The Cross X as a Symbol for Multiplication

Abstract

HISTORIANS of mathematics attribute the first use of the cross x as a symbol for multiplication to William Oughtred (“Clavis Mathematicae”, London, 1631). See W. W. R. Ball's “Short Account of the History of Mathematics”, fifth edition, 1912, p. 239; M. Cantor's “Geschichte der Mathematik,” Bd. i., 1892, p. 658; J. Tropfke's Geschichte der Elementar Mathematik, Bd. i., 1902, p. 135. In some places, as, for instance, in Oughtred's “Circles of Proportion” (London, 1632, p. 38), the two bars of the cross are not quite straight, giving the symbol the appearance of the small letter x. In some of John Wallis's writings, as, for example, his “Elenchus geometriae Hobbianae”, etc. (Oxford, 1655, p. 23), the symbol is not the usual cross, but is plainly the capital letter X turned on its side. In a paper by Lord Viscount Brouncker in the Philosophical Transactions (vol. ii., 1668, p. 646), the capital letter X occurs regularly as the symbol for multiplication. These and similar cases lead to the inference that the cross and the letter x were considered practically one and the same symbol for multiplication.