The Museum of HP Calculators Slide Rules In 1614, John Napier discovered the logarithm which made it possible to perform multiplications and divisions by addition and subtraction. (ie: a*b = 10^(log(a)+log(b)) and a/b = 10^(log(a)-log(b)).) This was a great time saver but there was still quite a lot of work required. The mathematician had to look up two logs, add them together and then look for ...

Table of Contents Subscription info UNITED STATES PATENT OFFICE EDWIN THACHER, OF PITTSBURG, PENNSYLVANIA SLIDE-RULE SPECIFICATION forming part of Letters Patent No. 249117, dated November 1, 1881 To whom it may concern: Be it known that I, EDWIN THACHER of Pittsburg county of Allegheny State of Penn sylvania, have invented or discovered a new and useful Improvement in Slide-Rules; and 1 do ...

Sphere's Slide Rule Universe is a repository for slide rule information, pictures, history and links to sellers, other slide rule sites and experts, and an on-line slide rule store. Located in Kelowna, BC, CANADA.

Napier's Bones This is a 6-inch Pickett all-metal slide rule (Model N 200-ES), with case. Let me explain: I was playing with Apple's Make QTVR beta yesterday and suddenly had the urge to rotate a very wide image just a skosh to make its ends match exactly. (Fancy that.) But how much to rotate Hmmm. Looks like a job for Trig. So I asked my wife if we have a scientific calculator that works. No, ...