WASHINGTON, June 28.

The Pawnee arrived at the Navy Yard this morning, bringing intelligence from Mathias Point According to a statement of persons in the expedition, Capt. Ward, of the Freeborn, yesterday obtained from the Pawnee a reinforcement of about twenty men, and united with others from his own vessel, comprising between thirty and forty men in all. They started in several cutters for Mathias Point, taking with them about two hundred bags, which were filled with sand on the shore, and with which breastworks were soon erected.

Whilst on returning to the Freeborn to obtain cannon for the battery, a force of the Confederate troops variously estimated at from 1,200 to 1,500, suddenly emerged from thick woods, where they were concealed, and poured a volley of shot into the party, who made a hasty retreat. Several of the men jumped into the water, swimming to the Freeborn. Capt. Ward protected the men as far as possible, firing twelve or fifteen shots among the rebels, but the effect could not be ascertained.