twelve o'clock
The log indicated that the ship was making six knots an hour , the rate being ascertained every two hours , and entered on the log-slate , to be used in making up the `` dead reckoning . '' The Young America had taken her `` departure , '' that is , left the last land to be seen , at half past three o'clock . At four , when the log was heaved , she had made three miles ; at six , fifteen miles ; at eight , the wind diminishing and the log indicating but four knots , only eight miles were to be added for the two hours ' run , making twenty-three miles in all . The first sea day would end at twelve o'clock on the morrow , when the log-slate would indicate the total of nautical miles the ship had run after taking her departure . This is called her dead reckoning , which may be measured off on the chart , and should carry the vessel to the point indicated by the observations for latitude and longitude . The wind was very light , and studding-sails were set alow and aloft . The ship only made her six knots as she pitched gently in the long swell of the ocean .