The logbook was where the captain kept track of the days work. The date, and longitude and latitude of the ship were recorded. The logbook was usually very boring, recording whales, weather and wind, but sometimes the days activity would be noted. The log was usually kept by the captain or the first mate. If the first mate was unable to read and write this job would sometimes fall to the captain's wife, when the captain was too busy.
Here is a log entry by Mary Brown. She did not like to sail with her husband, and she writes, "Adieu to Whalegrounds and now for home and right glad am I. And now my Dear, allow me to inform you that this is the last time you are to leave, or visit these waters which to you have become familiar according to your own assertions. Martha."