heavens, and the places of the fixed stars, in order to find out the so much desired longitude at sea, for the perfecting of the art of navigation."

In 1714, the British parliament offered £10,000 for the discovery of longitude, if the method determined it to 10; £15,000 if it determined to 40'; and £20,000 if it determined to 30'; with a proviso, that if such method extended but to 80 miles adjoining the coast, the proposer should have but half the reward. On this act, Mr. John Harrison received the premium of £20,000, for his time-keeper. Several other acts were passed in the reigns of George II. and George III. for the encouragement of finding longitude. An act passed in 1774, said to be the last of that government on the subject, repealing all the former acts. This act diminishes the premium to half the first great offer.

The United States have not been inattentive to the subject of longitude; so far, at least, as respects the establishment for themselves of a first meridian. In the year 1809, Mr. Lambert of Virginia presented to congress a memorial on the subject of longitude. He commences by stating, "that the establishment of a first meridian for the United States of America, at the permanent seat of government, by which a further dependence on Great Britain, or any other foreign nation, for such a meridian, may be entirely removed, is deemed to be worthy the consideration and patronage of the national legislature." An interesting report on this memorial was made in March, 1810, by a select committee of the house of representatives, of which Mr. Pitkin, of Connecticut, was chairman. An extract from this report may deserve a place even in a compendium of astronomy.

"The committee have deemed the subject worthy the attention of congress, and would therefore beg leave to observe, that the necessity of the establishment of a first meridian, or a meridian which should pass through some particular place on the globe, from which geogra-.

phers and navigators could compute their longitude, is too obvious to need elucidation.

"The ancient Greek geographers placed their first meridian to pass through one of the islands, which by them were called the Fortunate Islands, since called the Canaries. Those islands were situated as far west as any islands that had then been discovered, or were known by ancient navigators in that part of the world.

"They reckoned their longitude east from Hera, or Junonia, 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 risen 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 maps, 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 sea-coasts, which have been published in this country, the committee find that the publishers have assumed different places in the United States, as first meridian. This creates confusion, and renders it difficult, without considerable calculation, to ascertain the relative situation of places in this country. This difficulty is 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 place. And no place, perhaps, is more proper than the seat of government."

The memorial, the report of the committee, and other papers, were afterwards referred to Mr. Monroe, then secretary of state, and late president of the United States. His opinion fully accorded with that of the committee, in favor of establishing a first meridian for the United States, and that it should be at Washington, the seat of government.

The subject was afterwards referred to another committee of the house of representatives, of which Dr. Samuel L. Mitchill of New York was chairman. The report of this committee was in full accordance with the preceding sentiment, and in favor of the establishment of a first meridian at the seat of govern

ment.

To these high authorities, that of the illustrious Washington may be added, as stated by Mr. Lambert, in 1821, in his address on the subject to the president of the United States.

"The illustrious personage, by whose name the me

tropolis of the American Union has been designated, unquestionably intended, that the capitol, situated at, or near, the centre of the District of Columbia, should be a first meridian for the United States, by causing, during the first term of his presidency, the geographical position of that point, in longitude 0° 0', and its latitude, 38° 53′ north, as found by Mr. Andrew Ellicott, to the nearest minute of a degree, to be recorded in the original plan of the city of Washington."

Relative or apparent time differs four minutes for a degree, or one hour for every 15° of longitude. To the east, it is later; to the west, earlier. When it is noon with us, it is one, P. M., 15° east; eleven, A. M., 150 west. Washington, according to Mr. Lambert, is 76° 55′ 30′′ west of Greenwich. It is 6 h. 52 m. 18 s., A. M., at Washington, when it is noon at Greenwich. Boston is 159° 32' west of Calcutta. When it is noon at Boston, it is 10 h. 38 m. 8 s., P. M., at Calcutta. If, therefore, by an exact time-keeper, or observation on the heavenly bodies, the time of day at the meridian, from which longitude is reckoned, and also the time at the place of observation, can be known, the difference converted into motion will show the longitude.

A good time-keeper, clock or watch, forms one method of computing longitude. Such time-keeper, set for any meridian, will not, when carried east or west, correspond with the apparent time. But its difference from the time at the place of observation, turned into motion, would, if true, give the longitude. If a ship, sailing from London to Boston, should set a watch for the meridian of London 6' west of Greenwich, such watch, if perfectly accurate, would give the time 4 h. 43 m. 25 s., P,. M. when the Sun is on the meridian at Boston. No clock or watch, however, yet invented, has been found entitled to perfect dependence. Even the time-keeper of Mr. William Harrison was found subject to considerable error, when tried at the royal observatory by Dr. Maskelyne; though it had

made a voyage from England to Barbadoes and back again, varying but 54 seconds in 156 days, or, as was thought, with proper allowance, only 15 seconds in that

time.

The eclipses of Jupiter's satellites, happening very often, form an excellent method of determining longitude on land. Like those of the Moon, they are seen at the same absolute time in all places, where they are visible. The difference in relative time, then, will show the longitude. Suppose an eclipse of the 4th satellite of Jupiter be set in the Nautical Almanac published for Greenwich at 4 h. 25 m., A. M., on a particular day, and the same is observed in the United States at 11 h. 17 m. 18 s., P. M., of the preceding day. What is the difference of longitude?.

In making this subtraction, it will be perceived, from the nature of the case, that 12 must be added to the hours of the minuend, or upper number. Convert 5 h. 7 m. 42 s. into motion, by allowing 150 for each hour, 10 for every 4 minutes, and 1 minute for every 4 seconds, and so on for thirds, you have the difference of longitude 76° 55' 30".

It is said, the difficulty of observation at sea renders eclipses of Jupiter's satellites of but little practical utility to the mariner in computing longitude.

Lunar observations form another method of determining longitude. This method is a great modern improvement in navigation. The idea is not very modern. "M. de la Lande mentions certain astronomers, who, above two hundred years ago, proposed this method, and contended for the honor of the discovery; but its present state of improvement and universal practice he very justly ascribes to Dr. Maskelyne." This lastmentioned astronomer first proposed and superintended