Henry Ernest Dudeney/Puzzles and Curious Problems/326 - Strange Though True

by : $326$

 * Strange Though True
 * There is a district in where any healthy horse can travel, quite regularly, $30$ miles per day,
 * yet while its legs on one side travel $30$ miles, the legs on its other side travel $31$ miles.
 * The horse, apparently, does not seem to mind this.
 * How can this be?