minute-glasses; and sometimes want of care, as in so long a run cause often a difference of many leagues in the whole account.
Most of my men that kept journals imputed it to the half-minute-glasses: and indeed we had not a good glass in the ship beside the half-watch or two-hour-glasses. As for our half-minute-glasses we tried them all at several times, and we found those that we had used from Brazil as much too short, as others we had used before were too long; which might well make great errors in those several reckonings. A ship ought therefore to have its glasses very exact; and besides, an extraordinary care ought to be used in heaving the log, for fear of giving too much stray line in a moderate gale; and also to stop quickly in a brisk gale, for when a ship runs 8, 9 or 10 knots, half a knot or a knot is soon run out, and not heeded: but to prevent danger, when a man thinks himself near land, the best way is to look out betimes, and lie by in the night, for a commander may err easily himself; beside the errors of those under him, though never so carefully eyed.
Another thing that stumbled me here was the variation, which, at this time, by the last amplitude I had found to be but 7 degrees 58 minutes west, whereas the variation
