The log covers the period from 13 November 1763 - 15 August 1764, and includes observations of stars and planets and errors and adjustments to instruments and clocks. It mentions the arrival of John Harrison and his chronometers on board HMS 'Tartar' on 13 May 1764 [RGO 4/323: 15v], and includes ratings for these chronometers [RGO 4/323: 15v-16v].
The log also includes details of how and when the astronomer conveyed copies of his observations to Sir Philip Stephens, using different ships and their Captains as go-betweens [MS RGO 4/323: 1r]. There are also additional computations on loose pieces of paper [RGO 4/323: 18a-18c] and a note about the repayment of money which Maskelyne had advanced to Richard Shee of London [MS RGO 4/323: back cover (inside)].