Complex sentence: The main source of traffic was from the pits at Moira, which steadily expanded, particularly in the 1820s, enabling the loans to be paid off between 1820 and 1827, and the first dividend to be paid in 1828.
Split into simpler sentences: The main source of traffic was from the pits at Moira, which steadily expanded, particularly in the 1820s. The loans were paid off between 1820 and 1827, and the first dividend was paid in 1828.