# Ivory, Sir James

**IVORY, SIR JAMES** (1765-1842), Scottish mathematician, was born in Dundee in 1765. In 1779 he entered the university of St Andrews,
distinguishing himself especially in mathematics. He then studied theology; but, after two sessions at St Andrews and one at Edinburgh, he abandoned all idea of
the church, and in 1786 he became an assistant-teacher of mathematics and natural philosoghy in a newly established academy at Dundee. Three years later he
became partner in and manager of a flaxspinning company at Douglastown in Forfarshire, still, however, prosecuting in moments of leisure his favourite studies.
He was essentially a self -trained mathematician, and was not only deeply versed in ancient and modern geometry, but also had a full knowledge of the analytical
methods and discoveries of the continental mathematicians. His earliest memoir, dealing with an analytical expression for the rectification of the ellipse, is
published in the Transactions of the Royal Society of Edinburgh (1796); and this and his later papers on " Cubic Equations" (1799) and " Kepler's Problem "
(1802) evince great facility in the handling of algebraic formulae. In 1804 after the dissolution of the flax-spinning company of which he was manager, he
obtained one of the mathematical chairs in the Royal Military College at Marlow (afterwards removed to Sandhurst); and till the year 1816, when failing health
obliged him to resign, he discharged his professional duties with remarkable success. During this period he published in the Philosophical Transactions several
important memoirs, which earned for him the Copley medal in 1814 and ensured his election as a Fellow of the Royal Society in 1815. Of special importance in the
history of attractions is the first of these earlier memoirs (Phil. Trans., 1809), in which the problem of the attraction of a homogeneous ellipsoid upon an
external point is reduced to the simpler case of the attraction of another but related ellipsoid upon a corresponding point interior to it. This theorem is
known as Ivory's theorem. His later papers in the Philosophical Transactions treat of astronomical refractions, of planetary perturbations, of equilibrium of
fluid masses, etc. For his investigations in the first named of these he received a royal medal in 1826 and again in 1839. In 1831, on the recommendation of
Lord Brougham, King William IV. granted him a pension of 300 per annum, and conferred on him the Hanoverian Guelphic order of knighthood. Besides being directly
connected with the chief scientific societies of his own country, the Royal Society of Edinburgh, the Royal Irish Academy, etc., he was corresponding member of
the Royal Academy of Sciences both of Paris and Berlin, and of the Royal Society of Gb'ttingen. He died at London on the 2 1st of September 1842.

A list of his works is given in the Catalogue of Scientific Papers of the Royal Society of London.

*Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)*