1 1 SECTION V. 231 named; together with the north and south poles. z. is the Path of London, N the Nadir, n the south point of the Horizon, o the north point, c the east and west points, s the summer solstice, w the winter solstice, a the ecliptic's north pole,'ethe ecliptic's south pole. The two equinoctial points are represented by c, supposing one to be on this side, the other on theopposite side of the globe. If you would have the two colures represented here in this figure, you must suppose the meridian to be the solsticial colore, and the axis of the world to represent the equinoctial colore. Note, .Phis representation or projection of the sphere in strait lines is usually called the analemma. See how to project it or to erect this scheme, Sect. XX. Probl. XV. Fig. xxiii. SECT. V. Of Longitude and Latitude on the .Earthly Globe, and of different Climates. THE various parts of the earth and heavens bear various relations both to one another and to these several points and cir- cles, which have been described. First, The earth shall be considered here. Every part of the earth is supposed to have a meridian line passing over its zenith from north to south through thepoles of the world. It is called the meridian line of that place, because the sun is on it at noon. That meridian line which passes through Ferro, one of the Canary Islands, has been usually agreed upon by geographers as a first meridian, from which the rest are counted by thenum- ber of degrees on the equator. Others have placed their first meridian in Teneriff, another ofthe Canary Islands, which is two degrees more to the east, but this is matter of choice and custom, not of necessity. The longitude of a place is its distancefrom the first meri- dian toward the east' measured by the degrees upon the equator. Sothe longitude of London is about 20 degrees, counting the first meridian at Ferro. Note, In English globes or maps sometimes the longitude is computed from the meridian of London, in French maps from Paris, &c. for it being purely arbitrary wheré to fix a first meridian, mariners and map- makers determine this according to their inclination. When only the word longitude is mentioned in general, it always means the distance eastward ; but some- times we mention the longitude westward as well as eastward, i. e. from London to Paris, &c. especially in maps of particular countries. By the meridian circles on a map or globe the eye is direct- ed to the true longitude of any place according to the degrees marked on the equator : and upon this account the myridians are sometimes called lines of longitude.
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