Captain Cook's navigational instruments

• Small magnifying glass in a silver case, and a wooden plane table frame
• Linked to an astonomer who sailed with Captain James Cook,
  and a British naval scholar
• Objects used to make accurate maps
• Help to llustrate Cook's skill as a navigator

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

The magnifier and folding plane table frame have 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.

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 at the mast, following the explorer's death in Hawaii.

Cook's plane table frame.

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.

The 18th century surveyor's plane table frame was used to assist in accurate coastal mapping. The frame was used with a plane table, a compass and a sighting device called an alidade.

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.

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

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

The Cook magnifier and plane table frame are expected to go on show in the National Museum's Australian Journeys gallery.

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