Correspondence and papers on pure mathematics and other subjects, including A. de Morgan's thoughts on equations, area and probability; quadratic equations and the quadrature of a circle; J.W. Woollgar's use of the slide rule; J.D. Forbes on the probability of double stars, with an account in the 'Philosophical Magazine'; pendulum experiments by G.G. Stokes; Airy's report on sound navigation signals; a calculating machine; the properties of a circle; W.H. Smyth on the origin of the word 'Cold Harbour'; and Newton's report on gold and silver coin of 1717. Other correspondents to feature are J.R. Young and J.J. Sylvester.