Theswallow-tailorunionjetwasalsohisinvention，andithassincecomeintogeneraluse。
WhilemanagingtheGas-works，oneofMr。Neilson’slaboursoflovewastheestablishmentanddirectionbyhimofaWorkmen’sInstitutionformutualimprovement。Havingbeenaworkmanhimself，andexperiencedthedisadvantagesofanimperfecteducationinearlylife，aswellasthebenefitsarisingfromimprovedcultureinlateryears，hedesiredtoimpartsomeoftheseadvantagestotheworkmeninhisemployment，whoconsistedchieflyofpersonsfromremotepartsoftheHighlandsorfromIreland。Mostofthemcouldnotevenread，andhisprincipaldifficultyconsistedinpersuadingthemthatitwasofanyusetolearn。ForsometimetheyresistedhispersuasionstoformaWorkmen’sInstitution，withaviewtotheestablishmentofalibrary，classes，andlectures，urgingasasufficientpleafornotjoiningit，thattheycouldnotread，andthatbookswouldbeofnousetothem。AtlastMr。Neilsonsucceeded，thoughwithconsiderabledifficulty，ininducingfourteenoftheworkmentoadopthisplan。
Eachmemberwastocontributeasmallsummonthly，tobelaidoutinbooks，theGasCompanyprovidingthememberswithacomfortableroominwhichtheymightmeettoreadandconverseintheeveningsinsteadofgoingtothealehouse。Thememberswereafterwardsallowedtotakethebookshometoread，andtheroomwasusedforthepurposeofconversationonthesubjectsofthebooksreadbythem，andoccasionallyforlecturesdeliveredbythemembersthemselvesongeography，arithmetic，chemistry，andmechanics。Theirnumbersincreasedsothattheroominwhichtheymetbecameinsufficientfortheiraccommodation，whentheGasCompanyprovidedthemwithanewandlargerplaceofmeeting，togetherwithalaboratoryandworkshop。
Intheformertheystudiedpracticalchemistry，andinthelattertheystudiedpracticalmechanics，makingforthemselvesanairpumpandanelectrifyingmachine，aswellaspreparingthevariousmodelsusedinthecourseofthelectures。Theeffectsontheworkmenwereeminentlybeneficial，andtheinstitutioncametobecitedasamongthemostvaluableofitskindinthekingdom。*
[footnote……
ArticlebyDugaldBannatyneinGlasgowMechanic’sMagazine，No。53，Dec。1824。
Mr。Neilsonthroughoutwatchedcarefullyoveritsworking，andexertedhimselfinallwaystopromoteitsusefulness，inwhichhehadthezealousco-operationoftheleadingworkmenthemselves，andthegratitudeofall。Ontheopeningofthenewandenlargedroomsin1825，wefindhimdeliveringanadmirableaddress，whichwasthoughtworthyofrepublication，togetherwiththereplyofGeorgeSutherland，oneoftheworkmen，inwhichMr。Neilson’sexertionsasitsfounderandchiefsupporterweregratefullyandforciblyexpressed。*
[footnote……
GlasgowMechanic’sMagazine，vol。iii。p。159。
ItwasduringtheperiodofhisconnectionwiththeGlasgowGas-worksthatMr。Neilsondirectedhisattentiontothesmeltingofiron。Hisviewsinregardtothesubjectwereatfirstsomewhatcrude，asappearsfromapaperreadbyhimbeforetheGlasgowPhilosophicalSocietyearlyin1825。Itappearsthatinthecourseoftheprecedingyearhisattentionhadbeencalledtothesubjectbyaniron-maker，whoaskedhimifhethoughtitpossibletopurifytheairblownintotheblastfurnaces，inlikemannerascarburettedhydrogengaswaspurified。Theironmastersupposedthatitwasthepresenceofsulphurintheairthatcausedblast-furnacestoworkirregularly，andtomakebadironinthesummermonths。Mr。Neilsonwasofopinionthatthiswasnotthetruecause，andhewasratherdisposedtothinkitattributabletothewantofadueproportionofoxygeninsummer，whentheairwasmorerarefied，besidescontainingmoreaqueousvapourthaninwinter。Hethereforethoughtthetrueremedywasinsomewayorothertothrowinagreaterproportionofoxygen；andhesuggestedthat，inordertodrytheair，itshouldbepassed，onitswaytothefurnace，throughtwolongtunnelscontainingcalcinedlime。Butfurtherinquiryservedtocorrecthisviews，andeventuallyledhimtothetruetheoryofblasting。
