From about 1936, Soddy became increasingly interested in mathematical problems, especially the geometry of the circle. He published papers in Nature (1936-1937) and Proc. Roy. Soc. (1942-1943), and devoted much time in his later years to cubic equations. Like the notebooks, the manuscripts and working papers on mathematics often bear explanatory notes dated 1955-1956 indicative of the value Soddy attached to them.