Complex sentence: Wills returned to Australia aboard the "Oneida" steamship, arriving in a radically transformed Melbourne on 23 December 1856; the fledgling port city had risen to world renown as the booming financial centre of the Victorian gold rush.
Split into simpler sentences: Wills returned to Australia aboard the "Oneida" steamship, arriving in Melbourne on 23 December 1856. The city he left nearly seven years earlier had risen to international prominence as the booming financial centre of the Victorian gold rush.