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OPERATION VIII. To know how many hours the Moon has been up, and how many she lacks of her setting, as also how long she is to be that day above the Horizon.
THis is done by numbring the Hours or Hour Circles between the Moons place in her Parallel on the Globe and the intersections of her said Parallel with the Horizon; for ha∣ving found that her Parallel cuts the Horizon in the East at the five a clock hour circle, and in the West at that of seven, and seeing that her present Place is (v. g.) at that of two in the afternoon, you may conclude that she has bin up nine hours wanting eighteen minutes, that is, eight hours and forty two minutes; and will set within 5 hours wanting ten minutes, or four hours and fifty minutes; for the Moon goes from East to West (by the Motion of the Primum Mobile or Motum Raptus) two Minutes (as we suppose) every hour (take one time with the o∣ther) slower than the Sun; which happens by her being too quick for the Sun in her own Motion, that is to say, in the Motion of the Center of her Epicicle, which carries her from West to East; therefore the Moon according to the present Example or Sup∣position will be above the Horizon fourteen Hours wanting twen∣ty eight Minutes, i. e. about thirteen hours and a half.