A Brief History of Sundials
Sun dials are an ancient method of telling time. The oldest known was constructed in Egypt around 1500 B.C. It was shaped like an L, and the length of the shadow cast by the vertical leg along the horizontal leg indicated the time. Romans perfected the horizontal sundial we know today, and even invented portable versions for travelling.
As the Earth rotates on its axis, the sun appears to move across the sky. Thus, the shadow of a gnomon (Greek for Know) pointing toward the celestial pole, will move across the hour band of the sundial. The sun travels 15 degrees westward every hour. Thhe gnomon's shadow on the dial plate moves at the same rate. You can therefore read the time by noting the hour line closest to the edge of the shadow.
During the Renaissance, sundials of every description were produced. In addition to marking hours and minutes, some sundials recorded the date, seasons, and signs of the Zodiac. Some even carried tide tables, which indicated the time of high tide at named ports.
Those who couldn't afford their own sundials had only to look up, for vertical sundials were mounted on the outside walls of many churches and public buildings.
By the 18th century, though, increasingly efficient mechanical clocks began to supersede shadow-chasing sundials. Still, the French railway regulated its clocks by sundials until the end of the 19th century.
Gardeners, of course, don't need to mourn the passing of shadow clocks. We can perpetuate the 3,500-year tradition simply by placing a sundial in a sunny spot in the yard. Set on a stone pedestal, a sun dial can both anchor the garden and trace the hours we spend digging.
Not only did the Romans perfect sundials as we know them today, but they were also among the first to use them in gardens. Roman gardens were private spaces, most often set behind houses and enclosed on all sides by colonnades and rooms. In the midst of this ordered scene was the sundial - set on a stone pedestal to catch the shadow of the sun god Sol as he crossed the sky.
Of the 8 types of sundials - horizontal (flat) and armillary are best suited for garden use. Horizontal sundials, the type commonly seen on pedestals, consist of a dial plate, marked in hour lines, and a "gnomon," the raised projection that casts a shadow. There are also wall mounted or vertical sundials for use where space or access to the sun is restricted. |
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