Complex sentence: Cooper took an active part in the politics of the time, and was sent with James Watt Jr., son and heir of the inventor James Watt, by the democratic clubs of England to those of France, where his sympathies were with the Girondists.
Split into simpler sentences: Cooper took an active part in the politics of the time. Cooper was sent with James Watt Jr., son and heir of the inventor James Watt, by the democratic clubs of England to those of France, where his sympathies were with the Girondists.