Complex sentence: At the Paris Exposition Universelle of 1855 he won a gold medal, but felt obliged to carry out public demonstrations of his craft in the exhibition hall after accusations that he was using some type of fraudulent transfer technique.
Split into simpler sentences: At the Paris Exposition Universelle of 1855 he won a gold medal. Afterwards he felt obliged to carry out public demonstrations of his craft in the exhibition hall after accusations that he was using some type of fraudulent transfer technique.