This paper is intended to provide an outline of how the lead and line formed a vital, but often overlooked, role in safe navigation during the 16th Century, with some comments on its later use up to, and into the 20th Century. During this period, the development of the more mathematical dead-reckoning and the more exciting astro-navigation attracted the attention of the literate commentators who were responsible for record keeping while the often illiterate sailors got on with practising their craft. Also, May (1970), has commented that, “the navigators during the great age of discovery must have made extensive use of the lead and line, but references are extremely sparse, for all their rough log-books were destroyed and only the most important references to their navigational proceedings were copied into the fair accounts of their voyages which have come down to us.”
