An online 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. This is a work in progress and nowhere close to completion Some paragraphs are coherent; others are not. Sometimes paragraphs are only a phrase or a note to myself. Nothing has been professionally edited. It is best viewed ...