' s ▁critical ▁insight , ▁arrived ▁at ▁in ▁May ▁ 1 7 6 5 , ▁was ▁to ▁cause ▁the ▁steam ▁to ▁con den se ▁in ▁a ▁separate ▁chamber ▁apart ▁from ▁the ▁p ist on , ▁and ▁to ▁maintain ▁the ▁temperature ▁of ▁the ▁cyl inder ▁at ▁the ▁same ▁temperature ▁as ▁the ▁inject ed ▁steam ▁by ▁surrounding ▁it ▁with ▁a ▁" ste am ▁jack et ." ▁Thus ▁very ▁little ▁energy ▁was ▁absor bed ▁by ▁the ▁cyl inder ▁on ▁each ▁cycle , ▁making ▁more ▁available ▁to ▁perform ▁useful ▁work . ▁W att ▁had ▁a ▁working ▁model ▁later ▁that ▁same ▁year . ▁ ▁Despite ▁a ▁potentially ▁work able ▁design , ▁there ▁were ▁still ▁substantial ▁difficulties ▁in ▁construct ing ▁a ▁full - scale ▁engine . ▁This ▁required ▁more ▁capital , ▁some ▁of ▁which ▁came ▁from ▁Black . ▁More ▁substantial ▁backing ▁came ▁from ▁John ▁Ro eb uck , ▁the ▁founder ▁of ▁the ▁celebrated ▁Car ron ▁Iron ▁Works ▁near ▁F alk irk , ▁with ▁whom ▁he ▁now ▁formed ▁a ▁partners hip . ▁Ro eb uck ▁lived ▁at ▁Kin ne il ▁House ▁in ▁Bo ' ness , ▁during ▁which ▁time ▁W att ▁worked ▁at ▁perfect ing ▁his ▁steam ▁engine ▁in ▁a ▁c ott age ▁adjacent ▁to ▁the ▁house . ▁The ▁shell ▁of ▁the ▁c ott age , ▁and ▁a ▁very ▁large ▁part ▁of ▁one ▁of ▁his ▁projects , ▁still ▁exist ▁to ▁the ▁rear . ▁ ▁The ▁principal ▁difficulty ▁was ▁in ▁mach ining ▁the ▁p ist on ▁and ▁cyl inder . ▁Iron ▁workers ▁of ▁the ▁day ▁were ▁more ▁like ▁black sm ith