Complex sentence: In 1751 Philip Doddridge's health, which had never been good, broke down, and he sailed for Lisbon on September 30 of that year; but the change was unavailing, and he died there.
Split into simpler sentences: In 1751 Philip Doddridge's health, which had never been good, broke down. He sailed for Lisbon on September 30 of that year; the change was unavailing, and he died there.