delivered the opinion of the Court::

The prosecution is founded upon the act of Congress of February 28, 1887 (24 Stat. at L. 427, chap. 272), the 6th section of which is as follows:

“Sec. 6. That any owner or lessee of steamboifer or engine,, or the secretSry of any corporation, who shall knowingly employ a steam engineer, as such, who has not been regularly licensed to act as such, shall, on conviction thereof by the police, court of the District of Columbia, be fined, fifty dollars, and, in default of payment of such fine shall be confined for a period of one month in the workhouse of the District of Columbia! Provided, that boilers used for steam-heating, where the water-returns to the boiler without the use of a pump and injector, or inspirator, and which are worked automatically, shall be exempt from the provisions of this section.” And, by § 7 of the act, it is provided: “That the foregoing section shall not apply to engineers who have been licensed by the United States government, or the law of any State.”

This act is a police regulation intended as a means of protection to lives and property of the people of the District. The-frequent occurrence of accidents and casualties resulting from the want of adequate skill and knowledge in the management of steam engines by those entrusted with their operation renders the regulation one of importance, and justifies its enforcement by criminal prosecution. The defendant conducted a business within the limits of the District of Columbia, in which he employed a steam dredge with an engine aboard, used for-*271dredging and loading and unloading scows of the defendant on the Potomac river. He owned the dredge and the engine aboard, and had employed a man to run the engine, knowing that the man was not regularly licensed as a steam engineer. This was clearly in violation of the provision of the act of Congress. That act applies to the whole District of Columbia, including the Potomac river as it runs through the District; and the power of Congress to provide for the exercise of police power and regulation over the Potomac river, within the limits of the District of Columbia, is quite as clear as it is in respect to any other portion of the District. The entire river, within the limits of the District, is subject to the legislative control of Congress, as well in respect to matters of police as to all other subjects of legislation.

The defenses set up by the defendant are: That the Commissioners of the District of Columbia have no power over the Potomac river beyond the dock of pier lines; or that the defendant was not liable to this prosecution because the vessel owned by him, and upon which the engine was operated, was engaged in commerce on the public navigable waters of the Potomac river, and therefore within the admiralty jurisdiction of the United States; and that there was no power in the eomsioners of the District to require a license to be obtained in such case. But we perceive no ground for any such defenses as those offered by the defendant. The offense of which the defendant has been convicted is one for the violation of a mere police regulation prescribed by the act of Congress, and clearly there can be no question of the power of Congress to prescribe such regulation; and there is no ground for supposing that the Potomac river, a part of the District of Columbia, as defined in the act of cession to the United States, was intended to be excluded from the operation of the act of Congress of 1887. It may be conceded that the act was not intended to apply to the cases of engineers employed in the navigation of steam vessels coming into the harbor from other ports or harbors beyond the District, or to engineers on the steam railroads running into. *272this District But the reasons upon which engineers in such cases are exempt do not apply in a case such as the present.

Finding no error in the rulings of the Police Court its judgment must be affirmed; and it is so ordered.

Judgment affirmed.