an autobiography-第82部分

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CHRONOLOGICAL　LIST　OF　MECHANICAL　INVENTIONS　AND　TECHNICAL　CONTRIVANCES。

by　James　Nasmyth。

1825。　A　mode　of　applying　Steam　Power　for　the　Traction　of　Canal　Barges；　　　　　　　without　injury　to　the　Canal　Banks。

A　CANAL　having　been　formed　to　connect　Edinburgh　with　the　Forth　and　Clyde　Canal；　and　so　to　give　a　direct　waterway　communication　between　Edinburgh　and　Glasgow；　I　heard　much　talk　about　the　desirableness　of　substituting　Steam　for　Horse　power　as　the　means　of　moving　the　boats　and　barges　along　the　canal。　　But；　as　the　action　of　paddle　wheels　had　been　found　destructive　to　the　canal　banks；　no　scheme　of　that　nature　could　be　entertained。　　Although　a　tyro　in　such　matters；　I　made　an　attempt　to　solve　the　problem；　and　accordingly　prepared　drawings；　with　a　description　of　my　design；　for　employing　Steam　power　as　the　tractive　agency　for　trains　of　canal　barges；　in　such　a　manner　as　to　obviate　all　risk　of　injury　to　the　banks。

＇Image＇

The　scheme　consisted　in　laying　a　chain　along　the　bottom　of　the　canal；　and　of　passing　any　part　of　its　length　between　three　grooved　and　notched　pulleys　or　rollers；　made　to　revolve　with　suitable　velocity　by　means　of　a　small　steam…engine　placed　in　a　tug…boat；　to　the　stern　of　which　a　train　of　barges　was　attached。*　　＇footnote。。。　Had　this　simple　means　of　〃tugging〃　vessels　through　water…ways　been　employed　in　our　late　attempts　to　ascend　the　rapids　of　the　Nile；　some　very　important　results　might　have　issued　from　its　adoption。　　。。。＇　The　steam…engine　could　thus　warp　its　way　along　the　chain；　taking　it　up　between　the　rollers　of　the　bow　of　the　tug…boat；　and　dropping　it　into　the　water　at　the　stern；　so　as　to　leave　the　chain　at　the　service　of　the　next　following　tug…boat　with　its　attached　train　of　barges。　　By　this　simple　mode　of　employing　the　power　of　a　steam…engine　for　canal　boat　traction；　all　risk　of　injury　to　the　banks　would　be　avoided；　as　the　chain　and　not　the　water　of　the　canal　was　the　fulcrum　or　resistance　which　the　steam…engine　on　the　tug…boat　operated　upon　in　thus　warping　its　way　along　the　chain；　and　thus　effectually；　without　slip　or　other　waste　of　power；　dragging　along　the　train　of　barges　attached　to　the　stern　of　the　steam…tug。　　I　had　arranged　for　two　separate　chains；　so　as　to　allow　trains　of　barges　to　be　conveyed　along　the　canal　in　opposite　directions；　without　interfering　with　each　other。

I　submitted　a　complete　set　of　drawings；　and　a　full　description　of　my　design　in　all　its　details；　to　the　directors　of　the　Canal　Company；　and　I　received　a　complimentary　acknowledgment　of　them　in　writing。　　But　such　was　the　prejudice　that　existed；　in　consequence　of　the　injury　to　the　canal　banks　resulting　from　the　use　of　paddle　Wheels；　that　it　extended　to　the　use　of　steam　power　in　any　form；　as　a　substitute　for　ordinary　horse　traction；　and　although　I　had　taken　every　care　to　point　out　the　essential　difference　of　my　system　（as　above　indicated）　by　which　all　such　objections　were　obviated；　my　design　was　at　length　courteously　declined；　and　the　old　system　of　horse　traction　continued。

In　1845　I　had　the　pleasure　to　see　this　simple　mode　of　moving　vessels　along　a　definite　course　in　most　successful　action　at　the　ferry　across　the　Hamoaze　at　Devonport；　in　which　my　system　of　employing　the　power　of　a　steam…engine　on　board　the　ferry　boat；　to　warp　its　way　along　a　submerged　chain　lying　along　the　bottom　of　the　channel　from　side　to　side　of　the　ferry；　was　most　ably　carried　out　by　my　late　excellent　friend；　James　Rendell；　Esq。；　C。E。；　and　is　still；　I　believe；　in　daily　action；　giving　every　satisfaction。


1826。　An　Instrument　for　Measuring　the　Total　and　Comparative　Expansion　　　　　　　of　all　Solid　Bodies。

My　kind　friend　and　patron；　Professor　Leslie；　being　engaged　in　some　investigations　in　which　it　was　essential　to　know　the　exact　comparative　total　expansion　in　bulk　of　metals　and　other　solid　bodies；　under　the　same　number　of　degrees　of　heat；　mentioned　the　subject　in　the　course　of　conversation。　　The　instrument　at　that　time　in　use　was　defective　in　principle　as　well　as　in　construction；　and　the　results　of　its　application　were　untrustworthy。　　As　the　Professor　had　done　me　the　honour　to　request　me　to　assist　him　in　his　experiments；　I　had　the　happiness　to　suggest　an　arrangement　of　apparatus　which　I　thought　might　obviate　the　sources　of　error；　and；　with　his　approval；　I　proceeded　to　put　it　in　operation。

