Thomson explores his discovery regarding correlation co-efficients, or what he refers to as profile correlations, in a doubly centred matrix in relation to Thurstone’s centroid process.

He also refers to Ledermann's assertion regarding the approach of a powered matrix to rank one as the power rises, stating that he disagrees, and referring to the work of Burt.

Also includes a post script which continues the discussion, referring to Thurstone’s repetitive process, as well as containing a transcript of a letter written by M S Bartlett to Nature regarding a letter of Thomson's.