SUNDIAL SECTIONS:

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History of Sundials

Why the Sun Dial keeps time

Developing and Making Sundials

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Sundial Hour Lines Lay out

Sundial "Furniture"

Declination Lines of Sundials

Portable Sundials

Interesting Sundials of the World

LAYING OUT THE SUNDIAL HOUR LINES - Page 22

THE ARMILLARY PLATE X The armillary consists of several rings put together in the form of a hollow sphere. Usually ten rings are employed, de-noting the ten major circles of the celestial and terrestrial spheres placed in proper relation to each other. These circles represent the (I) Meridian, (2) Horizon, (3) Equator, (4) Ecliptic, (5) Tropic of Cancer, (6) Tropic of Capricorn, (7) North Polar or Arctic Circle, (8) South Polar or Antarctic Circle, (g) Equinoctial Colure, and (so) Solstitial Colure. The Construction The circle HENAS represents the meridian; the line SN the polar axis of the sphere, with its poles at N and S. The point C marks the center of the sphere and the horizontal line HO, drawn through C, represents the horizon, which makes an angle with the polar axis SCN equal to the latitude of the place. The Equator, EA, is perpendicular to the polar axis at C. The Ecliptic, PT, is drawn through C (which also represents the east and west points of the horizon) making an angle with the equator equal to 23°27', cutting the sphere at P and T. The points P and T denote the greatest northern and southern declination of the sun. The Tropic of Cancer is shown by PL, which is drawn through P parallel to the equator, because it is a circle of latitude. The Tropic of Capricorn, TB, is drawn through T parallel to the equator. The North and South Polar Circles are similarly drawn. The dotted line KCW is perpendicular to the ecliptic at C, and cuts the sphere at W and K.

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