an autobiography-第56部分

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g　an　important　part　of　their　contract。　　Happily；　I　had　already　given　some　attention　to　this　application　of　the　powers　of　the　steam　hammer。　　In　fact；　I　had　secured　a　patent　for　it。　　I　had　the　drawings　for　the　steam　hammer　pile…driving　machine　with　me。　　I　submitted　them　to　Mr。　Baker；　and　he　saw　its　importance　in　a　moment。　　〃That；〃　he　'said；　〃is　the　very　thing　that　I　want　to　enable　me　to　complete　my　contract　satisfactorily。〃　　Thousands　of　enormous　piles　had　to　be　driven　down　into　the　deep　silt　of　the　Shore；　and　to　have　driven　them　down　by　the　old　system　of　pile…driving　would　have　occupied　a　long　time；　and　would　also　have　been　very　expensive。

The　drawings　were　of　course　submitted　to　Captain　Brandreth。　He　was　delighted　with　my　design。　　The　steam　pile…driver　would　be；　in　his　opinion；　the　prime　agent　for　effecting　the　commencement　of　the　great　work　originated　by　himself。　　At　first　the　feat　of　damming　out　such　a　high　tide　as　that　of　the　Hamoaze　seemed　very　doubtful；　because　the　stiff　slate　silt　was　a　treacherous　and　difficult　material　to　penetrate。　　But　now；　he　thought；　the　driving　would　be　rendered　comparatively　easy。　　With　Captain　Brandreth's　consent　the　contractors　ordered　of　me　two　of　my　steam　hammer　pile…drivers。　　They　were　to　be　capable　of　driving　18…inch　square　piles　of　70　feet　in　length　into　the　silt　of　the　Hamoaze。

＇Image＇　　Space　to　be　enclosed　at　the　Hamoaze

This　first　order　for　my　pile…driver　was　a　source　of　great　pleasure　to　me。　I　had　long　contemplated　this　application　of　the　power　of　the　steam　hammer。　　The　machine　had　long　been　in　full　action　in　my　〃mind's　eye；〃　and　now　I　was　to　see　it　in　actual　reality。　　I　wrote　down　to　my　partner　by　that　night's　post　informing　him　of　the　happy　circumstance。　The　order　was　for　two　grand　steam　hammer　pile…drivers；　each　with　four…ton　hammer…blocks。The　wrought…iron　guide　case　and　the　steam　cylinder　were　to　weigh　in　all　seven　tons。　　All　this　weight　was　to　rest　on　the　shoulders　of　the　pile。　　The　blows　were　to　be　about　eighty　in　the　minute。　　This；　I　thought；　would　prove　thoroughly　effective　in　rapidly　driving　the　piles　down　into　the　earth。

I　have　said　that　the　steam　pile…driver　was　in　my　mind's　eye　long　before　I　saw　it　in　action。　　It　is　one　of　the　most　delightful　results　of　the　possession　of　the　constructive　faculty；　that　one　can　build　up　in　the　mind　mechanical　structures　and　set　them　to　work　in　imagination；　and　observe　beforehand　the　various　details　performing　their　respective　functions；　as　if　they　were　in　absolute　material　form　and　action。　Unless　this　happy　faculty　exists　ab　initio　in　the　brain　of　the　mechanical　engineer；　he　will　have　a　hard　and　disappointing　life　before　him。　　It　is　the　early　cultivation　of　the　imagination　which　gives　the　right　flexibility　to　the　thinking　faculties。　　Thus　business；　commerce；　and　mechanics　are　all　the　better　for　a　little　healthy　imagination。

