A vessel sinks and the ship’s log goes down with it, making the log useless for recovery purposes, right? Yes, but the log from another ship can sometimes help locate lost ships by pinpointing the lost vessel’s location. In fact, that’s how the RMS Titanic was finally located.

Entries from the log aboard the California were used to help locate the Titanic.In 1912 the Titanic’s distress signal placed it at 41°46' North, 50º 14' West. But despite numerous attempts to find it, the Titanic was not located until 1985, when Dr. Robert Ballard, an oceanographer who has discovered many lost ships, decided to try a different approach.

Rather than search for the Titanic itself, he decided to search for the path of debris, called the “debris field,” left by the Titanic as it descended to the depths of the Atlantic. To do so, Ballard studied the logbook of the Californian, a vessel that was between five and ten miles away from the Titanic when the distress signal sounded, and which reported a debris drift.

From the logbook entries, he was able to estimate the speed and direction of drift of the lifeboats. Knowing that the Titanic had to have gone down to the north of where the lifeboats were found, he redirected the area of search. Within a week, he spotted the ship’s boiler and not long thereafter, he found the Titanic’s final resting place.