Complex sentence: During the lieutenant-governorship of Francis Grose, who unmercifully exploited the convicts, a great traffic in alcoholic spirits sprang up, on which there was an enormous profit for the officers concerned.
Split into simpler sentences: During the lieutenant-governorship of Francis Grose unmercifully exploited the convicts. A great traffic in alcoholic spirits sprang up, on which there was an enormous profit for the officers concerned.