A new treatise on the use of the globes, or a philosophical view of the earth and heavens / [Thomas Keith].

  • Thomas Keith
Date:
1808
Catalogue details

Licence: Public Domain Mark

Credit: A new treatise on the use of the globes, or a philosophical view of the earth and heavens / [Thomas Keith]. Source: Wellcome Collection.

    37/398 (page 11)
    41. Parallels of declination ai-e fmall circles pa- rallel to the equinoctial on the celellial globe, and are limilar to tlie parallels of latitude, on the terreltrial globe. 42. The Colures are two great circles palling through the poles of the world ; one of them palTes through the equinodial points, Aries* and Libra ; the other through the folilitial points, Cancer and Capricorn ; hence they arc called the equinoctial and folititial colures. They divide the ecliptic into four equal parts, and mark the four feafoiis of the year. 43. Azimuth, or Vertical Circles, are imaginary great circles palfing through the zenith and the nadir, cut- ting the horizon at right angles. ITe altitudes of tlu^ hea- venly bodies are meafured on thefe circles, which circles may be reprefented by I'crewing the quadrant of altitude on tlie zenith of any place, and making the other end move along the wooden horizon of the globe. 44. The Prime Vertical is that azimuth circle which pali'es through the eall and weft points of the horizon, and is always at right angles with the brafs meridian, which may be confidered as another vertical circle palling through the north and fouth points of the horizon. 45. The Altitude of any objeCf in the heavens, is an arch of a vertical circle, contained between the centre of the ol^eft and the horizon. When th& objeft is upon the me- ridian, this arch is called tlie meridian altitude. 46. The Zenith Distance of any celeftial objeft, i» the arch of a vertical circle contained between the centre of that objecl and the zenith ; or it is what the altitude of the objeft wants of 90 degrees. When the objeft is on the meridian, this arch is called the meridian zenith diftance. 47. The Polar Distance of any celellial obje£l, is an arch of a meridian, contained between the centre of that objetft and the pole of the equino<ftiF.»]. •Ill the time of Hij>p4,rcbti} die equinodtial colure is I’uppofed to have jpsfled througli the middle of theLitton Aries. Hipparchus \va a native of Nicata, a town of By thinia in Afia Minor, about 73 miles S. E. of Conftantinople, now called ll'uic; he made his v.blervations between i60 and 13s ye.irs before ChrL'l. 48. The