Sundial: 1036
State/Province:  Maryland Country:  USA
Dial Type:  Noon Mark or Meridian Dial Condition:  Good
  Latitude and Longitude: 38° 58.927' N  76° 29.547' W
  • On the campus of St. John's College, southeast of McKeldin Planetarium, in front of Mellon Hall on a small, circular brick plaza.
  • This brass mariner's compass about 12 inches in diameter is mounted on the east side of a concrete pillar. It is known on campus as "The Ptolemy Stone". It functions as a meridian transit with altitude marks every half degree engraved on the upper south quadrant. The alidade has a notch on the upper end and a plate at the lower end, designed for measuring the altitude of the sun using the notch shadow (preventing eye damage of sighting the sun directly). The pillar is just over 3 feet tall with a sloped top. The main slope is that of the site latitude. A steeper "north face" is cut plane to the celestial equator. To make the equator "visible", a ring is mounted to the face. The ring casts no shadow on the equinox and from September to March is in shadow. A similar Ptolemy Stone is at St. John's campus in Santa Fe, NM.
General Information:
  • Owner: St. John's College
  • Designer: unknown
  • Builder: unknown
  • Construction Date: circa 1987 or earlier
References: Web Links:
  • St. John's is one of the oldest academic institutions in the US, a successor to King William's School founded in 1696. SJC received a collegiate charter in 1784, providing a liberal arts education based on Great Books curriculum.

Last Revised: 2021-12-09 15:20