Thus what Vieta would have written A Quadrate, into B Cube, ------------------------ Equal to FG Plane, CDE Solid, would with him be thus expressed A_q B_c ------- = FG. C D E And the better to distinguish upon the first view, what quantities were Known, and what Unknown, he doth (usually) denote the Known to Consonants, and the Unknown by Vowels; as Vieta (for the same reason) had done before him. He doth also (to very great advantage) make use of several Ligatures, or Compendious Notes, to signify Summs, Differences, and Rectangles of several Quantities. As for instance, Of two Quantities A (the Greater), and E (the Lesser), the Sum he calls Z, the Difference X, the Rectangle AE. . . . . Which being of (almost) a constant signification with him throughout, do save a great circumlocution of words, (each Letter serving instead of a Definition;) and are also made use of (with very great advantage) to discover the true nature of divers intricate Operations, arising from the various compositions of such Parts, Sums, Differences, and Rectangles; (of which there is great plenty in his Clavis, Cap. 11, 16, 18, 19. and elsewhere,) which without such Ligatures, or Compendious Notes, would not be easily discovered or apprehended. . . . . I know there are who find fault with his Clavis, as too obscure, because so short, but without cause; for his words be always full, but not Redundant, and need only a little attention in the Reader to weigh the force of every word, and the Syntax of it; . . . . And this, when once apprehended, is much more easily retained, than if it were expressed with the prolixity of some other Writers; where a Reader must first be at the pains to weed out a great deal of superfluous Language, that he may have a short prospect of what is material; which is here contracted for him in a short Synopsis. . . . .