﻿158 
  Mr. 
  Rollo 
  Appleyard 
  on 
  the 
  Failure 
  of 
  

  

  prove 
  that 
  paraffin-wax 
  is 
  an 
  absorbent 
  of 
  moisture, 
  and 
  con- 
  

   sequently 
  useless 
  for 
  purposes 
  of 
  protection 
  against 
  climate 
  ; 
  

   but 
  I 
  have 
  no 
  evidence 
  that 
  it 
  is 
  aggressively 
  harmful 
  to 
  the 
  

   wires. 
  Chemists 
  have 
  variously 
  attributed 
  the 
  failure 
  to 
  the 
  

   presence 
  of 
  zinc, 
  copper, 
  antimony, 
  arsenic, 
  sulphur, 
  phos- 
  

   phorus, 
  and 
  tungsten 
  in 
  the 
  wires: 
  the 
  chemistry 
  of 
  the 
  

   question 
  must 
  therefore 
  be 
  regarded 
  as 
  sub 
  judice. 
  

  

  Tropical 
  heat 
  and 
  moisture 
  accelerate 
  failure, 
  but 
  not 
  in 
  all 
  

   cases. 
  Moisture 
  has 
  been 
  proved 
  by 
  Brereton 
  Baker 
  to 
  be 
  

   essential 
  to 
  certain 
  chemical 
  combinations; 
  and 
  there 
  is 
  

   evidence 
  enough 
  in 
  what 
  follows 
  that 
  the 
  same 
  agency 
  is 
  

   effective 
  in 
  bringing 
  about 
  changes 
  in 
  the 
  constitution 
  of 
  

   alloys. 
  The 
  deteriorating 
  effect 
  of 
  heat 
  and 
  moisture 
  is 
  not 
  

   limited 
  to 
  mixed 
  metals 
  ; 
  for 
  I 
  have 
  recently 
  examined 
  a 
  large 
  

   tube 
  made 
  of 
  electrolytic 
  copper 
  which, 
  under 
  the 
  influence 
  

   of 
  steam, 
  quickly 
  became 
  very 
  seriously 
  " 
  pitted." 
  Another 
  

   tube, 
  of 
  the 
  same 
  electrolytic 
  copper, 
  became 
  similarly 
  "pitted" 
  

   when 
  used 
  for 
  conveying 
  sea-water. 
  When 
  these 
  were 
  replaced 
  

   by 
  tubes 
  of 
  ordinary 
  copper, 
  there 
  was 
  no 
  further 
  trouble. 
  

  

  During 
  the 
  past 
  six 
  years 
  some 
  very 
  remarkable 
  instances 
  

   of 
  the 
  failure 
  of 
  alloys 
  have 
  come 
  to 
  my 
  notice, 
  particularly 
  

   with 
  regard 
  to 
  wires 
  of 
  german-silver 
  and 
  platinoid 
  used 
  in 
  

   the 
  construction 
  of 
  resistance-coils. 
  Specimens 
  of 
  these 
  wires, 
  

   insulated 
  with 
  white 
  silk, 
  were 
  submitted 
  to 
  various 
  conditions 
  

   of 
  climate 
  ; 
  they 
  were 
  sent 
  respectively 
  to 
  India, 
  Brazil, 
  Chile, 
  

   Peru, 
  Ecuador, 
  Nicaragua, 
  Mexico, 
  and 
  Texas. 
  For 
  com- 
  

   parison 
  and 
  reference, 
  similar 
  wires 
  were 
  in 
  some 
  instances 
  

   kept 
  in 
  England. 
  Several 
  thousands 
  of 
  bobbins 
  were 
  thus 
  

   distributed 
  in 
  widely 
  different 
  latitudes, 
  i. 
  e., 
  to 
  Valparaiso, 
  

   Iquique, 
  Chorillos, 
  Santa 
  Elena, 
  Panama, 
  San 
  Juan 
  del 
  Sur, 
  

   Salina 
  Cruz, 
  Coatzacoalcos, 
  Vera 
  Cruz, 
  Galveston, 
  Per- 
  

   nambuco, 
  Bahia, 
  Rio 
  Janeiro, 
  Monte 
  Video, 
  and 
  Calcutta. 
  

  

  A 
  few 
  years 
  after 
  this 
  distribution 
  faulty 
  bobbins 
  were 
  

   reported 
  from 
  San 
  Juan 
  del 
  Sur, 
  Santa 
  Elena, 
  Panama, 
  

   Vera 
  Cruz, 
  Bahia, 
  and 
  Calcutta. 
  These 
  six 
  towns 
  all 
  lie 
  on 
  

   or 
  near 
  sea-coasts, 
  and 
  they 
  are 
  nearly 
  on 
  the 
  same 
  terrestrial 
  

   isotherm, 
  i. 
  e. 
  the 
  isotherm 
  including 
  the 
  area 
  of 
  high 
  ter- 
  

   restrial 
  mean 
  temperature. 
  25° 
  C. 
  

  

  In 
  all 
  cases 
  of 
  failure 
  the 
  alloy 
  had 
  become 
  brittle 
  and 
  the 
  

   wires 
  had 
  broken, 
  not 
  only 
  at 
  the 
  outer 
  layers, 
  but 
  also 
  within 
  

   the 
  coils. 
  The 
  following 
  is 
  a 
  short 
  history 
  of 
  the 
  wires 
  that 
  

   failed 
  : 
  — 
  

  

  (1) 
  In 
  April 
  1891 
  some 
  german-silver 
  wire, 
  16 
  mils 
  dia- 
  

   meter, 
  doubly 
  covered 
  with 
  silk, 
  was 
  wound 
  on 
  small 
  boxwood 
  

   bobbins 
  and 
  then 
  treated 
  with 
  paraffin-wax. 
  Each 
  bobbin 
  

   was 
  afterwards 
  lapped 
  with 
  a 
  strip 
  of 
  leather. 
  They 
  were 
  all 
  

  

  