I think it right to give the proof that the ratio of the circumference to
the diameter is incommensurable. This method of proof was given by
Lambert,[672] in the _Berlin Memoirs_ for 1761, and has been also given in
the notes to Legendre's[673] Geometry, and to the English translation of
the same. Though not elementary algebra, it is within the reach of a
student of ordinary books.[674]