Getting from A to B

In 'The Discovers', Daniel J. Boorstin describes the process by which 14th & 15th century sailors of the North Sea and Baltic transitioned from their tried and true navigational method of depth sounding to the new-fangled magnetic compass.

Much of their sailing was in shallow waters where sailors had long since been finding their way by feeling their way along the bottom....  Their soundings traced the shape and character of the floor of the sea by "lead and line".... After the compass arrived, pilots off the north European coasts still felt more secure when they could combine the new device with their old reliable lead and line.

Hmmm.