Complex sentence: Following the amalgamation of the two companies on 1 July 1889 all the remaining viaducts were replaced, those between Saltash and St Germans being replaced by a deviation line, the remainder being either rebuilt in situ or having a replacement viaduct built immediately alongside.
Split into simpler sentences: Following the amalgamation of the two companies on 1 July 1889 all the remaining viaducts were replaced. Most were either rebuilt in situ or by a replacement viaduct built immediately alongside.