PRODUCTION  OF  NITRE  IN  INDIA. 
437 
nitre  was  formed.  These  changes  only  occur  in  the  neighbor- 
hood of  villages;  or  densely  populated  localities,  but  the  process 
of  artificial  generation  of  saltpetre  had  been  successfully  carried 
out  in  connection  with  the  Indian  jails.  The  author  adds  a 
speculation  as  to  the  influence  of  electrical  agencies  (thunder- 
storms) in  contributing  towards  a  more  rapid  formation  of  salt- 
petre. 
The  President,  in  proposing  a  vote  of  thanks  to  Dr.  Palmer, 
invited  discussion  upon  the  electrical  theory  of  the  generation  of 
nitric  acid  ;  whether,  all  other  circumstances  being  the  same, 
most  nitre  should  be  formed  during  the  season  in  which  thunder- 
storms were  prevalent. 
Mr.  W.  H.  Perkin  expressed  his  surprise  in  noticing  how  few 
sparks  from  a  RiihmkorfF  coil  sufficed  to  produce  red  fumes  in  a 
jar  of  air,  especially  if  the  temperature  was  somewhat  raised, 
and  the  indigo  test  at  once  showed  the  presence  of  nitric  acid. 
Mr.  David  Forbes  had  had  opportunities  of  studying  the  salt- 
petre manufacture  in  several  parts  of  the  world.  In  order  to 
ensure  a  supply  of  saltpetre  in  case  of  war,  in  Sweden,  every 
peasant  was  bound  to  supply  a  certain  amount  of  nitre  to  the 
Government,  as  part  payment  of  the  taxes.  It  was  the  practice 
to  rely  upon  wood  ashes  from  the  household  fires  as  the  source  of 
potash,  the  other  ingredients  being  nearly  the  same  as  in  India, 
with  lime  added  where  it  did  not  occur  naturally.  In  the  cold 
climate  of  that  northern  latitude  there  was  no  suspicion  of  light- 
ning having  any  direct  influence  upon  the  generation  of  nitric 
acid.  Spain  formerly  got  much  saltpetre  from  the  plains  of  the 
south,  where  nitrogenous  organic  matter  was  somewhat  scarce, 
but  potash  abundant,  as  the  result  of  the  decomposition  of  the 
felspar  of  the  granites.  In  Peru,  Chili,  and  other  parts  of  the 
continent  of  South  America,  where  rain  never  falls,  immense 
accumulations  of  nitrate  of  soda  were  known  to  exist ;  in  fact,  it 
appeared  only  necessary  to  place  organic  matter  in  contact  with 
carbonate  of  lime  and  common  salt  to  secure  the  production  of 
the  nitrate  of  soda  or  Chilian  saltpetre  in  that  climate,  and  in 
these  districts  all  the  wells  were  so  fully  charged  with  saline 
matter,  that  it  was  necessary  to  procure  water  distilled  from  the 
sea  with  English  coal,  at  the  cost  of  £3  or  c£4  per  ton,  for  ordi- 
