This is a beautiful map of the Cape peninsular from the famous Grey collection.
It has numerous soundings and rhumb lines. On this chart, east is at the top, rather than north, as was the practice on most sea maps of the time. They carried a scale of distances and a pattern of rhumb lines (each of constant bearing) in different colours. To set a course between two ports, the pilot would join the corresponding points on the chart with a straight line, find the rhumb line most nearly parallel to it, and trace the rhumb line back to its parent wind rose, from which he obtained the required heading. As long as the ship's location was to be found by dead reckoning (keeping a running record of the distances and directions travelled), the chart was entirely adequate. Questions of latitude, longitude, compass variation, and curvature of the Earth's surface could be safely ignored.
