The Astronomical Observatories of Jai Singh c13.13

c13.13

The Nari Valaya (‘circular dial’), or Uttara dakṣiṇo Gola (north and south dial), is a cylindrical dial—the axis of the cylinder pointing north and south, and the northern and southern faces being parallel to the plane of the equator. At the centre of each face, and at right angles to it, is a short iron style surrounded by two circles—the outer one (on the northern face)¹ graduated in hours, etc., and the inner one in ghaṭis, etc. Besides serving as an ordinary dial the instrument marks the equinoxes, since the northern face can only be used for sun observations when the sun is north of the equator. The inscription on the instrument reads:—“Narivalaya Dakshin and Uttra Gola. The use of this instrument is to find whether the heavenly bodies are in the northern or southern hemisphere. It gives time also.”