II。；　who　died　270　A。D。　　We　see　in　the　accompanying　section；　Fig。
  15；　that　the　tesselated　pavement　has　subsided　to　a　less　degree　over
  the　buried　wall　than　elsewhere；　so　that　a　slight　convexity　or
  protuberance　here　stretched　in　a　straight　line　across　the　room。
  This　led　to　a　hole　being　dug；　and　the　buried　wall　was　thus
  discovered。
  We　see　in　these　three　sections；　and　in　several　others　not　given；
  that　the　old　pavements　have　sunk　or　sagged　considerably。　　Mr。　Joyce
  formerly　attributed　this　sinking　solely　to　the　slow　settling　of　the
  ground。　　That　there　has　been　some　settling　is　highly　probable；　and
  it　may　be　seen　in　Fig。　15　that　the　pavement　for　a　width　of　5　feet
  over　the　southern　enlargement　of　the　room；　which　must　have　been
  built　on　fresh　ground；　has　sunk　a　little　more　than　on　the　old
  northern　side。　　But　this　sinking　may　possibly　have　had　no
  connection　with　the　enlargement　of　the　room；　for　in　Fig。　13　one
  half　of　the　pavement　has　subsided　more　than　the　other　half　without
  any　assignable　cause。　　In　a　bricked　passage　to　Mr。　Joyce's　own
  house；　laid　down　only　about　six　years　ago；　the　same　kind　of　sinking
  has　occurred　as　in　the　ancient　buildings。　　Nevertheless　it　does　not
  appear　probable　that　the　whole　amount　of　sinking　can　be　thus
  accounted　for。　　The　Roman　builders　excavated　the　ground　to　an
  unusual　depth　for　the　foundations　of　their　walls；　which　were　thick
  and　solid；　it　is　therefore　hardly　credible　that　they　should　have
  been　careless　about　the　solidity　of　the　bed　on　which　their
  tesselated　and　often　ornamented　pavements　were　laid。　　The　sinking
  must；　as　it　appears　to　me；　be　attributed　in　chief　part　to　the
  pavement　having　been　undermined　by　worms；　which　we　know　are　still
  at　work。　　Even　Mr。　Joyce　at　last　admitted　that　this　could　not　have
  failed　to　have　produced　a　considerable　effect。　　Thus　also　the　large
  quantity　of　fine　mould　overlying　the　pavements　can　be　accounted
  for；　the　presence　of　which　would　otherwise　be　inexplicable。　　My
  sons　noticed　that　in　one　room　in　which　the　pavement　had　sagged　very
  little；　there　was　an　unusually　small　amount　of　overlying　mould。
  As　the　foundations　of　the　walls　generally　lie　at　a　considerable
  depth；　they　will　either　have　not　subsided　at　all　through　the
  undermining　action　of　worms；　or　they　will　have　subsided　much　less
  than　the　floor。　　This　latter　result　would　follow　from　worms　not
  often　working　deep　down　beneath　the　foundations；　but　more
  especially　from　the　walls　not　yielding　when　penetrated　by　worms；
  whereas　the　successively　formed　burrows　in　a　mass　of　earth；　equal
  to　one　of　the　walls　in　depth　and　thickness；　would　have　collapsed
  many　times　since　the　desertion　of　the　ruins；　and　would　consequently
  have　shrunk　or　subsided。　　As　the　walls　cannot　have　sunk　much　or　at
  all；　the　immediately　adjoining　pavement　from　adhering　to　them　will
  have　been　prevented　from　subsiding；　and　thus　the　present　curvature
  of　the　pavement　is　intelligible。
  The　circumstance　which　has　surprised　me　most　with　respect　to
  Silchester　is　that　during　the　many　centuries　which　have　elapsed
  since　the　old　buildings　were　deserted；　the　vegetable　mould　has　not
  accumulated　over　them　to　a　greater　thickness　than　that　here
  observed。　　In　most　places　it　is　only　about　9　inches　in　thickness；
  but　in　some　places　12　or　even　more　inches。　　In　Fig。　11；　it　is　given
  as　20　inches；　but　this　section　was　drawn　by　Mr。　Joyce　before　his
  attention　was　particularly　called　to　this　subject。　　The　land
  enclosed　within　the　old　walls　is　described　as　sloping　slightly　to
  the　south；　but　there　are　parts　which；　according　to　Mr。　Joyce；　are
  nearly　level；　and　it　appears　that　the　mould　is　here　generally
  thicker　than　elsewhere。　　The　surface　slopes　in　other　parts　from
  west　to　east；　and　Mr。　Joyce　describes　one　floor　as　covered　at　the
  western　end　by　rubbish　and　mould　to　a　thickness　of　28。5　inches；　and
  at　the　eastern　end　by　a　thickness　of　only　11。5　inches。　　A　very
  slight　slope　suffices　to　cause　recent　castings　to　flow　downwards
  during　heavy　rain；　and　thus　much　earth　will　ultimately　reach　the
  neighbouring　rills　and　streams　and　be　carried　away。　　By　this　means；
  the　absence　of　very　thick　beds　of　mould　over　these　ancient　ruins
  may；　as　I　believe；　be　explained。　　Moreover　most　of　the　land　here
  has　long　been　ploughed；　and　this　would　greatly　aid　the　washing　away
  of　the　finer　earth　during　rainy　weather。
  The　nature　of　the　beds　immediately　beneath　the　vegetable　mould　in
  some　of　the　sections　is　rather　perplexing。　　We　see；　for　instance；
  in　the　section　of　an　excavation　in　a　grass　meadow　（Fig。　14）；　which
  sloped　from　north　to　south　at　an　angle　of　30　degrees　40　seconds；
  that　the　mould　on　the　upper　side　is　only　six　inches　and　on　the
  lower　side　nine　inches　in　thickness。　　But　this　mould　lies　on　a　mass
  （25。5　inches　in　thickness　on　the　upper　side）　〃of　dark　brown　mould；〃
  as　described　by　Mr。　Joyce；　〃thickly　interspersed　with　small　pebbles
  and　bits　of　tiles；　which　present　a　corroded　or　worn　appearance。
  The　state　of　this　dark…coloured　earth　is　like　that　of　a　field　which
  has　long　been　ploughed；　for　the　earth　thus　becomes　intermingled
  with　stones　and　fragments　of　all　kinds　which　have　been　much　exposed
  to　the　weather。　　If　during　the　course　of　many　centuries　this　grass
  meadow　and　the　other　now　cultivated　fields　have　been　at　times
  ploughed；　and　at　other　times　left　as　pasture；　the　nature　of　the
  ground　in　the　above　section　is　rendered　intelligible。　　For　worms
  will　continually　have　brought　up　fine　earth　from　below；　which　will
  have　been　stirred　up　by　the　plough　whenever　the　land　was
  cultivated。　　But　after　a　time　a　greater　thickness　of　fine　earth
  will　thus　have　been　accumulated　than　could　be　reached　by　the
  plough；　and　a　bed　like　the　25。5…inch　mass；　in　Fig。　14；　will　have
  been　formed　beneath　the　superficial　mould；　which　latter　will　have
  been　brought　to　the　surface　within　more　recent　times；　and　have　been
  well　sifted　by　the　worms。
  Wroxeter；　Shropshire。　The　old　Roman　city　of　Uriconium　was　founded
  in　the　early　part　of　the　second　century；　if　not　before　this　date；
  and　it　was　destroyed；　according　to　Mr。　Wright；　probably　between　the
  middle　of　the　fourth　and　fifth　century。　　The　inhabitants　were
  massacred；　and　skeletons　of　women　were　found　in　the　hypocausts。
  Before　the　year　1859；　the　sole　remnant　of　the　city　above　ground；
  was　a　portion　of　a　massive　wall　about　20　ft。　in　height。　　The
  surrounding　land　undulates　slightly；　and　has　long　been　under
  cultivation。　　It　had　been　noticed　that　the　corn…crops　ripened
  prematurely　in　certain　narrow　lines；　and　that　the　snow　remained
  unmelted　in　certain　places　longer　than　in　others。　　These
  appearances　led；　as　I　was　informed；　to　extensive　excavations　being
  undertaken。　　The　foundations　of　many　large　buildings　and　several
  streets　have　thus　been　exposed　to　view。　　The　space　enclosed　within
  the　old　walls　is　an　irregular　oval；　about　1　mile　in　length。　　Many
  of　the　stones　or　bricks　used　in　the　buildings　must　have　been
  carried　away；　but　the　hypocausts；　baths；　and　other　underground
  buildings　were　found　tolerably　perfect；　being　filled　with　stones；
  broken　tiles；　rubbish　and　soil。　　The　old　floors　of　various　rooms
  were　covered　with　rubble。　　As　I　was　anxious　to　know　how　thick　the
  mantle　of　mould　and　rubbish　was；　which　had　so　long　concealed　these
  ruins；　I　applied　to　Dr。　H。　Johnson；　who　had　superintended　the
  excavations；　and　he；　with　the　greatest　kindness；　twice　visited　the
  place　to　examine　it　in　reference　to　my　questions；　and　had　many
  trenches　dug　in　four　fields　which　had　hitherto　been　undisturbed。
  The　results　of　his　observations　are　given　in　the　following　Table。
  He　also　sent　me　specimens　of　the　mould；　and　answered；　as　far　as　he
  could；　all　my　questions。
  MEASUREMENTS　BY　DR。　H。　JOHNSON　OF　THE　THICKNESS　OF　THE　VEGETABLE
  MOULD　OVER　THE　ROMAN　RUINS　AT　WROXETER。
  Trenches　dug　in　a　field　called　〃Old　Works。〃
  （Thickness　of　mould　in　inches　shown　in　parenthesisDP。）
  1。　　At　a　depth　of　36　inches　undisturbed　sand　was　reached　（20）
  2。　　At　a　depth　of　33　inches　concrete　was　reached　（21）
  3。　At　a　depth　of　9　inches　concrete　was　reached　（9）
  Trenches　dug　in　a　field　called　〃Shop　Leasows；〃　this　is　the　highest
  field　within　the　old　walls；　and　slopes　down　from　a　sub…central
  point　on　all　sides　at　about　an　angle　of　2　degrees。
  4。　　Summit　of　field；　trench　45　inches　deep　（40）
  5。　　Close　to　summit　of　field；　trench　36　inches　deep　（26）
  6。　　Close　to　summit　of　field；　trench　28　inches　deep　（28）
  7。　　Near　summit　of　field；　trench　36　inches　deep　（24）
  8。　　Near　summit　of　field；　trench　at　one　end　39　inches　deep；　the
  mould　here　graduated　into　the　underlying　undisturbed　sand；　and　its
  thickness　（24　inches）　is　somewhat　arbitrary。　　At　the　other　end　of
  the　trench；　a　causeway　was　encountered　at　a　depth　of　only　7　inches；
  and　the　mould　was　here　only　7　inches　thick　（24）
  9。　　Trench　close　to　the　last；　28　inches　in　depth　（24）
  10。　　Lower　part　of　same　field；　trench　30　inches　deep　（15）
  11。　　Lower　part　of　same　field；　trench　31　inches　deep　（17）
  12。　　Lower　part　of　same　field；　trench　36　inches　deep；　at　which
  depth　undisturbed　sand　was　reached　（28）
  13。　　In　another　part　of　same　field；　trench　9。5　inches　dee