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  be 
  resorted 
  to 
  where 
  occasion 
  offers 
  and 
  the 
  cost 
  is 
  low. 
  The 
  use 
  of 
  

   formahn 
  or 
  potassium 
  cyanide 
  is 
  condemned, 
  for 
  both 
  are 
  said 
  to 
  have 
  

   a 
  bad 
  effect 
  on 
  the 
  plants 
  and, 
  furthermore, 
  the 
  latter 
  substance 
  is 
  

   too 
  deadly 
  a 
  poison 
  to 
  be 
  recommended 
  in 
  any 
  case. 
  Carbon 
  bisulphide 
  

   is 
  a 
  very 
  useful 
  substance 
  [see 
  this 
  Review, 
  Ser. 
  A. 
  ii, 
  p. 
  255]. 
  Potas- 
  

   sium 
  sulphocarbonate 
  is 
  produced 
  commercially 
  in 
  the 
  form 
  of 
  a 
  dark 
  

   red 
  solution 
  containing 
  14 
  to 
  16 
  per 
  cent, 
  of 
  sulphide 
  and 
  18 
  to 
  20 
  per 
  

   cent, 
  potash. 
  Under 
  the 
  action 
  of 
  the 
  carbonic 
  acid 
  contained 
  in 
  

   air 
  and 
  in 
  water 
  this 
  chemical 
  slowly 
  decomposes 
  and 
  resolves 
  itself 
  

   into 
  carbon 
  bisulphide 
  and 
  sulphuretted 
  hydrogen 
  — 
  both 
  of 
  which 
  

   gases 
  are 
  insecticides 
  — 
  and 
  a 
  residue, 
  potassium 
  carbonate, 
  which 
  is 
  

   a 
  useful 
  manure 
  

  

  Some 
  years 
  ago 
  about 
  20,000 
  acres 
  of 
  vineyards 
  were 
  treated 
  with 
  

   potassium 
  sulphocarbonate. 
  Its 
  cost 
  prevented 
  more 
  extensive 
  use, 
  

   for 
  much 
  labour 
  was 
  required 
  and 
  a 
  huge 
  quantity 
  of 
  water 
  had 
  to 
  

   be 
  transported 
  to 
  the 
  vineyards 
  in 
  order 
  to 
  saturate 
  the 
  soil 
  infested 
  

   by 
  Phylloxera. 
  This 
  question 
  of 
  cost 
  is 
  of 
  less 
  importance 
  in 
  horti- 
  

   culture. 
  As 
  this 
  chemical 
  killed 
  Phylloxera, 
  which 
  is 
  so 
  refractory 
  to 
  

   control, 
  it 
  is 
  surprising 
  that 
  its 
  use 
  has 
  not 
  become 
  general 
  in 
  deahng 
  

   with 
  pests 
  usually 
  found 
  in 
  the 
  soil. 
  Of 
  its 
  value 
  as 
  an 
  insecticide 
  

   there 
  can 
  be 
  no 
  doubt 
  at 
  all. 
  The 
  author 
  made 
  the 
  following 
  test 
  

   personally 
  : 
  1 
  part 
  of 
  the 
  commercial 
  solution 
  was 
  diluted 
  in 
  100 
  parts 
  

   of 
  water, 
  both 
  by 
  volume, 
  and 
  the 
  liquid 
  was 
  poured 
  from 
  a 
  watering 
  

   can 
  in 
  such 
  quantity 
  as 
  to 
  ensure 
  adequate 
  penetration. 
  In 
  the 
  case 
  

   of 
  tuhps, 
  the 
  watering 
  can 
  was 
  fitted 
  with 
  its 
  rose, 
  but 
  this 
  was 
  removed 
  

   when 
  treating 
  carnations, 
  as 
  the 
  stream 
  of 
  liquid 
  had 
  to 
  hit 
  the 
  soil 
  

   exactly 
  at 
  the 
  point 
  where 
  the 
  stems 
  emerged. 
  Slugs, 
  cut 
  worms, 
  

   earth 
  worms, 
  white 
  grubs, 
  Longicorn 
  larvae, 
  and 
  millipedes 
  were 
  

   speedily 
  killed. 
  When 
  digging 
  out 
  the 
  tuhps 
  a 
  fortnight 
  later, 
  a 
  large 
  

   number 
  of 
  slugs 
  were 
  found 
  dead, 
  thus 
  conclusively 
  proving 
  the 
  

   efficacy 
  of 
  the 
  treatment. 
  Potassium 
  sulphocarbonate 
  has 
  the 
  

   advantage 
  over 
  carbon 
  bisulphide 
  that 
  it 
  acts 
  more 
  slowly 
  and 
  for 
  a 
  

   longer 
  time, 
  and 
  that 
  it 
  entirely 
  impregnates 
  the 
  mass 
  of 
  soil 
  on 
  which 
  

   it 
  is 
  poured. 
  Those 
  insects 
  which 
  are 
  buried 
  deep 
  enough 
  cannot 
  

   escape 
  to 
  the 
  surface, 
  while 
  those 
  which 
  can 
  escape 
  to 
  the 
  surface 
  are 
  

   easily 
  killed. 
  Any 
  soil 
  may 
  be 
  treated, 
  the 
  quantity 
  of 
  hquid 
  being 
  

   suitably 
  varied, 
  and 
  appHcation 
  is 
  very 
  easy. 
  Tuhps 
  and 
  carnations 
  

   are 
  not 
  affected 
  by 
  a 
  1 
  per 
  cent, 
  solution, 
  even 
  2 
  per 
  cent, 
  may 
  be 
  

   used 
  ; 
  only 
  when 
  a 
  5 
  per 
  cent, 
  solution 
  is 
  employed 
  do 
  carnations 
  

   begin 
  to 
  suffer. 
  There 
  is 
  no 
  object 
  in 
  increasing 
  the 
  strength 
  beyond 
  

   2 
  per 
  cent. 
  Flowers 
  are 
  not 
  injured 
  if 
  the 
  Uquid 
  is 
  spilled 
  on 
  them. 
  

   The 
  only 
  essential 
  condition 
  is 
  to 
  saturate 
  the 
  soil 
  right 
  through 
  to 
  

   the 
  depth 
  of 
  the 
  pests 
  buried 
  deepest. 
  Soimdings 
  are 
  necessary 
  to 
  

   acquire 
  certainty 
  on 
  this 
  vital 
  point. 
  Where 
  boxes 
  are 
  used, 
  planting 
  

   may 
  be 
  done 
  after 
  the 
  earth 
  contained 
  in 
  them 
  has 
  had 
  time 
  to 
  dry 
  

   after 
  disinfection. 
  Potassium 
  sulphocarbonate 
  solution 
  costs 
  about 
  

   325. 
  per 
  cwt. 
  and 
  has 
  a 
  specific 
  gravity 
  of 
  about 
  1*200. 
  Its 
  cost 
  is, 
  

   therefore, 
  not 
  very 
  high 
  and 
  the 
  manurial 
  value 
  of 
  the 
  potassium 
  

   carbonate 
  might 
  also 
  be 
  deducted. 
  Lastly 
  it 
  is 
  one 
  of 
  the 
  rare 
  insecti- 
  

   cides 
  which 
  are 
  not 
  extremely 
  poisonous, 
  while 
  the 
  products 
  of 
  its 
  

   decomposition 
  are 
  harmless. 
  

  

  