Complex sentence: He frequented some areas also frequented by some members of the English labour and Chartist movements, whom he met, and wrote for several journals, including "The Northern Star", Robert Owen's "New Moral World" and the "Democratic Review" newspaper.
Split into simpler sentences: He frequented some areas also habituated by some members of the English labour and Chartist movements, whom he met. He also wrote for several journals, including "The Northern Star", Robert Owen's "New Moral World" and the "Democratic Review" newspaper.