If you are a mechanical sort, and have an hour or two to while away, may I suggest spending it at 507movements.com, a website that contains an enhanced version of the book of the same name by Henry Brown, which was originally published in 1868. 

“Multiple gearing”—a recent invention. The smaller triangular wheel drives the larger one by the movement of its attached friction-rollers in the radial grooves.

The website features the 21st edition of this long-popular technical book which was published in 1908.  (The satisfyingly wordy and descriptive frontispiece of which is roughly reproduced below: Continue reading →