Complex sentence: He was promoted to lieutenant on 19 December 1846 and joined the steam frigate HMS "Spiteful" at Woolwich that same month and then transferred to second-rate HMS "Powerful" in the Mediterranean Fleet in 1848.
Split into simpler sentences: He was promoted to lieutenant on 19 December 1846 and joined the steam frigate HMS "Spiteful" at Woolwich that same month. He transferred to second-rate HMS "Powerful" in the Mediterranean Fleet in 1848.