The Use of the Lead and Line by Early Navigators in the North Sea?
By J.F. Kemp
Transnav: the International Journal on Marine Navigation and Safety of Sea Transportation, Vol.8:4 (2014)
Abstract: This paper draws attention to the lack of information as to how early North Sea sailors navigated, particularly during the one thousand year period that followed Roman times. The lead and line was the only navigational aid available for most of this period, but there is little recorded as to whether it was used simply for ensuring a ship or boat had enough water to proceed or whether, together with the knowledge it provided of the nature of the sea bed, it was used as a more positive position fixing device. The author would appreciate any information relating to navigation techniques used during this period.
Introduction: Every sailor, at the back of his or her mind, is aware that the nearest land is likely to be directly beneath the ship’s keel and, as a result, he or she is interested to know just how near. This information has been readily available to mariners for many years. It can be found by plotting a position on a chart where depths are recorded or by direct measurement using an echo sounder.
In ancient times, charts were virtually non‐existent but the depth of water could be measured by a sounding lead and line or, in shallow water, by sounding rods. Somewhat later, the base of the weight was made hollow to accept a plug of tallow or a similar material so that a sample of the river or sea‐bed could be recovered. A sounding in deep water has a more general use than simply avoiding stranding. Together with knowledge of the nature of the sea‐bed, it provides clues to a ship’s position and, it therefore, has real navigational significance.