The log-book of the East Indiaman Osterley, 1758–1760 (India Office Library, L/MAR/B.400A), is of considerable interest as Captain Frederick Vincent not only gives the ordinary records of navigation—hourly reading of the log, courses steered; daily northing or southing, easting or westing; meridian distance (departure); difference of longitude (Captain Vincent measures his longitude from the Lizard, except where otherwise stated, but I have converted to longitude from Greenwich throughout); latitudes by account and by observation; variation—but in the remarks column he frequently gives his opinions on the situation of the ship and his reasons for forming them.