Part 23

It is noticed by the writer of the article “Astronomy,” in Dr. Brewster’s New Edinburgh Encyclopædia, (the first volume of which has been very lately reprinted in Philadelphia,) that the venerable Herschel, at the advanced age of seventy-two years, still continued to observe the heavens with the most unwearied assiduity: and that his contemplated “successor,” who, it is presumed, is his son, “promises to inherit the virtues and the talents of his father.”

Footnote 85a:

Herschel, in calling his newly-discovered planet by the name of his patron, was not without illustrious precedents for so doing. When Galileo discovered the four Satellites of Jupiter, in the year 1610, he named them the Medicea Sidera, in honour of the family of Medici, his patrons. And Cassini, who, in the years 1671, 1672, and 1684, successively, discovered the fifth, the third, and the first and second Satellites of Saturn, denominated these stars, Sidera Lodoicea, in honour of Louis XIV. in whose reign, and observatory, they were first discovered. The fourth Satellite of Saturn (but the first of them, in the order of time, that was known) had been previously discovered by Huygens, sixteen years before any one of the others was known to exist.

Footnote 85b:

So written by Lalande. There is an Asiatic island called Panay: it is one of the Philippines, and lies, as Panchay is said to do, “to the east of Africa.”

Footnote 85c:

“Herschel, with ample mind and magic glass, Mid worlds and worlds revolving as they pass, Pours the full cluster’d radiance from on high, That fathomless abyss of Deity.” Purs. of Lit. dial. the fourth.

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Further improvements may also be expected to take place, in the construction of watches and other spring-chronometers; so as to render them still more useful for the purposes of navigation, by ascertaining with greater precision the longitude at sea. For this purpose, the finely-improved English time-keepers of Harrison, Mudge, and others, have been found of the greatest utility. Mr. de Zach, (in his Explanation and uses of the Tables of the Motions of the Sun,) after some observations on determining differences of longitude by means of astronomical observation, says,—“De cæteris longitudinem determinandi modis, non est hic disserendi locus;—de uno vero, horologiâ maritimâ seu nauticâ, quidquam adjicere non alienum erit. Triginta jam abhinc annis, ingeniosissimi horologiorum artifices, Harrison, Cummings, Kendal, Arnold, Mudge, apud Anglos,—Le Roy et Berthoud apud Gallos, varia navigantium usui, egregia excogitaverant, et ad magnum perduxerant perfectionis gradum, horologia nautica, (Anglis, Time-keeper.) Cum eorum in longitudinibus itenere maritimo definiendis, usum quisque norit, plura hic dicere abstineo; simile horologium ab ingenioso horolopega Thom. Mudge constructum, in Observatorio Regio Grenovicensi sæpius exploratum, anno 1784, a Clar. D. Campbell, classis navalis præfecto ad Terram Novam (Newfoundland) vectum, et reductum, ab hoc tempore in Observatorio Excellentissimi Comitis de Bruhl, Londini, Doverstreet, assidue observatum est. Hoc ipsum horologium maritimum, anno 1786, in terrestribus, iteneris longitudines determinandi gratia, concreditum mihi fuit, cum â Serenissimo Duce Saxe-Gothanâ, omnium scientiarum bonarumque artium patrono, imprimis astronomiæ, faventissimo, Londino evocatus in Germaniam me conferrem, ubi amplissimæ splendidissimæ Speculæ, Astronomicæ Gothanæ extruendæ cura mihi demandata erat; attuli eodem hoc tempore, ad Serenissimi mandatum, minoris molis horologium, quod in braccis gestari solet (Anglis, Pocket-chronometer,) a Londiniensi artifice, D. Josiah Emery, constructum, quod summâ accuratione et subtilitate elaboratum, nil majoribus cedit horologiis nauticis, ut videre licet ex tribus horum motuum elenchis ab Ilustr. Comite de Bruhl, et â aliorum Dr. Arnold, nuperrime publici juris factis. Sub finem anni 1786 et ad initium 1787, Serenissimum in itenere per Germaniam, Galliam, et Italiam, comitatus sum: hoc itenere quorundam locorum et Specularum astronomicarum longitudines definitæ sunt ex comparatione temporis horologii maritimi (quod ad tempus solare medium Londinense, in Doverstreet incedebat) cum tempore medio loci, quod sextante Hadleianâ per solis altitudines, quas correspondentes dicimus, vel ex comparatione cum illo, quod in Speculis Astronomicis ab ipsis astronomis traditum nobis fuit. Iisdem itaque automatis, cum primum Gotham advenissem, observatorii futuri longitudinem maximâ cum curâ atque diligentiâ definivi, quam paucis post diebus Serenissimus Dux Londinum profectus, chronometro suo secum deportato denuo perbelle comprobaverat.”

