Conversation so far:
What was the relation between Thomas Mitchell and Fourth expedtition?
Explorer Thomas Mitchell's fourth expedition was into Queensland in 1845–46, convinced that a significant river must flow north-west into the Gulf of Carpentaria.
Where did Thomas Mitchell's Fourth expedition take place?
Explorer Thomas Mitchell's fourth expedition was into Queensland in 1845–46, convinced that a significant river must flow north-west into the Gulf of Carpentaria.

Question: Which other people were there with him?
Self-contained rewrite: Which other people were there with Thomas Mitchell on the Fourth expedition?