Magarey was born the second son of Thomas Magarey and Elizabeth Magarey. He was educated at Adelaide Educational Institution (schoolmate Charles Kingston was born just one day before him) and Saint Peter"s College. He worked for a few years in his father"s milling business before studying medicine at the University of Melbourne (Doctor Benjamin Poulton was a fellow student), graduating Bachelor of Medicine in 1873.
He qualified Bachelor of Surgery in 1887, and Doctor of Medicine in 1888. Magarey was an Honorary Physician at the Adelaide Homeopathic Dispensary in King William Street, that offered free service to the poor, along with (later fellow parliamentarian) Doctor Allan Campbell. Magarey was particularly interested in the health of children, and was for some years honorary medical officer to the Adelaide Children"s Hospital.
Magarey published two pamphlets:
Our climate and infant mortality (1879)
Most fatal diseases of infancy and childhood (1880)
Magarey was briefly involved with medical training for Ellen Arnold, one of South Australia"s first female missionaries.
Magarey was elected to the Legislative Council for Central Districts from May 1888 with G. Witherage Cotton and retired at the end of his term in April 1897. While in parliament he fought for temperance causes and succeeded in mandating Sunday closing and raising the legal drinking age to 21.
He spoke on the platform of the Women"s Christian Temperance Union, being in favour of their aims and advocating the suffrage for women. A man of compassion and of science, his clearly stated arguments were of great value to the Women"s Suffrage League.
Mary Lee, one of the founders of the South Australian Women"s Suffrage League, said in her estimation there were four men whose names should live on South Australian history"s "brightest page" for their part in gaining the suffrage: they were Doctor Edward Stirling, Robert Caldwell Master of Health Administration, the Honorary.Sylvanus Magarey and the Reverend J C Kirby.
Lee said Magarey " has never failed whenever and wherever he could help us."
Magarey married M. R. Robertson, sister of Doctor William Robertson (ca1860 17 March 1940). They had seven children. Their son Frank William Ashley Magarey (ca1878 – 31 January 1912) married Louise Koeppen "Louie" Henderson on 3 July 1907.
He, too, was a physician, teetotaler and churchman, and a noted football player and cricketer.
He was a founding member of the South Australian Alliance. He favoured payment of members of parliament, a State Bank, and women"s franchise. Magarey was an active member of the Field Naturalists" section of the Royal Society, with a particular interest in seashells.
Magarey"s father Thomas Magarey was an earlier member of the Legislative Council and Thomas Magarey"s nephew William James Magarey sat in the House of Assembly from 1878 to 1881 for the seat of West Torrens.
