The two Memoirs by M. Chaslcs, " On the Properties of Cones of the second Degree," and " On the Spherical
Conies," of which a translation is now presented to English geometers, were printed in the sixth volume of the
Transactions of the Royal Academy of Brussels. Whether they arc considered merely as exercises of pure
geometry, exhibiting its elegance and power in a remarkable degree, or as a rich and early contribution to
the theory of spherical curves, they possess strong claims on the attention of mathematicians.