The Armstrong scale: a hypothesis
Among the more ubiquitous instruments named after their inventors - from Captain Field's parallel to the Napier compass, Gunter's chain to Marquois' triangles - arguably the most widely-known and numerous…
Rules are made to be broken
When is a rule not a rule? When it's four rules! This deceptively simple rolling ruler offers an unexpected "twist" on the conventional design. Made of what appears to be…
More patent sticks
Here is a trio of glorified wooden sticks for ruling parallel lines that each somehow managed to secure patent protection. Two are so similar that they could easily be mistaken…
Thornton on folding pocket rules
I recently took a gamble on a job lot of plastic slide rules and other oddments on account of a blurry pocket rule in one corner of the photo. Superficially…