Complex sentence: The next six years saw a series of fine watercolours at the same gallery; but in 1870, Burne-Jones resigned his membership following a controversy over his painting "Phyllis and Demophoön".
Split into simpler sentences: The next six years saw a series of fine watercolours at the same gallery. In 1870, Burne-Jones resigned his membership following a controversy over his painting "Phyllis and Demophoön".