Complex sentence: He also began to preach to the Wesleyan Methodists and lead a Bible class; but in 1842, he became so captivated by the doctrine of the Second Coming of Christ that he severed his connection with the Methodists and joined the Plymouth Brethren.
Split into simpler sentences: He also began to preach to the Wesleyan Methodists and lead a Bible class. Nevertheless, in 1842, he became so captivated by the doctrine of the Second Coming of Christ that he severed his connection with the Methodists and joined the Plymouth Brethren.