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.”