Stephen Hawking, the British mathematician and physicist famed for his work on black holes, was rushed to a hospital and was seriously ill, Cambridge University said. Hawking has been fighting a chest infection for several weeks and was being treated Monday at Addenbrooke's Hospital in Cambridge, the university city northeast of London, the university said. "Professor Hawking is very ill," said Gregory Hayman, the university's head of communications. "He is undergoing tests. He has been unwell for a couple of weeks." Later in the afternoon, Hayman said Hawking was "now comfortable but will be kept in hospital overnight." Hawking, 67, gained renown for his work on black holes, and has remained active despite being diagnosed at 21 with ALS, (amyotrophic lateral sclerosis), an incurable degenerative disorder also known as Lou Gehrig's disease.