earth　as　food　instead　of　leaves；　and　when　they　are　making　deep
  burrows。　　This　is　rendered　almost　certain　by　the　following　weights
  of　the　castings　thrown　up　at　the　mouths　of　single　burrows；　the
  whole　of　which　appeared　to　have　been　ejected　within　no　long　time；
  as　was　certainly　the　case　in　several　instances。　　The　castings　were
  dried　（excepting　in　one　specified　instance）　by　exposure　during　many
  days　to　the　sun　or　before　a　hot　fire。
  WEIGHT　OF　THE　CASTINGS　ACCUMULATED　AT　THE　MOUTH　OF　A　SINGLE　BURROW。
  （Weight　in　ounces　given　in　parenthesisDP。）
  （1。）　　Down；　Kent　（sub…soil　red　clay；　full　of　flints；　over…lying　the
  chalk）。　　The　largest　casting　which　I　could　find　on　the　flanks　of　a
  steep　valley；　the　sub…soil　being　here　shallow。　　In　this　one　case；
  the　casting　was　not　well　dried　（3。98）
  （2。）　　Down。Largest　casting　which　I　could　find　（consisting　chiefly
  of　calcareous　matter）；　on　extremely　poor　pasture　land　at　the　bottom
  of　the　valley　mentioned　under　（1。）　（3。87）
  （3。）　　Down。A　large　casting；　but　not　of　unusual　size；　from　a
  nearly　level　field；　poor　pasture；　laid　down　in　a　grass　about　35
  years　before　（1。22）
  （4。）　　Down。　　Average　weight　of　11　not　large　castings　ejected　on　a
  sloping　surface　on　my　lawn；　after　they　had　suffered　some　loss　of
  weight　from　being　exposed　during　a　considerable　length　of　time　to
  rain　（0。7）
  （5。）　　Near　Nice　in　France。Average　weight　of　12　castings　of
  ordinary　dimensions；　collected　by　Dr。　King　on　land　which　had　not
  been　mown　for　a　long　time　and　where　worms　abounded；　viz。；　a　lawn
  protected　by　shrubberies　near　the　sea；　soil　sandy　and　calcareous；
  these　castings　had　been　exposed　for　some　time　to　rain；　before　being
  collected；　and　must　have　lost　some　weight　by　disintegration；　but
  they　still　retained　their　form　（1。37）
  （6。）　　The　heaviest　of　the　above　twelve　castings　（1。76）
  （7。）　　　Lower　Bengal。Average　weight　of　22　castings；　collected　by
  Mr。　J。　Scott；　and　stated　by　him　to　have　been　thrown　up　in　the
  course　of　one　or　two　nights　（1。24）
  （8。）　　The　heaviest　of　the　above　22　castings　（2。09）
  （9。）　　Nilgiri　Mountains；　S。　India；　average　weight　of　the　5　largest
  castings　collected　by　Dr。　King。　　They　had　been　exposed　to　the　rain
  of　the　last　monsoon；　and　must　have　lost　some　weight　（3。15）
  （10。）　　The　heaviest　of　the　above　5　castings　（4。34）
  In　this　table　we　see　that　castings　which　had　been　ejected　at　the
  mouth　of　the　same　burrow；　and　which　in　most　cases　appeared　fresh
  and　always　retained　their　vermiform　configuration；　generally
  exceeded　an　ounce　in　weight　after　being　dried；　and　sometimes　nearly
  equalled　a　quarter　of　a　pound。　　On　the　Nilgiri　mountains　one
  casting　even　exceeded　this　latter　weight。　　The　largest　castings　in
  England　were　found　on　extremely　poor　pasture…land；　and　these；　as
  far　as　I　have　seen；　are　generally　larger　than　those　on　land
  producing　a　rich　vegetation。　　It　would　appear　that　worms　have　to
  swallow　a　greater　amount　of　earth　on　poor　than　on　rich　land；　in
  order　to　obtain　sufficient　nutriment。
  With　respect　to　the　tower…like　castings　near　Nice　（Nos。　5　and　6　in
  the　above　table）；　Dr。　King　often　found　five　or　six　of　them　on　a
  square　foot　of　surface；　and　these；　judging　from　their　average
  weight；　would　have　weighed　together　7。5　ounces；　so　that　the　weight
  of　those　on　a　square　yard　would　have　been　4　lb。　3。5　oz。　　Dr。　King
  collected；　near　the　close　of　the　year　1872；　all　the　castings　which
  still　retained　their　vermiform　shape；　whether　broken　down　or　not；
  from　a　square　foot；　in　a　place　abounding　with　worms；　on　the　summit
  of　a　bank；　where　no　castings　could　have　rolled　down　from　above。
  These　castings　must　have　been　ejected；　as　he　judged　from　their
  appearance　in　reference　to　the　rainy　and　dry　periods　near　Nice；
  within　the　previous　five　or　six　months；　they　weighed　9。5　oz。；　or　5
  lb。　5。5　oz。　per　square　yard。　　After　an　interval　of　four　months；　Dr。
  King　collected　all　the　castings　subsequently　ejected　on　the　same
  square　foot　of　surface；　and　they　weighed　2。5　oz。；　or　1　lb。　6。5　oz。
  per　square　yard。　　Therefore　within　about　ten　months；　or　we　will　say
  for　safety's　sake　within　a　year；　12　oz。　of　castings　were　thrown　up
  on　this　one　square　foot；　or　6。75　pounds　on　the　square　yard；　and
  this　would　give　14。58　tons　per　acre。
  In　a　field　at　the　bottom　of　a　valley　in　the　chalk　（see　No。　2　in　the
  foregoing　table）；　a　square　yard　was　measured　at　a　spot　where　very
  large　castings　abounded；　they　appeared；　however；　almost　equally
  numerous　in　a　few　other　places。　　These　castings；　which　retained
  perfectly　their　vermiform　shape；　were　collected；　and　they　weighed
