During the years 1666 to 1669 Newton's studies were very diverse. He bought prisms and lenses on two or three occasions, and also chemicals and a furnace, apparently for chemical experiments; but he also employed part of his time on the theory of fluxions and other branches of pure mathematics. He wrote a paper, "De Analysi per Aequationes Numero Terminorum Infinitas", which he put, probably in June 1669, into the hands of Isaac Barrow (then Lucasian Professor of Mathematics), at the same time permitting him to communicate its contents to their common friend John Collins (1624–1683), a mathematician of no mean order. Barrow did so on 31 July 1669, but kept the name of the author a secret, and merely told Collins that he was a friend staying at Cambridge, who had a powerful genius for such matters. In a subsequent letter on 20 August Barrow expressed his pleasure at hearing the favourable opinion which Collins had formed of the paper, and added, "the name of the author is Newton, a fellow of our college, and a young man, who is only in his second year since he took the degree of Master of Arts, and who, with an unparalleled genius ("examine quo est acumen"), has made very great progress in this branch of mathematics". Shortly afterward Barrow resigned his chair and was instrumental in securing Newton's election as his successor.