Mallet's Monster Mortar - and the Birth of Seismology

Mallet's Monster Mortar – and the Birth of Seismology. Today the Crimean War (1854-56) is remembered for organisational and tactical ... Skiptocontent Mallet’sMonsterMortar–andtheBirthofSeismologyAntoineVanner2017-04-08T15:52:06+00:00 Mallet’sMonsterMortar–andtheBirthofSeismology TodaytheCrimeanWar(1854-56)isrememberedfororganisationalandtacticalincompetencethatledtospectaculardisasterssuchastheChargeoftheLightBrigadeatBalaclava,andthelessspectacular,butmoredeadlylarge-scalelossesresultingfrompoorlogisticsandinadequatemedicalcare. ThoughlimitedoperationswereconductedintheBaltic,thefocusofthealliedBritish,FrenchandTurkishforcesarraignedagainstRussiawereconcentratedincaptureofthehugenavalbaseofSebastopolintheCrimea.Theconflictdevelopedintoanextendedsiege,inwhichalliedforceswerefacedwiththereductionofwell-engineeredRussianfortifications.Enduringthesavagewinterof1854-55inexposedtrenches,thebesiegerssufferedappallinglossesfromcoldanddiseaseandtheirartillerywastoproveinadequateinblastingbreachesthroughwhichsuccessfulassaultscouldbelaunched.Thoughmajorfortificationsknownasthe“GreatRedan”and“TheMalakoffRedoubt”werefinallystormedbytheBritishandFrenchrespectivelyinSeptember1855,thecostinliveswasappalling. Sebastopoldefences–seemfromRussianside–a panoramicpaitingbytheRussianartistFranzRouobaud  Oneofthemajorlessonsofthewar–indeedonethatwaslearnedearlyonduringtheSebastopolsiege–wasthatmoreeffectiveartillerywasrequired.Thiswasespeciallythecaseasregardsmortars,capableofsupplyingplungingfirewhichwouldraindowndestructionnotonlyonwalls,butthedefendersbehindthem. RobertMallet It isatthispoint–intheearlystageofthewar–atwhichoneoftheunjustly-forgottentechnologicalgiantsoftheVictorianperiodentersthestory.RobertMallet(1810–1881),wasborninDublin,on3June1810,thesonoftheownerofanironfoundry.In1830MalletgraduatedinscienceandmathematicsatTrinityCollege,Dublin,andthereafterworkedwithhisfathertobuildtheirbusinessintooneofIreland’smostimportantengineeringcompanies.Notableachievementsweresupplyofironworkfortheexpandingrailwaynetwork,forthefirstFastnetRocklighthouseandforaswingbridgeovertheRiverShannon. InparallelwiththesebusinessinterestsMalletdevelopedaninterestinearthquakesandin1846presentedapapertotheRoyalIrishAcademy“OntheDynamicsofEarthquakes”.Thisisnowconsideredtobeoneofthefoundationsofmodernseismology–indeedMalletiscreditedwithcoiningtheword“seismology”aswellas“epicentre”.MalletwasparticularlyinterestedinassessingtheenergyunleashedbyearthquakesandwithhissonJohnundertookaseriesofexperimentsonhowsoundorenergymovesthroughsandandrock.Themostimportantoftheselaidthefoundationofmodernseismictechniquesusedinexplorationofoilandgasreserves. Inthis,akegofgunpowderwasburiedonKillineyBeach,southofDublin,andthendetonated.UsingaprimitiveformofseismometerhalfamileawayMalletmeasuredtheresultingenergywave,thusdemonstratingitsabilitytotravelthoughsandandrock. RAFpersonnelwith22,000lb“GrandSlam”1945 