# Delamain, Richard

# Delamain, Richard

(*fl*. London, England, first half of the seventeenth century)

*mathematics*.

Delamain was a joiner by trade, and after studying mathematics at Gresham College, London, he supported himself by teaching practical mathematics in London. Later he became mathematical tutor to King Charles I, for whom he fashioned a number of mathematical instruments. He was a pupil of William Oughtred, and in the early days of their association the two men became close friends. Unhappily this did not last, and later they quarreled violently over priority in the invention of the circular slide rule, which Delamain described in his *Grammelogia, or the Mathematicall Ring*.

Delamain’s fame rests mainly on this essay, a pamphlet of thirty-two pages. The manuscript was sent to the king in 1629, and the work was published the following year. The king retained Delamain’s services as tutor at a salary of £40 per annum. A few years later Delamain petitioned for an engineer’s post at a salary of £100 per annum. Following an interview with the king at Greenwich in 1637, he was granted a warrant for making a number of mathematical instruments.

The appearance of the *Grammelogia* was the signal for the beginning of the quarrel. Oughtred had invented the rectilinear slide rule as early as 1622, but his *Circles of Proportion*, which contained a description of the circular slide rule, was not made public until 1632—by which time the *Grammelogia* had been in circulation for two years. William Forster, a friend and pupil of Oughtred, translated from the Latin and published the *Circles of Proportion*, the preface to which contains some ungenerous references to Delamain, who, it states, purloined the design of the circular slide rule from Oughtred. Delamain retaliated vigorously, attacking both Forster and Oughtred; the latter replied with a pamphlet, *The Apologeticall Epistle*, in which he refers to the “slaunderous insimulations of Richard Delamain in a Pamphlet called *Grammelogia, or the Mathematicall Ring”* and maintains that the latter’s horizontal quadrant is no other than the horizontal instrument he had invented thirty years earlier.

Delamain perished in the Civil War sometime before 1645. Oughtred lived until 1660, but his last years were embittered by the dispute with his former friend and pupil.

Delamain was a competent mathematician whose genius lay in the practical realm. He excelled in the construction of a number of mathematical instruments. It is thought that the silver sundial which the king always carried with him and, at his execution, entrusted to Mr. Herbert to be given to the young duke of York, was one of Delamain’s creations.

He likewise commanded Mr.

Herbertto give his son, the Duke ofYork, his large Ring Sundial of silver, a Jewel his Majesty much valued: it was invented and made byRich. Delamainea very able Mathematician, who projected it, and in a little printed book did shew its excellent use in resolving many questions in Arithmetick and other rare operations to be wrought by it in the Mathematicks (Wood,Athenae Oxonienses. His tory of Oxford Writers, II, 1692, 525].

## BIBLIOGRAPHY

I. Original Works. Delamain’s writings are *Grammelogia, or the Mathematicall Ring* (London, 1630); and *The Making, Description and Use of a Small Portable Instrument for the Pocket... Called a Horizontal Quadrant* (London,1632).

II. Secondary Literatori. On Delamain or his work, see Florian Cajori, *William Oughtred. A Great Seventeenth Century Teacher of Mathematics* (London-Chicago, 1916), *passim; Dictionary of National Biography;* and E. G. R. Taylor, *The Mathematical Practitioners of Tudor and Stuart England* (Cambridge, 1954), p. 201.

J. F. Scott

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**Delamain, Richard**