RUNAWAY AND SERIOUS ACCIDENT. – Today, about noon, a serious accident occurred on South Fairfax street, between Wolfe and Wilkes. A horse attached to a Spring Wagon, which was standing near the Tunnel, took fright at the whistle of a passing locomotive, and started at full speed up Fairfax street. A little girl of some six years of age – daughter of John Boyer – was crossing the street at the time, and was knocked down by the horse, which with the vehicle passed over her. She was considerable injured, but proper assistance having been given, she is now improving.