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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