numerous；　being　carbon　and　nitrate　of　ammonia；
  carburetted　and　sulphuretted　hydrogen；　and　water；
  and　these　ammoniacal　salts　greatly　favor　the　growth
  of　fungi。　Now　paper　consists　essentially　of　woody
  fibre；　having　animal　matter　as　size　on　its　surface。
  The　first　microscopic　symptom　of　decay　in　paper　is
  irregularity　of　surface；　with　a　slight　change　of　color；
  indicating　the　commencement　of　the　process　just
  noticed；　during　which；　in　addition　to　carbonic　acid；
  certain　organic　acids　are　formed；　as　crenic　and　ulmic
  acids；　which；　if　the　paper　has　been　stained　by
  a　coloring　matter；　will　form　spots　of　red　on　the
  surface。　The　same　process　of　decay　goes　on　in
  parchment　as　in　paper；　only　with　more　rapidity；
  from　the　presence　of　nitrogen　in　its　composition。
  When　this　decay　has　begun　to　take　place；　fungi　are
  produced；　the　most　common　species　being
  Penicilium　glaucum。　They　insinuate　themselves　between
  the　fibre；　causing　a　freer　admission　of　air；　and
  consequently　hasten　the　decay。　The　substances　most
  successfully　used　as　preventives　of　decay　are　the
  salts　of　mercury；　copper；　and　zinc。　Bichloride　of
  mercury　（corrosive　sublimate）　is　the　material　employed
  in　the　kyanization　of　timber；　the　probable
  mode　of　action　being　its　combination　with　the　albumen
  of　the　wood；　to　form　an　insoluble　compound
  not　susceptible　of　spontaneous　decomposition；　and
  therefore　incapable　of　exciting　fermentation。　The
  antiseptic　power　of　corrosive　sublimate　may　be
  easily　tested　by　mixing　a　little　of　it　with　flour
  paste；　the　decay　of　which；　and　the　appearance　of
  fungi；　are　quite　prevented　by　it。　Next　to　corrosive
  sublimate　in　antiseptic　value　stand　the　salts　of
  copper　and　zinc。　For　use　in　the　preservation　of
  paper　the　sulphate　of　zinc　is　better　than　the　chloride；
  which　is　to　a　certain　extent　delinquescent。〃
  There　are　numerous　paper　tests　which　include　the
  matter　of　sizing；　direction　of　the　grain；　absorbing
  powers；　character　of　ingredients；　etc。　A　few　of　them
  are　cited。
  SIZING。The　everyday　tests　as　to　hardness　of
  sizing　answer　every　ordinary　purpose：　Moisten　with
  the　tongue；　and　if　the　paper　is　slack…sized　you　can
  detect　it　often　by　the　instant　drawing　or　absorption
  of　the　moisture。　Watch　the　spot　moistened；　and　the
  longer　it　remains　wet　the　better　the　paper　is　sized。
  Look　through　the　spot　dampenedthe　poorer　the
  sizing　the　more　transparent　is　the　paper　where　it　is
  wet。　If　thoroughly　sized　no　difference　will　be　apparent
  between　the　spot　dampened　and　the　balance
  of　the　sheet。　When　there　is　a　question　as　to　whether
  a　paper　is　tub　or　engine　sized；　it　can　be　usually　decided
  by　wetting　the　forefinger　and　thumb　and　pressing
  the　sheet　between　them。　If　tub…sized；　the　glue
  which　is　applied　to　the　surface　will　perceptibly　cling
  to　the　fingers。
  TO　TEST　THE　INK　RESISTING　QUALITY　OF　PAPER。
  Draw　a　heavy　ink　line　across　the　sheet。　If　the　paper
  is　poorly　sized；　a　feathery　edge　will　appear；　caused
  by　spreading　of　the　ink。　Slack…sized　paper　will　be
  penetrated　by　the　ink；　which　will　plainly　appear　on
  the　reverse　side　of　the　sheet。
  TO　DETERMINE　THE　DIRECTION　OF　THE　GRAIN。
  An　easy　but　sure　test　to　determine　the　direction　of
  the　grain　in　a　sheet　of　paper；　which　will　be　found
  useful　and　worth　remembering；　is　as　follows：
  For　instance；　the　size　of　sheet　is　17x22　inches。
  Cut　out　a　circular　piece　as　nearly　round　as　the　eye
  can　judge；　before　entirely　detaching　from　the　sheet；
  mark　on　the　circle　the　17…inch　way　and　the　22…inch
  way；　then　float　the　cut　out　piece　on　water　for　a　few
  seconds；　then　place　on　the　palm　of　the　hand；　taking
  care　not　to　let　the　edges　stick　to　the　hand；　and　the
  paper　will　curl　until　it　forms　a　cone；　the　grain　of　the
  paper　runs　the　opposite　way　from　which　the　paper
  curls。
  ABSORBING　POWERS　OF　BLOTTING　PAPER。Comparative
  tests　as　to　absorbing　powers　of　blotting
  can　be　made　between　sheets　of　same　weight　per
  ream　by　allowing　the　pointed　corner　of　a　sheet　to
  touch　the　surface　of　a　drop　of　ink。　Repeat　with　each
  sheet　to　be　tested；　and　compare　the　height　in　each　to
  which　the　ink　has　been　absorbed。　A　well…made
  blotting　paper　should　have　little　or　no　free　fibre　dust
  to　fill　with　ink　and　smear　the　paper。
  TEST　FOR　GROUND　WOOD。Make　a　streak　across
  the　paper　with　a　solution　of　aniline　sulphate　or　with
  concentrated　nitric　acid；　the　first　will　turn　ground
  wood　yellow；　the　second　will　turn　it　brown。　I　give
  aniline　sulphate　the　preference；　as　nitric　acid　acts
  upon　unbleached　sulphite；　if　present　in　the　paper；　the
  same　as　it　acts　upon　ground　wood；　viz。；　turning　it
  brown。
  Phloroglucin　gives　a　rose…red　stain　on　paper　containing
  （sulphite）　wood　pulp；　after　the　specimen　has　been
  previously　treated　with　a　weak　solution　of　hydrochloric
  acid。
  About　the　end　of　the　eighteenth　century　it　became
  necessary　to　make　special　papers　denominated　〃safety
  paper。〃　Their　manufacture　has　continued　until　the
  present　day　although　much　limited；　largely　because
  of　the　employment　of　mechanical　devices　which　seek
  to　safety　monetary　instruments。　Such　safety　papers
  are　of　several　kinds。
  1。　Paper　made　with　distinguishing　marks　to　indicate
  proprietorship；　as　with　the　Bank　of　England
  water　mark；　to　imitate　which　is　a　felony。　Or　the
  paper　of　the　United　States　currency；　which　has　silk
  fibers　united　with　the　pulp；　the　imitation　of　which　is
  a　felony。
  2。　Paper　made　with　layers　or　materials　which　are
  disturbed　by　erasure　or　chemical　discharge　of　written
  or　printed　contents；　so　as　to　prevent　fraudulent
  tampering。
  3。　Paper　made　of　peculiar　materials　or　color；　to
  prevent　copying　by　photographic　means。
  A　number　of　processes　may　be　cited：
  One　kind　is　made　of　a　pulp　tinged　with　a　stain
  easily　affected　by　chlorine；　acids；　or　alkalis；　and　is
  made　into　sheets　as　usual。
  Water　marks　made　by　wires　twined　among　the
  meshes　of　the　wire　cloth　on　which　the　paper　is
  made。
  Threads　embodied　in　the　web　of　the　paper。
  Colored　threads　systematically　arranged　were　formerly
  used　in　England　for　post…office　envelopes　and　exchequer
  bills。
  Silken　fibers　mixed　with　the　pulp　or　dusted　upon
  it　in　process　of　formation；　as　used　in　the　United
  States　currency。
  Tigere；　1817；　treated　the　pulp　of　the　paper；　previous
  to　sizing；　with　a　solution　of　prussiate　of　potash。
  Sir　Win。　Congreve；　1819；　prepared　a　colored　layer
  of　pulp　in　combination　with　white　layers；　also　by
  printing　upon　one　sheet　and　covering　it　with　an
  outer　layer；　either　plain　or　water…marked。
  Glynn　and　Appel；　1821；　mixed　a　copper　salt　in　the
  pulp　and　afterward　added　an　alkali　or　alkaline　salt　to
  produce　a　copious　precipitate。　The　pulp　was　then
  washed　and　made　into　paper　and　thereafter　dipped　in
  a　saponaceous　compound。
  Stevenson；　1837；　incorporated　into　paper　a　metallic
  base　such　as　manganese；　and　a　neutral　compound　like
  prussiate　of　potash；　to　protect　writing　from　being　tampered
  with。
  Varnham；　1845；　invented　a　paper　consisting　of　a
  white　sheet　or　surface　on　one　or　both　sides　of　a　colored
  sheet。
  Stones；　1851。　An　iodide　or　bromide　in　connection
  with　ferrocyanide　of　potassium　and　starch　combined
  with　the　pulp。
  Johnson；　1853；　employed　the　rough　and　irregular
  surface　produced　by　the　fracture　of　cast　iron　or　other
  brittle　metal　to　form　a　water　mark　for　paper　by　taking
  an　impression　therefrom　on　soft　metal；　gutta…
  percha；　etc。；　and　afterward　transferring　it　to　the　wire
  cloth　on　which　the　paper　is　made。
  Scoutteten；　1853；　treated　paper　with　caoutchoue
  dissolved　in　bisulphide　of　carbon；　in　order　to　render
  it　impermeable　and　to　prevent　erasures　or　chemical
  action。
  Ross；　1854；　invented　water…lining　or　printing　the
  denomination　of　the　note　in　colors　while　the　pulp　was
  yet　soft。
  Evans；　1854；　commingled　a　lace　or　open…work　fabric
  in　the　pulp。
  Courboulay；　1856；　mixed　the　pulp　and　applied　to
  the　paper　salts　of　iodine　or　bromine。
  Loubatieres；　1857；　manufactured　paper　in　layers；
  any　or　all　of　which　might　be　colored；　or　have　impressions
  or　conspicuous　marks　for　preventing　forgery。
  Herapath；　1858；　saturated　paper　during　or　after　its
  manufacture　with　a　solution　of　a　ferrocyanide；　a　ferriccyanide；
  or　sulphocyanide　of　potassium；　sodium；　or
  ammonium。
  Seys　and　Brewer；　1858；　applied　aqueous　solutions
  of　ferrocyanide　of　potassium　or　other　salts；　which
  formed　an　indelible　compound　with　the　ferruginous
  base　of　writing　ink。
  Sparre；　1859；　utilized　opaque　matter；　such　as　prussian
  blue；　white　or　red　lead；　insoluble　in　water　and
  stenciled　on　one　layer　of　the　paper　web；　forming　a
  regular　pattern；　this　was　then　covered　by　a　second
  layer　of　paper。
  Moss；　1859；　invented　a　coloring　matter　prepared
  from　burned　china　or　other　clay；　oxide　of　chromium
  or　sulphur；　and　combined　it　with　the　pulp。
  Barclay；　1859；　incorporated　with　the　paper：
  1。　Soluble　ferrocyanides；　ferricyanides；　and　sulp