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History of the Cannon
Proceding,then,totheattractionoftheearth,thatis,theweightoftheshell,weknowthatthisweightwilldiminishintheinverseratioofthesquareofthedistance.Whenabodylefttoitselffallstothesurfaceoftheearth,itfallsfivefeetinthefirstsecond;andifthesamebodywereremoved257,542milesfurtheroff,inotherwords,tothedistanceofthemoon,itsfallwouldbereducedtoabouthalfalineinthefirstsecond.Thatisalmostequivalenttoastateofperfectrest.Ourbusiness,then,istoovercomeprogressivelythisactionofgravitation.Themodeofaccomplishingthatisbytheforceofimpulsion."
"There’sthedifficulty,"brokeinthemajor.
"True,"repliedthepresident;"butwewillovercomethat,fortheforceofimpulsionwilldependonthelengthoftheengineandthepowderemployed,thelatterbeinglimitedonlybytheresistingpoweroftheformer.Ourbusiness,then,to-dayiswiththedimensionsofthecannon."
"Now,uptothepresenttime,"saidBarbicane,"ourlongestgunshavenotexceededtwenty-fivefeetinlength.Weshallthereforeastonishtheworldbythedimensionsweshallbeobligedtoadopt.Itmustevidentlybe,then,agunofgreatrange,sincethelengthofthepiecewillincreasethedetentionofthegasaccumulatedbehindtheprojectile;butthereisnoadvantageinpassingcertainlimits."
"Quiteso,"saidthemajor.
