The small magnifying glass is held in a tortoiseshell mount and housed in a silver capstan-style case. The case, which is almost 7 cm 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.'
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. The boxwood frame has brass hinges and measures 34.2 cm x 41.1 cm.