Herschel's intellectual curiosity and interest in music eventually led him to astronomy. After reading Robert Smith's "Harmonics, or the Philosophy of Musical Sounds" (1749), he took up Smith's "A Compleat System of Opticks" (1738), which described techniques of telescope construction. He also read James Ferguson's "Astronomy explained upon Sir Isaac Newton's principles and made easy to those who have not studied mathematics" (1756) and William Emerson's "The elements of trigonometry" (1749), "The elements of optics" (1768) and "The principles of mechanics" (1754).