﻿234 
  GEOLOGY. 
  

  

  tlie 
  aiDplication 
  of 
  barnyard 
  manure, 
  at 
  a 
  cost 
  of 
  two 
  

   hundred 
  dollars. 
  

  

  A 
  marl 
  is 
  mentioned 
  by 
  Professor 
  Kogers, 
  as 
  contain- 
  

   ing 
  less 
  than 
  sixty 
  per 
  cent, 
  of 
  green-sand, 
  which 
  had 
  

   the 
  disadvantage 
  of 
  a 
  slight 
  impregnation 
  of 
  sulphate 
  of 
  

   iron 
  or 
  copperas, 
  and 
  he 
  states 
  that 
  the 
  privilege 
  of 
  

   digging 
  it 
  at 
  the 
  pits 
  sold 
  readily 
  at 
  thirty-seven 
  and 
  a 
  

   half 
  cents 
  per 
  load. 
  It 
  was 
  largely 
  transported 
  in 
  

   wagons 
  to 
  a 
  distance 
  of 
  twenty 
  miles, 
  and 
  retailed 
  at 
  the 
  

   rate 
  of 
  ten 
  cents 
  or 
  more 
  per 
  bushel. 
  

  

  In 
  respect 
  to 
  calcareous 
  marls, 
  they 
  generally 
  require 
  

   some 
  time, 
  after 
  their 
  application 
  to 
  land, 
  to 
  become 
  

   effectual; 
  they 
  are 
  best 
  spread 
  on 
  the 
  surface 
  before 
  

   winter, 
  leaving 
  them 
  to 
  be 
  acted 
  upon 
  by 
  the 
  rain, 
  frost, 
  

   and 
  air, 
  before 
  ploughing 
  in. 
  They 
  are 
  most 
  advan- 
  

   tageously 
  applied 
  to 
  land 
  when 
  in 
  grass, 
  and 
  are 
  im- 
  

   proved 
  by 
  repeated 
  harrowing 
  and 
  rolling. 
  

  

  They 
  should 
  be 
  applied 
  cautiously 
  to 
  clay 
  lands. 
  

   Sandy 
  lands 
  will 
  bear 
  a 
  larger 
  quantity. 
  

  

  Some 
  consider 
  that 
  the 
  best 
  mode 
  of 
  using 
  marls 
  is 
  to 
  

   form 
  a 
  compost 
  of 
  it 
  with 
  alternate 
  layers 
  of 
  stable- 
  

   manure, 
  or 
  of 
  marsh 
  muck, 
  peat, 
  or 
  other 
  vegetable 
  

   matter. 
  

  

  In 
  the 
  application 
  of 
  marls, 
  it 
  is 
  important 
  to 
  avoid 
  

   those 
  containing 
  any 
  astringent 
  matter. 
  Such 
  are 
  se- 
  

   riously 
  detrimental 
  to 
  the 
  soil, 
  and 
  noxious 
  to 
  all 
  vege- 
  

   tation. 
  

  

  This 
  pernicious 
  property 
  may 
  be 
  distinguished 
  by 
  an 
  

   acrid, 
  inky 
  taste, 
  and 
  by 
  a 
  white 
  efiioresence 
  resembling 
  

   frost 
  which 
  often 
  overspreads 
  the 
  marl 
  in 
  dry 
  weather 
  

   when 
  exposed 
  for 
  some 
  time 
  to 
  the 
  atmosphere 
  ; 
  this 
  is 
  

   generally 
  sulphate 
  of 
  iron, 
  derived 
  from 
  the 
  decomposi- 
  

   tion 
  of 
  pyrites 
  in 
  the 
  associated 
  clays. 
  

  

  The 
  intermixture 
  of 
  this 
  deleterious 
  ino;redient 
  in 
  the 
  

  

  