Complex sentence: Turnbull who meanwhile had returned to the Delta from San Francisco with another cargo and a more powerful engine for the Uncle Sam, returned for a new hull, while the army sent wagons to recover the cargo from the delta again.
Split into simpler sentences: Turnbull who meanwhile had returned to the Delta from San Francisco with another cargo and a more powerful engine for the Uncle Sam. He returned for a new hull, while the army sent wagons to recover the cargo from the delta again.