Sidney Jeffryes (born c. 1885), was an Australian spark-gap radio operator. He is best known for his service as the wireless officer at Cape Denison during the second year (February 1913 − December 1913) of the Australasian Antarctic Expedition under the command of explorer Douglas Mawson. His service ended in September 1913, two months prior to the relief of the shore party, when Jeffryes developed symptoms of paranoia and had to be relieved of his duties.
Jeffryes, from Toowoomba, Queensland, had qualified as a wireless operator with the Australasian Wireless Company and was in his late 20's when an appeal was made for a wireless operator to serve during the second winter of the Australasian Antarctic Expedition (AAE). A series of tragedies and mishaps had led to the Cape Denison shore base on Antarctica being kept open for a second winter, March–December 1913. As the radioman who had served in 1912−1913 was returning home, the expedition needed a new specialist.
The AAE expedition was the first Antarctic expedition in history, and the only one during the Heroic Age of Antarctic Exploration, to maintain radio contact with its country of origin. The equipment available in 1912 and 1913 did not allow the Cape Denison base to transmit directly to Tasmania. The expedition had also organized a second winter-over base, at Macquarie Island, which served as a radio relay station. By means of a two-step process, messages in Morse code were transmitted back and forth between Australia and the Antarctic coast.
Jeffryes arrived at the Cape Denison shore base in February 1913 as the base was enduring a near-nightmare situation. The expedition's leader and commander, Douglas Mawson, stumbled into the base, the sole survivor of a sled dog probe eastward along the previously unknown interior coastline of the Australian Antarctic Territory. As the new wireless operator, Jeffryes was able to start the relay of communications that would inform Australia of the expedition leader's survival. However, within days of Mawson's arrival, the Antarctic winter began.
Mawson's expedition hut was located close to what was then the location of the South Magnetic Pole, and continued radio interference and static associated with polar conditions threatened the base's minimal ability to contact Macquarie Island. The expedition leader at first admired Jeffryes's assiduity with earphones and Morse-code key, but grew increasingly guarded in his praise. In Mawson's words, Jeffryes "applied himself to work with enthusiasm and perhaps an over-conscientious spirit." Climate conditions outside the hut made winter outdoor exercise impossible, leading to cabin fever.
In July 1913, as Antarctica neared midwinter, wireless operator Jeffryes began to present symptoms of paranoia to his fellow shore-party winter explorers, none of whom knew how to receive or transmit messages in Morse code. Expedition leader Mawson began to encourage another expedition member, airman Frank Bickerton, to learn Morse code as quickly as possible. Jeffryes's condition waxed and waned; for some weeks his comrades believed he was recovering, but in September of the same year the radioman experienced a psychotic break and began transmitting a message, through Macquarie Island, to Australia. Declaring himself to be the only sane man on the expedition, Jeffryes accused all of his comrades of having joined a criminal conspiracy to murder him. Mawson thereupon relieved Jeffryes of his duties.
In December 1913, the expedition's sea vessel Aurora relieved the troubled Antarctic shore party. Upon Jeffryes's return to Australia, his paranoia was diagnosed as paranoid schizophrenia and he was confined to a mental health center in Ararat, Victoria. Little is known of his later life.
The expedition's head and designated spokesman, Douglas Mawson, had little to say in his published histories about Jeffryes' active service in Antarctica. For almost 100 years, the unfortunate wireless operator's name was suppressed from most Antarctic records. In August 2010, the Australian Antarctic Division honored Jeffryes for his pioneering winter service by naming a previously unnamed glacier after him. The Jeffryes Glacier is located at 67°4' South, 143°59' East, in the Australian Antarctic Territory. It should not be confused with the Jeffries Glacier.
In December 2013, the first opera to be based on Mawson's 1911–14 expedition to Antarctica, "The Call of Aurora" (by Tasmanian composer Joe Bugden) was performed at The Peacock Theatre in Hobart. "The Call of Aurora" investigates the relationship between Douglas Mawson and his wireless operator, Sidney Jeffryes.
- "Home of the Blizzard - The people: Sidney Jeffryes". Department of Sustainability, Environment, Water, Population and Communities. Retrieved 2011-03-12.
- "Australian Antarctic glaciers named". Australian Antarctic Division. Retrieved 2011-03-12.
- "Home of the Blizzard - Cape Denison: Radio waves". Department of Sustainability, Environment, Water, Population and Communities. Retrieved 2014-01-04.
- "Manuscripts, oral history and pictures: Miss Eckford". State Library of New South Wales. Retrieved 2011-03-12.