He edited The Academy and the wrote and compiled various books and publications on Indian life and history.
He was the third son of Joseph John Cotton, of the Madras Civil Service, his mother being a daughter of James Minchin, Master in Equity of the Supreme Court at Madras.
Among his Oxford friends and contemporaries were E. W. B. Nicholson, Bodley's Librarian, F. T. Richards, first of Queen's and afterwards of Trinity, and Grant Allen of Merton, and he was in pronounced sympathy with the rather uncompromising views of that academic and philosophic Liberalism which had set in strongly years before.
For many years he was the principal assistant of William Wilson Hunter in his manifold literary undertakings in exposition of Indian life and history.
Cotton and Isabella, daughter of John Carter, of Clifton, Bristol, were married in 1873.