The cause of the fhining appearance exhibited by the Milky-Way, has been long a subject of difpute among aftronomers; but Ďr. Herschell, by a continued feries of obfervations, is confirmed in the opinion, that this lucid zone is compofed of a moft extenfive ftratum of ftars, of various fizes, whofe number conftantly increases and decreases in proportion to its apparent brightness to the naked eye. That the Milky-Way is occafioned by the confufed light of an infinity of ftars was firft afferted by Democritus *.

The Milky-Way may be traced on the globe from Argo Navis, between Canis Major and Monoceros, then feparating Taurus and Gemini, afterwards paffing through Auriga, Perfeus, Caf fiopeia, Cephus, Cygnus, Taurus Poniatowski, Scutum Sobieski, Sagittarius, Ara, Crofiers, and Robur Caroli, then revisiting Argo Navis.

PROBLEM LXVIII.

The Day of the Month being given, to find at what Hour any Star will be on the Meridian.

Bring the fun's place for the propofed day to the meridian, without regarding the pofition of the globe with refpect to the elevation of the pole, and fet the index to twelve o'clock; then

revolve

* Democritus, the parent of experimental philofophy, was a native of Abdera, a maritime city of Thrace +, and flourished about 456 years B. C. Seneca, on account of his many useful inventions, reckons him the most acute and ingenious of the ancients; others have deemed him the wifeft

+ See Grecia Antiqua, in Wilkinson's Atlas Claffica.

man

revolve the globe till the ftar comes to the meridian, and the index will point to the time required.

N. B. The ftar's right afcenfion being fubtracted from the right ascension of the fun, the remainder, reduced to time, fhews how long the ftar comes to the meridian before the fun and the fun's right afcenfion being taken from the right afcenfion of the ftar, exhibits the length of time taken by the ftar to come to the meridian after the fun.

This Problem is used for directing what time to look for any ftar on the meridian, in order to find the latitude of a place to adjust a clock, &c.

EXAMPLES.

At what time does a, Vega, in Lyra, come to the meridian on the 17th of Auguft?--Anf. About three-quarters paft eight in the evening.

At what time does the brightest of the Pleiades come to the meridian on the 14th of September?— Anf. About four in the morning.

Required the time when, on the following days, the annexed ftars come to the meridian.

January 31, and 6 in Microfcopium; a and 8 in Pyxis Nauticus; a in Scorpio.

February

man of the age; hence he has been ftyled the "Sage of Abdera." Often laughing at the follies of mankind, he has been also called the "Laughing philofopher."-Heraclitus, a celebrated natural philofopher of Ephefus, has been denominated the "Weeping philofopher, because he frequently wept at the vices and confequent miseries of mankind.

* Microscopium is a Southern constellation North of Indus. A miciofcope is an optical inftrument, by means of which

February 18,

in Quadra Euclidis *

Argo Navis; B in Cameleon.

; y and xi

March 8, B in Indus; B in Octans Hadleianus the ftar over the eye in Monoceros.

April 3, angu. Auft. 8 in Grus; in Centaurus. May 15, in Sagittarius; & in Telescopiam in Orion's Girdle; & in Lepus; in Columb Noachi; B in Canis Major. June 16, in Hydra, near the feet of Corvus in Corvus; 6 in Crufero, or Crux, or Crofiers Canopus, in Argo Navis; 6 and 6 in Canis Major July 1, Albireo, in the Milky-Way near the heads of Cygnus and Vulpecula; Bin Sagitta,

in Apis Indica, or Apus; a in Tri

very minute objects are reprefented exceedingly large, and viewed very diftinctly, according to the laws of refraction or reflection:

-whofe oracle

Reveals the wonders of minutest worlds.

EUDOSIA.

When, and by whom, microfcopes were invented, is not certainly known. Huygens tells us, that one Debrell, a Dutchman, had the firft, in the year 1621, and that he was reputed the inventor of it: though F. Fontana, a Neapolitan, in 1646, claims the invention to himself, but dates it from the year 1618. As a telescope inverted is a microscope, the difcovery might eafily enough have arifen from thence.

Nothing more, however, is certain concerning microscopes, than that they were firft ufed in Germany about the year 1621. According to Betellus, they were invented by Zacharius Janfen, in conjunction with his fon, who prefented the first they had conftructed to Prince Maurice, and Albert Archduke of Auftria.

* Euclid was the founder of a celebrated school at Alexandria, in Egypt, where he taught mathematics with vaft applaufe. He flourished about 300 years B. C. but of the place of his nativity we have no diftinct account.

between

between Aquila and Vulpecula; a, 6, 7, in Aquila.

Auguft 17, B Sheat, a Marhab, and y in Pegafus; in the Left Horn of Aries;

in the Body of Cetus; a in Eridanus, near Phoenix; Regel, y Bellatrix, in Orion.

Sept. 26, a Aldebaran in the Face, and B in the North Horn of Taurus; a Capella, in Auriga; a Cor Leonis, or Regulus, in Leo; x in the Left Hind Foot of Urfa Major.

Oct. 16, a, ß, in Gemini; y in the Body of Cancer; in the Arm of Virgo; & Alioth, in the Tail of Urfa Major.

E

November 3, 6 in the Beam of Libra; & in the Shoulder of Boötes, near Corona Borealis ; ß in the Back of Urfa Minor; a Antares, in Scorpio; 8 in the extremity of the Hair of Hercules.

E

December 18, in the Bow of Sagittarius; B in the Forehead of Capricornus; in the Eye of Pavo; Scheat, in the Right Leg of Aquarius; and about the middle of the ftring which unites the conftellation Pifces.

PROBLEM LXIX.

To find on what Day a given Star will come to the Meridian at any propofed Hour.

*

Bring the given ftar to the meridian, and fet the index to the propofed hour; then revolve the globe till the index points to twelve at noon and obferve the degree of the ecliptic then in contact with the meridian; this is the fun's place;

* See the note, page 41.

and the day correfponding to it, found on the calendar, is the answer to the Problem.

N. B. The ufe of this Problem is to fhew on what night it will be expedient to observe any particular star on the meridian.

EXAMPLES.

On what day does Ar&urus come to the meridian at three in the morning?—Ans. March 5.

On what day does Cor Leonis, or Regulus, come to the meridian at eight in the evening.-Anf. April 21.

Find on what days the following stars will come to the meridian at the hours annexed:

B, in Andromeda, one in the morning-8, Algol, in Caput Medusa, two-a, Algenib, in Perfeus, three-B, in the Shoulder of Auriga next to Lynx, four-Cor Caroli, five-B, Deneb, in the tail of Leo, fix-y and, in the Head of Draco, feven-the ftars in the Head and Back of Lacerto, eight-the ftars in the Wings of Mufca, near Aries, nine-the ftars in the Tail of Lynx, ten-the moft Wefterly ftar in Mons Menalus, eleven-the star in the Southern Head of Cerberus, held by Hercules, noon-the ftars in the Tail of Camelopardalus, one in the afternoon-y, in the Head of Serpens, two-a, Ras Albagus, in the Head of Serpentarius, the Serpent-Bearer, threethe brightest ftar in the crofs in Scutum Sobieski, four- in the Heel of Antinoüs, five-a, in Equalus, fix-a, in Triangulum, seven-a, Alphard, or Cor Hydra, in Hydra, eight-the ftar in the South-Weft extremity of Sextans Uraniæ, near Hydra, nine-y, in the Thigh of Lupus, ten

in