Judgment was entered in the Supreme Court, January 18th 1875,

The rock upon which the schooner “ Amanda Flanigan ” rested at the ebb of tide, was a part of the natural bed of the river at the place where this vessel sunk. That it was uneven in surface is evident from the fact that as the tide ebbed and the schooner pressed her bottom upon it, she dipped her bow and stern, while the middle remained stationary, thus causing her to “break her hack.” Whether the rock was embedded in mud, which gave way under the bow and stern, or whether it rose in projection from the general surface of its adjacent parts, is not disclosed by the evidence. It would be dangerous to carry the defi*25nition of an obstruction, as the term is used in the Act of May 2d 185.4, sect. 28, to a natural bottom of the river such as this. Without holding that no natural formation lying in the way of safe navigation is an obstacle, or that the ■ city is not compellable to remove any obstacle to navigation of the most dangerous sort, we may safely say, that the alleged obstruction in this case is not shown to be within the act, especially where no notice has been given to the city authorities of its existence. The case of Winpenny v. Philadelphia, 15 P. F. Smith 140, decided that the navigable waters within the city were not confined to the waters within the port wardens’ line, but did not. hold the converse, that the waters within that line were not navigable waters within the meaning of the act. That question remains untouched.

We discover no error to be corrected, and the judgment is therefore affirmed.