Simplify the following text for a Grade 9 native English-speaking person.
Original: In 1818 , Hume went on a journey with James Meehan , the deputy surveyor-general , and Charles Throsby during which Lake Bathurst and the Goulburn Plains were discovered .
Simplified: In March 1817 he went on a journey with James Meehan , the deputy surveyor-general , and discovered Lake Bathurst and the Goulburn Plains .