Complex sentence: Before heading homeward, Biscoe again began charting the new coastline the expedition had found and by the end of April 1832, he had become the third man to circumnavigate the Antarctic continent, following James Cook and Fabian von Bellingshausen.
Split into simpler sentences: Before heading homeward, Biscoe again began charting the new coastline the expedition had found. By the end of April 1832, he had become the third man to circumnavigate the Antarctic continent, after James Cook and Fabian von Bellingshausen.