Humphry Ditton (May 29, 1675–October 15, 1715), was an English mathematician.
Ditton was born at Salisbury. He studied theology, and was for some years a dissenting minister at Tonbridge, but on the death of his father he devoted himself to the congenial study of mathematics. Through the influence of Sir Isaac Newton he was elected mathematical master in Christ's Hospital. He was author of the following memoirs and treatises: Of the Tangents of Curves, published in the Phil. Trans. vol. xxiii; A Treatise on Spherical Catoptrics, published in the Phil. Trans. vol. xxiv, from which it was copied and reprinted in the Acta Eruditorum (1707), and also in the Memoirs of the Academy of Sciences at Paris; General Laws of Nature and Motion (1705), a work which is commended by Wolfius as illustrating and rendering easy the writings of Galileo Galilei and Christiaan Huygens, and the Principia of Newton; An Institution of Fluxions, containing the First Principles, Operations, and Applications of that admirable Method, as invented by Sir Isaac Newton (1706).
In 1709 he published the Synopsis Algebraica of John Alexander, with many additions and corrections. In his Treatise on Perspective (1712) he explained the mathematical principles of that art; and anticipated the method afterwards elaborated by Brook Taylor.
In 1714 Ditton published his Discourse on the Resurrection of Jesus Christ, and The New Law of Fluids, or a Discourse concerning the Ascent of Liquids in exact Geometrical Figures, between two nearly contiguous Surfaces. To this was annexed a tract ("Matter not a Cogitative Substance") to demonstrate the impossibility of thinking or perception being the result of any combination of the parts of matter and motion. There was also added an advertisement, from him and William Whiston, concerning a method for discovering the longitude, which it seems they had published about half a year before. Although the method had been approved by Sir Isaac Newton before being presented to the Board of Longitude, and successfully practised in finding the longitude between Paris and Vienna, the board determined against it. This disappointment, aggravated as it was by certain lines written by Dean Swift, affected Ditton's health to such a degree that he died in the following year.