▁circular s ▁to ▁the ▁Central ▁and ▁Provin cial ▁Offic ers . ▁It ▁co - ordin ated ▁the ▁work ▁of ▁all ▁Bo ards ▁and ▁de alt ▁with ▁all ▁correspond ence ▁as ▁the ▁chief ▁secret ariat . ▁ ▁Di wan ▁al - K hat am ▁In ▁order ▁to ▁reduce ▁forg ery , ▁Di wan ▁al - K hat am ▁( B ureau ▁of ▁Reg istry ), ▁a ▁kind ▁of ▁state ▁ch an cell ery , ▁was ▁instit uted ▁by ▁Mu ' aw iy ah . ▁It ▁used ▁to ▁make ▁and ▁preserve ▁a ▁copy ▁of ▁each ▁official ▁document ▁before ▁se aling ▁and ▁des patch ing ▁the ▁original ▁to ▁its ▁destination . ▁Thus ▁in ▁the ▁course ▁of ▁time ▁a ▁state ▁archive ▁developed ▁in ▁Dam asc us ▁by ▁the ▁Um ay y ads ▁under ▁Abd ▁al - Mal ik . ▁This ▁department ▁surv ived ▁till ▁the ▁middle ▁of ▁the ▁Abb as id ▁period . ▁ ▁Di wan ▁al - Bar id ▁ ▁Mu ' aw iy ah ▁introduced ▁postal ▁service , ▁Abd ▁al - Mal ik ▁extended ▁it ▁throughout ▁his ▁emp ire , ▁and ▁Wal id ▁made ▁full ▁use ▁of ▁it . ▁U mar ▁bin ▁Abd ul - Az iz ▁developed ▁it ▁further ▁by ▁building ▁car av ans era is ▁at ▁stages ▁along ▁the ▁Kh uras an ▁highway . ▁Rel ays ▁of ▁horses ▁were ▁used ▁for ▁the ▁convey ance ▁of ▁dispatch es ▁between ▁the ▁cal i ph ▁and ▁his ▁agents ▁and ▁officials ▁posted ▁in ▁the ▁provinces . ▁The ▁main ▁high ways ▁were ▁divided ▁into ▁stages ▁of ▁ ▁each