returning to london – he had been made chaplain at st gabriel fenchurch in 1643 – wallis joined the group of scientists that was later to evolve into the royal society. he was finally able to indulge his mathematical interests, mastering william oughtred's "clavis mathematicae" in a few weeks in 1647. he soon began to write his own treatises, dealing with a wide range of topics, which he continued for the rest of his life. wallis wrote the first survey about mathematical concepts in england where he discussed the hindu-arabic system.