Astronomical observation furnishes by far the best means of defining the boundaries of States, especially when the lines are of great length and run through unsettled countries.  Natural indications, like rivers and mountains, however indistinct in appearance, are in practice subject to unavoidable error.  By the treaty of 1783, a boundary was established between the United States and Great Britain, depending chiefly on the course of rivers and highlands dividing the waters which flow into the Atlantic Ocean from those which flow into the St. Lawrence.  It took twenty years to find out which river was the true St. Croix, that being the starting point.  England then having made the extraordinary discovery that the Bay of Fundy is not a part of the Atlantic Ocean, forty years more were passed in the unsuccessful attempt to re-create the highlands which this strange theory had annihilated; and just as the two countries were on the verge of a war, the controversy was settled by compromise.  Had the boundary been accurately described by lines of latitude and longitude, no dispute could have arisen.  No dispute arose as to the boundary between the United States and Spain, and her successor, Mexico, where it runs through untrodden deserts and over pathless mountains along the 42d degree of latitude.  The identity of rivers may be disputed, as in the case of the St. Croix; the course of mountain chains is too broad for a dividing line; the division of streams, as experience has shown, is uncertain; but a degree of latitude is written on the heavenly sphere, and nothing but an observation is required to read the record.

QUESTIONS OF BOUNDARY.

But scientific elements, like sharp instruments, must be handled with scientific accuracy.  A part of our boundary between the British Provinces ran upon the forty-fifth degree of latitude; and about forty years ago, an expensive fortress was commenced by the government of the United States, at Rouse’s Point, on Lake Champlain, on a spot intended to be just within our limits.  When a line came to be more carefully surveyed, the fortress turned out to be on the wrong side of the line; we had been building an expensive fortification for our neighbor.  But in the general compromises of the Treaty of Washington by the Webster and Ashburton Treaty in 1842, the fortification was left within our limits.[A]

[Footnote A:  Webster’s Works.  Vol.  V., 110, 115.]

Errors still more serious had nearly resulted, a few years since, in a war with Mexico.  By the treaty of Guadalupe Hidalgo, in 1848, the boundary line between the United States and that country was in part described by reference to the town of El Paso, as laid down on a specified map of the United States, of which a copy was appended to the treaty.  This boundary was to be surveyed and run by a joint commission of men of science.  It soon appeared that errors of two or three degrees existed in the projection of the map.  Its lines of latitude and longitude did