Complex sentence: He returned at 23 to Charters Towers and worked 1908--13 as a bookkeeper to a butcher; bad health brought the job to an end, as it did most of his Queensland jobs.
Split into simpler sentences: He returned at 23 to Charters Towers and worked 1908--13 as a bookkeeper to a butcher. Bad health brought the job to an end, as it did most of his Queensland jobs.