Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
What Is a Nation? Language, by contrast, "invites us but does not force us, to unite". Countries which share the Spanish or English language don't merge with one another, while the people of Switzerland speak several languages. Modern nationhood also cannot be based on religion, which Renan observes, is currently practiced according to individual belief. "You can be French, English, German, yet Catholic, Protestant, Jewish, or practicing no religion". Mutuality of interests is fine for corporations and their affiliates, but nationality is based on sentiment. Geography merely leads us astray, and often to violence: "Mountains don't know how to carve out countries". Renan concludes