SECTION VIII. 239 If themoon's path and the sun's were precisely thesame, or parallel circles in the same plane, then at every new moon thesun would be eclipsed by the moon's coining between the earth and the sun : And at every full moon the moon would be eclipsed by the earth's coming been the sun and the moon. But since the planes of their orbits or paths are different, and make angles with each other there cannot be eclipses but in or near the place where the planes of their orbits or paths intersect or cross each other. In or very near these nodes, therefore, is the only place ;where the earth or moon can hide the sun or any part of it from each other, and cause an eclipse either total or partial; And for these reasons the orbit or path of the sun is called the ecliptic. The eclipses of other planets, or of any part of the sun by their interposition, are so very inconsiderable as deserve not our present notice. SECT. VIII. Of Altitude, Azi;nalh, Amplitude, and various Risings and Settings of the Sun and Stars. THE altitude of the sun or star is its heighth above the horizon, measured by the degrees on the quadrant ofaltitudes. As the height of the sun at noon is called its meridian alti- tude, or its culminating, so the height of the sun in the east or west is sometimes called its vertical altitude. The quadrant of altitudes is a thin label of brass, with a nut and skrew at the end of it, whereby it is fastened to the meridian at the zenith of any place now by bending this down to the horizon, you find the altitude of any star or point in the Leavens, because the label is divided into 90 degrees counting from the horizon upward. Circles parallel to the horizon, supposed to be drawn round the globe, through every degree of the quadrant of altitudes less and less till they come to a point in the zenith, arecalledparallels of altitude, or sometimes in the old arabic name almicantars. But these can never be actually drawn on the globe, because the horizon and zenith are infinitely variable, according to the dif- ferent latitudes of places. In the .vith figure, supposez to be the zenith, te the nadir, sa a the horizon, and the strait lines a b, fg, k an, will represent the parallels of altitude. Note, The sun, being always highest on the meridian, or at noon, it descends in an arch towards thehorizon in order to set, by the same degrees by which it ascended from the horizon after its rising. Stars and planets rise and set and come to the meri- dian at all different hours of the day or night according to the various seasons of the year, or according to the signs in which the planets are.
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