﻿219 
  

  

  them 
  to 
  reduced 
  pressure 
  some 
  of 
  the 
  insects 
  were 
  introduced 
  into 
  the 
  

   vacuum 
  at 
  the 
  top 
  of 
  a 
  mercury 
  barometer, 
  but 
  half 
  an 
  hour 
  under 
  these 
  

   conditions 
  had 
  no 
  effect. 
  

  

  The 
  chemical 
  methods 
  tried 
  were 
  chiefly 
  based 
  on 
  the 
  poisonous 
  

   effects 
  of 
  various 
  gases. 
  Carbon 
  bisulphide 
  vaporised 
  at 
  the 
  rate 
  of 
  

   1 
  c.c. 
  of 
  the 
  fluid 
  to 
  each 
  litre 
  of 
  the 
  seed 
  gave 
  perfect 
  results 
  at 
  the 
  end 
  

   of 
  half 
  an 
  hour. 
  Three 
  methods 
  were 
  used, 
  the 
  fluid 
  carbon 
  bisulphide 
  

   being 
  sprayed 
  on 
  the 
  cotton 
  seed 
  whilst 
  passing 
  into 
  the 
  container 
  ; 
  

   the 
  carbon 
  bisulphide 
  introduced 
  into 
  the 
  container 
  before 
  filling 
  with 
  

   seed 
  ; 
  and 
  the 
  carbon 
  bisulphide 
  vapour 
  circulated 
  through 
  an 
  evapor- 
  

   ating 
  chamber 
  into 
  the 
  container 
  through 
  an 
  air-pump 
  and 
  back 
  

   through 
  the 
  evaporating 
  chamber 
  to 
  the 
  container. 
  The 
  last 
  method 
  

   is 
  the 
  best, 
  but 
  the 
  last 
  two 
  both 
  gave 
  perfect 
  results. 
  A 
  machine 
  to 
  

   utilise 
  the 
  last 
  method 
  could 
  be 
  constructed 
  on 
  the 
  following 
  general 
  

   lines 
  : 
  — 
  Five 
  or 
  six 
  vats 
  to 
  contain 
  the 
  seeds 
  to 
  be 
  treated 
  form 
  the 
  

   " 
  battery." 
  These 
  vats 
  must 
  be 
  constructed 
  so 
  that 
  they 
  can 
  be 
  

   hermetically 
  closed 
  when 
  charged. 
  Arrangements 
  must 
  be 
  made 
  to 
  

   pump 
  the 
  gases 
  in 
  below, 
  and 
  a 
  diffuser 
  would 
  be 
  required 
  at 
  the 
  top 
  

   to 
  draw 
  off 
  the 
  gases. 
  The 
  circulating 
  system 
  would 
  consist 
  of 
  an 
  

   exhaust 
  main 
  and 
  a 
  blast 
  main 
  connected 
  by 
  a 
  rotary 
  or 
  turbine 
  air- 
  

   pump. 
  From 
  these 
  mains, 
  branches 
  would 
  be 
  given 
  off 
  to 
  each 
  of 
  

   the 
  vats. 
  This 
  would 
  enable 
  a 
  constant 
  current 
  of 
  air 
  or 
  gas 
  to 
  be 
  run 
  

   through 
  any 
  or 
  all 
  of 
  the 
  vats, 
  since 
  each 
  branch 
  would 
  be 
  arranged 
  

   so 
  that 
  it 
  could 
  be 
  cut 
  off 
  from 
  the 
  main 
  by 
  a 
  tap. 
  In 
  practice 
  one 
  

   vat 
  would 
  be 
  filling 
  with 
  seed, 
  the 
  following 
  filHng 
  with 
  gas, 
  the 
  next 
  

   two 
  would 
  be 
  standing 
  to 
  let 
  the 
  gas 
  act, 
  the 
  fifth 
  would 
  be 
  discharging 
  

   gas 
  and 
  the 
  sixth 
  discharging 
  seed. 
  By 
  this 
  method 
  the 
  charges 
  of 
  

   carbon 
  bisulphide 
  required 
  when 
  the 
  machine 
  is 
  going 
  will 
  be 
  consider- 
  

   ably 
  reduced, 
  and 
  the 
  advantage 
  of 
  having 
  two 
  vats 
  " 
  standing 
  " 
  full 
  

   of 
  gas 
  is 
  that 
  the 
  period 
  of 
  action 
  for 
  the 
  gas 
  is 
  thereby 
  doubled. 
  

   Carbon 
  bisulphide 
  vapour 
  has 
  no 
  effect 
  on 
  the 
  germination 
  of 
  cotton 
  

   seed. 
  As 
  the 
  time 
  proposed 
  for 
  action 
  of 
  the 
  gas 
  is 
  not 
  more 
  than 
  one 
  

   hour, 
  no 
  fear 
  need 
  be 
  entertained 
  of 
  deterioration 
  of 
  the 
  seed. 
  Motor 
  

   spirit 
  was 
  tried 
  and 
  although 
  used 
  in 
  larger 
  quantities 
  was 
  less 
  effec- 
  

   tive 
  than 
  carbon 
  bisulphide. 
  Ammonia 
  was 
  unsatisfactory, 
  especially 
  

   as 
  germination 
  appeared 
  to 
  suffer. 
  Hydrocyanic 
  acid 
  gas, 
  even 
  in 
  

   very 
  small 
  doses, 
  kills 
  a 
  very 
  high 
  percentage 
  of 
  larvae, 
  but 
  requires 
  a 
  

   longer 
  time 
  to 
  act 
  than 
  carbon 
  bisulphide. 
  The 
  expense 
  for 
  chemicals 
  

   however, 
  would 
  be 
  less. 
  The 
  use 
  of 
  sulphur 
  dioxide 
  produced 
  by 
  a 
  

   " 
  Clayton 
  machine 
  " 
  gave 
  distinctly 
  promising 
  results, 
  but 
  they 
  

   cannot 
  be 
  compared 
  vnth 
  the 
  results 
  of 
  other 
  experiments, 
  owing 
  to 
  

   the 
  impossibility 
  of 
  using 
  the 
  machine 
  for 
  small 
  scale 
  trials. 
  Tobacco 
  

   smoke 
  and 
  vaporised 
  Cyllin 
  were 
  ineffective, 
  although 
  Cyllin 
  in 
  solu- 
  

   tions 
  of 
  1 
  : 
  1,000 
  were 
  all 
  that 
  could 
  be 
  desired, 
  if 
  the 
  seed 
  containing 
  

   the 
  larvae 
  were 
  soaked 
  for 
  a 
  period 
  of 
  twenty- 
  four 
  hours. 
  " 
  Salva- 
  

   torine 
  " 
  in 
  dilution 
  of 
  1 
  : 
  1,000 
  was 
  effective 
  in 
  kilHng 
  the 
  caterpillars, 
  

   but 
  affected 
  germination 
  also. 
  It 
  has 
  been 
  found 
  that 
  no 
  treatment 
  

   is 
  possible 
  when 
  the 
  seed 
  is 
  in 
  sacks, 
  and 
  in 
  order 
  that 
  such 
  treatments 
  

   as 
  are 
  mentioned 
  above 
  may 
  be 
  effective, 
  rigorous 
  measures 
  should 
  be 
  

   adopted 
  to 
  destroy 
  all 
  cotton 
  bolls 
  left 
  on 
  the 
  cotton 
  sticks 
  after 
  the 
  

   last 
  picking. 
  

  

  (C26) 
  B2 
  

  

  