Why did Thomas Mitchell go on 4 expeditions?

Answer 1

Thomas Mitchell was Surveyor-General of New South Wales: thus, it was his role to explore new land.

Mitchell's first expedition was to investigate rumours of a north-flowing river situated in northern New South Wales: a river that did not exist, but stories of which were spread by an escaped convict. His second journey, which set out in 1835, was to follow and map the course of the Darling River which Sturt had discovered some years earlier. Mitchell was determined to prove Sturt wrong in the latter's belief that the river flowed southward into the Murray, as Mitchell believed it must flow northwest. After travelling for several months and following the Darling for almost 500km, Mitchell was forced to admit that Sturt was indeed correct.

Mitchell was notorious for disobeying orders. Believing that his own experience gave him the right to divert from his course if he felt it was prudent to do so, he continually ignored the orders he was given. He was sent on his third journey in 1836 because he did not stick to the orders he was given, and he was directed to finish what he did not do in 1835. Again, he departed from the planned route.

As for his final expedition - one of the reasons for Thomas Mitchell's 1845-46 expedition into western Queensland was that he hoped to find an overland route from Sydney to Port Essington.