Royal Navy logbooks as secondary sources and their use in climatic investigations: introducing the log-board

This investigation encompasses the first presentation of the log-board, which was the primary source used to compile logbooks on board Royal Navy vessels in the 18th century. All wind force and weather descriptions during the day were entered on the log-board before they were transcribed to the logbook, which is why the logbook should be approached as a secondary source. This study shows that although Royal Navy logbooks represent valuable compilations of what was written on the log-board, it cannot be ascertained exactly how the logbooks were compiled. Seven logbooks from the Cumberland for August 1782 were evaluated by comparing them to the log-board from the same vessel, and the purpose was to determine the validity of logbook wind and weather entries. The results show that wind direction was most consistently transcribed according to the log-board and, furthermore, that a majority of the wind force entries derived from the 1 p.m. entry on the log-board. The kappa statistic shows that both wind force and weather conditions were most consistently copied from the 1 p.m. entry on the log-board. The study concludes that the first wind force and weather entries in the logbooks were not made at noon when the vessel was positioned. While the positioning of the vessel was made at the end of the nautical day, the first wind force and weather entries most likely describe the conditions 23 h earlier.