California Trail's Roadometer

This picture of a wagon wheel and its odometer was taken at the California Trail Interpretive Center in Elko, Nevada.  It seems that in 1847 Orson Pratt designed what he called a roadometer to log the miles they were to travel during their Wagon Train trek to California.  When the wagon wheel goes around six (six) times, the peg on the inner-hub turns the worm gear shaft one full revolution.  Each full revolution of this worm gear shaft advances the sixty (60) tooth one-mile gear wheel by one tooth.  This translates into for every 360 rotations of the wagon wheel, one full mile has been traveled.  This can be repeated for ten (10) miles.  After the ten miles, it has to be reset by removing the lynch pin and manually turning it back to zero.  Rather crude I would say, but better than having to count how many times a handkerchief tied to the wheel goes around.  I am not volunteering for that job.