Now, what is the inevitable consequence of this mode of reasoning? Does it not admit the power of Congress, at once, upon all these minor objects of legislation? If all these be regulations of commerce, within the meaning of the Constitution, then certainly Congress, having a concurrent power to regulate commerce, may establish ferries, turnpike-roads, and bridges, and provide for all this detail of interior legislation. To sustain the interference of the State in a high concern of maritime commerce, the argument adopts a principle which acknowledges the right of Congress over a vast scope of internal legislation, which no one has heretofore supposed to be within its powers. But this is not all; for it is admitted that, when Congress and the States have power to legislate over the same subject, the power of Congress, when exercised, controls or extinguishes the State power; and therefore the consequence would seem to follow, from the argument, that all State legislation over such subjects as have been mentioned is, at all times, liable to the superior power of Congress; a consequence which no one would admit for a moment. The truth is, in my judgment, that all these things are, in their general character, rather regulations of police than of commerce, in the constitutional understanding of that term. A road, indeed, may be a matter of great commercial concern. In many cases it is so; and when it is so, there is no doubt of the power of Congress to make it. But, generally speaking, roads, and bridges, and ferries, though of course they affect commerce and intercourse, do not possess such importance and elevation as to be deemed commercial regulations. A reasonable construction must be given to the Constitution; and such construction is as necessary to the just power of the States, as to the authority of Congress. Quarantine laws, for example, may be considered as affecting commerce; yet they are, in their nature, health laws. In England, we speak of the power of regulating commerce as in Parliament, or the king, as arbiter of commerce; yet the city of London enacts health laws. Would any one infer from that circumstance, that the city of London had concurrent power with Parliament or the crown to regulate commerce? or that it might grant a monopoly of the navigation of the Thames? While a health law is reasonable, it is a health law; but if, under color of it, enactments should be made for other purposes, such enactments might be void. In the discussion in the New York courts, no small reliance was placed on the law of that State prohibiting the importation of slaves, as an example of a commercial regulation enacted by State authority. That law may or may not be constitutional and valid. It has been referred to generally, but its particular provisions have not been stated. When they are more clearly seen, its character may be better determined.