Abstract
In this article, a new aspect of a possible connection between the development of ancient
Greek and Roman sundials and the history of conic sections is analyzed: On conical sundials,
a conic section occurs at the edge between the plane top surface and a conical surface
which is most commonly used in sundials as the shape of the dial face. Based on an analysis
of 3D models of conical sundials, this paper argues that the curve is not the result of
a method of shaping the conical surface, but rather the basis to do so. A method is given
by which the curve can be drawn approximately by connecting points. The latter can be
found using a geometrical construction. This procedure suggests that craftsmen who built
sundials had basic knowledge of the geometry of cones and conic sections.