ItisprobablyMallet’sinsightintotheeffectsofadeepexplosionthatledtohisproposalinlate1854,whentheSiegeofSebastopolwasstillinitsearlystages,forthecreationofagiantmortar.HisreasoningmayhavebeensimilartothatofthegreatBritishengineer,BarnesWallis,whichledtothedevelopmentofthe22000lb“GrandSlam”bombofWW2.Droppedfromanaircraft,suchbombsweredesignedtodetonateonlyaftertheyhadpenetrateddeepintheground,thussettingoffalocalearthquake.Theyprovedespeciallyeffectiveindemolishinghard-to-hittargetssuchasrailwayviaductssinceadirecthitwasnotnecessary,theearthquakeeffectbeingsufficienttobringthemdown.InMallet’sdayaircraftwerenotavailableandtheonlywayofachievingasimilareffectwastolobabombsufficientlyhighintheair–andforthisamortarwasrequired. Malletrecognisedthatthebombthrownbysuchamortarneededtobemassive–hewasthinkingintermsofaton,morethanhadbeeneverattemptedpreviously–andthemortaritselfmustbealsobeenormousandlikelytobetooheavyfordeploymentinthefield.ItwasnowthatMalletbroughthisiron-founder’sinsightsintoplayandhedesignedamortarwhichwouldbemadeupofmultipleparts–eachlargeinitsownright,buttransportablewiththemeansthenavailable–andassembledclosetothetarget.Theillustrationbelowshowstheconstructionofthebarrel.Theborewas36inchesandthetotalweightcameto42tons. TherewaslittleofficialinterestintheproposalinitiallybutinMarch1855,withthesiegedraggingonwithlittleimmediatehopeofsuccess,MalletapproachedthePrimeMinister,LordPalmerston.HewasimpressedandheinstructedtheArmy’sBoardofOrdnancetoarrangeconstructionoftwoweapons.Completionofthemortarswastoprovelongerthanthesiegeitself–notleastbecauseofbankruptcyofthecompanyinitiallycontractedtoprovidethem,andthelettingoftheworktothreeothers.TheweaponswerefinallydeliveredfortestinginMay1857,overayearafterthewarhadended. MalletMortarontestingrange1857  Nineteenbombswerefiredduringthreeseparatetestingrounds,eachbeingbroughttoanendbydamagetothemortar.Arateoffourfiringsperhourwasachieved.Thebombsvariedinweightbetween2,352and2,940pounds–welloveraton.An80poundfiringchargepropelledthelightershell2,759yards(Overamileandahalf,twoandahalfkilometres)andtheflighttimewas23seconds.Theconclusionfromthetestingwasthattheweaponswerenotusable.Thismaywellhavebeenduetothemetallurgicallimitationsofthetime,fortheconceptwasvalid.Largemortars,butnoneaslargeastheMallet,weretobeusedwithdevastatingeffectintheAmericanCivilWar,theRusso-TurkishWarof1877/78andtheRusso-JapaneseWarof1904/05. MalletMortaratFortNelson AntoineVannerprovidesahintastoscale–andbombsinforegroundare36″diameter Methodofelevationcanbeseen–timberbaulksusedtochangeangle Sebastopolwashowevertoseedeploymentofgiantmortarsinalatersiege.In1942Germanforcesusedself-propelled“Karl-Gerät”siegemortarstoreducethefortress.Thesemonstersfired24inchshellsof4780poundsmaximum,andachievedasix-milerangewithlighter2,760lbshells.Eachweaponwasbyacrane,aheavytransporttrailer,andseveralmodifiedtankstocarryshells. ThetwoMalletMortarsstillexist.TheweaponusedfortestingcanbeseenatWoolwich,SELondon(junctionofRepositoryandHillreachRoads,easilyvisibleonGoogleEarthstreetview),closetowhatwasthearsenalthere.Theunfiredmortar isondisplayattheRoyalArmouriesMuseumatFortNelson,justnorthof nearPortsmouth.Thephotographsweretakenthererecently. Karl-GeratinactioninWW2 Despitethefailureofhismortar,RobertMallet’scareercontinuedtoprosper.Hisdetailedinvestigationofthe1857GreatNeapolitanEarthquake,whichcaused11,000deaths,producedatwo-volumereport, subtitled“TheFirstPrinciplesofObservationalSeismology”andinithedemonstratedthattheearthquakehadsomeeighttoninemilesbelowthesurface.Malletwasalsotodopioneeringworkonvolcanology.HewaselectedFellowoftheRoyalSocietyin1854,andmovedtoLondonin1861.Highlyhonoured,itissadtorecordthathewasblindforthelastsevenyearsofhislife.HeisburiedatWestNorwoodCemetery–anEminentVictorianwhodeservestoberemembered. ClickheretoreturntoSteam,SteelandStrife… Pageloadlink GotoTop