Itappears，then，thatthemechanicalstudiesofGalileo，takenasawhole，werenothinglessthanrevolutionary。TheyconstitutedthefirstgreatadvanceuponthedynamicstudiesofArchimedes，andthenledtothesecurefoundationforoneofthemostimportantofmodernsciences。WeshallseethatanimportantcompanyofstudentsenteredthefieldimmediatelyafterthetimeofGalileo，andcarriedforwardtheworkhehadsowellbegun。
Butbeforepassingontotheconsiderationoftheirlabors，wemustconsiderworkinalliedfieldsoftwomenwhowerecontemporariesofGalileoandwhoseoriginallaborswereinsomerespectsscarcelylessimportantthanhisown。ThesemenaretheDutchmanStevinus，whomustalwaysberememberedasaco-laborerwithGalileointhefoundationofthescienceofdynamics，andtheEnglishmanGilbert，towhomisduetheunqualifiedpraiseoffirstsubjectingthephenomenonofmagnetismtoastrictlyscientificinvestigation。
Stevinuswasbornintheyear1548，anddiedin1620。Hewasamanofapracticalgenius，andheattractedtheattentionofhisnon-scientificcontemporaries，amongotherways，bytheconstructionofacuriousland-craft，which，mountedonwheels，wastobepropelledbysailslikeaboat。Notonlydidhewriteabookonthiscurioushorselesscarriage，butheputhisideaintopracticalapplication，producingavehiclewhichactuallytraversedthedistancebetweenScheveningenandPetton，withnofewerthantwenty-sevenpassengers，oneofthembeingPrinceMauriceofOrange。Thisdemonstrationwasmadeabouttheyear1600。Itdoesnotappear，however，thatanyimportantusewasmadeofthestrangevehicle；butthemanwhoinventeditputhismechanicalingenuitytootherusewithbettereffect。Itwashewhosolvedtheproblemofobliqueforces，andwhodiscoveredtheimportanthydrostaticprinciplethatthepressureoffluidsisproportionatetotheirdepth，withoutregardtotheshapeoftheincludingvessel。
ThestudyofobliqueforceswasmadebyStevinuswiththeaidofinclinedplanes。Hismostdemonstrativeexperimentwasaverysimpleone，inwhichachainofballsofequalweightwashungfromatriangle；thetrianglebeingsoconstructedastorestonahorizontalbase，theobliquesidesbearingtherelationtoeachotheroftwotoone。Stevinusfoundthathischainofballsjustbalancedwhenfourballswereonthelongersideandtwoontheshorterandsteeperside。Thebalancingofforcethusbroughtaboutconstitutedastableequilibrium，Stevinusbeingthefirsttodiscriminatebetweensuchaconditionandtheunbalancedconditioncalledunstableequilibrium。Bythissimpleexperimentwaslaidthefoundationofthescienceofstatics。Stevinushadafullgraspoftheprinciplewhichhisexperimentinvolved，andheappliedittothesolutionofobliqueforcesinalldirections。
EarlierinvestigationsofStevinuswerepublishedin1608。HiscollectedworkswerepublishedatLeydenin1634。