This section is from the book "Bepler's Handy Manual of Knowledge And Useful Infomation", by David Bepler. Also available from Amazon: Bepler's Handy Manual of Knowledge and Useful Information.
The "knot" and the mile are terms often used interchangeably, but erroneously so. The fact is that a mile is less than 87 per cent of a knot. Three and one-half miles are equal, within a very small frac-tion to three knots. The knot is 6,082.66 feet in length. The statute mile is 5,280 feet. The result of the difference is that speed in miles per hour is always considerably larger than when stated in knots, and if a person forgets this and states the speed at so many knots, when it was really so many miles, he may be giving figures verging on the incredible.