Thomson thanks Ledermann for his letter, and asks him to clarify some points for him. He refers to Thurstone's way of finding simple structure, and discusses reference vectors and primary factors at length.

Thomson also asks Ledermann if his post at St Andrews is coming to an end, and expresses regret that he cannot offer help to him. He asks Ledermann if he would mind reading part of his manuscript for the forthcoming edition of The Factorial Analysis of Human Ability.

Also includes a postscript, referring to Ledermann's reciprocity of reference vectors and primary factors, and Thomson's puzzlement at the absence of a diagonal matrix in Ledermann's formulae, illustrated with several pages of notes and formulae.