So　soon　as　I　had　returned　home；　I　set　to　work　and　prepared　the　working　drawings　of　the　steam　pile…drivers。　　They　were　soon　completed；　conveyed　to　Devonport；　and　erected　on　the　spot　where　they　were　to　be　used。　They　were　ready　on　the　3d　of　July　1845。　　Some　preliminary　pile…driving　had　been　done　in　the　usual　way；　in　order　to　make　a　stage　or　elevated　way　for　my　pile…driver　to　travel　along　the　space　where　the　permanent　piles　were　to　be　driven。　　I　arranged　my　machines　so　that　they　might　travel　by　their　own　locomotive　powers　along　the　whole　length　of　the　coffer　dam；　and　also　that　they　should　hoist　up　the　great　logs　of　Baltic　timber　which　formed　the　Piles　into　their　proper　places　before　being　driven。

The　entire　apparatus　of　the　machine　was　erected　on　a　strong　timber　platform；　and　was　placed　on　wheels；　so　that　it　might　move　along　the　rails　laid　down　upon　the　timber　way。　　The　same　boiler　that　supplied　the　steam　hammer　part　of　the　apparatus　served　to　work　the　small　steam…engine　fixed　to　the　platform　for　its　locomotion；　and　also　to　perform　the　duty　of　rearing　the　next　pile　which　had　to　be　driven。　　The　steam　was　conveyed　to　the　hammer　cylinder　by　the　jointed　pipe　seen　in　the　annexed　engraving。　　The　pipe　accommodated　itself　to　any　elevation　or　descent　of　the　hammer。　　The　whole　weight　of　the　cylinder；　hammer…block；　and　guide　box；　supported　by　the　shoulders　of　the　pile；　amounting　to　seven　tons　in　all；　rested　upon　the　shoulders　of　the　pile　as　a　〃persuader；〃　and　the　eighty　blows　per　minute　of　the　four…ton　hammer　came　down　with　tremendous　energy　upon　the　top　of　the　pile　head。　　No　soil；　that　piles　could　penetrate；　could　resist　such　effective　agencies。

＇Image＇　　Diagram　of　the　Steam　Pile…Driver

Explanation　of　the　Diagram　of　the　Steam　Pile…Driver。The　chief　feature　of　novelty　of　this　pile…driving　machine　consists　in　the　employment　of　the　direct　action　of　the　Steam　Hammer　as　the　blow　giving　agent；　and　also　in　the　manner　in　which　the　dead　weight　of　the　entire　apparatus；　consisting　of　the　hammer…block　C；　the　steam　cylinder　A；　and　its　guide…case　B；　is　employed　to　importantly　aid　the　effect　of　the　rapid　and　energetic　blows　of　the　steam　hammer。　　These　ponderous　parts　rest　on　the　shoulders　of　the　pile　H　all　the　while　it　is　being　driven；　the　pile　in　this　respect　being　the　only　support　of　the　apparatus　A　B　C。　So　that；　besides　the　eighty　blows　per　minute　that　the　four…ton　steam　hammer　energetically　deals　out　to　the　head　of　the　pile　from　a　four　foot　fall　the　dead　weight　of　the　apparatus　constantly　acts　as　a　most　effective　〃predisposer〃　to　the　sinking　of　the　pile　into　the　ground；　the　hoisting　chain　D　being　let　slack　the　while；　so　as　to　allow　A　B　C　to　〃follow　down〃　the　pile　H；　while　the　eighty　blows　per　minute　are　incessantly　showered　on　its　head。　　The　upward　stroke　of　the　piston；　with　its　attached　hammer…block　C；　is　arrested　at　the　proper　height　not　only　by　allowing　the　steam　that　raised　it　to　escape；　but　as　soon　as　the　piston　passes　the　escape　holes　X　X；　the　confined　air　above　the　piston　at　O　rebounds；　and　so　aids　most　effectively　in　increasing　the　energy　of　the　fall　of　the　hammer…block　C　on　the　pile　head。

