hemifpheres, the one north and the other fouth. This eircle is every where equally diftant from the two poles; and upon this circle the degrees of longitude are marked. s. The two tropical circles: viz. The tropic of Cancer, or the northern tropic, which encompaffes the globe at the distance of 23 degrees from the equator; and the tropic of Capricorn, or fouthern tropic, which encompaffes the globe at the fame diftance on the fouth fide of the equator. The space between these two tropics is called the Torrid Zane. 3. The two polar circles: viz. the ar&ic circle, which furrounds the north pole; and the antarctic circle, which furrounds the fouth pole; each at the distance of 23 degrees from its refpective pole. The fpace included hetween the tropic of Cancer and the arctic circle is called the northern Temperate Zone, and that space between the arctic circle and the north pole, is called the north Frigid Zone; and the correfponding fpaces on the fouthern hemifphere have fimilar names, as the fouthern Temperate Zone, and the fouthern Frigid Zone. 4. The meridional lines, which are lines drawn at right angles to the equator, and coinciding at the poles. These lines run directly north and fouth: and when the fun appears full fouth of any place, he is then faid to be on the meridian of that place; and it is then twelve o'clock at noon at that place The latitude of places is always numbered on these lines.

17. The longitude is the diftance of one country from anather, and is either caft or weft, and measured on the equator. The longitude of a place is always measured from the capital of the country where the author or traveller is; thus, when a perfon in England mentions the longitude of any other place, it is always understood that the longitude is reckoned from London; that is, the degrees of longitude are measured on the equator, and from that part of the equator, where the meridian paffing through London, interfects the equator, at that part of the equator which is cut by the meridian of the other place meafured to.

18.

18. The latitude of a place is the distance of that place from the equator, measured on the meridional line; and is either north or fouth.

19. The inhabitants of the earth are diftinguished from each other by their relative situations; of which there are reckoned three forts, Periaci, Antiæci, and Antipodes: 1. The Periaci are those people who live at the fame distance from the equator, but under oppofite meridians: the length of their days and feafons is the fame; but when it is mid-day with one, it is midnight with the other. 2. The Antiaci live under the fame meridian, but oppofite parallels, and live equally diftant from the equator; the one being in the fouth latitude, and the other in the north. These have the fun at the same hour at noon; but the longest day of the one is the shortest day of the other, and their feafons of the year are different; for when it is fummer with one, it is winter with the other. 3. The Antipodes are fituated directly on oppofite fides of the globe to each other, the feet of the one being directly oppofite to the feet of the other. Thefe lie under oppofite meridians, and oppofite parallels: it is noon. day with the one, when it is midnight with the other; the longest day with the one, is the shortest day with the other; and when it is fummer with the one, it is winter with the other.

20. The inhabitants of the earth are sometimes diftinguifhed from each other (in geography) by the direction of their shadows at noon-day; and are called Amphifcii, Afeii, Heterofcii, or Perifcii. 2. The Amphifcii are those fituated in the torrid zone, and have their fhadows, one part of the year, directed towards the north at noon-day, and at another part of the year, towards the south, at noon-day, according to the part of the ecliptic the fun is in; confequently, the fun is vertical to these people twice a year. They are then called : -2. Afcii, fhowing no fhadow at noon-day. 3. The HeteTofcii, are those who inhabit the temperate zones, and whose fhadows at mid-day always fall one way: viz. The fhadows

of

of thofe in the northern temperate zone, falling always towards the north, at noon-day; and thofe in the fouthern zone, always fouth at noon-day. 4. The Perifcii are those who inhabit either of the frigid zones. These have their fhadows moved entirely round them every 24 hours, when the fun is in their hemifpheres, and fo far declined towards their pole, as not to set for several days.

: 21. The horizon is properly a double circle; one of the horizons being called the fenfible, and the other the rational horizon. The former comprehends only that space which we can fee around us, upon any part of the earth; and is very different, according to the difference of our fituation. The other, called rational, is parallel to the former, but paffing through the centre of the earth, and fuppofed to be con tinued as far as the celestial fphere itself; whereas the former is fuppofed to pass over the surface of the earth, where the spectator ftands: but in geography, when the hos rizon is mentioned, the rational horizon is always underftood. By reason of the round figure of the earth, every different part has a different horizon. The poles of the ho rizon, that is, the points directly above the head, and oppofite the feet of the observer, are called the zenith and nadir.

22. The zenith is that pole of the horizon directly over the observer's head.

23. The nadir is the oppofite pole of the horizon, or that directly under the observer's feet.

A TABLE

A TABLE,

SHOWING

The Number of Miles in a Degree of Longitude, in every Degree of Latitude, from the Equator.

Defcription and Ufe of the Globes and Armillary Sphere.

By means of maps, the true fituations of the different places of the earth, with regard to one another, and every other particular relative to them, may be easily known; confequently the hour of the day, feafon of the year, &c. for any particular place may be difcovered. But thefe problems, to be refolved by maps, would be tedious and complex; therefore, thofe machines called the celeftial and terrestrial globes, and the armillary fphere, have been invented, by which many calculations are faved, and every problem in geography may be folved mechanically, in the most easy and expeditious manner.

If a map of the world be accurately delineated on a spherical ball, the furface thereof will represent the furface of the earth; for the higheft hills bear no greater proportion to the bulk of the whole earth than so many grains of fand do to a common mathematical globe of twelve or eighteen inches. diameter; the diameter of the earth being near Sooo miles, and no bill upon its furface is above three miles in perpendicular height.

The armillary fphere is a large hollow fphere of glafs, having as many bright ftuds fixed on its infide, as there are vifible ftars in the heavens, and of the fame magnitude, and at the fame angular distances from each other. This sphere is a true representation of the heavens, to an eye fuppofed to be placed in the centre; for to an obferver placed any where within the furface of an indefinite sphere, all objects will appear equally diftant, though fome be much nearer than others and if a small globe, having a map of the earth upon it, be placed on an axis in the centre of this sphere, and the sphere be made to turn round its axis, it will reprefent the apparent motion of the heavens round the earth: but if the globe be turned round its axis, while the sphere. remains fixed, it will reprefent the true motion of the earth.

If