The ocean has marked three boundaries to it, but the fourth is undefined.

There is no word of the 'Hinterland;' for neither the term nor the idea had then been thought of.

Had Great Britain bought those vast regions which extended beyond the settlements?
Or were the discontented Dutch at liberty to pass onwards and found fresh nations to bar the path of the Anglo-Celtic colonists?
In that question lay the germ of all the trouble to come.

An American would realise the point at issue if he could conceive that after the founding of the United States the Dutch inhabitants of the State of New York had trekked to the westward and established fresh communities under a new flag.

Then, when the American population overtook these western States, they would be face to face with the problem which this country has had to solve.