SECTION XIX. 279 nets, his ascensionandifference, his amplitude, the length of day and night." Rectify for the latitude, and for the sun's place, then bring the sun's place down to the eastern part of the horizon, and the index will.shew the time of sun-rise on the dial, viz. fiveminutes after four in the morning. Bring the sun's place to the western side of the horizon, and the dial will shew the hour of sunsetting, viz. five minutes before eight at night. Thus his ascensional.difference will appear, that is, how long he rises or sets before or after six o'clock, which is one hour and ,55 minutes. Thus also his amplitudewill appear in the horizon to bealmost 34 degrees to the north of the east. The hour of the sun's rising doubled gives the length of the night, viz. eight hours and 10 minutes ; and the hour of the sun's setting doubled gives the lengthof the day, which will be 16 hours wanting 10 minutes, i. e. 15 hours 50 minutes. Problem XX. " The place and day being given, to find the altitude of the sun at any given hour." Rectify for the latitude, for the zenith and for the sun's place: Bring the quadrant of altitude under the meridian, and it will meet the sun's place in the meridian altitude of the sun that day, and thus shew how high it is at noon. Turn the globe till the index point to any other given hour on the dial, then observe where the sun's place is, bring the quadrant of altitude to it, and it will shew the son's altitude at that hour; thus May 10th at London, the sun's meridian alti- tude will be a little above 581 degrees, and at nine o'clock in the morningwill be 43f. Problem XXI. " The place and day being given, to find the azimuth of the sun at any given hour." Rectify the globe for the latitude, the zenith and the sun's place ; then turn the globe till the index point to the hour given then observe the sun's place ; bring the edge of the quadrant of altitude down upon it, and it will cut the horizon -in the azimuth of the sun, or shewwhat point of the compass the sun is in. Thus May 10th at 20 minutes past 9 in the morning, the sun's azimuth will be about 60 degrees from the south toward the east, that is, near south-east and by east. Problem XXII. "The sun's altitude being given at any certain place and day, to find the hour of the day, and also his azimuth." Rectify as before for the latitude, the zenith and the sun's. place; turn the globe, and move the quadrant of altitudes su that the sun'splace maymeet the degree of altitude given on the quadrant, then the index will shew the hour on the dial ? and the quadrant of altitude will cut the azimuth ou the horizon.
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