Story: Charting the sea floor
This chart of Port Nicholson (now Wellington Harbour) was created in 1826 by Captain Barnett of the ship Lambton, and presented to the Sydney harbour master Captain John Nicholson, after whom Barnett had named the port. The chart measures depth in fathoms (1 fathom is about 1.8 metres), and shows rocks above and below water. Barrett Reef, guarding the harbour’s western entrance (where the inter-island ferry Wahine was to founder in a storm in 1968), is marked with depths of 6–7 fathoms. The shallow sandy sea floor off Eastbourne (middle right) would have been mapped by using tallow on the end of a sinker – the tallow picks up particles of sand, and when drawn aboard, indicates if the bottom is sandy.