Complex sentence: He gave his support to Henry Grattan and the Whigs during the greater part of his parliamentary career, but in his latter days became identified with the court party and voted for the Act of Union 1800, for which his viscounty was a reward.
Split into simpler sentences: He gave his support to Henry Grattan and the Whigs during the greater part of his parliamentary career. In his latter days he became identified with the court party and voted for the Act of Union 1800, for which his viscounty was a reward.