SECTION VII. 239 Thus while the sun's declination increases or decreases by slow degrees, the length of the days must increase and de- crease but very slowly ; and when the sun's declination in- creases and decreases swiftly, so also must the length of the days ; all which are very naturally and easily represented by the globe. SECT. VII. Of Longitude and Latitude on the Heavenly Globe, and of the Nodes and Eclipses of the Planets. THE longitude and latitude in astronomy are quite dif. ferent thingsfrom longitude and latitude in geography, which is ready to create some confusion to learners. The longitude of the sun or any star is its distancefrom the point aries eastward, measuredin the ecliptic. This is a short way of describing it, and agrees perfectly to the sun ; but in truth a star's longitude is its distance eastward from agreat arch drawn perpendicular to the ecliptic through the point aries, and measured on the ecliptic. We do not so' usually talk of the sun's longitude, because we call it his place in the ecliptic, reckoning it no farther back- ward than from the beginning of the sign in which he is. So the 25th day of June, we say the sun is in the 14th degree of cancer, and not in the 104th degree of longitude. The latitude of a star or planet is its distancefrom the eclip- tic, measured by an arch, drawn through that star perpendicular to the ecliptic. Longitude and latitude on the heavenlyglobe bear exactly the same' relation to the ecliptic as they do on the earthly globe to the equator. As the equator is the line from which the lati- tude is counted, and on which the longitude is counted on the earthly:globe, so the ecliptic is the linefrom which the latitude, and on which the longitude are counted on the heavenly globe. And thus the lines of latitude in the heavenly globe are all supposed parallels to the ecliptic, and the lines of longitude, cut the ecliptic at right angles, and all meet in the poles of the eclip- tic; bearing the same relation to it as on the earthly globe they do to the equator. The latitude of a star or planet is called northern or southern as it lies on the north or south side of the ecliptic. The sun has no latitude, because it is always in the ecliptic. This relation of latitude therefore chiefly concerns the planets and stars. The fixed stars as well as the planets have their various longitudes and latitudes ; and their particular place in the hea- vens may be assigned and determined thereby, as well as by their right,ascension and declination which I mentioned before; and astronomers use this method to fix exactly the place of a
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