III.

Other Works

Ptolemy also contributed substantially to mathematics by advancing the study of trigonometry, and he applied his theories to the construction of astrolabes and sundials. In his Tetrabiblos, he applied astronomy to astrology and the creation of horoscopes. Of considerable historical importance, is Ptolemy's Geography, which charts the world as people of his time knew it. This work, which employs a system of longitude and latitude, influenced mapmakers for hundreds of years, but it suffered from a lack of reliable information. Ptolemy also devoted a treatise, Harmonica, to music theory, and in Optics he explored the properties of light, especially refraction and reflection. Optics, known only from an Arabic version, stresses experimentation and the construction of special apparatus to promote the study of light and to develop a mathematical theory of its properties.