Shortlyafter，hisattentionwasdirectedbyMr。JamesEwingtoadefectinoneoftheMuirkirkblast-furnaces，situatedabouthalfamiledistantfromtheblowing-engine，whichwasfoundnottoworksowellasotherswhichweresituatedclosetoit。ThecircumstancesofthecaseledMr。Neilsontoformtheopinionthat，asairincreasesinvolumeaccordingtotemperature，ifheweretoheatitbypassingitthroughared-hotvessel，itsvolumewouldbeincreased，accordingtothewell-knownlaw，andtheblastmightthusbeenabledtodomoredutyinthedistantfurnace。HeproceededtomakeaseriesofexperimentsattheGas-works，tryingtheeffectofheatedairontheilluminatingpowerofgas，bybringingupastreamofitinatubesoastosurroundthegas-burner。Hefoundthatbythismeansthecombustionofthegaswasrenderedmoreintense，anditsilluminatingpowergreatlyincreased。Heproceededtotryasimilarexperimentonacommonsmith’sfire，byblowingthefirewithheatedair，andtheeffectwasthesame；thefirewasmuchmorebrilliant，andaccompaniedbyanunusuallyintensedegreeofheat。
Havingobtainedsuchmarkedresultsbythesesmallexperiments，itnaturallyoccurredtohimthatasimilarincreaseinintensityofcombustionandtemperaturewouldattendtheapplicationoftheprocesstotheblast-furnaceonalargescale；butbeingonlyagas-maker，hehadthegreatestdifficultyinpersuadinganyironmastertopermithimtomakethenecessaryexperiment’swithblast-furnacesactuallyatwork。Besides，histheorywasaltogetheratvariancewiththeestablishedpractice，whichwastosupplyairascoldaspossible，theprevailingideabeingthatthecoldnessoftheairinwinterwasthecauseofthebestironbeingthenproduced。
Actingontheseviews，theeffortsoftheironmastershadalwaysbeendirectedtothecoolingoftheblast，andvariousexpedientsweredevisedforthepurpose。Thustheregulatorwaspaintedwhite，asbeingthecoolestcolour；theairwaspassedovercoldwater，andinsomecasestheairpipeswereevensurroundedbyice，allwiththeobjectofkeepingtheblastcold。When，therefore，Mr。Neilsonproposedentirelytoreversetheprocess，andtoemployhotinsteadofcoldblast，theincredulityoftheironmastersmaywellbeimagined。What！Neilson，ameremakerofgas，undertaketoinstructpracticalmeninthemanufactureofiron！Andtosupposethatheatedaircanbeusedforthepurpose！Itwaspresumptionintheextreme，oratbestthemerevisionaryideaofapersonaltogetherunacquaintedwiththesubject！
Atlength，however，Mr。NeilsonsucceededininducingMr。CharlesMacintoshofCrossbasket，andMr。ColinDunlopoftheClydeIronWorks，toallowhimtomakeatrialofthehotairprocess。Inthefirstimperfectattemptstheairwasheatedtolittlemorethan80
degreesFahrenheit，yettheresultsweresatisfactory，andthescoriaefromthefurnaceevidentlycontainedlessiron。Hewasthereforedesirousoftryinghisplanuponamoreextensivescale，withtheobject，ifpossible，ofthoroughlyestablishingthesoundnessofhisprinciple。Inthishewasagooddealhamperedevenbythoseironmasterswhowerehisfriends，andhadpromisedhimtherequisiteopportunitiesformakingafairtrialofthenewprocess。
