Sundials - World's Oldest Clocks

North American Sundial Society

Dallas  

Sundial: 385
State/Province:  Texas Country:  USA
Dial Type:  Horizontal Dial Condition:  Excellent
  Latitude and Longitude: 32° 54.607' N  96° 45.080' W
Location:
  • Entrance Court, Texas Instruments Forest Lane Facility (south campus),
    12500 TI Boulevard, Dallas, Texas
 
Description:
  • This is large horizontal dial with a 20-foot-long polar gnomon that rises obliquely from the center of a 34-foot-diameter circle. The hour lines are embedded in the terrazzo pavement showing hour marks and quarter hour ticks. Hour labels (standard time 6-7 and daylight-saving time 7-8) are etched into 12-inch diameter stainless steel plates, each tipped toward the dial's center and supported on a 6-inch-high bollard. The tick marks run further, extending from 5:30am to 7:15 standard time. Hour marks and labels are offset for site longitude, making the time correction between solar and civil time no more than +/- 15 minutes, depending on season. The stainless-steel gnomon has a rectangular cross section that tapers from 12 x 4 inches at the base to 4 x 4 inches at the upper end. The center of the gnomon's shadow (not the shadow's edge) indicates the time. The terrazzo circular plaza is slightly beveled (a squat cone) for proper runoff of rain. The cone's apex coincides with the base of the gnomon and is 10 inches higher than the circumference of the 34-foot circle. The layout of time lines takes this radially sloping surface into account. The terrazzo pavement also includes an embedded polar map of the world adjusted in longitude so that the longitude of Dallas with a star at the dial's location in Texas is due south of the gnomon.

    Surrounding the sundial are a dozen rectangular plinths, each standing 16 feet tall with a circular glass emblem near the top. They represent the many areas of technology and industry to which Texas Instruments has contributed over the years. The plinths and gnomon are illuminated from underneath at night.
 
General Information:Inscription:
  • Owner: Texas Instruments
  • At the gnomon's base plate is a plaque with instructions for reading the hours and a table for the equation of time to correct for the difference between solar and civil time. Around the ring of the plaque reads:
    Entrance Court Sundial - Texas Instruments Forest Lane Facility
  • Designer: Sundial Design by: Adrian Levin (Donovan & Green, New York) for overall structural design; Roger W. Sinnott (Sky & Telescope) for astronomical calculations
  • Builder: Multiple contractors
  • Construction Date: Summer, 1996
 
References:
  • Closeup photos courtesy Arlo Blank

Last Revised: 2020-03-09 20:59

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