There was a famous eclipfe of the fun on the 22d of April 1745, to obferve which two French mathematicians came from Paris to London, by the direction of the Royal Academy of Sciences, and were entertained by the members of our Royal Society, with whom they joined in making their obfervations.

Dionyfius of Halicarnaffus mentions two total eclipfes of the fun which occurred, one at the birth of Romulus, and the other at his death, in each of which the obfcurity was as great as in the middle of the darkest night. But this account, like that of the prodigies which were seen at the death of Cæfar*, deferves but little credit. In ancient times, every great event was faid to have been accompanied with comets or other portentous appearances, and eclipfes of the fun in particular were always regarded as calamitous omens, prefaging the death of kings or fome illuftrious character. This fuperftition is frequently alluded to by the poets, and is the foundation of the follow. ing noble fimile in the Paradife Loft:

As when the fun new rifen

Looks through the horizontal mifly air
Shorn of his beams, or from behind the moon
In dim eclipfe difaftrous twilight sheds
On half the nations, and with fear of change
Perplexes monarchs: darken'd fo, yet hone
Above them all the arch-angel.

MILTON.

To folve this problem, find the fun's fituation in the ecliptic for the given day, and the particular place to which he is vertical at the proposed time,

# See Chron. Tab. Sept. 3, 1658.

by

by Problem 33; keep that fpot under the brafs meridian, and elevate the pole, i. e. rectify the globe for the latitude of that place; to almost all thofe parts of the earth which are then in the apper hemifphere, the fun, if the eclipfe be large, will be more or lefs vifibly eclipfed.

EXAMPLES.

Suppofe the fun fhould be eclipfed at London on the 21ft of June, at half an hour after five in the afternoon, to what other places would the eclipfe be visible?-Anf. To almost all Europe; to the North-Weft part of Africa; and to the whole of North and South America.

Suppofe a folar eclipfe fhould ever happen at London, on each of the following days and hours, to what places would the fame be visible?

Jan. 21, nine o'clock in the morning-Feb. 6, ten in the morning-March 27, eleven in the morning-April 17, noon-May 21, two in the afternoon-June 10, three in the afternoonJuly 19, four in the afternoon-Aug. 8, five in the afternoon Sept. 1, fix in the afternoonOct. 23, nine in the morning-Nov. 3, ten in the morning-Dec. 29, eleven in the morning.

To find all thofe Places in which a lunar Eclipfe will be visible, a particular Day and Hour being given.

An eclipfe of the moon is occafioned by a diametrical oppofition of the earth between it and the fun. When the moon's entire light is intercept. ed, it is called total; when only part, partial. Eclipfes of the moon happen only when that planet is at the full; because then only does the earth intervene between the fun and it; neither do they occur every full moon, by reafon of the obliquity of its way with refpect to the fun's; but only in thofe full moons which happen in the nodes, or very near them. Were the moon's orbit in the plane of the ecliptic, i. e. did the move in the fame plane with the earth and fun, there would be an eclipfe of the fun every new moon or change, and an eclipfe of the moon every time fhe was at the full; but thefe frequent and regular privations of light in the fun and moon are prevented by the latter's courfe being in an oblique direction to the ecliptic, which the only twice interfects in every period. Accordingly, eclipfes, as we have juft obferved, can only take place in the new moons that occur in thefe interfections, or nodes, or very near them.

The number of eclipfes of both luminaries, in any year, cannot be lefs than two, nor exceed feven. They ordinarily amount to four, but rarely to fix.

In aftronomy eclipfes of the moon determine the fpherical figure of the earth, and also that the fun

is bigger than the earth, and the earth than the noon. In geography, they difcover the longitudes. of different places; for which purpose those of the noon are the most useful, becaufe they are more requently vifible, and the fame lunar eclipfe is of qual magnitude and duration at all places where t is feen. In chronology, both folar and lunar clipses serve to determine exactly the time of any aft event. Thus

We, in the dark eclipfe, with filial awe
Trace the all-gracious Parent of the spheres;
Their distances and their proportion learn
Extending navigation; fecuring

The mariner thro' the tremendous waves *.

EUDOSIA.

To folve this problem, find where the fun is vertical at the given hour, bring that point to the zenith, and rectify the globe for its latitude; then the eclipfe will be vifible in all thofe places that are then under the horizon or find the place to which the fun is vertical at the affigned time, and rectify the globe for the antipodes of that place, and the parts of the earth then above the horizon, are thofe to which the eclipfe will be visible.

To comprehend the reafon of thefe operations, the pupil has only to be reminded, that the moon, as we have juft obferved, must be directly oppofite to the fun whenever fhe is eclipfed.

* The terrific ideas which the ancients entertained concerning eclipses of the moon will be noticed hereafter. See Moon, Index.

EXAMPLES.

EXAMPLES.

Suppofe there fhould be a total eclipfe of th moon at London, on the 27th of May, at feve in the evening, what are the places to which would be vifible in the middle-Anf. To Ital the Eastern part of Germany, Pruffia, Poian Ruffia, and Turkey. To all Afia, excepting th Northern and North-Eastern parts of Siberia. 7 all Africa, except the North-Western shores. T the Afiatic Iflands, and to New Holland.

Suppofe a lunar eclipfe fhould ever happen a London at the following times, to what place would the fame be vifible?

January 30, fix in the evening-Feb. 18, fever in the evening-March 18, eight in the eveningApril 23, nine in the evening-May 2, ten in the evening-June 1, eleven in the eveningJuly 6, midnight-Auguft 5, two in the morning-Sept. 28, three in the morning-Oct. 27, four in the morning-Nov. 12, five in the evening-Dec. 13, fix in the morning.

To find in what Latitude the longest Day is of any given Length, lefs than twenty-four Hours.

Bring the folftitial point to the meridian, and fet the index to 12; then turn the globe Weftward, till the index points at half the number of hours given; keep the globe from turning round on its axis, and flide the meridian up or down in the notches, till the folftitial point comes to the ho