d by Congress's powers over
commerce; and the same is true of the property of riparian owners which
is damaged.[349] And while it was formerly held that lands adjoining
nonnavigable streams were not subject to the above mentioned
servitude,[350] this rule has been impaired by recent decisions;[351]
and at any rate it would not apply as to a stream which had been
rendered navigable by improvements.[352]

In exercising its power to foster and protect navigation Congress
legislates primarily on things external to the act of navigation. But
that act itself and the instruments by which it is accomplished are also
subject to Congress's power if and when they enter into or form a part
of "commerce among the several States." When does this happen? Words
quoted above from the Court's opinion in the Gilman case answered this
question to some extent; but the decisive answer to it was returned five
years later in the case of The "Daniel Ball."[353] Here the question at
issue was whether an act of Congress, passed in 1838 and amended in
1852, which required that steam vessels engaged in transporting
passengers or merchandise upon the "bays, lakes, rivers, or other
navigable waters of the United States," applied to the case of a vessel
which navigated only the waters of the Grand River, a stream which lies
entirely in the State of Michigan. Argued counsel for the vessel: "The
navigable rivers of the United States pass through States, they form
their boundary lines, they are not in any one State, nor the exclusive
property of any one, but are common to all. To make waters navigable
waters of the United States, some other incident must attach to them
besides the territorial and the capability for public use. This term
contrasts with _domestic_ waters of the United States, and implies, not
simply that the waters are public and within the Union, but that they
have attached to them some circumstance that brings them within the
scope of the sovereignty of the United States as defined by the
Constitution." Then as a sort of _reductio ad absurdum_ counsel added:
"* * * if merely because a stream is a highway it becomes a navigable
water of the United States, in a sense that attaches to it and to the
vessels trading upon it the regulating control of Congress, then every
highway must be regarded as a highway of the United States, and the
vehicles upon _it_ must be subject to the same control. But this will
not be asserted on the part of the Go