Complex sentence: After his term as tutor ended, Gibbs travelled to Europe with his sisters, spending the winter of 1866--67 in Paris, where he attended lectures at the Sorbonne and the Collège de France.
Split into simpler sentences: After his term as tutor ended, Gibbs travelled to Europe with his sisters. They spent the winter of 1866--67 in Paris, where Gibbs attended lectures at the Sorbonne and the Collège de France.