▁join ▁the ▁c ement ▁business , ▁re using ▁some ▁of ▁the ▁technology ▁he ▁had ▁developed ▁for ▁ore - m illing . ▁ ▁Early ▁develop ments ▁Ed ison ▁made ▁significant ▁improvements ▁to ▁the ▁production ▁process ▁of ▁c ement . ▁ ▁His ▁mill ▁in ▁the ▁valley ▁of ▁the ▁Del aware ▁River ▁in ▁New ▁Jersey ▁featured ▁the ▁first ▁long , ▁rot ating ▁kil ns ▁in ▁the ▁world . ▁ ▁While ▁the ▁standard ▁length ▁was ▁between ▁ 6 0 ▁and ▁ 8 0 ▁feet , ▁Ed ison ' s ▁kil ns ▁were ▁up ▁to ▁ 1 5 0 ▁feet . ▁ ▁To ▁improve ▁his ▁financial ▁stability ▁he ▁lic ensed ▁the ▁kil ns ▁to ▁other ▁manufact ur ers , ▁but ▁this ▁helped ▁his ▁compet itors ▁to ▁improve ▁their ▁production . ▁Event ually , ▁the ▁industry ▁became ▁s atur ated ▁and ▁Ed ison ' s ▁business ▁was ▁not ▁particularly ▁prof itable . ▁ ▁Con crete ▁housing ▁ ▁Some what ▁ahead ▁of ▁his ▁time ▁Ed ison ▁believed ▁that ▁concrete ▁would ▁have ▁a ▁wide ▁range ▁of ▁applications , ▁but ▁in ▁the ▁early ▁ 2 0 th ▁century ▁its ▁production ▁was ▁not ▁sufficiently ▁econom ical . ▁ ▁He ▁en vision ed ▁a ▁future ▁with ▁concrete ▁houses ▁filled ▁with ▁concrete ▁furn iture , ▁re fr iger ators , ▁and ▁pian os . ▁ ▁While ▁none ▁of ▁these ▁items ▁were ▁made ▁Ed ison ▁did ▁create ▁concrete ▁ph on ograph ▁cabin ets . ▁ ▁Ed ison ▁investig ated ▁the ▁use ▁of ▁form work ▁m olds ▁that ▁could ▁repeatedly ▁be ▁used ▁to ▁create ▁concrete ▁houses ,