Complex sentence: In 1818 a protest meeting was held there by coal miners to publicise their case for better pay, because of the dangers they faced at work, then, on 24 September 1838, the largest of a series of Chartist meetings was held on the moor.
Split into simpler sentences: In 1818 a protest meeting was held there by coal miners to publicise their case for better pay, because of the dangers they faced at work. Then, on 24 September 1838, the largest of a series of Chartist meetings was held on the moor.