The first known artificial refrigeration was demonstrated by William Cullen at the University of Glasgow in 1748. He let ethyl ether boil into a partial vacuum. Oliver Evans, and American inventor, designed the first refrigeration machine that used vapor instead of liquid, in 1805. Shortly after 1856, James Harrison introduced vapor-compression refrigeration to the brewing and meat packing industries. In 1915, the first "Guardian" refrigerator was introduced, which was a predecessor of the Frigidaire. It was assembled in a wash house in a Fort Wayne backyard. In 1923, Frigidaire introduced the first self-contained unit.