American Practical Navigator, by Bowditch and Modern Seamanship, by Knight advise that a ship's dead reckoning plot should be updated every hour, on the hour. I wonder what White Star Line's rules specified? After the accident, both the Capt. and Mr. Boxhall endeavored to determine the ship's position, for an emergency message, by extending a DR plot from the last celestial fix. Both officers came up with mistaken positions. So, it seems that an updated DR plot was not being maintained. The mistaken position probably did not delay rescue efforts, but still.... The need for two officers to work on a DR position may have distracted them from attending to some other important activities. Was the failure to maintain a DR plot simply the customary practice at the time or does it possibly speak to some deviation from established practice?