This small chart measures 63x 36cms & covers the English Channel as it was in the 18th century. It not only shows depths, but also details coastal cross sections. Responsible for compiling most of the information here was Astronomer Royal Captain Edmund Halley, whose work with one comet, lead to it being named after him. He also revolutionized cartography with Isolines (the lines connecting points of equal value), more commonly known now as contour lines.