Priestley had completed his second year of studies when he enlisted as a
geologist for
Shackleton's
Nimrod Expedition (1907–09) to
Antarctica. There he worked closely with renowned geologists
(Sir) Edgeworth David and
Douglas Mawson, also members of the expedition. Priestley collected
mineral and
lichen samples from the region including islands in the
Ross Sea, the North face of the
Mount Erebus volcano, and mountains near the
Ferrar Glacier. He was part of the advance team that laid the food and fuel depots for Shackleton's nearly successful attempt to be the first to reach the
South Pole in 1909. In a November 1908 expedition, due to a lack of space in a tent, Priestley spent three days of a blizzard sleeping outside in his sleeping bag. As the blizzard raged, he slowly slipped down the glacier and nearly fell off its end to his death. On his return from the expedition, he spent four months in England before returning to
Sydney,
Australia, to work with Edgeworth David on the geological report, eventually published in 1914. Priestley returned to the Antarctic as a member of
Robert Falcon Scott's ill-fated
Terra Nova Expedition (1910–1913), after being recruited by Scott when the Terra Nova arrived in Sydney. Three weeks after landing at
Cape Evans in January 1911, Priestley and five others departed in the expedition ship, the
Terra Nova to explore and carry out scientific work in King Edward VII land to the east under the leadership of
Victor Campbell. Unable to find a suitable landing site, they decided to return West with the intention of landing at the
Bay of Whales but arriving on 3 February 1911 they encountered
Roald Amundsen's ship
Fram and his expedition already camped there. Unwilling to establish a camp so close to the Norwegians, Campbell decided to explore the coastline of
Victoria Land instead. After returning to Cape Evans and reporting Amundsen's location to Scott, they set off North to Victoria Land where they established a hut near
Carsten Borchgrevink's 1898 site at
Cape Adare. In January 1912, the six-man party was taken 200 miles farther south by the
Terra Nova to
Terra Nova Bay, midway between Cape Evans and Cape Adare, for summer fieldwork. They had provisions for eight weeks but their tents were badly damaged by a gale, and the
Terra Nova was unable to penetrate the ice pack and pick up the party as arranged. Realising that they would have to winter where they were, they excavated a small 12 foot by 9 foot ice cave in a snow drift and remained there in the shelter they nicknamed "
Inexpressible Island" for almost 7 months until the end of the Austral winter, supplementing their meagre rations with seal and penguin. With two of the party weak from
enteritis, they left their temporary home on 30 September 1912 and walked for five weeks, fortuitously finding a cache of food and fuel along the way which had been left by the expedition's western party the previous year. They eventually arrived safely back at
Cape Evans on 7 November 1912, only to be informed that Scott and the entire Polar party had perished months earlier. ==First World War==