dirk • Link
“Based on John Napier’s principle of the logarithm, it came into use after Edmund Gunter created a logarithmic scale in 1620. Gunter’s rule consisted of a straight line on which numbers were spaced at intervals proportional to their common logarithms. Using this scale, William Oughtred and Edmund Wingate developed independently (c.1630) the first slide rules.”
Also have a look at:
See also the annotations to the diary entry for 25 November 1662:
JWB • Link
Timber scale from the Mary Rose:
Gresham College | Lecture Archive
HISTORY FROM BELOW: MATHEMATICS, INSTRUMENTS AND ARCHAEOLOGY
Dr Stephen Johnston
Ed • Link
A slide rule you can actually use
A slide-rule's initial value for Pepys is indicated by this descriptive title:
Everard, Thomas. "Stereometry, Or, The Art of Gauging Made easie by the Help of a New Sliding-Rule Which Shews the Area's of Circles in Gallons and Barrels and the Square and Cube-Root of any Number under 100,000 by inspection; and also Resolves Many other Arithmetical Problems Without Pen or Compasses: With an Appendix of Conick Sections, in Which the Nature and Original of Several Solids (frequently mentioned in Books of Gauging) is Explained, and their Magnitudes Compared." London: Peacock, 1689.
in Aqua scripto • Link
L&M says that Pepys designed his own slide-rule for the measure of Timbers and it be made by Brown [7 Aug '63]
Chart showing the number of references in each month of the diary’s entries.