Ancient Roman Pedometer Called a Hodometer

While I was looking for the history of pedometers on the web I came across this illustration of a device used by the Romans.



Here is a closeup:

A description on how it worked:

A gear with one tooth (A) fastened to the wheel

of the cart turned a larger wheel (B) with 399

short teeth and one long tooth (C). The tooth

turned the drum (D) with teeth and holes for

pebbles. As the drum was turned, a rounded

pebble would fall into the metal bowl (E),

indicating that the cart had traveled one Roman

mile.

I lost the link to this site but here's a link with more information:

http://encyclopedia.tfd.com/pedometer