Complex sentence: In 1898 Thomson offered Rutherford the chance of a post at McGill University in Montreal, Canada, to replace Hugh Longbourne Callendar who held the chair of Macdonald Professor of physics and was coming to Cambridge.
Split into simpler sentences: In 1898 Thomson offered Rutherford the chance of a post at McGill University in Montreal, Canada. He was to replace Hugh Longbourne Callendar who held the chair of Macdonald Professor of physics and was coming to Cambridge.