In Italy Oughtred's modified notation a, b::c, d was used by Maria G. Agnesi in her Instituzioni analitiche, Milano, 1748. The notation a:b::c:d found entrance the latter part of the eighteenth century. In Germany the symbolism a:b=c:d, suggested by Leibniz, found wider acceptance.[115]
It is evident from the data presented that Oughtred proposed his notation for ratio and proportion at a time when the need of a specific notation began to be generally felt, that his symbol for ratio a.b was temporarily adopted in England and France but gave way in the eighteenth century to the symbol a:b, that Oughtred's symbol for proportion :: found almost universal adoption in England and France and was widely used in Italy, the Netherlands, the United States, and to some extent in Germany; it has survived to the present time but is now being gradually displaced by the sign of equality =.
Oughtred's notation to express aggregation of terms has received little attention from historians but is nevertheless interesting. His books, as well as those of John Wallis, are full of parentheses but they are not used as symbols of aggregation in algebra; they are simply marks of punctuation for parenthetical clauses. We have seen that Oughtred writes (a+b)^2 and { root}(a+b) thus, Q:a+b:, { root}:a+b:, or Q:a+b, { root}:a+b, using on rarer occasions a single dot in place of the colon. This notation did not originate with Oughtred, but, in slightly modified form, occurs in writings from the Netherlands. In 1603 C. Dibvadii in geometriam Evclidis demonstratio numeralis, Leyden, contains many expressions of this sort, { root}·136+{ root}2048, signifying { root}(136+{ root}2048). The dot is used to indicate that the root of the binomial (not of 136 alone) is called for. This notation is used extensively in Ludolphi à Cevlen de circulo, Leyden, 1619, and in Willebrordi Snellii De circuli dimensione, Leyden, 1621. In place of the single dot Oughtred used the colon (:), probably to avoid confusion with his notation for ratio. To avoid further possibility of uncertainty he usually placed the colon both before and after the algebraic expression under aggregation. This notation was adopted by John Wallis and Isaac Barrow. It is found in the writings of Descartes. Together with Vieta's horizontal bar, placed over two or more terms, it constituted the means used almost universally for denoting aggregation of terms in algebra. Before Oughtred the use of parentheses had been suggested by Clavius[116] and Girard.[117] The latter wrote, for instance, { root}(2+{ root}3). While parentheses never became popular in algebra before the time of Leibniz and the Bernoullis they were by no means lost sight of. We are able to point to the following authors who made use of them: I. Errard de Bar-le-Duc (1619),[118] Jacobo de Billy (1643),[119] one of whose books containing this notation was translated into English, and also the posthumous works of Samuel Foster.[120] J. W. L. Glaisher points out that parentheses were used by Norwood in his Trigonometrie (1631), p. 30.[121]