﻿new 
  Ili/grometric 
  Method. 
  381 
  

  

  t 
  = 
  0, 
  /=</>, 
  and 
  4> 
  is 
  known 
  from 
  Regnault's 
  work. 
  Hence 
  

   / 
  follows. 
  In 
  studying 
  wet 
  bulbs 
  by 
  this 
  method 
  assume 
  

   further 
  that 
  over 
  a 
  small 
  range 
  of 
  conditions 
  

  

  and 
  from 
  two 
  such 
  comparisons 
  obtain 
  c 
  and 
  k, 
  or 
  from 
  a 
  

   large 
  number 
  treated 
  by 
  the 
  method 
  of 
  least 
  squares. 
  

  

  The 
  range 
  of 
  conditions 
  over 
  which 
  it 
  is 
  admissible 
  to 
  

   assume 
  that 
  c 
  and 
  k 
  are 
  constant 
  must 
  be 
  found 
  by 
  experi- 
  

   ment, 
  but 
  it 
  must 
  be 
  admissible 
  over 
  some 
  range. 
  Special 
  

   attention 
  is 
  drawn 
  to 
  this 
  device 
  for 
  finding 
  c 
  and 
  k, 
  since 
  it 
  

   does 
  not 
  involve 
  an 
  appeal 
  to 
  any 
  method 
  supposed 
  to 
  be 
  

   standard. 
  

  

  (4) 
  Manipulation. 
  — 
  To 
  apply 
  this 
  theory 
  to 
  the 
  study 
  of 
  

   wet 
  bulbs, 
  the 
  bulb 
  of 
  a 
  thermometer 
  is 
  wrapped 
  in 
  linen 
  

   secured 
  by 
  a 
  rubber 
  band 
  just 
  above 
  the 
  bulb. 
  A 
  little 
  

   higher 
  the 
  stem 
  passes 
  through 
  a 
  rubber 
  stopper, 
  which 
  

   closes 
  the 
  mouth 
  of 
  a 
  test-tube 
  containing 
  a 
  little 
  acid 
  

   which 
  wets 
  the 
  rag. 
  When 
  this 
  thermometer 
  reads 
  about 
  

   the 
  same 
  as 
  the 
  dry 
  bulb, 
  withdraw 
  the 
  test-tube 
  exposing 
  the 
  

   rag 
  to 
  air. 
  Between 
  the 
  fourth 
  and 
  sixth 
  minutes 
  after 
  this, 
  

   read 
  repeatedly 
  the 
  acid 
  thermometer 
  and 
  the 
  wet 
  and 
  dry 
  

   bulbs, 
  and 
  take 
  the 
  respective 
  means. 
  Rinse 
  the 
  linen 
  

   repeatedly 
  with 
  the 
  stock 
  of 
  acid 
  and 
  replace 
  the 
  test-tube. 
  

   A 
  very 
  little 
  experience 
  enables 
  one 
  (from 
  a 
  reading 
  of 
  the 
  

   wet 
  and 
  dry 
  bulbs 
  at 
  8 
  a.m.) 
  to 
  select 
  a 
  solution 
  which 
  will 
  

   be 
  appropriate 
  to 
  the 
  humidities 
  met 
  with 
  during 
  most 
  of 
  the 
  

   morning 
  and 
  again 
  in 
  the 
  evening. 
  A 
  point 
  is 
  made 
  of 
  

   the 
  simplicity 
  of 
  the 
  method. 
  

  

  (5) 
  Illustrative 
  results. 
  — 
  The 
  results 
  below 
  are 
  to 
  illustrate 
  

   the 
  method 
  and 
  to 
  show 
  that 
  k 
  may 
  be 
  taken 
  constant 
  between 
  

   limits 
  t 
  — 
  9= 
  ±2° 
  and 
  in 
  very 
  different 
  ventilations. 
  Table 
  I. 
  

   gives 
  results 
  with 
  the 
  apparatus 
  described 
  and 
  an 
  ordinary 
  

   psychrometer. 
  Light 
  winds 
  prevailed, 
  but 
  an 
  exact 
  record 
  

   was 
  not 
  kept. 
  The 
  series 
  is 
  preliminary 
  : 
  k 
  appears 
  constant, 
  

   but 
  the 
  question 
  of 
  ventilation 
  remains. 
  To 
  test 
  this 
  the 
  

   ordinary 
  psychrometer 
  was 
  replaced 
  by 
  Assmann's 
  well-known 
  

   construction. 
  The 
  high 
  artificial 
  ventilation 
  of 
  this 
  instrument 
  

   is 
  thought 
  to 
  render 
  it 
  independent 
  of 
  changes 
  in 
  the 
  natural 
  

   ventilation. 
  The 
  acid 
  bulb 
  was 
  still 
  exposed 
  to 
  the 
  natural 
  

   ventilation 
  which 
  was 
  estimated 
  on 
  a 
  scale 
  whose 
  unit 
  is 
  about 
  

   6 
  kilometres 
  per 
  hour. 
  The 
  agreement 
  of 
  columns 
  f\ 
  f 
  2 
  in 
  

   Table 
  II. 
  is 
  held 
  to 
  show 
  the 
  acid 
  bulb's 
  independence 
  of 
  

   ventilation, 
  k 
  is 
  practically 
  the 
  same 
  as 
  in 
  Table 
  I. 
  over 
  

   range 
  t 
  — 
  0= 
  +2°. 
  The 
  value 
  of 
  c 
  ivas 
  taken 
  as 
  unknown. 
  

  

  