Oughtred’s most original line of scientific activity is the one least known to the present generation. Augustus De Morgan, in speaking of Oughtred, who was sometimes called “Oughtred Aetonensis,” remarks: “He is an animal of extinct race, an Eton mathematician. Few Eton men, even of the minority which knows what a sliding rule is, are aware that the inventor was of their own school and college.”[50] The invention of the slide rule has, until recently,[51] been a matter of dispute; it has been erroneously ascribed to Edmund Gunter, Edmund Wingate, Seth Partridge, and others. We have been able to establish that William Oughtred was the first inventor of slide rules, though not the first to publish thereon. We shall see that Oughtred invented slide rules about 1622, but the descriptions of his instruments were not put into print before 1632 and 1633. Meanwhile one of his own pupils, Richard Delamain, who probably invented the circular slide rule independently, published a description in 1630, at London, in a pamphlet of 32 pages entitled Grammelogia; or the Mathematicall Ring. In editions of this pamphlet which appeared during the following three or four years, various parts were added on, and some parts of the first and second editions eliminated. Thus Delamain antedates Oughtred two years in the publication of a description of a circular slide rule. But Oughtred had invented also a rectilinear slide rule, a description of which appeared in 1633. To the invention of this Oughtred has a clear title. A bitter controversy sprang up between Delamain on one hand, and Oughtred and some of his pupils on the other, on the priority and independence of invention of the circular slide rule. Few inventors and scientific men are so fortunate as to escape contests. The reader needs only to recall the disputes which have arisen, involving the researches of Sir Isaac Newton and Leibniz on the differential and integral calculus, of Thomas Harriot and René Descartes relating to the theory of equations, of Robert Mayer, Hermann von Helmholtz, and Joule on the principle of the conservation of energy, or of Robert Morse, Joseph Henry, Gauss and Weber, and others on the telegraph, to see that questions of priority and independence are not uncommon. The controversy between Oughtred and Delamain embittered Oughtred’s life for many years. He refers to it in print on more than one occasion. We shall confine ourselves at present to the statement that it is by no means clear that Delamain stole the invention from Oughtred; Delamain was probably an independent inventor. Moreover, it is highly probable that the controversy would never have arisen, had not some of Oughtred’s pupils urged and forced him into it. William Forster stated in the preface to the Circles of Proportion of 1632 that while he had been carefully preparing the manuscript for the press, “another to whom the Author [Oughtred] in a louing confidence discouered this intent, using more hast then good speed, went about to preocupate.” It was this passage which started the conflagration. Another pupil, W. Robinson, wrote to Oughtred, when the latter was preparing his Apologeticall Epistle as a reply to Delamain’s countercharges: “Good sir, let me be beholden to you for your Apology whensoever it comes forth, and (if I speak not too late) let me entreat you, whip ignorance well on the blind side, and we may turn him round, and see what part of him is free.”[52] As stated previously, Oughtred’s circular slide rule was described by him in his Circles of Proportion, London, 1632, which was translated from Oughtred’s Latin manuscript and then seen through the press by his pupil, William Forster. In 1633 appeared An Addition vnto the Vse of the Instrvment called the Circles of Proportion which contained at the end “The Declaration of the two Rulers for Calculation,” giving a description of Oughtred’s rectilinear slide rule. This Addition was bound with the Circles of Proportion as one volume. About the same time Oughtred described a modified form of the rectilinear slide rule, to be used in London for gauging.[53]
CHAPTER III
MINOR WORKS
Among the minor works of Oughtred must be ranked his booklet of forty pages to which reference has already been made, entitled, The New Artificial Gauging Line or Rod, London, 1633. His different designs of slide rules and his inventions of sun-dials as well as his exposition of the making of watches show that he displayed unusual interest and talent in the various mathematical instruments. A short tract on watchmaking was brought out in London as an appendix to the Horological Dialogues of a clock- and watchmaker who signed himself “J. S.” (John Smith?). Oughtred’s tract appeared with its own title-page, but with pagination continued from the preceding part, as An Appendix wherein is contained a Method of Calculating all Numbers for Watches. Written originally by that famous Mathematician Mr. William Oughtred, and now made Publick. By J. S. of London, Clock-maker. London, 1675.
“J. S.” says in his preface:
The method following was many years since Compiled by Mr. Oughtred for the use of some Ingenious Gentlemen his friends, who for recreation at the University, studied to find out the reason and Knowledge of Watch-work, which seemed also to be a thing with which Mr. Oughtred himself was much affected, as may in part appear by his putting out of his own Son to the same Trade, for whose use (as I am informed) he did compile a larger tract, but what became of it cannot be known.
Notwithstanding Oughtred’s marked activity in the design of mathematical instruments, and his use of surveying instruments, he always spoke in deprecating terms of their importance and their educational value. In his epistle against Delamain he says:
The Instruments I doe not value or weigh one single penny. If I had been ambitious of praise, or had thought them (or better then they) worthy, at which to have taken my rise, out of my secure and quiet obscuritie, to mount up into glory, and the knowledge of men: I could have done it many yeares before. . . . .
Long agoe, when I was a young student of the Mathematicall Sciences, I tryed many wayes and devices to fit my selve with some good Diall or Instrument portable for my pocket, to finde the houre, and try other conclusions by, and accordingly framed for that my purpose both Quadrants, and Rings, and Cylinders, and many other composures. Yet not to my full content and satisfaction; for either they performed but little, or els were patched up with a diversity of lines by an unnaturall and forced contexture. At last I . . . . found what I had before with much studie and paines in vaine sought for.[54]
Mention has been made in the previous pages of two of his papers on sun-dials, prepared (as he says) when he was in his twenty-third year. The first was published in the Clavis of 1647. The second paper appeared in his Circles of Proportion.
Both before and after the time of Oughtred much was written on sun-dials. Such instruments were set up against the walls of prominent buildings, much as the faces of clocks in our time. The inscriptions that were put upon sun-dials are often very clever: “I count only the hours of sunshine,” “Alas, how fleeting.” A sun-dial on the grounds of Merchiston Castle, in Edinburgh, where the inventor of logarithms, John Napier, lived for many years, bears the inscription, “Ere time be tint, tak tent of time” (Ere time be lost, take heed of time).
Portable sun-dials were sometimes carried in pockets, as we carry watches. Thus Shakespeare, in As You Like It, Act II, sc. vii: