The papers consist of Maclear's journal of magnetic observations kept in HMS CHALLENGER, 1872 to 1876; two logs for HMS ALERT, 1879 to 1881, and one for HMS FLYING FISH, 1885 to 1887; captain's out-letterbooks from Maclear to the Hydrographer of the Navy, 1878 to 1882, and 1884 to 1887; workbooks, 1879 to 1882, and 1885 to 1886; and two remark books kept by Captain Alfred Carpenter of HMS MAGPIE, 1881 to 1882, annotated by Maclear.

Administrative / biographical background
Maclear entered the Navy in 1851, became a lieutenant in 1859 and a commander in 1868. He sailed on HMS CHALLENGER (1858) with the expedition led by Captain George S. Nares in 1872. When Nares left the ship at Hong Kong, Maclear was the most senior officer to complete the voyage which lasted until 1876, the year he was promoted to captain. In 1879 he succeeded Nares in command of HMS ALERT (1856) and completed his survey of the Magellan Straits before moving to the Indian Ocean and Australian waters. From 1883 to 1887 he commanded the survey ship HMS FLYING FISH (1873), charting the Korean and China coasts. In 1891 he became a rear-admiral and retired. He was promoted to vice-admiral in 1897, to admiral in 1903, and continued working at the Hydrographic Department compiling Admiralty sailing directions. See 'The Admiralty Hydrographic Service 1795-1919' by Vice-Admiral Sir Archibald Day, London, 1967.