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Captain Cook's navigational instruments

At a glance

  • Small magnifying glass in a silver case, and a wooden plane table frame
  • Magnifier linked to an astonomer who sailed with Captain James Cook, and a British naval scholar
  • Objects used to make accurate maps
  • Help to illustrate Cook's skill as a navigator
Silver capstan-style case with magnifier in tortoiseshell mount, alongside a detailed image of the inscription on top of the silver case.
The silver-capstan style case and Captain Cook's magnifier, left. The detailed inscription on the top of the silver case, right. Photo: George Serras.

Mapping made easy

Artefacts illustrating Captain James Cook's great skill as a navigator have been acquired by the National Museum of Australia in Canberra.

The magnifier has been traced back to an astronomer who sailed with Cook and a renowned British naval scholar.

Both pieces would have been used in the making of accurate maps, essential for safe navigation.

Silver case and small magnifying glass, mounted in tortoiseshell.
The silver-capstan style case housing a small magnifying glass. Photo: George Serras.

The small magnifying glass is held in a tortoiseshell mount and housed in a silver capstan-style case. The case, which is almost seven centimetres high, dates from 1844. It bears the inscription:

This magnifier was given by Captain James Cook, the celebrated navigator to Mr Willm. Bayley the astronomer to the expedition during Cook's 3rd voyage and was presented by Mr Bayly to his Pupil, friend & Executor Mark Beaufoy Esqr. F.R.S.

Astronomer William Bayly sailed on Cook's second and third Pacific voyages and later published his observations.

It is thought the magnifier may have been bought by Bayly when Cook's effects were sold 'before the mast', following the explorer's death in Hawaii.

The magnifier passed from Bayly to Beaufoy and subsequently descended in the family until it was offered for auction in London and bought by the National Museum.

Accurate surveying

The 18th century surveyor's plane table frame was used to assist in accurate coastal mapping. The frame held paper firmly in place on the top of the plane table, a level surface used for surveying with a compass and a sighting device called an alidade.

Folded wooden frame with brass hinges.
Cook's plane table frame. Photo: Lannon Harley.

Cook adapted this land surveying method to rapidly chart Pacific coastlines as a running survey from the deck of a moving ship. His charts of the coasts of New Zealand and Australia were drawn up using the plane table method, which required Cook to sail close to shore.

The boxwood frame has brass hinges and measures 34 x 41 centimetres.

A grandson of British naval scholar Dr William Burney reported his grandfather received the frame from Cook.

The frame was then acquired by Reverend Frederick Johnson from Dr Burney's grandson. It was later bought from a descendant of Reverend Johnson by a private collector; then at auction by the National Museum.

These navigational aids complement the National Museum's Cook collection which includes:

  • a hand-painted tea cup and saucer which belonged to the explorer
  • a cannon and anchor from the Endeavour.

Australian Journeys

Captain Cook's magnifier and plane table frame are on show in the National Museum's Australian Journeys gallery.

Australian Journeys