﻿454 
  

  

  Mr. 
  F. 
  E. 
  Smith 
  on 
  the 
  Variation 
  of 
  

  

  from 
  time 
  to 
  time, 
  and 
  the 
  seasonal 
  changes 
  o£ 
  resistance 
  — 
  

   especially 
  in 
  the 
  case 
  of 
  the 
  Paul 
  box 
  — 
  must 
  have 
  been 
  very 
  

   small, 
  certainly 
  less 
  than 
  1 
  part 
  in 
  10,000. 
  

  

  The 
  floor 
  of 
  the 
  standardizing 
  room 
  at 
  the 
  National 
  Physical 
  

   Laboratory 
  is 
  about 
  four 
  feet 
  below 
  the 
  outer 
  ground-level, 
  and 
  

   the 
  room 
  is 
  maintained 
  at 
  a 
  temperature 
  not 
  less 
  than 
  17° 
  C. 
  

   In 
  the 
  summer 
  months 
  the 
  temperature 
  rises 
  at 
  times 
  to 
  20° 
  C. 
  

   We 
  have 
  no 
  records 
  of 
  the 
  hygrometric 
  state 
  of 
  the 
  air 
  of 
  

   the 
  room 
  over 
  long 
  periods 
  of 
  time, 
  but 
  a 
  series 
  of 
  observations 
  

   has 
  been 
  commenced. 
  

  

  In 
  Table 
  II. 
  the 
  results 
  are 
  given 
  of 
  some 
  measurements 
  

   on 
  manganin 
  coils 
  in 
  a 
  box 
  by 
  Messrs. 
  Nalder 
  Bros. 
  The 
  

   outer 
  case 
  was 
  removed, 
  and 
  a 
  larger 
  one 
  substituted 
  for 
  it. 
  

   In 
  this 
  larger 
  box, 
  water, 
  fused 
  calcium 
  chloride, 
  or 
  phos- 
  

   phoric 
  anhydride 
  could 
  be 
  placed, 
  and 
  the 
  air 
  inside 
  the 
  box 
  

   could 
  be 
  heated 
  by 
  an 
  electric 
  lamp 
  and 
  stirred 
  by 
  a 
  small 
  

   motor-driven 
  fan. 
  The 
  shellaced 
  cylinder, 
  previously 
  referred 
  

   to, 
  was 
  also 
  hung 
  inside 
  the 
  case, 
  and 
  was 
  weighed 
  from 
  

   time 
  to 
  time 
  to 
  roughly 
  determine 
  the 
  hygrometric 
  state 
  of 
  

   the 
  atmosphere. 
  

  

  Table 
  II. 
  

   Observations 
  on 
  Coils 
  in 
  Nalder 
  Box 
  3921. 
  

  

  