A logbook is an official record book which is used to keep information about a journey. Originally, logbooks were used for ships, and the concept was adopted for aircraft as well; most pilots keep a logbook in addition to relying on the black boxes installed in aircraft. People may also keep logbooks in other contexts; for example, a logbook could be kept to record information about an exercise regimen, or about a business.
Originally, a logbook would have served as a repository for very basic information, like readings meant to determine the ship's speed and heading. Keeping a logbook was crucial for captains who wanted to know where their ships were, and logbooks could also be compared against each other for navigational information and to get general data about things like weather conditions, tides, and other regional phenomena.
Over time, logbooks became more detailed, including information about ports of call, crew complements, and events on board ship. Because a logbook served as an official record of a journey, captains tended to be careful about which information was included, as logbooks could be used in criminal trials. Many captains took advantage of the official status of the logbook to record information about trades made for various goods on board ship, and to note the results of contact with regional government officials and tribal representatives.
Because the logbook was such a vital document, it tended to be well protected, and in the event of an accident or shipwreck, most captains tried to rescue their logbooks. This became especially important when seamen started to receive benefits after calamities at sea, as the logbook would be used to determine the nature and amount of the benefits seamen were entitled to. In the modern era, logbooks continue to be valuable records of journeys and careers; pilots, for example, carry their own logbooks, rather than leaving them with specific aircraft.
Historic logbooks can be very interesting and informative, and many people who research the history of seafaring like to rely on logbooks. These books can show readers how sailors lived, what they ate, what kind of discipline was used on ships, and how crews dealt with contact with native peoples. Many notable logbooks are on display in museums, so that people can examine them for themselves, and some have been published so that interested members of the public can read them at leisure.