Complex sentence: He then obtained employment in the drawing office of the GER Works at Stratford, London where he remained until September 1879 when he was then appointed as the Locomotive Carriage & Wagon and Marine Superintendent for the LT&SR at their Plaistow Works.
Split into simpler sentences: He then obtained employment in the drawing office of the GER Works at Stratford, London where he remained until September 1879. Next, he was then appointed as the Locomotive Carriage & Wagon and Marine Superintendent for the LT&SR at their Plaistow Works.