Long description
This is a map of the world with coloured lines in the oceans explained in Figure 19, below. The lines are contour lines in the range 0 to 10, e.g. they pass from Africa to South America with values that increase as you look North. However, there are some points where several of these lines meet, amphidromic points e.g. in the south-west Pacific, south of South Africa and between Somalia in east Africa and the southern tip of India.