Complex sentence: Work on railway expansion from Port Elizabeth into the interior was already underway in 1874 and the locomotive was put to work as construction engine on the mainline that was being built northward from Swartkops via Barkly Bridge, Addo, Alicedale and Cookhouse to Cradock.
Split into simpler sentences: Work on railway expansion from Port Elizabeth into the interior was already underway in 1874. The locomotive was put to work as construction engine on the mainline, which was being built northward from Swartkops via Barkly Bridge, Addo, Alicedale and Cookhouse to Cradock.