  In this paper we discuss Chasles's construction on ellipsoid to draw the
semi-axes from a complete system of conjugate diameters. We prove that there is
such situation when the construction is not planar (the needed points cannot be
constructed with compasses and ruler) and give some others in which the
construction is planar.In this paper we discuss Chasles's construction on
ellipsoid to draw the semi-axes from a complete system of conjugate diameters.
We prove that there is such situation when the construction is not planar (the
needed points cannot be constructed with compasses and ruler) and give some
others in which the construction is planar.
