Many years ago, the gilded surface of the Singing Tower Sundial gnomon had worn off due to the harsh Florida environment. During the early years of Bok Tower Gardens, the sundial gnomon gleamed with gold leaf. A photo in the January 1930 edition of the National Geographic featured a photograph of the sundial with the golden gnomon.
To restore the gnomon to its previous glory, it was cleaned and re-gold leafed with 23k gold. The work was made possible through gifts and was the last phase of the tower restoration work. In addition to the sundial restoration, the tower was cleaned, mortar joints repointed and the stone sealed. The gleaming gnomon complements the vibrant colors in the stone brought out by the sealer.
A bit of historical trivia, the sundial was raised into place on October 26, 1928, and the gnomon was installed on February 17, 1929, however, the final touches were not completed until March 21, 1929.
An unusual design, the vertical sundial was conceived by architect Milton Medary as a decorative means to seal the opening through which the bells were hoisted up to the bell chamber. Dominque Berninger, an architect with the firm of Ratzinger, Borie, and Medary, did the mathematical calculations and created the design for the timepiece.
This design was given to tower sculptor Lee Lawrie to create the art of the piece. Lawrie’s assistant, Robert C. Wakeman, designed the signs of the zodiac that surround the sundial. The zodiac signs are in astrological order: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. The signs represent the constellations used by ancient astronomers to determine the seasons of the year.
Carved from pink Etowah marble, the sundial was one of the final touches completed on the Singing Tower. The sundial was raised into place on October 26, 1928, and the gnomon was installed on February 17, 1929, seventeen days after the dedication ceremony. The final touches were completed on March 21, 1929.
The word “gnomon” originated in Greece and means “one that knows or examines” and is the part of a sundial that casts a shadow. Cast in the shape of a snake, an ancient symbol of time, the gnomon forms a line parallel to the axis of the Earth and points to the North Star. The top edge of the gnomon called the “style,” casts the straight-line shadow that determines the time of day.
As the Earth revolves around the Sun, its axis remains pointed to the North Star but the angle of the Sun to the Earth changes from season to season; in the summer, the angle is less, in the winter, the angle is greater. Most sundials are tilted to adjust to the angle of the sun depending on the time of the year. As the sundial cannot be tilted, an “equation of time” chart was calculated and inscribed below the Tower’s sundial. This chart is a calendar showing how many minutes to add to the sundial time to get an accurate time of day in Eastern Standard Time.
Getting Watch Time from Shadow Time
(instructions provided by Derek Bunker, from the Bok Tower Gardens archives)
The rotation of the Earth, in relation to the fixed stars, remains virtually constant over centuries. Unfortunately, solar time is not regular, as the path of the Earth around the Sun is an ellipse and not a circle, (the Moon also causes monthly irregularities). On any given day of the year, determining the correct time requires additional calculation.
Step 1: Look first at the outside rectangle of the 12 signs of the zodiac and then at the inside roman numerals which are the hours starting at VI (6 am) at the top left. The roman numerals are listed vertically to X (10 am) and then horizontally from XI (11 am) to I (1 pm). The chart continues along the right side of II (2 pm) to V (5 pm). Determine where the gnomon casts a shadow to find the shadow time. The shadow of the gnomon moves in a counterclockwise around the dial face.
Each dash and space between the roman numerals represent 10-minute increments.
Use the chart below the sundial account to obtain Eastern Standard Time if it is currently daylight savings time.
1. Find the current month on the top of the chart. Then find the vertical line corresponding to the closest date.
2. Move your eyes down the curved line and determine which horizontal line is the closest.
3. Trace along that horizontal line to the number columns (between March/April or September/October) and find the number of minutes, between 10 and 40 to add to your shadow time.