Complex sentence: He held office from 1885 to 1907 and was succeeded by his son Stephen (1908-1912), who enlarged the type into the capable 1500 4-6-0 design.
Split into simpler sentences: He held office from 1885 to 1907, being succeeded by his son Stephen (1908-1912). The latter enlarged the type into the capable 1500 4-6-0 design.