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Footnote 86:

Philip III. king of Spain, first offered a reward for the discovery of the longitude, about two centuries ago; and the States of Holland, soon after, followed his example. The Regent of France, during the minority of Louis XV. also promised a great reward to any person who should discover the longitude at sea.

In the year 1714, the parliament of Great Britain offered a reward for a like discovery; and if the method, to be proposed, should determine the longitude to twenty geographical miles, the premium was to be twenty-thousand pounds sterling. The act of parliament established a board of Commissioners of the Longitude. Several other acts were passed, in the reigns of Geo. II. and III. directed to the same purpose. Finally, in the year 1774, all those acts were repealed, by one offering separate premiums for finding the longitude; either by the lunar method, or by a watch keeping true time,—or by any other method practicable at sea. This act proposes as a reward for a time-keeper, 5000l., if it determine the longitude to one degree or sixty geographical miles,—7500l., if to forty miles,—and 10,000l., if to thirty miles. If the method be by improved Solar and Lunar Tables, constructed upon Sir Isaac Newton’s theory of gravitation, the author is to receive 5000l.; provided such Tables shall show the distance of the Moon from the Sun and Stars within fifteen seconds of a degree, answering to about seven minutes of longitude, after making an allowance of a half a degree for the errors of observation. The Commissioners have the power of giving smaller rewards, at their discretion, to persons making any discovery for finding the longitude at sea, though it may not be within the above limits.

The set of Solar and Lunar Tables which were sent to the Board of Longitude, about the year 1763, by the widow of the celebrated astronomer, Tobias Mayer, were honoured with a reward of 3000l. sterling, by an act of the British parliament, in consideration of their great usefulness in finding the longitude at sea.

Footnote 87:

See Mr. de Zach’s great work, entitled, Tabulæ Motuum Solis novæ et correctæ, &c.

Footnote 88:

For the use of such readers as may not be acquainted with the Latin language, the following translation of the above is given, from the original of Mr. de Zach.

“Concerning the means of determining the longitude, this is not the proper place to treat: of one, however, the marine or nautical time-keeper, it will not be foreign to our purpose to say something.

“It is now about thirty years, since those very ingenious makers of time-keepers, Harrison, Cummings, Kendal, Arnold, and Mudge, among the English,—Le Roy, and Berthoud, among the French,—devised various and excellent ones for the use of navigators, and brought to a great degree of perfection those marine watches, called by the English, Time-keepers. As every one knows their use in ascertaining the longitude, on a sea-voyage, I shall not say any thing more of them here.—A similar time-piece, made by the celebrated watch-maker Mr. Thomas Mudge, and often referred to in the royal observatory of Greenwich, was, in 1784, made use of by the Hon. Vice-Admiral (John) Campbell, commander of the naval squadron on the Newfoundland station,—going thither and returning; and from that time was diligently examined, at the observatory of his Excellency Count Bruhl, in Dover street London.

“This very marine time-piece was confided to my charge, in the year 1786, for the purpose of determining the longitudes of my journey by land; when, called from London by his Serene Highness the Duke of Saxe-Gotha,—the patron of all the sciences and liberal arts, but more especially favouring astronomy,—I returned to Germany; where the erecting of a complete and splendid Observatory, at Gotha, was placed under my direction. I then took with me, by the command of his Serene Highness, a watch of a smaller size, which he usually carried in his fob,—called by the English a Pocket-chronometer,—made by a London artist, Mr. Josiah Emery: which, being made with the greatest accuracy and ingenuity, yielded nothing in point of correctness to the larger nautical time-keepers, as may be seen from three tables of their movements by the illustrious Count Bruhl, and also of others, by Dr. Arnold, lately established by authenticated certificates.

“About the end of the year 1786 and the beginning of 1787, I accompanied His Serene Highness, in a tour through Germany, France and Italy. In this journey, the longitudes of several places and astronomical observatories were determined, from a comparison of the time of a nautical time-keeper (which was set by the solar mean time in Dover street, London,) with the mean time of the place; which appears by the altitudes of the sun, by Hadley’s sextant—those which we call corresponding, or by a comparison with it, as transmitted to us in observatories, by those astronomers. By the same instruments, therefore, when I arrived at Gotha, I ascertained the longitude of the future observatory there, with the greatest care and attention; which the Duke, going to London a few days after, taking with him his chronometer, at length fully verified.”

Footnote 88a:

Here is a reference, in the text, to note 89.

Footnote 88b:

Here is a reference, in the text, to note 90.

Footnote 88c:

Here is a reference, in the text, to note 91.