. 
  

  

  No. 
  5 
  (see 
  Table 
  No. 
  5). 
  — 
  " 
  Extremely 
  close 
  " 
  &c. 
  : 
  the 
  maximum 
  

   point 
  of 
  differentiation 
  by 
  the 
  senses. 
  

  

  1. 
  Temperature. 
  — 
  The 
  temperature 
  in 
  the 
  outer 
  air 
  was 
  51°*86, 
  and 
  

   in 
  the 
  inhabited 
  air-spaces 
  65°*05, 
  giving 
  a 
  mean 
  difference 
  of 
  13°* 
  19. 
  

  

  2. 
  Vapour 
  and 
  Humidity. 
  — 
  The 
  mean 
  vapour 
  in 
  the 
  outer 
  air 
  was 
  

   3*875, 
  and 
  in 
  the 
  inhabited 
  air-spaces 
  5*194, 
  showing 
  an 
  excess 
  of 
  

   1*319 
  grain, 
  corresponding 
  to 
  a 
  lowering 
  of 
  relative 
  humidity 
  of 
  9*88 
  

   per 
  cent. 
  

  

  3. 
  Carbonic 
  Acid. 
  — 
  The 
  mean 
  amount 
  in 
  the 
  outer 
  air 
  was 
  0*4001, 
  or 
  

   exactly 
  the 
  average 
  amount. 
  In 
  the 
  inhabited 
  air-spaces 
  it 
  was 
  1*2818, 
  

   showing 
  an 
  excess 
  due 
  to 
  respiratory 
  impurity 
  of 
  0*8817 
  per 
  1000 
  

   volumes, 
  the 
  range 
  for 
  the 
  probable 
  error 
  of 
  result 
  being 
  between 
  0*9202 
  

   and 
  0*8432. 
  

  

  The 
  extreme 
  point 
  of 
  differentiation 
  by 
  the 
  senses 
  is 
  thus 
  reached 
  when 
  

   the 
  following 
  conditions 
  are 
  found 
  : 
  — 
  

   Vapour 
  5*100 
  grains 
  per 
  cubic 
  foot. 
  

  

  Carbonic 
  acid 
  in 
  excess 
  over 
  the 
  amount 
  in 
  the 
  outer 
  air 
  beyond 
  

   0*8500 
  per 
  1000 
  volumes. 
  

  

  It 
  will 
  at 
  once 
  be 
  seen 
  that 
  the 
  figures 
  in 
  No. 
  5 
  differ 
  but 
  little 
  from 
  

   those 
  in 
  No. 
  4, 
  and 
  that 
  the 
  probable 
  limit 
  of 
  differentiation 
  by 
  the 
  senses 
  

   is 
  reached 
  in 
  No. 
  4. 
  The 
  number 
  of 
  recorded 
  observations 
  in 
  No. 
  5 
  is 
  

   also 
  very 
  few 
  comparatively 
  ; 
  and 
  I 
  think 
  it 
  w 
  T 
  ould 
  therefore 
  be 
  better 
  to 
  

   group 
  the 
  two 
  together, 
  as 
  below. 
  

  

  Nos. 
  4 
  and 
  5 
  combined, 
  being 
  the 
  probable 
  limit 
  of 
  possible 
  differen- 
  

   tiation 
  by 
  the 
  senses. 
  

  

  1. 
  Temperature. 
  — 
  In 
  the 
  outer 
  air 
  51°*43, 
  in 
  the 
  inhabited 
  air-spaces 
  

   65°*12, 
  or 
  a 
  mean 
  difference 
  of 
  13°*69. 
  

  

  2. 
  Vapour 
  and 
  Humidity. 
  — 
  The 
  vapour 
  in 
  the 
  outer 
  air 
  was 
  3*729, 
  

   inside 
  5*108, 
  or 
  a 
  mean 
  difference 
  of 
  1*379 
  grain, 
  corresponding 
  to 
  a 
  

   lowering 
  of 
  relative 
  humidity 
  of 
  8*92 
  per 
  cent. 
  

  

  3. 
  Carbonic 
  Acid. 
  — 
  In 
  the 
  outer 
  air 
  0*3928, 
  in 
  the 
  inhabited 
  air-spaces 
  

   1*2461, 
  or 
  a 
  mean 
  difference 
  due 
  to 
  respiratory 
  impurity 
  of 
  0*8533, 
  the 
  

   range 
  for 
  probable 
  error 
  of 
  result 
  being 
  between 
  0*8717 
  and 
  0*8349. 
  

  

  We 
  may 
  therefore, 
  I 
  think, 
  say 
  that 
  when 
  the 
  vapour* 
  reaches 
  

   5*100 
  grains 
  per 
  cubic 
  foot, 
  and 
  the 
  C0 
  2 
  in 
  excess 
  0*8000 
  volume 
  per 
  

   1000, 
  the 
  maximum 
  point 
  of 
  differentiation 
  by 
  the 
  senses 
  is 
  reached. 
  

  

  * 
  It 
  is 
  to 
  be 
  understood 
  that 
  the 
  amounts 
  of 
  vapour 
  stated 
  in 
  these 
  cases 
  are 
  in 
  

   reference 
  to 
  a 
  mean 
  temperature 
  of 
  about 
  63° 
  F. 
  

  

  