Governor Phillip appointed Jamison as surgeon to the Norfolk Island colony. He would perform this role in an effective manner for the next decade despite being hindered in his work by a persistent lack of logistical support from Sydney. One of his achievements was to reduce the number of deaths occurring on the island due to dysentery. In 1790, he witnessed the catastrophic wrecking of the "Sirius" on a Norfolk Island reef after the vessel got into difficulties during a supply operation. Eleven months would elapse before another ship reached the isolated colonists. Norfolk Island's remoteness from Sydney enabled Jamison to live openly with a convict mistress, Elizabeth Colley, by whom he had numerous illegitimate offspring. He was also able to enrich himself by trading in pork, wheat and, later, Indian sandalwood and alcohol. One of Jamison's friends and business associates during this period was the surgeon, explorer and entrepreneur George Bass, who disappeared at sea in 1803.