books.google.fr - To most mechanics a gear is a gear."A yellow primrose by the shore, A yellow primrose was, to him And it was nothing more;"And, in fact, the gear is often a gear and nothing more, sometimes barely that. But, if the mechanic will look beyond the tips of his fingers, he will find that it can be something...https://books.google.fr/books/about/A_Treatise_on_Gear_Wheels.html?id=iauMTmKxfBoC&utm_source=gb-gplus-shareA Treatise on Gear Wheels
