On a Dynamical Top, for exhibiting the phenomena of the motion of a system of invariable form about a fixed point, with some suggestions as to the Earth's motion

by James Clerk Maxwell

. The first figure represents a section of the various cones by a plane perpendicular to the axis of

, which is that of greatest moment of inertia. These sections are ellipses having their major axis parallel to the axis of

. The value of

corresponding to each of these curves is indicated by figures beside the curve. The ellipticity increases with the size of the ellipse, so that the section corresponding to

would be two parallel straight lines (beyond the bounds of the figure), after which the sections would be hyperbolas.