'A Collection of Letters and other Papers, which were at severall times intercepted, written in cipher. Deciphered by John Wallis, Professor of Geometry in the University of Oxford': then added 'Given to the Publike Library there, Anno Domini 1653'. These are fifty-two Royalist letters, 1640-53, deciphered and usually with the cipher attached as well as a copy of the original letter. One of the letters is from the king (p. 34, from Newcastle, 1646), and one from prince Charles (p. 70, from st. Germain's, July 1, 1648).

It is only a partial collection, and Wallis, who was no politician, was subsequently able to prove to Royalist friends that he had not by his deciphering discovered much of importance to the Parliamentarians. The preface which he here prefixes to the letters (which has been printed in John Davys An essay on the art of Decyphering, London, 1737, 4°), avoids all political references.