  In 1864 Mach received an appointment in mathematics at Graz. For the first time he had the money and freedom to carry out his own experiments. In 1866 he exchanged his math chair for one in physics. While at Graz he had personal contact with Fechner and carried out his important work on Mach Bands. It was in this work that Mach first made use of evolutionary theory. Mach started work on what later became Analysis of Sensations, but apparently was discouraged by Fechner’s criticism. He returned to this work twenty years later, after further developing his own ideas. It was also in Graz that Mach first encountered Ewald Hering’s thought, both in physiology and evolution. In Mach’s first article on Mach Bands [Mach 1865] he refers to Hering, and in 1866 Hering gave his famous address on Unconscious Memory to the Vienna Academy. In 1867 Mach went to Prague as a professor of physics. He stayed in Prague for twenty-eight years, until 1895, whereupon he returned to Vienna. It was in Prague that his mature thought developed.