You may find this hard to believe, but there are people still alive today who once did their mathematical calculations by sliding sticks back and forth. No keypads, no batteries, no LEDs. Just sticks.

THE author makes his title, “Quick and Easy Methods of Calculating”—at least, that is all that is in large print on the title-page; but the binder calls it, on the outside of the book, “The Slide-Rule ...

THE first portion of this book treats of the way to use logarithms so as to apply no more figures than necessary; the author pointing out that probably one half of the time expended in computations is ...