My　contrivance　consisted　of　an　arrangement　by　means　of　which　the　metal　bar　or　other　solid　substance；　whose　total　expansion　under　a　given　number　of　degrees　of　heat　had　to　be　measured；　was　in　a　manner　itself　converted　into　a　thermometer。　　Absolutely　equal　bulks　of　each　solid　were　placed　inside　a　metal　tube　or　vessel；　and　surrounded　with　an　exact　equal　quantity　of　water　at　one　and　the　same　normal　temperature。　A　cap　or　cover；　having　a　suitable　length　of　thermometer　tube　attached　to　it；　was　then　screwed　down；　and　the　water　of　the　index　tube　was　adjusted　to　the　zero　point　of　the　scale　attached　to　it；　the　whole　being　at　say　50deg　of　heat；　as　the　normal　temperature　in　each　case。　　The　apparatus　was　then　heated　up　to　say　200deg　by　immersion　in　water　at　that　temperature。　　The　expansion　of　the　enclosed　bar　of　metal　or　other　solid　substance　under　experiment　caused　the　water　to　rise　above　the　zero；　and　it　was　accordingly　so　indicated　on　the　scale　attached　to　the　cap　tube。　　In　this　way　we　had　a　thermometer　whose　bulb　was　for　the　time　being　filled　with　the　solid　under　investigation；the　water　surrounding　it　imply　acting　as　the　means　by　which　the　expansion　of　each　solid　under　trial　was　rendered　visible；　and　its　amount　capable　of　being　ascertained　and　recorded　with　the　utmost　exactness；　as　the　expansion　of　the　water　was　in　every　case　the　same；　and　also　that　of　the　instrument　itself　which　was　〃a　constant　quantity。〃

In　this　way　we　obtained　the　correct　relative　amount　of　expansion　in　bulk　of　all　the　solid　substances　experimented　upon。　　That　each　bar　of　metal　or　other　solid　substance　was　of　absolutely　equal　bulk；　was　readily　ascertained　by　finding　that　each；　when　weighed　in　water；　lost　the　exact　same　weight。

＇Image＇　　James　Nasmyth's　Expansometer；　1826。

My　friend；　Sir　David　Brewster；　was　so　much　pleased　with　the　instrument　that　he　published　a　drawing　and　description　of　it　in　the　Edinburgh　Philosophical　Journal；　of　which　he　was　then　editor。


1827。　A　Method　of　increasing　the　Effectiveness　of　Steam　by　　　　　　　super…heating　it　on　its　Passage　from　the　Boiler　to　the　Engine。

One　or　the　earliest　mechanical　contrivances　which　I　made　was　for　preventing　water；　in　a　liquid　form；　from　passing　along　with　the　steam　from　the　boiler　to　the　cylinder　of　the　steam…engine。　The　first　steam…engine　I　made　was　employed　in　grinding　oil　colours　for　my　father's　use　in　his　paintings。　　When　I　set　this　engine　to　work　for　the　first　time　I　was　annoyed　by　slight　jerks　which　now　and　then　disturbed　the　otherwise　smooth　and　regular　action　of　the　machine。　After　careful　examination　I　found　that　these　jerks　were　caused　by　the　small　quantities　of　water　that　were　occasionally　carried　along　with　the　current　of　the　steam；　and　deposited　in　the　cylinder；　where　it　accumulated　above　and　below　the　piston；　and　thus　produced　the　jerks。

In　order　to　remove　the　cause　of　these　irregularities；　I　placed　a　considerable　portion　of　the　length　of　the　pipe　which　conveyed　the　steam　from　the　boiler　to　the　engine　within　the　highly　heated　side　flue　of　the　boiler；　so　that　any　portion　of　water　in　the　liquid　form　which　might　chance　to　pass　along　with　the　steam；　might；　ere　it　reached　the　cylinder；　traverse　this　highly…heated　steam　pipe；　and；　in　doing　so；　be　converted　into　perfectly　dry　steam；　and　in　that　condition　enter　the　cylinder。　　On　carrying　this　simple　arrangement　into　practice；　I　found　the　result　to　be　in　every　way　satisfactory。　　The　active　little　steam…engine　thence…forward　performed　its　work　in　the　most　smooth　and　regular　manner。

So　far　as　I　am　aware；　this　early　effort　of　mine　at　mechanical　contrivance　was　the　first　introduction　of　what　has　since　been　termed　〃super…heated　steam〃a　system　now　extensively　employed；　and　yielding　important　results；　especially　in　the　case　of　marine　steam…engines。　Without　such　means　of　supplying　dry　steam　to　the　engines；　the　latter　are　specially　liable　to　〃break…downs；〃　resulting　from　water；　in　the　liquid　form；　passing　into　the　cylinders　along　with　the　steam。


1828。　A　Method　of　〃chucking〃　delicate　Metal…work；　in　order　that　it　may　　　　　　　be　turned　with　perfect　truth

In　fixing　portions　of　work　in　the　turning…lathe；　one　of　the　most　important　points　to　attend　to　is；　that　while　they　are　held　with　sufficient　firmness　in　order　to　be　turned　to　the　required　form；　they　should　be　free　from　any　strain　which　might　in　any　way　distort　them。　In　strong　and　ponderous　objects　this　can　be　easily　accomplished　by　due　care　on　the　part　of　an　intelligent　workman。　　It　is　in　operating　by　the　lathe　on　delicate　and　flexible　objects　that　the　utmost　care　is　requisite　in　the　process　of　chucking；　as　they　are　easily　strained　out　of　shape　by　fastening　them　by　screws　and　bolts；　or　suchlike　ordinary　means。　　This　is　especially　the　case　with　disc…like　objects。　　As　I　had　on　several　occasions　to　operate　in　the　lathe　with　this　class　of　work　I　contrived　a　method　of　chucking　or　holding　them　firm　while　receiving　the　required　turning　process；　which　has　in　all