Complex sentence: The canal was built to reduce the cost of transporting coal from the Tyrone coalfields to Dublin and, in conjunction with Dukart's Canal, linked the coalfields with Lough Neagh, via the River Blackwater.
Split into simpler sentences: The canal was built to reduce the cost of transporting coal from the Tyrone coalfields to Dublin. An extension "Dukart's Canal", linked the coalfields with Lough Neagh via the River Blackwater.