Abridgment of the Debates of Congress, from 1789 to 1856, Vol. 4 (of 16)

by United States. Congress

They reckoned their longitude east, from Heria or Junonia, one of these islands supposed to be the present Island of Teneriffe.

The Arabians, it is said, fixed their first meridian at the most westerly part of the continent of Africa. In the fifteenth and sixteenth centuries, when Europe was emerging from the dark ages, and a spirit of enterprise and discovery had arisen in the South of Europe, and various plans were formed, and attempts made to find a new route to the East Indies, geographers and navigators continued to calculate longitude from Ferro, one of the same islands, though some of them extended their first meridian as far west as the Azores or Western islands.

In more modern times, however, most of the European nations, and particularly England and France, have established a first meridian to pass through the capital, or some place in their respective countries, and to which they have lately adapted their charts and astronomical tables.

It would perhaps have been fortunate for the science of geography and navigation, that all nations had agreed upon a first meridian, from which all geographers and navigators might have calculated longitude; but as this has not been done, and in all probability never will take place, the committee are of opinion that, situated as we are in this Western hemisphere, more than three thousand miles from any fixed or known meridian, it would be proper, in a national point of view, to establish a first meridian for ourselves; and that measures should be taken for the eventual establishment of such a meridian in the United States.

In examining the maps and charts of the United States, and the particular States, or their seacoasts, which have been published in this country, the committee find that the publishers have assumed different places in the United States, as first meridians.

This creates confusion, and renders it difficult, without considerable calculation, to ascertain the relative situation of places in this country. This difficulty is also increased, by the circumstance that, in Louisiana, our newly-acquired territory, longitude has heretofore been reckoned from Paris the capital of the French Empire.

The exact longitude of any place in the United States being ascertained from the meridian of the observatory at Greenwich, in England, a meridian with which we have been conversant, it would not be difficult to adapt all our maps, charts, and astronomical tables, to the meridian of such a place. And no place, perhaps, is more proper than the seat of Government.

It appears by the papers submitted to the consideration of the committee, that Mr. Lambert has calculated the longitude of the Capitol in the City of Washington, from the Royal observatory at Greenwich, by one of the most approved methods now in use for that purpose, viz: an occultation of a known fixed star by the moon.

His calculations are founded on an occultation of η pleiadum, (Alcyone,) one of the seven stars, on the night of the 20th of October, 1804. By these calculations it appears, that the longitude of the Capitol, in the city of Washington, as reduced according to the true figure of the earth, (being that of an oblate spheroid,) is 76° 53´ 6".920 degrees west. The committee would observe, that Mr. Lambert appears to be well acquainted with astronomical calculations; and that, so far as the committee have had time to examine them, they appear to be correct. In a question, however, of so much nicety, the correct decision of which depends so much on the accuracy of the observations made, and the goodness of the instruments used, and when the smallest error in the data will necessarily produce an erroneous result, full reliance ought not to be placed on calculations made from a single observation.

Indeed, in order to be certain of a correct result, it may be proper that more than one of the various methods of ascertaining longitude should be used; that calculations should be made from observations of the eclipses of Jupiter's satellites, of solar eclipses, of the angular distances between the sun and moon, or the moon and a fixed star, or other methods, as well as from observations on occultations of fixed stars.