  when　partially　dried；　1　lb。　13。5　oz。　　This　field　had　been　rolled
  with　a　heavy　agricultural　roller　fifty…two　days　before；　and　this
  would　certainly　have　flattened　every　single　casting　on　the　land。
  The　weather　had　been　very　dry　for　two　or　three　weeks　before　the　day
  of　collection；　so　that　not　one　casting　appeared　fresh　or　had　been
  recently　ejected。　　We　may　therefore　assume　that　those　which　were
  weighed　had　been　ejected　within；　we　will　say；　forty　days　from　the
  time　when　the　field　was　rolled；that　is；　twelve　days　short　of　the
  whole　intervening　period。　　I　had　examined　the　same　part　of　the
  field　shortly　before　it　was　rolled；　and　it　then　abounded　with　fresh
  castings。　　Worms　do　not　work　in　dry　weather　during　the　summer；　or
  in　winter　during　severe　frosts。　　If　we　assume　that　they　work　for
  only　half　the　yearthough　this　is　too　low　an　estimatethen　the
  worms　in　this　field　would　eject　during　the　year；　8。387　pounds　per
  square　yard；　or　18。12　tons　per　acre；　assuming　the　whole　surface　to
  be　equally　productive　in　castings。
  In　the　foregoing　cases　some　of　the　necessary　data　had　to　be
  estimated；　but　in　the　two　following　cases　the　results　are　much　more
  trustworthy。　　A　lady；　on　whose　accuracy　I　can　implicitly　rely；
  offered　to　collect　during　a　year　all　the　castings　thrown　up　on　two
  separate　square　yards；　near　Leith　Hill　Place；　in　Surrey。　　The
  amount　collected　was；　however；　somewhat　less　than　that　originally
  ejected　by　the　worms；　for；　as　I　have　repeatedly　observed；　a　good
  deal　of　the　finest　earth　is　washed　away；　whenever　castings　are
  thrown　up　during　or　shortly　before　heavy　rain。　　Small　portions　also
  adhered　to　the　surrounding　blades　of　grass；　and　it　required　too
  much　time　to　detach　every　one　of　them。
  On　sandy　soil；　as　in　the　present　instance；　castings　are　liable　to
  crumble　after　dry　weather；　and　particles　were　thus　often　lost。　　The
  lady　also　occasionally　left　home　for　a　week　or　two；　and　at　such
  times　the　castings　must　have　suffered　still　greater　loss　from
  exposure　to　the　weather。　　These　losses　were；　however；　compensated
  to　some　extent　by　the　collections　having　been　made　on　one　of　the
  squares　for　four　days；　and　on　the　other　square　for　two　days　more
  than　the　year。
  A　space　was　selected　（October　9th；　1870）　for　one　of　the　squares　on
  a　broad；　grass…covered　terrace；　which　had　been　mowed　and　swept
  during　many　years。　　It　faced　the　south；　but　was　shaded　during　part
  of　the　day　by　trees。　　It　had　been　formed　at　least　a　century　ago　by
  a　great　accumulation　of　small　and　large　fragments　of　sandstone；
  together　with　some　sandy　earth；　rammed　down　level。　　It　is　probable
  that　it　was　at　first　protected　by　being　covered　with　turf。　　This
  terrace；　judging　from　the　number　of　castings　on　it；　was　rather
  unfavourable　for　the　existence　of　worms；　in　comparison　with　the
  neighbouring　fields　and　an　upper　terrace。　　It　was　indeed　surprising
  that　as　many　worms　could　live　here　as　were　seen；　for　on　digging　a
  hole　in　this　terrace；　the　black　vegetable　mould　together　with　the
  turf　was　only　four　inches　in　thickness；　beneath　which　lay　the　level
  surface　of　light…coloured　sandy　soil；　with　many　fragments　of
  sandstone。　　Before　any　castings　were　collected　all　the　previously
  existing　ones　were　carefully　removed。　　The　last　day's　collection
  was　on　October　14th；　1871。　　The　castings　were　then　well　dried
  before　a　fire；　and　they　weighed　exactly　3。5　lbs。　　This　would　give
  for　an　acre　of　similar　land　7。56　tons　of　dry　earth　annually　ejected
  by　worms。
  The　second　square　was　marked　on　unenclosed　common　land；　at　a　height
  of　about　700　ft。　above　the　sea；　at　some　little　distance　from　Leith
  Hill　Tower。　　The　surface　was　clothed　with　short；　fine　turf；　and　had
  never　been　disturbed　by　the　hand　of　man。　　The　spot　selected
  appeared　neither　particularly　favourable　nor　the　reverse　for　worms；
  but　I　have　often　noticed　that　castings　are　especially　abundant　on
  common　land；　and　this　may；　perhaps；　be　attributed　to　the　poorness
  of　the　soil。　　The　vegetable　mould　was　here　between　three　and　four
  inches　in　thickness。　　As　this　spot　was　at　some　distance　from　the
  house　where　the　lady　lived；　the　castings　were　not　collected　at　such
  short　intervals　of　time　as　those　on　the　terrace；　consequently　the
  loss　of　fine　earth　during　rainy　weather　must　have　been　greater　in
  this　than　in　the　last　case。　　The　castings　moreover　were　more　sandy；
  and　in　collecting　them　during　dry　weather　they　sometimes　crumbled
  into　dust；　and　much　was　thus　lost。　　Therefore　it　is　certain　that
  the　worms　brought　up　to　the　surface　considerably　more　earth　than
  that　which　was　collected。　　The　last　collec