﻿200 
  HUBERT 
  M. 
  MORRIS. 
  

  

  In 
  dealing 
  with 
  a 
  turf, 
  it 
  is 
  broken 
  up 
  into 
  small 
  pieces 
  before 
  the 
  water 
  is 
  turned 
  

   on. 
  Material 
  of 
  this 
  kind 
  requires 
  longer 
  to 
  wash 
  than 
  arable 
  soil, 
  and 
  the 
  plants 
  

   require 
  examination 
  after 
  the 
  soil 
  has 
  been 
  removed. 
  

  

  The 
  first 
  sieve, 
  with 
  a 
  mesh 
  3-5 
  mm. 
  in 
  diameter, 
  retains 
  the 
  stones 
  from 
  the 
  

   soil 
  and 
  only 
  very 
  large 
  insects 
  ; 
  the 
  second 
  sieve, 
  with 
  a 
  mesh 
  of 
  1-5 
  mm., 
  retains 
  

   the 
  smaller 
  stones 
  and 
  large 
  insects, 
  and 
  the 
  third, 
  with 
  50 
  meshes 
  to 
  the 
  inch, 
  retains 
  

   the 
  coarse 
  sand 
  and 
  the 
  remaining 
  insects. 
  The 
  residue 
  on 
  each 
  sieve 
  has 
  to 
  be 
  

   examined 
  for 
  insects, 
  that 
  on 
  the 
  first 
  and 
  second 
  being 
  quickly 
  done, 
  as 
  only 
  the 
  

   largest 
  insects 
  would 
  be 
  retained 
  by 
  them. 
  The 
  residue 
  on 
  the 
  third 
  sieve 
  has 
  to 
  

   be 
  very 
  carefully 
  examined, 
  as 
  most 
  of 
  the 
  insects 
  are 
  found 
  in 
  it. 
  This 
  can 
  be 
  done 
  

   by 
  drying 
  the 
  sand 
  and 
  then 
  examining 
  it, 
  or 
  it 
  may 
  be 
  done 
  by 
  taking 
  the 
  sand 
  

   in 
  small 
  portions 
  in 
  a 
  basin 
  of 
  water. 
  As 
  the 
  clay 
  has 
  all 
  been 
  washed 
  away, 
  the 
  

   water 
  is 
  quite 
  clear 
  in 
  a 
  few 
  seconds, 
  and 
  many 
  of 
  the 
  insects, 
  such 
  as 
  Collembola 
  

   and 
  most 
  adult 
  forms, 
  float 
  on 
  the 
  surface, 
  while 
  those 
  that 
  sink 
  can 
  be 
  readily 
  

   seen, 
  as 
  they 
  tend 
  to 
  lie 
  on 
  the 
  surface 
  of 
  the 
  sand 
  at 
  the 
  bottom 
  of 
  the 
  basin. 
  

  

  The 
  sieves 
  were 
  made 
  of 
  the 
  sizes 
  given 
  above 
  in 
  order 
  to 
  wash 
  about 
  121b. 
  of 
  

   soil 
  at 
  a 
  time, 
  but 
  up 
  to 
  14 
  or 
  15 
  lb. 
  of 
  soil 
  could 
  be 
  dealt 
  with 
  by 
  these 
  sieves. 
  It 
  

   is 
  found 
  with 
  Rothamsted 
  soil 
  that 
  the 
  water 
  has 
  to 
  run 
  for 
  about 
  40 
  minutes 
  to 
  

   remove 
  all 
  the 
  clay 
  from 
  this 
  quantity 
  of 
  soil, 
  the 
  washing 
  being 
  much 
  accelerated 
  

   by 
  occasional 
  stirring. 
  

  

  It 
  was 
  considered 
  advisable 
  to 
  have 
  three 
  sieves 
  in 
  the 
  present 
  instance 
  owing 
  to 
  

   the 
  large 
  number 
  of 
  stones 
  in 
  the 
  soil 
  of 
  this 
  district, 
  but 
  in 
  a 
  less 
  stony 
  district 
  the 
  

   upper 
  sieve 
  might 
  possibly 
  be 
  dispensed 
  with, 
  or 
  one 
  with 
  perforations 
  of 
  intermediate 
  

   diameter 
  might 
  be 
  substituted 
  for 
  the 
  upper 
  two. 
  Gauze 
  with 
  50 
  meshes 
  to 
  the 
  inch 
  

   was 
  considered 
  most 
  suitable 
  for 
  the 
  lowest 
  sieve, 
  as 
  a 
  finer 
  mesh 
  increases 
  the 
  quantity 
  

   of 
  soil 
  that 
  is 
  retained, 
  while 
  a 
  larger 
  mesh 
  would 
  allow 
  many 
  of 
  the 
  smaller 
  insects 
  

   to 
  be 
  washed 
  away. 
  

  

  Possibly 
  the 
  two 
  lower 
  sieves 
  need 
  not 
  have 
  been 
  quite 
  so 
  deep, 
  but 
  it 
  was 
  con- 
  

   sidered 
  advisable 
  not 
  to 
  run 
  any 
  risk 
  of 
  the 
  water 
  overflowing, 
  as 
  if 
  it 
  did 
  so 
  some 
  

   of 
  the 
  insects 
  might 
  be 
  carried 
  away 
  by 
  it. 
  If 
  the 
  insects 
  are 
  subjected 
  to 
  the 
  washing 
  

   for 
  too 
  long 
  a 
  time 
  it 
  is 
  possible 
  that 
  they 
  would 
  be 
  injured, 
  but 
  after 
  the 
  time 
  

   mentioned 
  above, 
  40 
  minutes, 
  they 
  seem 
  to 
  be 
  little 
  affected. 
  

  

  Various 
  other 
  methods 
  of 
  treating 
  the 
  soil 
  have 
  been 
  tried, 
  in 
  the 
  hope 
  of 
  finding 
  

   a 
  method 
  by 
  which 
  it 
  would 
  be 
  possible 
  to 
  remove 
  the 
  insects 
  completely 
  from 
  the 
  

   soil, 
  but 
  it 
  has 
  not 
  been 
  found 
  possible 
  to 
  do 
  so 
  owing 
  to 
  the 
  variation 
  in 
  size 
  and 
  

   specific 
  gravity 
  of 
  the 
  insects. 
  By 
  the 
  method 
  described 
  above 
  the 
  volume 
  of 
  soil 
  

   requiring 
  careful 
  examination 
  is 
  reduced 
  to 
  a 
  minimum, 
  and 
  as 
  this 
  portion 
  consists 
  

   of 
  clean 
  sand 
  it 
  is 
  much 
  easier 
  to 
  examine 
  than 
  an 
  equal 
  quantity 
  of 
  clayey 
  soil. 
  

  

  The 
  use 
  of 
  liquids 
  of 
  different 
  specific 
  gravities 
  was 
  also 
  considered, 
  but 
  it 
  was 
  

   not 
  thought 
  to 
  be 
  a 
  suitable 
  method, 
  owing 
  to 
  the 
  quantity 
  of 
  the 
  liquid 
  which 
  would 
  

   be 
  required 
  ; 
  its 
  possible 
  injurious 
  effect 
  on 
  larvae, 
  some 
  of 
  which 
  it 
  is 
  desirable 
  to 
  

   obtain 
  alive 
  ; 
  and 
  the 
  variation 
  in 
  the 
  specific 
  gravity 
  of 
  the 
  insects. 
  

  

  