The standard gauge Aberystwyth and Welsh Coast Railway was expanding rapidly from its base at Machynlleth however . In 1863 this railway had reached Tywyn , so McConnel decided to build his line from the quarry to Tywyn . The standard gauge Aberystwyth and Welsh Coast Railway was expanding rapidly from its base at Machynlleth , however , and in 1863 had reached Tywyn , so McConnel decided to build his line from the quarry to Tywyn , as the nearest point where slate could be transferred to the standard gauge railway .