A word should be said on Oughtred’s definition of + and -. He recognizes their double function in algebra by saying (Clavis, 1631, p. 2): “Signum additionis, sive affirmationis, est + plus” and “Signum subductionis, sive negationis est - minus.” They are symbols which indicate the quality of numbers in some instances and operations of addition or subtraction in other instances. In the 1694 edition of the Clavis, thirty-four years after the death of Oughtred, these symbols are defined as signifying operations only, but are actually used to signify the quality of numbers as well. In this respect the 1694 edition marks a recrudescence. The characteristic in the Clavis that is most striking to a modern reader is the total absence of indexes or exponents. There is much discussion in the leading treatises of the latter part of the sixteenth and the early part of the seventeenth century on the theory of indexes, but the modern exponential notation, aⁿ, is of later date. The modern notation, for positive integral exponents, first appears in Descartes’ Géométrie, 1637; fractional and negative exponents were first used in the modern form by Sir Isaac Newton, in his announcement of the binomial formula, in a letter written in 1676. This total absence of our modern exponential notation in Oughtred’s Clavis gives it a strange aspect. Like Vieta, Oughtred uses ordinarily the capital letters, A, B, C, . . . . to designate given numbers; A² is written Aq, A³ is written Ac; for A⁴, A⁵, A⁶ he has, respectively, Aqq, Aqc, Acc. Only on rare occasions, usually when some parallelism in notation is aimed at, does he use small letters[27] to represent numbers or magnitudes. Powers of binomials or polynomials are marked by prefixing the capital letters Q (for square), C (for cube), QQ (for the fourth power), QC (for the fifth power), etc.