Two round balls sit on the rings of the tropics. At noon each day their shadows will appear. The shadow of the upper ball shows on the vertical band in the summer months, and the lower ball in winter, and they each will follow the height of the sun during the year. Summer and winter solstice are at the turning points of their travel. At the equinox in spring and autumn the two shadows both appear. Mathematical spirals form the three sundial legs. This armillary sundial is a delight of ancient science and an intriguing and beautiful object for the garden.