when it is noon day with the other; the longest day with the one is the fhortest with the other; the length of the day with the one is equal to the other's night; and the feafons are oppofite, being fummer with one, when it is winter with the other.

The Real Parts are earth and water, generally divided into four parts or quarters, called Europe, Afia, Africa, and America; each of these, and confequently the whole Globe, is divided into continents, iflands, feas, &c.

A Continent is a great quantity of land, not divided by the fea, wherein are several empires, kingdoms, and countries conjoined, as Europe, Afia, and Africa, is one Continent, and America another.

An Island is a part of the earth that is environed or encompassed round by the fea, as Great Britain and Ireland.

A Peninsula is a part of land almost surrounded with water, fave one narrow neck of land which joins the fame to the Continent.

An Ifthmus is a narrow neck of land joining the Peninsula to the Continent, by which the people may pass from one to the other.

A Promontory is a high part of land, ftretching itfelf into the fea, the extremity of which is called a Cape or Headland.

A Mountain is a rifing part of dry land, over-topping the adjacent country, and appearing firft at a diftance.

The Earth being encompaffed by water, whose washings, in furrounding the dry land, cut and fhape many winding bays, creeks, and meandering inlets, and extending itself round them all, is but one continued ocean.

An Ocean is a vaft collection of falt water, feparating Continents from one another, and washing their borders or fhores.

A Sea is part of the Ocean, to which we must fail through some Strait, as the Mediterranean and Baltic Seas.

A Strait is a narrow part of the ocean, lying between two shores, and opening a way into fome fea, as the Straits of Gibraltar, that lead into the Mediterranean Sea, and the Sound, which leads into the Baltic Sea.

A Creek or Cove is a small narrow part of the fea or river, that goes up but a little way into the land.

A Bay is a great inlet of the land, as the Bay of Biscay, and the Bay of Mexico; otherwise a Bay is a station or road for fhips to

anchor in.

A River is a confiderable stream of water, iffuing out of one or various fprings, and continually gliding along till it discharges itfelf into the Sea. The leffer ftreams are called Rivulets.

A Lake is that which continually retains and keeps water in it, as the Lake Zair, in Africa, and Nicaragua, in America.

A Gulph is a part of the Ocean or Sea, contained between two

shores, and is every where environed by land, except its entrance, where it communicates with other bays, feas, or oceans.

There are five Oceans, namely, the Northern, the Atlantic, the Pacific, the Indian, and the Southern.

The Atlantic Ocean is usually divided into two parts, one called the North Atlantic Ocean, and the other the South Atlantic or Ethiopic Ocean.

The Northern Ocean ftretches to the northward of Europe, Afia, and America, towards the north pole.

The Atlantic Ocean lies between the Continents of Europe and Africa on the east, and America on the west.

That part of the North Atlantic Ocean lying between Europe and America is frequently called the Western Ocean.

The Pacific Ocean, or, as it is fometimes called, the South Sea, is bounded by the western and north-weft fhores of America, and by the eastern and north-east shores of Afia.

The Indian Ocean washes the fhores of the eastern coafts of Africa, and the south of Afia, and is bounded on the east by the Indian iflands and the fouthern continent.

The Southern Ocean extends to the southward of Africa and America towards the fouth pole.

ABBREVIATIONS.

Alt. Altitude-A. M. before Noon-App. Apparent.

AR. Right Afcenfion-Amp. Amplitude-Aug. Augmentation -Comp. Complement.

Col. Column-Cor. Correction-Cou. Courfe-Dec. Declination-Dep. Departure.

Dia. Diameter-Dift. Distance-Diff. Difference-Dip. Depreffion of the Horizon-Ela. Elapsed.

Equ. Equation-Equa. Equator-Hor. Horizon-Lat. Latitude-Log. or L. Logarithm.

L. L. Lower Limb-Mag. Magnetic-Mer. MeridianMerid. Meridional-Mid. Middle.

Nat. Natural-Nau. Alm. Nautical Almanac-Obf. Obferved or Obfervation-Par. Parallel.

Parx. Parallax-Perp. Perpendicular-Pol. Polar-Pro. or P. Proportional-P. M. before Noon.

