In　turning　a　piece　of　work　on　the　old…fashioned　lathe；　the　workman
  applied　and　guided　his　tool　by　means　of　muscular　strength。　　The　work
  was　made　to　revolve；　and　the　turner；　holding　the　cutting　tool　firmly
  upon　the　long；　straight；　guiding　edge　of　the　rest；　along　which　he
  carried　it；　and　pressing　its　point　firmly　against　the　article　to　be
  turned；　was　thus　enabled　to　reduce　its　surface　to　the　required　size
  and　shape。　　Some　dexterous　turners　were　able；　with　practice　and
  carefulness；　to　execute　very　clever　pieces　of　work　by　this　simple
  means。　　But　when　the　article　to　be　turned　was　of　considerable　size；
  and　especially　when　it　was　of　metal；　the　expenditure　of　muscular
  strength　was　so　great　that　the　workman　soon　became　exhausted。　　The
  slightest　variation　in　the　pressure　of　the　tool　led　to　an
  irregularity　of　surface；　and　with　the　utmost　care　on　the　workman's
  part；　he　could　not　avoid　occasionally　cutting　a　little　too　deep；　in
  consequence　of　which　he　must　necessarily　go　over　the　surface　again；
  to　reduce　the　whole　to　the　level　of　that　accidentally　cut　too　deep；
  and　thus　possibly　the　job　would　be　altogether　spoiled　by　the　diameter
  of　the　article　under　operation　being　made　too　small　for　its　intended
  purpose。
  The　introduction　of　the　slide　rest　furnished　a　complete　remedy　for
  this　source　of　imperfection。　　The　principle　of　the　invention　consists
  in　constructing　and　fitting　the　rest　so　that；　instead　of　being
  screwed　down　to　one　place；　and　the　tool　in　the　hands　of　the　workman
  travelling　over　it；　the　rest　shall　itself　hold　the　cutting　tool
  firmly　fixed　in　it；　and　slide　along　the　surface　of　the　bench　in　a
  direction　exactly　parallel　with　the　axis　of　the　work。　　Before　its
  invention　various　methods　had　been　tried　with　the　object　of　enabling
  the　work　to　be　turned　true　independent　of　the　dexterity　of　the
  workman。　　Thus；　a　square　steel　cutter　used　to　be　firmly　fixed　in　a
  bed；　along　which　it　was　wedged　from　point　to　point　of　the　work；　and
  tolerable　accuracy　was　in　this　way　secured。　　But　the　slide　rest　was
  much　more　easily　managed；　and　the　result　was　much　more　satisfactory。
  All　that　the　workman　had　to　do；　after　the　tool　was　firmly　fitted　into
  the　rest；　was　merely　to　turn　a　screw…handle；　and　thus　advance　the
  cutter　along　the　face　of　the　work　as　required；　with　an　expenditure　of
  strength　so　slight　as　scarcely　to　be　appreciable。　　And　even　this
  labour　has　now　been　got　rid　of；　for；　by　an　arrangement　of　the
  gearing；　the　slide　itself　has　been　made　self…acting；　and　advances
  with　the　revolution　of　the　work　in　the　lathe；　which　thus　supplies　the
  place　of　the　workman's　hand。　　The　accuracy　of　the　turning　done　by　this
  beautiful　yet　simple　arrangement　is　as　mechanically　perfect　as　work
  can　be。　　The　pair　of　steel　fingers　which　hold　the　cutting　tool　firmly
  in　their　grasp　never　tire；　and　it　moves　along　the　metal　to　be　cut
  with　an　accuracy　and　precision　which　the　human　hand；　however　skilled；
  could　never　equal。
  The　effects　of　the　introduction　of　the　slide　rest　were　very　shortly
  felt　in　all　departments　of　mechanism。　　Though　it　had　to　encounter　some
  of　the　ridicule　with　which　new　methods　of　working　are　usually
  received；　and　for　a　time　was　spoken　of　in　derision　as　〃Maudslay's
  Go…cart；〃its　practical　advantages　were　so　decided　that　it　gradually
  made　its　way；　and　became　an　established　tool　in　all　the　best
  mechanical　workshops。　　It　was　found　alike　capable　of　executing　the
  most　delicate　and　the　most　ponderous　pieces　of　machinery；　and　as
  slide…lathes　could　be　manufactured　to　any　extent；　machinery；
  steam…engines；　and　all　kinds　of　metal　work　could　now　be　turned　out　in
  a　quantity　and　at　a　price　that；　but　for　its　use；　could　never　have
  been　practicable。　　In　course　of　time　various　modifications　of　the
  machine　were　introducedsuch　as　the　planing　machine；　the
  wheel…cutting　machine；　and　other　beautiful　tools　on　the　slide…rest
  principle；the　result　of　which　has　been　that　extraordinary
  development　of　mechanical　production　and　power　which　is　so
  characteristic　a　feature　of　the　age　we　live　in。
  〃It　is　not；　indeed；　saying　at　all　too　much　to　state；〃　says　Mr。
  Nasmyth；*
  ＇footnote。。。
  Remarks　on　the　Introduction　of　the　Slide　Principle　in　Tools　and
  Machines　employed　in　the　Production　of　Machinery；　in　Buchanan's
  Practical　Essays　on　Mill　Work　and　other　Machinery。　　3rd　ed。　p。　397。
  。。。＇
  a　most　competent　judge　in　such　a　matter；　〃that　its　influence　in
  improving　and　extending　the　use　of　machinery　has　been　as　great　as
