The Lost Art of Logarithms

Charles Petzold holding massive slide rule

A web-book-in-progress by
Charles Petzold
wherein is explored the utility, history, and ubiquity of that marvelous invention,
logarithms
including what the hell they are; with some demonstrations of their primary historical application in plane and spherical trigonometry; plus, that extraordinary tool known as the
slide rule
is fully explored in theory and use.

Chapter titles in green are pretty much finished; no substantial changes are anticipated but small edits, corrections, or cosmetic fixups might be required.

Chapter titles in red are unfinished and currently in a state of flux.

Chapter titles in black are not yet begun.

Nothing has yet been professionally edited. I anticipate that this book will be completed by year-end 2027.

I've been developing the pages in Edge using Visual Studio Code running under Windows 11 on a Microsoft Surface Pro 9. I've also been testing the pages in Chrome on that machine, and in Safari on a Mac Mini running Sequoia, and in Chrome (version 126, it says) on an Asus Chromebook.

However, my iPad Mini running iOS 12.5.7 has several problems with these webpages, and the pages often become quite awkward on phones.

Chapter 1. The 400-Year-Old Computer

Part I. The Book of Vlacq

Chapter 2. The Conquest of Multiplication

Chapter 3. The Magic Demystified

Chapter 4. Powers and Roots as Well

Chapter 5. Calculating a Logarithm by Hand

Part II. Varieties of the Slide Rule Experience

Chapter 6. The Logarithmic Scale

Chapter 7. Building the Slide Rule

Chapter 8. Beyond the C and D Scales

Chapter 9. Peter Mark Roget and the Log-Log Scale

Chapter 10. Slide Rules Go Cylindrical

Part III. Logarithms Everywhere

Chapter 11. Binary Logarithms

Chapter 12. Sound and Music

Chapter 13. The Natural e

Chapter 14. Logarithmic Phenomena

Chapter 15. Log-Log and Semi-Log Graphs

Part IV. Back to Vlacq: The Trigonometric Connection

Chapter 16. The Pythagorean Breakthrough

Chapter 17. Beyond the Straight Right Triangle

Chapter 18. The Ubiquitous Sinusoid

Chapter 19. Mapping Out the Earth

Chapter 20. Reaching for the Stars

Part V. Mathematicians at Work

Chapter 21. John Napier’s Life and Reformationary Times

Chapter 22. Countdown to the Apocalypse

Chapter 23. Conceiving the Logarithm

Chapter 24. The Handoff to Henry Briggs

Chapter 25. Logarithms at Your Fingertips

Chapter 26. The Meticulous Mr. Babbage

Back Matter

About the Author