Ref. Refraction-Rad. or R. Radius-L. R. Logarithm Ratio. Semi Dia. Half the Diameter.

U. L. Upper Limb-Zen. Zenith.

THE

NAVIGATION.

HE great end and bufinefs of Navigation is to inftruct the Mariner how to conduct a fhip through the wide and pathlefs ocean, to the remoteft parts of the world, the fafeft and shortest way, in paffages navigable.

For the due and regular performance of which are requifiteA perfect knowledge of the figure and motion of the earth, the various real and imaginary lines upon it, so as to be able to ascertain the real distance and fituation of places with respect to one another, with the use of the several inftruments made use of in meafuring the fhip's way; fuch as the log. half-minute glafs, quadrant, or fextant, to take the altitude of the fun and ftars; compafs, to represent the fenfible horizon; and azimuth compass, to take the azimuth or amplitude of the fun, in order to know the variation of the magnetic needle; maps and charts of the feas and lands, together with the depth of water, the times and fettings of the tides upon the coafts he may have occafion to approach near; a competent knowledge of currents; of the mould and trim of the fhip, and the fail fhe bears, that fo due allowance may be made for leeway: by help of these, and skill in the navigator, he may know at all times the place the fhip is in, which way he must steer, and how far, to gain his intended port.

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Notwithstanding what has been said, it may not be improper here to obferve, that

As latitude is counted from the equator upon an arch of the meridian, north and fouth, the difference of latitude between two places, both north, or both south, is found by fubtracting the lefs latitude from the greater; but if one latitude be north and the other fouth, the fum is the difference of latitude.

Confequently, if a ship in north latitude fails northerly, or in fouth latitude foutherly, fhe increases her latitude; but in north latitude failing foutherly, or in fouth latitude failing northerly, fhe decreases her latitude; because fhe fails nearer to the equator, from whence the latitude is reckoned.

Wherefore in north latitude failing northerly, or in fouth latitude failing foutherly, the difference of latitude, added to the latitude left, gives the latitude in.

In north latitude, failing foutherly, or in fouth latitude, failing northerly, the difference of latitude fubtracted from the latitude left, gives the latitude in.

When the latitude decreafes, and the difference of latitude is greater than the latitude failed from, fubtract the latitude left from the difference of latitude, the remainder will be the latitude in, and of a different name; for it is plain that the hip has croffed the equator.

As the longitude is counted from the firft meridian east and weft, until it comes to the oppofite meridian, it cannot exceed 180 degrees.

The difference of longitude between two places, being both east or weft, is found by fubtracting the lefs longitude from the greater; but if one be in eaft longitude, and the other in weft, their fum is the difference of longitude.

Therefore in eaft longitude failing eafterly, or in weft longitude failing wefterly, the difference of longitude added to the longitude left, gives the longitude in.

In eaft longitude failing wefterly, or in weft longitude failing eafterly, the difference of longitude fubtracted from the longitude left, gives the longitude in.

When a fhip fails eaft or weft, until fhe paffes the oppofite meridian, or 180 degrees, the changes her longitude, or comes into a longitude of a different name.

What has been faid will be rendered familiar to the learner by the following examples:

In the last example it is plain, that as the difference of latitude is more than the latitude left, the fhip must have crofled the Equator, and confequently come into fouth latitude.

NOTE. When one of the places has no latitude, or is on the Equator, then the latitude of the other place is their difference of latitude.

In failing due north or fouth, the fhip changes her latitude only; and failing east or weft, her longitude; but failing upon any other course, the must change both latitude and longitude.

Eafting or wefting, in Plane Sailing, is called Departure or Meridian Distance.

The inftrument used in measuring a fhip's way at fea, is the Log. Ships at fea are directed from one place to another by means of an inftrument called the Mariner's Cempafs, which is an artificial representation of the horizon of every place, by the means of a circular piece of paper, called a card, divided like the horizon into degrees and points, which are called Rhumbs. Now the card being properly fixed to a piece of steel, called the Needle, that has been touched with a loadstone, (whofe property is fuch as to caufe one end of the needle fo touched to point towards the north, when turning freely on fomething fupporting it) all the points of the card will be directed towards the correfponding points of the horizon: