TABLE OF CONTENTS

PAGE

I. Introduction 187

II. Innovations in Gunter’s Scale 188

Changes introduced by Edmund Wingate 188

Changes introduced by Milbourn 189

Changes introduced by Thomas Brown and John Brown 190

Changes introduced by William Leybourn 192

III. Richard Delamain’s “Grammelogia” 192

Different editions or impressions 194

Description of Delamain’s instrument of 1630 195

Delamain’s later designs, and directions for using his instruments 197

IV. Controversy between Oughtred and Delamain on the invention of the circular slide rule 199

V. Independence and priority of invention 203

VI. Oughtred’s “Gauging Line,” 1633 206

VII. Other seventeenth century slide rules 207

I. INTRODUCTION

In my history of the slide rule[1], and my article on its invention[2]it is shewn that William Oughtred and not Edmund Wingate is theinventor, that Oughtred’s circular rule was described in print in 1632,his rectilinear rule in 1633. Richard Delamain is referred to as havingtried to appropriate the invention to himself[3] and as having writtena scurrilous pamphlet against Oughtred. All our information[188]about Delamain was taken from De Morgan,[4] who, however, gives noevidence of having read any of Delamain’s writings on the slide rule.Through Dr. Arthur Hutchinson of Pembroke College, Cambridge, I learnedthat Delamain’s writings on the slide rule were available. In thisarticle will be given: First, some details of the changes introducedduring the seventeenth century in the design of Gunter’s scale byEdmund Wingate, Milbourn, Thomas Brown, John Brown and William Leybourn;second, an account of Delamain’s book of 1630 on the slide rule which antedatesOughtred’s first publication (though Oughtred’s date of invention is earlierthan the date of Delamain’s alleged invention) and of Delamain’s later designs ofslide rules; third, an account of the controversy between Delamain and Oughtred;fourth, an account of a later book on the slide rule written by William Oughtred,and of other seventeenth century books on the slide rule.

II. INNOVATIONS IN GUNTER’S SCALE

Changes introduced by Wingate

We begin with Anthony Wood’s account of Wingate’s introduction of Gunter’sscale into France....