Complex sentence: Soon after the voyage of the "Beagle", Charles Darwin went in October 1836 to stay with his brother Erasmus in London, and found him spending his days "driving out Miss Martineau".
Split into simpler sentences: Soon after the voyage of the "Beagle", Charles Darwin went in October 1836 to stay with his brother Erasmus in London. He found him spending his days "driving out Miss Martineau".