A Compilation of the Messages and Papers of the Presidents. Volume 4, part 2: John Tyler

by Unknown

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.

Ten principal points have been determined in latitude and longitude by means of 115 sets of astronomical observations, aided by three good chronometers, and seventeen other points have been determined by triangulation with a portable theodolite. Two hundred and five points have been determined in altitude by means of 1,319 barometric observations, and seventeen by means of the theodolite and spirit level. One hundred and ninety-two observations have been made for determining the variation of the magnetic needle at three important points.

The field duties above mentioned are considered to furnish sufficient data for a correct map of the line reported upon by the late British commissioners, Colonel Mudge and Mr. Featherstonhaugh, between the St. John River and the head of the Aroostook, besides some lateral explorations of considerable extent that will have an important bearing upon this branch of the subject. The work accomplished is full as much as could have been properly done in a single season, marked, as the last was, by an unusual drought of long continuance, which rendered it impossible to ascend, even with light canoes, some of the smaller streams, especially those forming the northwesternmost sources of the Aroostook. These might be profitably explored another season.

2. The division under the direction of A. Talcott has, besides verifying a part of the line of 1840 and tracing the course of Indian Stream (a branch of the Connecticut) to its source, explored and surveyed the line of highlands which extends from the Kennebec road to the Temiscouata portage, and so much of the line claimed by Great Britain as extends from the Kennebec road to the eastward as far as the head of the Aroostook River.