The knowledge of the heavens and the earth made easy: or, the first principles of astronomy and geography. Explain'd by the use of globes and maps with a solution of the common problems by a plain scale and compasses as well as by the globe / Written several years since for the use of learners.

  • Isaac Watts
Date:
1728
Catalogue details

Licence: Public Domain Mark

Credit: The knowledge of the heavens and the earth made easy: or, the first principles of astronomy and geography. Explain'd by the use of globes and maps with a solution of the common problems by a plain scale and compasses as well as by the globe / Written several years since for the use of learners. Source: Wellcome Collection.

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    It may not therefore be improper to note in this Place, that fuppofe a Planet to be at gy if the Eye of the Spedator were on the Surface of the Earth at s, he would be- hold it as level with the Horizon: But if his Eye were at the Centre of the Earth or c, he would behold it railed leveral De¬ grees or Minutes above the Horizon, even the Quantity of the Angle gcry or (which is all one) sgc. Now the • Difference between the Place where a Planet appears to a Spedator plac’d on the Centre of the Earth, and to a Specta¬ tor plac’d on the Surface, is called the Pa¬ rallax of that Planet at that time; and therefore the Difference between thole two Places g and r, or rather the Quantity of the Angle gcry or sgey is called its Hori¬ zontal Parallax. And this is of great ufe to adjuft the real Diitanccs, and confequent- jy the real Magnitudes of the feveral Pla¬ nets. But this Dodrine of Parallaxes be¬ longs rather to the iecond or fpecial Part of Aftronomy. II. The Meridian is a great Brazen Cir¬ cle in which the Globe moves; it erodes the Horizon at right Angles, and divides the Globe into the Eaftern and Weftern Blemifpheres. It reprefents that Line or Circle in the Heaven which paffcs juft over our Plead, and cutting the Horizon
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