Besides the astronomical observations necessary to obtain and continue the due north direction upon this line, numerous magnetic observations have also been made at a number of points upon it, in order to show the physical causes which must operate to produce serious discrepancies between a meridian line properly traced and such a one as has actually separated the jurisdiction of the two Governments since the attempt in the years 1817 and 1818 to define and mark this portion of the boundary under the provisions of the treaty of Ghent, although no portion of that line was ever ratified or made binding upon the parties to the treaty.

Upon this portion of the survey there have been chained, including measured offsets to the old line and to other important points, 85 miles.

Four hundred and fifty-two transit observations of heavenly bodies have been made, aided by three excellent chronometers, for the determination of the true meridian direction, most of which also served for the computation of the correct time.

For the determination of the longitude of this meridian west of the Royal Observatory of Greenwich and the latitudes of four important points upon it there were made eighty-five complete sets of astronomical observations, including altitudes of the sun and stars and the meridian transits of the moon and moon-culminating stars.

The number of barometric observations made upon the line and in its vicinity is 5,767; besides which there were made at Calais, for comparison with the level of mean tide on the St. Croix, 1,336 similar observations.

There have been determined in altitude above or below the level of the monument, by means of the spirit level, 1,716 points, and the altitudes of 1,816 other points have been similarly observed in order to verify the altitude of the monument above the level of mean tide at Calais.

For the determination of the magnetic variation at a number of points on the meridian line, more than 200 observations have been made upon four different needles, and for the determination of the magnetic dip at four principal stations on the same meridian 300 observations have been made upon two different needles.

Under the directions of the same commissioner the line claimed by Great Britain from Mars Hill and that recently chosen by Messrs. Mudge and Featherstonhaugh have been surveyed westward from the meridian line to the highlands near the head waters of the Aroostook, and the necessary data obtained for the construction of a correct map of that portion of country.

Upon this survey, without reckoning the distances traveled for approaching many important points of observation, there have been actually measured with the chain and coursed with proper instruments 267 miles, including the Aroostook River from its mouth to the point where it receives the Lapawmpeag Stream, a profile of the country from the head waters of the Moluncus to the St. John at Fish River, and such other important lines as were necessary for obtaining the correct topography of the country, and the altitudes of many points upon the line claimed by Great Britain as the boundary, in the vicinity of the Aroostook, have been obtained.