Theystronglyobjectedtohismakingthenecessaryalterationsinthefurnaces，andheseemedtobeasfarfromasatisfactoryexperimentasever。Inoneinstance，wherehehadsofarsucceededastobeallowedtoheattheblast-main，heaskedpermissiontointroducedeflectingplatesinthemainortoputabendinthepipe，soastobringtheblastmorecloselyagainsttheheatedsidesofthepipe，andalsoincreasetheareaofheatingsurface，inordertoraisethetemperaturetoahigherpoint；butthiswasrefused，anditwassaidthatifevenabendwereputinthepipethefurnacewouldstopworking。Theseprejudicesprovedaseriousdifficultyinthewayofourinventor，andseveralmoreyearspassedbeforehewasallowedtoputabendintheblast-main。Aftermanyyearsofperseverance，hewas，however，atlengthenabledtoworkouthisplanintoadefiniteshapeattheClydeIronWorks，anditspracticalvaluewasatonceadmitted。AtthemeetingoftheMechanicalEngineers’SocietyheldinMay，1859，Mr。Neilsonexplainedthathisinventionconsistedsolelyintheprincipleofheatingtheblastbetweentheengineandthefurnace，andwasnotassociatedwithanyparticularconstructionoftheintermediateheatingapparatus。This，hesaid，wasthecauseofitssuccess；andinsomerespectsitresembledtheinventionofhiscountryman，JamesWatt，who，inconnectionwiththesteam-engine，inventedtheplanofcondensingthesteaminaseparatevessel，andwassuccessfulinmaintaininghisinventionbynotlimitingittoanyparticularconstructionofthecondenser。OnthesameoccasionhetooktheopportunityofacknowledgingthefirmnesswithwhichtheEnglishironmastershadstoodbyhimwhenattemptsweremadetodeprivehimofthebenefitsofhisinvention；andtothemheacknowledgedhewasmainlyindebtedforthesuccessfulissueoftheseverecontestshehadtoundergo。Fortherewere，ofcourse，certainoftheironmasters，bothEnglishandScotch，supportersofthecauseoffreetradeinothers’inventions，whosoughttoresistthepatent，afterithadcomeintogeneraluse，andhadbeenrecognisedasoneofthemostvaluableimprovementsofmodemtimes。*
[footnote……
Mr。Mushetdescribeditas”awonderfuldiscovery，”andoneofthe”mostnovelandbeautifulimprovementsinhistime。”ProfessorGregoryofAberdeencharacterizeditas”thegreatestimprovementwithwhichhewasacquainted。”Mr。Jessop，anextensiveEnglishironmanufacturer，declaredittobe”ofasgreatadvantageintheirontradeasArkwright’smachinerywasinthecotton-spinningtrade；andMr。Fairbairn，inhiscontributionon”Iron”intheEncyclopaediaBritannica，saysthatit”haseffectedanentirerevolutionintheironindustryofGreatBritain，andformsthelasterainthehistoryofthismaterial。”
Thepatentwassecuredin1828foratermoffourteenyears；but，asMr。Neilsondidnothimselfpossesstherequisitecapitaltoenablehimtoperfecttheinvention，ortodefenditifattacked，hefounditnecessarytoinviteothergentlemen，abletosupporthimintheserespects，toshareitsprofits；retainingforhimselfonlythree-tenthsofthewhole。HispartnerswereMr。CharlesMacintosh，Mr。ColinDunlop，andMr。JohnWilsonofDundyvan。Thechargemadebythemwasonlyashillingatonforallironproducedbythenewprocess；thislowratebeingfixedinordertoensuretheintroductionofthepatentintogeneraluse，aswellastoreducetoaminimumthetemptationsoftheironmasterstoinfringeit。
Thefirsttrialsoftheprocessweremadeattheblast-furnacesofClydeandCalder；fromwhencetheuseofthehotblastgraduallyextendedtotheotheriron-miningdistricts。InthecourseofafewyearseveryfurnaceinScotland，withoneexceptionthatatCarron，hadadoptedtheimprovement；whileitwasalsoemployedinhalfthefurnacesofEnglandandWales，andinmanyofthefurnacesontheContinentandinAmerica。Incourseoftime，andwithincreasingexperience，variousimprovementswereintroducedintheprocess，moreparticularlyintheshapeoftheair-heatingvessels；thelastformadoptedbeingthatofacongeriesoftubes，similartothetubulararrangementintheboilerofthelocomotive，bywhichthegreatestextentofheatingsurfacewasprovidedforthethoroughheatingoftheair。Bythesemodificationsthetemperatureoftheairintroducedintothefurnacehasbeenraisedfrom240degreesto600degrees，orthetemperatureofmeltinglead。Toprotectthenozzleoftheair-pipeasitenteredthefurnaceagainsttheactionoftheintenseheattowhichitwassubjected，aspiralpipeforastreamofcoldwaterconstantlytoplayinhasbeenintroducedwithinthesidesoftheirontuyerethroughwhichthenozzlepasses；bywhichmeansthetuyereiskeptcomparativelycool，whilethenozzleoftheair-pipeiseffectuallyprotected。*
