They continued to live together at Trinity, though now they shared a cottage without the Great Gate. They performed experiments with lenses and prisms, and Isaac went to a hall twice a week and lectured to an empty room on mathematical topics so advanced that no one else could understand them. So in that sense nothing was different. But lately Isaac had obviously lost interest in optics (probably because he knew everything about the subject now) and become mysterious. Then three days ago he had announced, with studied nonchalance, that he was going to nip down to London for a few days. When Daniel had announced that he was planning to do the same – to pay a visit to poor Oldenburg, and attend a Royal Society meeting – Isaac had done a poor job of hiding his annoyance. But he had at least tried to hide it, which was touching.