 Continental travel failed to restore Ellis' health.An attack of rheumatic fever at Sanremo in 1849 left him an invalid, and he returned to Cambridge, living at Anstey Hall, Trumpington, next to his friend John Grote, vicar of Trumpington.From his sickbed he kept up contact with the young Trinity mathematician William Walton, and dictated his thoughts on a wide range of topics, including etymology, bees' cells, Roman money, the principles of a projected Chinese dictionary, and Boole's "The Laws of Thought" (1854).