There　was　a　great　deal　of　curiosity　in　the　dockyard　as　to　the　action　of　the　new　machine。　　The　pile…driving　machine…men　gave　me　a　good…natured　challenge　to　vie　with　them　in　driving　down　a　pile。　　They　adopted　the　old　method；　while　I　adopted　the　new　one。　　The　resident　managers　sought　out　two　great　pile　logs　of　equal　size　and　length70　feet　long　and　18　inches　square。　　At　a　given　signal　we　started　together。　I　let　in　the　steam；　and　the　hammer　at　once　began　to　work。　The　four…ton　block　showered　down　blows　at　the　rate　of　eighty　a　minute；　and　in　the　course　of　four　and　a　half　minutes　my　pile　was　driven　down　to　the　required　depth。　　The　men　working　at　the　ordinary　machine　had　only　begun　to　drive。　　It　took　them　upwards　of　twelve　hours　to　complete　the　driving　of　their　pile！

Such　a　saving　of　time　in　the　performance　of　similar　workby　steam　versus　　manual　labourhad　never　before　been　witnessed。　The　energetic　action　of　the　steam　hammer；　sitting　on　the　shoulders　of　the　pile　high　up　aloft；　and　following　it　suddenly　down；　the　rapidly　hammered　blows　keeping　time　with　the　flashing　out　of　〃the　waste　steam　at　the　end　of　each　stroke；　was　indeed　a　remarkable　sight。　　When　my　pile　was　driven；　the　hammer…block　and　guide　case　were　speedily　re…hoisted　by　the　small　engine　that　did　all　the　labouring　and　locomotive　work　of　the　machine；　the　steam　hammer　portion　of　which　was　then　lowered　on　to　the　shoulders　of　the　next　pile　in　succession。　Again　it　set　to　work。　At　this　the　spectators　crowding　about　in　boats；　pronounced　their　approval　in　the　usual　British　style　of　〃three　cheers！〃　My　new　pile…driver　was　thus　acknowledged　as　another　triumphant　proof　of　the　power　of　steam。

The　whole　of　the　piles　for　this　great　work　were　speedily　driven　in。　The　wall　was　constructed；　and　the　docks　were　completed　in　an　unusually　short　time。　　The　success　of　my　pile…driver　was　followed　by　numerous　orders。　　It　was　used　for　driving　the　immense　piles　required　for　the　High　Level　Bridge　at　Newcastle；　the　great　Border　Bridge　at　Berwick…upon…tweed；　the　Docks　at　Tynemouth；　the　Docks　at　Birkenhead；　the　Docks　at　Grimsby；　the　new　Westminster　Bridge；　the　great　bridge　at　Kief　in　Russia；　the　bridge　at　Petersburg；　the　forts　at　Cronstadt；　the　Embarrage　of　the　Nile；　at　Yokohama　in　Japan；　and　at　other　places。　It　enabled　a　solid　foundation　to　be　laid　for　the　enormous　superstructures　erected　over　them；　and　thus　contributed　to　the　permanence　of　many　important　undertakings。

The　mechanical　principles　on　which　the　efficiency　of　the　steam　pile…driver　chiefly　depends　are　as　simple　as　I　believe　they　are　entirely　novel　and　original。　　The　shoulder　of　the　pile　acts　as　the　sole　supporter　of　the　ponderous　mass　of　the　hammer…block；　cylinder；　and　guide…box。　　This　heavy　weight　acts　as　a　predisposing　agency　to　force　the　pile　down；　while　the　momentum　given　by　the　repeated　fall　of　the　hammer；　at　eighty　blows　the　minute；　brings　the　constant　dead　weight　into　full　action。　　I　am　not　aware　of　any　other　machine　in　which　such　a　combination　of　mechanical　forces　is　employed。

Another　very　effective　detail　consisted　in　employing　the　waste　steam　in　the　upper　part　of　the　cylinder　for　the　purpose　of　acting　as　a　buffer　to　resist　any　undue　length　of　the　upward　stroke　of　the　piston。　But　for　this　the　cylinder　covers　might　have　been　knocked　off。　The