Complex sentence: The touring Indian Gallery did not attract the paying public Catlin needed to stay financially sound, and (Congress) rejected his initial petition to purchase the works, so in 1839 Catlin took his collection across the Atlantic for a tour of European capitals.
Split into simpler sentences: The touring Indian Gallery did not attract the paying public Catlin needed to stay financially sound, and Congress rejected his initial petition to purchase the works. In 1839 Catlin took his collection across the Atlantic for a tour of European capitals.