Inourformerassumption，accordingtowhich6workinghoursaredailynecessaryinordertoreproducethelabour—poweritselfortoreplacethevalueofthecapitaladvancedinitspurchase，avariablecapitalof1，500s。，thatemploys500labourersatarateofsurplusvalueof100%witha12hours’
workingday，producesdailyasurplusvalueof1，500s。orof6x500workinghours。
Acapitalof300s。thatemploys100labourersadaywitharateofsurplusvalueof200%orwithaworkingdayof18hours，producesonlyamassofsurplusvalueof600s。or12x100workinghours;anditstotalvalue—product，theequivalentofthevariablecapitaladvancedplusthesurplus—value，can，dayin，dayout，neverreachthesumof1，200s。or24x100workinghours。Theabsolutelimitoftheaverageworkingday？thisbeingbynaturealwayslessthan24hours？setsanabsolutelimittothecompensationofareductionofvariablecapitalbyahigherrateofsurplusvalue，orofthedecreaseofthenumberoflabourersexploitedbyahigherdegreeofexploitationoflabour—power。Thispalpablelawisofimportancefortheclearingupofmanyphenomena，arisingfromatendency（tobeworkedoutlateron）ofcapitaltoreduceasmuchaspossiblethenumberoflabourersemployedbyit，oritsvariableconstituenttransformedintolabour—power，incontradictiontoitsothertendencytoproducethegreatestpossiblemassofsurplusvalue。
Ontheotherhand，ifthemassoflabour—poweremployed，ortheamountofvariablecapital，increases，butnotinproportiontothefallintherateofsurplusvalue，themassofthesurplusvalueproduced，falls。
Athirdlawresultsfromthedetermination，ofthemassofthesurplus—valueproduced，bythetwofactors:rateofsurplusvalueandamountofvariablecapitaladvanced。Therateofsurplusvalue，orthedegreeofexploitationoflabour—power，andthevalueoflabour—power，ortheamountofnecessaryworkingtimebeinggiven，itisselfevidentthatthegreaterthevariablecapital，thegreaterwouldbethemassofthevalueproducedandofthesurplusvalue。Ifthelimitoftheworking—dayisgiven，andalsothelimitofitsnecessaryconstituent，themassofvalueandsurplusvaluethatanindividualcapitalistproduces，isclearlyexclusivelydependentonthemassoflabourthathesetsinmotion。Butthis，undertheconditionssupposedabove，dependsonthemassoflabour—power，orthenumberoflabourerswhomheexploits，andthisnumberinitsturnisdeterminedbytheamountofthevariablecapitaladvanced。Withagivenrateofsurplusvalue，andagivenvalueoflabour—power，therefore，themassesofsurplusvalueproducedvarydirectlyastheamountsofthevariablecapitalsadvanced。Nowweknowthatthecapitalistdivideshiscapitalintotwoparts。Oneparthelaysoutinmeansofproduction。Thisistheconstantpartofhiscapital。Theotherparthelaysoutinlivinglabour—power。