Thecoal，therefore，hasvalue，mustbepaidforbyanequivalent，andhasacost。Thewaterfallisanaturalproductionagentintheproductionofwhichnolabourenters。
Butthisisnotall。Themanufacturerwhooperateswithsteamalsoemploysnaturalforceswhichcosthimnothingyetmakethelabourmoreproductiveandincreasethesurplus-valueandtherebytheprofit，inasmuchastheythuscheapenthemanufactureofthemeansofsubsistencerequiredforthelabourers。Thesenaturalforcesarethusquiteasmuchmonopolisedbycapitalasthesocialnaturalforcesoflabourarisingfromco-operation，divisionoflabour，etc。Themanufacturerpaysforcoal，butnotforthecapacityofwatertoalteritsphysicalstate，toturnintosteam，notfortheelasticityofthesteam，etc。Thismonopolisationofnaturalforces，thatis，oftheincreaseinlabour-powerproducedbythem，iscommontoallcapitaloperatingwithsteam-engines。Itmayincreasethatportionoftheproductoflabourwhichrepresentssurplus-valueinrelationtothatportionwhichistransformedintowages。Insofarasitdoesthis，itraisesthegeneralrateofprofit，butitdoesnotcreateanysurplus-profit，forthisconsistsoftheexcessofindividualprofitoveraverageprofit。Thefactthattheapplicationofanaturalforce，awaterfall，createssurplus-profitinthiscase，cannotthereforebeduesolelytothecircumstancethattheincreasedproductivityoflabourhereresultsfromtheapplicationofanaturalforce。Othermodifyingcircumstancesarenecessary。
Conversely。Themereapplicationofnaturalforcesinindustrymayinfluencethelevelofthegeneralrateofprofitbecauseitaffectsthequantityoflabourrequiredtoproducethenecessarymeansofsubsistence。
Butinitselfitdoesnotcreateanydeviationfromthegeneralrateofprofit，andthisispreciselythepointinwhichweareinterestedhere。
Furthermore，thesurplus-profitwhichsomeindividualcapitalotherwiserealisesinaparticularsphereofproduction-fordeviationsoftheratesofprofitinvariousspheresofproductionarecontinuallybalancedoutintoanaveragerate-isdue，asidefromfortuitousdeviations，toareductionincost-price，inproductioncosts。Thisreductionariseseitherfromthefactthatcapitalisusedingreaterthanaveragequantities，sothatfauxfraisofproductionarereduced，whilethegeneralcausesincreasingtheproductivenessoflabourcooperation，divisionoflabour，etc。canbecomeeffectivetoahigherdegree，withmoreintensity，becausetheirfieldofactivityhasbecomelarger；oritmayarisefromthefactthat，asidefromtheamountoffunctioningcapital，bettermethodsoflabour，newinventions，improvedmachinery，chemicalmanufacturingsecrets，etc。，inshort，newandimproved，betterthanaveragemeansofproductionandmethodsofproductionareused。Thereductionincost-priceandthesurplus-profitarisingfromitareheretheresultofthemannerinwhichthefunctioningcapitalisinvested。Theyresulteitherfromthefactthatthecapitalisconcentratedinthehandsofonepersoninextraordinarilylargequantitiesaconditionthatiscancelledoutassoonasequalmagnitudesofcapitalareusedontheaverage，orfromthefactthatacertainmagnitudeofcapitalfunctionsinaparticularlyproductivemanneraconditionthatdisappearsassoonastheexceptionalmethodofproductionbecomesgeneralorissurpassedbyastillmoredevelopedone。