This contrivance solves the equation 1.64x=1, yielding centesimal parts of a foot. James Atkinson[15] speaks of “Gunter’s scale” as “usually of Boxwood . . . commonly 2 ft. long, 1½ inch broad” and “of two kinds: long Gunter or single Gunter, and the sliding Gunter. It appears that during the seventeenth century (and long after) the Gunter’s scale was a rival of the slide rule. III. RICHARD DELAMAIN’S GRAMMELOGIA We begin with a brief statement of the relations between Oughtred and Delamain. At one time Delamain, a teacher of mathematics in London, was assisted by Oughtred in his mathematical studies. In 1630 Delamain published the Grammelogia, a pamphlet describing a circular slide rule and its use. In 1631 he published another tract, on the Horizontall Quadrant.[16] In 1632 appeared Oughtred’s Circles of Proportion[17] translated into English from Oughtred’s Latin manuscript by another pupil, William Forster, in the preface of which Forster makes the charge (without naming Delamain) that “another . . . went about to pre-ocupate” the new invention. This led to verbal disputes and to the publication by Delamain of several additions to the Grammelogia, describing further designs of circular slide rules and also stating his side of the bitter controversy, but without giving the name of his antagonist. Oughtred’s Epistle was published as a reply. Each combatant accuses the other of stealing the invention of the circular slide rule and the horizontal quadrant. The two title-pages of the edition of the Grammelogia in the British Museum in London which we have called “Grammelogia IV.” Different editions or impressions There are at least five different editions, or impressions, of the Grammelogia which we designate, for convenience, as follows: Grammelogia I, 1630. One copy in the Cambridge University Library.[18] Grammelogia II, I have not seen a copy of this. Grammelogia III, One copy in the Cambridge University Library.[19] Grammelogia IV, One copy in the British Museum, another in the Bodleian Library, Oxford.[20] Grammelogia V, One copy in the British Museum. In Grammelogia I the first three leaves and the last leaf are without pagination. The first leaf contains the title-page; the second leaf, the dedication to the King and the preface “To the Reader;” the third leaf, the description of the Mathematical Ring. Then follow 22 numbered pages. Counting the unnumbered pages, there are altogether 30 pages in the pamphlet. Only the first three leaves of this pamphlet are omitted in Grammelogia IV and V.