[footnote……
Theinventionofthetubularair-vesselsandthewater-tuyerebelongs，webelieve，toMr。JohnCondie，sometimemanageroftheBlairIronWorks。
Thisvaluableinventiondidnotescapetheusualfateofsuccessfulpatents，anditwasonseveraloccasionsthesubjectofprotractedlitigation。Thefirstactionoccurredin1832；buttheobjectorsshortlygavein，andrenewedtheirlicence。In1839，whentheprocesshadbecomegenerallyadoptedthroughoutScotland，and，indeed，wasfoundabsolutelyessentialforsmeltingthepeculiaroresofthatcountry——moreespeciallyMushet’sBlackBand——apowerfulcombinationwasformedamongsttheironmasterstoresistthepatent。Thelitigationwhichensuedextendedoverfiveyears，duringwhichperiodsometwentyactionswereproceedinginScotland，andseveralinEngland。Threejuriessatuponthesubjectatdifferenttimes，andonthreeoccasionsappealswerecarriedtotheHouseofLords。Onejurytrialoccupiedtendays，duringwhichahundredandtwowitnesseswereexamined；thelawcostsonbothsidesamounting，itissupposed，toatleast40，000L。Theresultwas，thatthenoveltyandmeritofMr。Neilson’sinventionwerefinallyestablished，andhewassecuredintheenjoymentofthepatentright。
Wearegratifiedtoadd，that，thoughMr。Neilsonhadtopartwithtwo-thirdsoftheprofitsoftheinventiontosecurethecapitalandinfluencenecessarytobringitintogeneraluse，herealizedsufficienttoenablehimtoenjoytheeveningofhislifeinpeaceandcomfort。Heretiredfromactivebusinesstoanestatewhichhepurchasedin1851intheStewartryofKirkcudbright，whereheisfoundreadytolendahandineverygoodwork——whetherinagriculturalimprovement，railwayextension，orthemoralandsocialgoodofthoseabouthim。MindfulofthesuccessofhisWorkmen’sInstitutionattheGlasgowGas-Works，hehas，almostathisowndoor，erectedasimilarInstitutionfortheuseoftheparishinwhichhispropertyissituated，thebeneficialeffectsofwhichhavebeenverymarkedinthedistrict。WemayaddthatMr。Neilson’smeritshavebeenrecognisedbymanyeminentbodies——bytheInstitutionofCivilEngineers，theChemicalSociety，andothers——thelasthonourconferredonhimbeinghiselectionasaMemberoftheRoyalSocietyin1846。
Theinventionofthehotblast，inconjunctionwiththediscoveryoftheBlackBandironstone，hashadanextraordinaryeffectuponthedevelopmentoftheiron-manufactureofScotland。Thecoalsofthatcountryaregenerallyunfitforcoking，andloseasmuchas55percent。intheprocess。Butbyusingthehotblast，thecoalcouldbesenttotheblast-furnaceinitsrawstate，bywhichalargesavingoffuelwaseffected。*
[footnote……
Mr。Mushetsays，”ThegreatestproduceinironperfurnacewiththeBlackBandandcoldblastneverexceeded60tonsa-week。Theproduceperfurnacenowaverages90tonsa-week。TentonsofthisIattributetotheuseofrawpit-coal，andtheothertwentytonstotheuseofhotblast。”[PapersonIronandSteel，127。]Theproduceperfurnaceisnow200tonsa-weekandupwards。ThehotblastprocesswasafterwardsappliedtothemakingofironwiththeanthraciteorstonecoalofWales；forwhichapatentwastakenoutbyGeorgeCranein1836。Beforethehotblastwasintroduced，anthracitecoalwouldnotactasfuelintheblast-furnace。Whenputin，itmerelyhadtheeffectofputtingthefireout。Withtheaidofthehotblast，however，itnowprovestobeamostvaluablefuelinsmelting。