The notebook contains observations made by De la Caille at the Cape and elsewhere; a list of expenses in connection with his observatory at St. Martin (Paris); and details of the mathematical basis for his calculations, including lists of formulae and trigonometrical proofs, used as an aide-memoire during his travels. There are calculations of some star coordinates, apparently made at the Cape, and, most important of all, a calculation of the difference in latitude between the Cape and Klipfontein for his determination of an arc of the meridian.