the era of the elocution movement, defined by the likes of sheridan and walker, evolved in the early and mid-1800s into what is called the scientific movement of elocution, defined in the early period by james rush's "the philosophy of the human voice" (1827) and richard whately's "elements of rhetoric" (1828), and in the later period by alexander melville bell's "a new elucidation of principles of elocution" (1849) and "visible speech" (1867).