  that　produced　by　the　improvement　of　the　steam…engine　in　respect　to
  perfecting　manufactures　and　extending　commerce；　inasmuch　as　without
  the　aid　of　the　vast　accession　to　our　power　of　producing　perfect
  mechanism　which　it　at　once　supplied；　we　could　never　have　worked　out
  into　practical　and　profitable　forms　the　conceptions　of　those　master
  minds　who；　during　the　last　half　century；　have　so　successfully
  pioneered　the　way　for　mankind。　　The　steam…engine　itself；　which
  supplies　us　with　such　unbounded　power；　owes　its　present　perfection　to
  this　most　admirable　means　of　giving　to　metallic　objects　the　most
  precise　and　perfect　geometrical　forms。　　How　could　we；　for　instance；
  have　good　steam…engines　if　we　had　not　the　means　of　boring　out　a　true
  cylinder；　or　turning　a　true　piston…rod；　or　planing　a　valve　face？　It
  is　this　alone　which　has　furnished　us　with　the　means　of　carrying　into
  practice　the　accumulated　result's　of　scientific　investigation　on
  mechanical　subjects。　　It　would　be　blamable　indeed；〃　continues　Mr。
  Nasmyth；　〃after　having　endeavoured　to　set　forth　the　vast　advantages
  which　have　been　conferred　on　the　mechanical　world；　and　therefore　on
  mankind　generally；　by　the　invention　and　introduction　of　the　Slide
  Rest；　were　I　to　suppress　the　name　of　that　admirable　individual　to
  whom　we　are　indebted　for　this　powerful　agent　towards　the　attainment
  of　mechanical　perfection。　　I　allude　to　Henry　Maudslay；　whose　useful
  life　was　enthusiastically　devoted　to　the　grand　object　of　improving
  our　means　of　producing　perfect　workmanship　and　machinery：　　to　him　we
  are　certainly　indebted　for　the　slide　rest；　and；　consequently；　to　say
  the　least；　we　are　indirectly　so　for　the　vast　benefits　which　have
  resulted　from　the　introduction　of　so　powerful　an　agent　in　perfecting
  our　machinery　and　mechanism　generally。　　The　indefatigable　care　which
  he　took　in　inculcating　and　diffusing　among　his　workmen；　and
  mechanical　men　generally；　sound　ideas　of　practical　knowledge　and
  refined　views　of　construction；　have　rendered　and　ever　will　continue
  to　render　his　name　identified　with　all　that　is　noble　in　the　ambition
  of　a　lover　of　mechanical　perfection。〃
  One　of　the　first　uses　to　which　Mr。　Maudslay　applied　the　improved
  slide　rest；　which　he　perfected　shortly　after　beginning　business　in
  Margaret　Street；　Cavendish　Square；　was　in　executing　the　requisite
  tools　and　machinery　required　by　Mr。　（afterwards　Sir　Marc　Isambard）
  Brunel　for　manufacturing　ships'　blocks。　　The　career　of　Brunel　was　of　a
  more　romantic　character　than　falls　to　the　ordinary　lot　of　mechanical
  engineers。　　His　father　was　a　small　farmer　and　postmaster；　at　the
  village　of　Hacqueville；　in　Normandy；　where　Marc　Isambard　was　born　in
  1769。　　He　was　early　intended　for　a　priest；　and　educated　accordingly。
  But　he　was　much　fonder　of　the　carpenter's　shop　than　of　the　school；
  and　coaxing；　entreaty；　and　punishment　alike　failed　in　making　a
  hopeful　scholar　of　him。　　He　drew　faces　and　plans　until　his　father　was
  almost　in　despair。　　Sent　to　school　at　Rouen；　his　chief　pleasure　was　in
  watching　the　ships　along　the　quays；　and　one　day　his　curiosity　was
  excited　by　the　sight　of　some　large　iron　castings　just　landed。　　What
  were　they？　How　had　they　been　made？　Where　did　they　come　from？　His
  eager　inquiries　were　soon　answered。　　They　were　parts　of　an　engine
  intended　for　the　great　Paris　water…works；　the　engine　was　to　pump
  water　by　the　power　of　steam；　and　the　castings　had　been　made　in
  England；　and　had　just　been　landed　from　an　English　ship。　　〃England！〃
  exclaimed　the　boy；　〃ah！　when　I　am　a　man　I　will　go　see　the　country
  where　such　grand　machines　are　made！〃　On　one　occasion；　seeing　a　new
  tool　in　a　cutler's　window；　he　coveted　it　so　much　that　he　pawned　his
  hat　to　possess　it。　　This　was　not　the　right　road　to　the　priesthood；　and
  his　father　soon　saw　that　it　was　of　no　use　urging　him　further：　　but　the
  boy's　instinct　proved　truer　than　the　father's　judgment。
  It　was　eventually　determined　that　he　should　qualify　himself　to　enter
  the　royal　navy；　and　at　seventeen　he　was　nominated　to　serve　in　a
  corvette　as　〃volontaire　d'honneur。〃　　His　ship　was　paid　off　in　1792；
  and　he　was　at　Paris　during　the　trial　of　the　King。　　With　the
  incautiousness　of　youth　he　openly　avowed　his　royalist　opinions　in　the
  cafe　which　he　frequented。　　On　the　very　day　that　Louis　was　condemned
  to　death；　Brunel　had　an　angry　altercation　with　some
  ultra…republicans；　after　which　he　called　to　his　dog；　〃Viens；
  citoyen！〃　　Scowling　looks　were　turned　upon　him；　and　he　deemed　it
  expedient　to　take　the　first　opportu