David Ngunaitponi (28 September 1872 – 7 February 1967), known as David Unaipon, was an Aboriginal Australian preacher, inventor and author. He was a Ngarrindjeri. Unaipon's contribution to Australian society helped to break many Aboriginal Australian stereotypes, and he is featured on the Australian $50 note in commemoration of his work. He was the son of preacher and writer James Unaipon. Biography Born at the Point McLeay Mission on the banks of Lake Alexandrina in the Coorong region of South Australia, Unaipon was the fourth of nine children of James and Nymbulda Ngunaitponi, of the Portaulun branch of the Ngarrindjeri people. Unaipon began his education at the age of seven at the Point McLeay Mission School and soon became known for his intelligence, with the former secretary of the Aborigines' Friends' Association stating in 1887: "I only wish the majority of white boys were as bright, intelligent, well-instructed and well-mannered, as the little fellow I am now taking charge of." Unaipon left school at 13 to work as a servant for C.B. Young in Adelaide where Young actively encouraged Unaipon's interest in literature, philosophy, science and music. In 1890, he returned to Point McLeay where he apprenticed to a bootmaker and was appointed the mission organist. In the late 1890s he travelled to Adelaide but found that his colour was a bar to employment in his trade and instead took a job as storeman for an Adelaide bootmaker before returning to work as book-keeper in the Point McLeay store. On 4 January 1902 he married Katherine Carter (), a Tangane woman. He was later employed by the Aborigines' Friends' Association as a deputationer, in which role he travelled and preached widely in seeking support for the Point McLeay Mission. Unaipon retired from preaching in 1959 but continued working on his inventions into the 1960s. Inventor Unaipon spent five years trying to create a perpetual motion machine. In the course of his work he developed a number of devices. He was still attempting to design such a device in his seventy-ninth year. Unaipon took out provisional patents for 19 inventions but was unable to afford to get any of his inventions fully patented, according to some sources. Muecke and Shoemaker say that between "1910 and 1944 he made ten ... applications for inventions as varied as an anti-gravitational device, a multi-radial wheel and a sheep-shearing handpiece". Provisional patent 15,624 which he