SECTION XIX. 281 Problem XXVI. " To know by the globe the length of the longest and shortest days and nights in any place of the world." Remember that the sun enters the first degree of cancer, on the longest day, at all places on the north side of the equator, and the first degree of capricorn on the south side. Also re- member that he enters the first degree of capeicorn, the shortest day in all places of the northern hemisphere, and the first de- gree of cancer in the southern. Then rectify the globe for the latitude and sun's place, and find the hour of sun rising, which doubled shews the length of the night. And the hour of the sun setting doubled, shews the length of the day, as in prob- lem XIX. Problem XXVII. "The declination and meridian altitude of the sun, or of any star, being given to find the latitude of the place." Mark the point of declination on the meridian, as it is either north or south from the equator; then slide the meridian up and down in the notches, till the point of the declination be so far distant from the horizon as is the given meridian altitude. Then is the pole elevated to the latitude sought. Thus where the sun or any star's meridian altitude is 581 degrees, and its declination 20 degrees northward, the latitude of that place will be 51-1 degrees north. See more problemVII, VI1I, IX. Sect. XX. Note, There are some few problems which relate to the sun and to the hour, which may be performedon the globe when the sun shines, though not with any great exactness, yet suffi cient for demonstration of the reason of them as follows. Problem XXVIII. " The latitude of a place being given, to find the hour of the day in the summer when the sun shines." Set the frame of the globe upon "a plane perfectly level or horizontal, and set the meridian due north and south ; both which are difficult to be done exactly ; even though you have a mariner's compass by you. Then rectify the globe for the latitude, and the iron pin of the pole will cast a shadow on the dial and shew the true hour. For when the globe is thus placed, the dial plate with the pole in the centre of it, is a true equinoctial dial for our summer halfyear, when the sua is on the north side of the equator. 'The same may be also done in the winter half-year, by depressing the north poleas much below the south part of the horizon as is equal to the latitude of the place ; for then the dial plate is a proper equinoctial dial for the winter half- year But this is not so commodiously performed, though the reason of it is the saine as the former. Problem XXIX. " To find the sun's altitude, when it shines, by the globe."
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